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15 pages, 6796 KiB

Open AccessArticle

The Construction and Application of a Deep Learning-Based Primary Support Deformation Prediction Model for Large Cross-Section Tunnels

by Junling Zhang, Min Mei, Jun Wang, Guangpeng Shang, Xuefeng Hu, Jing Yan and Qian Fang

Appl. Sci. 2024, 14(2), 912; https://doi.org/10.3390/app14020912 - 21 Jan 2024

Cited by 1 | Viewed by 612

Abstract

The deformation of tunnel support structures during tunnel construction is influenced by geological factors, geometrical factors, support factors, and construction factors. Accurate prediction of tunnel support structure deformation is crucial for engineering safety and optimizing support parameters. Traditional methods for tunnel deformation prediction [...] Read more.

The deformation of tunnel support structures during tunnel construction is influenced by geological factors, geometrical factors, support factors, and construction factors. Accurate prediction of tunnel support structure deformation is crucial for engineering safety and optimizing support parameters. Traditional methods for tunnel deformation prediction have often relied on numerical simulations and model experiments, which may not always meet the time-sensitive requirements. In this study, we propose a fusion deep neural network (FDNN) model that combines multiple algorithms with a complementary tunnel information encoding method. The FDNN model utilizes Convolutional Neural Networks (CNNs) and Long Short-Term Memory (LSTM) networks to extract features related to tunnel structural deformation. FDNN model is used to predict deformations in the Capital Ring Expressway, and the predictions align well with monitoring results. To demonstrate the superiority of the proposed model, we use four different performance evaluation metrics to analyze the predictive performance of FDNN, DNN, XGBoost, Decision Tree Regression (DTR), and Random Forest Regression (RFR) methods. The results indicate that FDNN exhibits high precision and robustness. To assess the impact of different data types on the predictive results, we use tunnel geometry data as the base and combine geological, support, and construction data. The analysis reveals that models trained on datasets comprising all four data types perform the best. Geological parameters have the most significant impact on the predictive performance of all models. The findings of this research guide predicting tunnel construction parameters, particularly in the dynamic design of support parameters. Full article

(This article belongs to the Special Issue Urban Underground Engineering: Excavation, Monitoring, and Control)

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16 pages, 14066 KiB

Open AccessArticle

Numerical Investigation on the Influence of Super-Large-Diameter Shield Tunneling on Nearby Existing Metro Tunnels and the Protection Scheme

by Yixiang Li and Zongxing Zou

Appl. Sci. 2023, 13(24), 13179; https://doi.org/10.3390/app132413179 - 12 Dec 2023

Cited by 2 | Viewed by 642

Abstract

To reduce traffic congestion and meet the demand for rail transportation, the diameters of shield tunnels are constantly expanded. The super-large diameter, deep depth and long distance of super-large-diameter shield tunnels, coupled with the limitation of existing structures on underground construction space, cause [...] Read more.

To reduce traffic congestion and meet the demand for rail transportation, the diameters of shield tunnels are constantly expanded. The super-large diameter, deep depth and long distance of super-large-diameter shield tunnels, coupled with the limitation of existing structures on underground construction space, cause many problems in the construction of these tunnels, such as affecting existing structures. This study takes a shield project in Wuhan as the research object, uses the finite element method to simulate the influence of super-large-diameter shield tunnelling on the displacement of the existing Line 5 tunnel segments, and analyzes the influence of the isolation pile arrangement and length on the isolation effect. The analysis indicates that (1) the displacement of Line 5 decreases with an increasing horizontal center distance between the tunnels and increases with an increasing vertical center distance between the tunnels, with a maximum displacement of 17.9 mm; (2) the displacement direction and position of the maximum displacement of Line 5 vary with changes in the vertical center distance between the tunnels, but remain essentially constant with changes in the horizontal center distance; and (3) the isolation piles closer to the shield tunnel improve support, with its isolation effect on the Line 5 segment becoming limited. Full article

(This article belongs to the Special Issue Urban Underground Engineering: Excavation, Monitoring, and Control)

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21 pages, 11553 KiB

Open AccessArticle

Supporting Structure of Steel Corrugated Plate-Mold Bag Concrete and Its Application in a Circular Shaft

by Pengfei Li, Shuo Wang, Mingju Zhang and Zhengdong Huang

Appl. Sci. 2023, 13(23), 12937; https://doi.org/10.3390/app132312937 - 4 Dec 2023

Cited by 1 | Viewed by 869

Abstract

To cater to the problems of a poor working environment, a large amount of rebound, and the high energy consumption of sprayed concrete in tunnel engineering, this paper proposes a new support scheme with a steel corrugated plate combined with mold bag concrete. [...] Read more.

To cater to the problems of a poor working environment, a large amount of rebound, and the high energy consumption of sprayed concrete in tunnel engineering, this paper proposes a new support scheme with a steel corrugated plate combined with mold bag concrete. Analytical solutions of stresses for steel corrugated plate and mold bag concrete were deduced based on the thin-walled cylinder, and then their strength safety factors were presented. Subsequently, a series of numerical simulations were conducted to investigate the mechanical performance of the third ring of the main structure based on the ‘load-structure’ 3D model. The numerical results were verified using the classical theoretical analysis and the proposed model, and then parametric studies were performed through the numerical method. Finally, field tests in a circular shaft were carried out to verify the feasibility of the structure and process and the engineering effect. The results show that the combination of steel corrugated plate and mold bag concrete is feasible and can realize rapid support technology for underground engineering, which provides a new idea for the supporting technology of underground engineering such as tunnels. Full article

(This article belongs to the Special Issue Urban Underground Engineering: Excavation, Monitoring, and Control)

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22 pages, 13755 KiB

Open AccessArticle

Experimental Investigation on the Anchorage Performance of a Tension–Compression-Dispersed Composite Anti-Floating Anchor

by Yuguo Liu, Kai Xia, Botong Wang, Ji Le, Yanqing Ma and Mingli Zhang

Appl. Sci. 2023, 13(21), 12016; https://doi.org/10.3390/app132112016 - 3 Nov 2023

Cited by 1 | Viewed by 741

Abstract

Rapid advancements in construction technologies have accelerated the development of complex and deep underground structures, raising concerns about the impact of groundwater on structures, particularly anti-floating measures. Traditional tensioned anchors, commonly used for preventing flotation, suffer from limitations like low pull-out bearing capacity, [...] Read more.

Rapid advancements in construction technologies have accelerated the development of complex and deep underground structures, raising concerns about the impact of groundwater on structures, particularly anti-floating measures. Traditional tensioned anchors, commonly used for preventing flotation, suffer from limitations like low pull-out bearing capacity, shallow critical anchoring depth, and localized stress concentration. To overcome these limitations, this paper introduces a tension–compression dispersed composite anchor, which combines casing, load-bearing plates, and tensioned anchors. Comparative tests were conducted between these composite anchors and traditional tensioned anchors to analyze their anchoring behavior. Our results show that tensioned anchors exhibit a stable axial force distribution as anchoring length increases. By identifying abrupt changes in the axial force curve, optimal anchoring lengths for load-dispersed anchors can be determined, thereby enhancing rock and soil strength utilization. The tension–compression-dispersed composite anchor outperforms tensioned anchors, with 1.44 times the ultimate bearing capacity for equivalent anchoring lengths and 1.1 times the capacity for an additional 1 m length. It also displays superior deformation adaptability and structural ductility under high-bearing loads compared to tensioned anchors with extended anchoring lengths. Effectively mobilizing the strength of the lower anchoring segment within the rock and soil results in a lower critical anchoring depth and a more uniform distribution of lateral friction resistance. In conclusion, the tension–compression-dispersed composite anchor offers significant advantages, making it a promising engineering solution for anti-floating anchor systems in complex underground environments. Full article

(This article belongs to the Special Issue Urban Underground Engineering: Excavation, Monitoring, and Control)

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14 pages, 3210 KiB

Open AccessArticle

Analytical Solutions of Water Inflow for Foundation Pit in Confined Water Stratum

by Jingjing Shen, Yue Jiang, Jie Wu and Pengfei Li

Appl. Sci. 2023, 13(21), 11765; https://doi.org/10.3390/app132111765 - 27 Oct 2023

Viewed by 699

Abstract

This paper is aimed at the problem of inaccurate calculation of the water inflow of a foundation pit with a suspended water-proof curtain in a confined water stratum. According to the groundwater hydraulics principle, the theoretical model of the seepage field of the [...] Read more.

This paper is aimed at the problem of inaccurate calculation of the water inflow of a foundation pit with a suspended water-proof curtain in a confined water stratum. According to the groundwater hydraulics principle, the theoretical model of the seepage field of the foundation pit is established, and the analytical formula of the water inflow for the circular, strip, and rectangular foundation pits is deduced. The seepage path influence coefficient α related to the water-proof curtain insertion ratio, the thickness of the confined aquifer, and the radius of the foundation pit is proposed and obtained by the positive and negative analysis of numerical simulation. The coefficient is used to correct the equivalent seepage length in the pit and directly affect the calculation result of water inflow. Finally, based on the calculation results of the analytical solution of water inflow, the relationship between the scale of the foundation pit and the water control effect is discussed. The research results show that the theoretical analysis results in this paper are in good agreement with the numerical results and the measured data in the field: when the size of the foundation pit is too large, it is not suitable to use the suspended water-proof curtain as the water control measure. Full article

(This article belongs to the Special Issue Urban Underground Engineering: Excavation, Monitoring, and Control)

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16 pages, 7141 KiB

Open AccessArticle

Research on Optimization Design of Tunnel Blasting Scheme Adjacent to Buildings

by Kuan Ren, Annan Jiang, Xinping Guo and Qinghua Min

Appl. Sci. 2023, 13(20), 11509; https://doi.org/10.3390/app132011509 - 20 Oct 2023

Cited by 1 | Viewed by 893

Abstract

The section of Jialingjiang Road Station to Xiangjiang Road Station along Qingdao Metro Line 13 is located in Qingdao, China. All of them show obvious characteristics, being soft on the top and hard on the bottom, and the interval tunnel is faced with [...] Read more.

The section of Jialingjiang Road Station to Xiangjiang Road Station along Qingdao Metro Line 13 is located in Qingdao, China. All of them show obvious characteristics, being soft on the top and hard on the bottom, and the interval tunnel is faced with the problem of existing adjacent buildings. In order to ensure the smooth progress of construction, as well as minimize the damage to the buildings, a new mechanical excavation combined with a blasting construction scheme for the adjacent buildings is proposed. In this scheme, the step method is used for excavation. The upper step is in the weak stratum, and the mechanical method is therefore used for excavation; the lower step is in the hard stratum, and the drilling-and-blasting method is thus used for excavation. Using FLAC^3D 5.0 finite difference software and the method based on blasting an equivalent load, the vibration velocity at adjacent buildings caused by the combined mechanical excavation and blasting scheme, as well as the traditional full-section blasting scheme, is compared and analyzed. Further, the construction parameters of the combined mechanical excavation and blasting scheme are compared and selected based on building settlement, the plastic zone of surrounding rocks, building vibration velocity and other factors. The results show that under the mechanical excavation blasting scheme, the peak particle velocity of each monitoring point decreases significantly compared with that under the full-section blasting scheme, with a maximum reduction of 61.1%, which is within the allowable range of the project, demonstrating the rationality of the new scheme. Finally, the mechanical excavation advance in the upper step is determined as 0.5 m. The optimized parameter construction effect is monitored and evaluated, the problems encountered in the project are successfully solved using the combined mechanical excavation and blasting scheme, and the expected construction period is shortened by 3 months, which shows the rationality of the blasting construction scheme proposed and its parameters, as well as the validity of the calculation results. The research results can be used as a reference for the construction scheme design of similar projects. Full article

(This article belongs to the Special Issue Urban Underground Engineering: Excavation, Monitoring, and Control)

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17 pages, 6307 KiB

Open AccessArticle

Numerical Study on the Effect and Mechanism of Supporting Pile Equivalent Calculation Methods in Pile–Anchor Support System

by Xiaoyang Liu, Changming Wang, Hailiang Liu and Di Wu

Appl. Sci. 2023, 13(20), 11144; https://doi.org/10.3390/app132011144 - 10 Oct 2023

Viewed by 1056

Abstract

In numerical analysis, the pile equivalent calculation method plays a key role in foundation pit calculation results. However, the effect and mechanism of different pile equivalent calculation methods in the foundation pit has remained unclear. To solve this question, based on FLAC3D, four [...] Read more.

In numerical analysis, the pile equivalent calculation method plays a key role in foundation pit calculation results. However, the effect and mechanism of different pile equivalent calculation methods in the foundation pit has remained unclear. To solve this question, based on FLAC3D, four pile equivalent calculation methods were introduced into a typical pile–anchor pit. This research was carried out from the perspective of soil displacement and stress, special points’ stress paths, and the plastic zone. The results revealed that there was a remarkable influence on the calculation results for different pile equivalent calculation methods. Specifically, compared with structural pile elements, displacements near the pile were smaller in solid pile element mode. Moreover, with the increase in excavation depth, stress concentration appeared in the solid pile element mode. The solid support pile with the interface, compared to that without the interface, had less displacement but more stress concentration around the pile, which led the special points’ stress paths around the solid pile to become irregular. Regarding the structural pile elements, it is suggested that both modeling approaches had a similar effect. These findings could help to provide a deeper insight into pile–anchor foundation pit numerical analysis. Full article

(This article belongs to the Special Issue Urban Underground Engineering: Excavation, Monitoring, and Control)

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18 pages, 8278 KiB

Open AccessArticle

Shaking Table Testing of Liquefied Soil Layer Located in the Bottom Slab of a Subway Station

by Shi Ming, Lianjin Tao and Zhigang Wang

Appl. Sci. 2023, 13(19), 10866; https://doi.org/10.3390/app131910866 - 29 Sep 2023

Cited by 1 | Viewed by 814

Abstract

In this study, a shaking table test was conducted to investigate the presence of a liquefied soil layer at a subway station bottom plate. The seismic responses to soil and station structure were investigated by inputting seismic waves of different intensities. The following [...] Read more.

In this study, a shaking table test was conducted to investigate the presence of a liquefied soil layer at a subway station bottom plate. The seismic responses to soil and station structure were investigated by inputting seismic waves of different intensities. The following test results were obtained. As the intensity of the seismic response increases, liquefaction occurs in the soils located at the base of the station. The remainder of the soil liquefies to a lesser degree but still results in soil subsidence and damage to the soils on both sides of the station. In seismic loading conditions, the pore water pressure undergoes a process of “rapid growth and slow dissipation”. As the seismic intensity increases, the main frequency of the soil near the structure develops from a high to a low frequency, and the main frequency of the soil far away from the structure does not change significantly, indicating that the presence of the structure has a significant effect on the working conditions of the soil. The peak acceleration, as well as the peak maximum dynamic strain in the center column of the station, occurs at the bottom of the center column at the platform level, and the maximum dynamic strain in the slab occurs at the bottom slab at the concourse level. Full article

(This article belongs to the Special Issue Urban Underground Engineering: Excavation, Monitoring, and Control)

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14 pages, 5635 KiB

Open AccessArticle

Study on Ground Settlement Patterns and Prediction Methods in Super-Large-Diameter Shield Tunnels Constructed in Composite Strata

by Jinlan Li, Anyu Liu and Huang Xing

Appl. Sci. 2023, 13(19), 10820; https://doi.org/10.3390/app131910820 - 29 Sep 2023

Cited by 1 | Viewed by 842

Abstract

This study focuses on investigating the surface settlement characteristics induced by the construction of a super-large-diameter shield tunnel in composite strata. By utilizing a combination of field monitoring and numerical simulation analysis, the surface settlement patterns encountered during the construction process in horizontally [...] Read more.

This study focuses on investigating the surface settlement characteristics induced by the construction of a super-large-diameter shield tunnel in composite strata. By utilizing a combination of field monitoring and numerical simulation analysis, the surface settlement patterns encountered during the construction process in horizontally distributed typical soil–rock composite strata were summarized based on the 16.03 m super-large-diameter shield tunnel project in the southerly extension of He’ping Avenue in Wuhan. In addition, the collected data were used to enhance the Peck empirical formula. The results of the study show the following: (1) Significant non-uniform settlement occurs along the tunneling direction when the shield machine passes through soil–rock composite strata. The range of non-uniform settlement is approximately 3.1 times the tunnel diameter (D) in soil sections and 1.9 times the tunnel diameter (D) in rock sections. (2) The impact of composite strata on the maximum settlement is greater than its effect on the settlement trough width, with a larger impact within the soil sections compared to the rock sections. (3) The Peck correction formula, which takes into account the distance between the monitoring cross-section and the composite interface, provides more accurate predictions than the original Peck empirical formula. Full article

(This article belongs to the Special Issue Urban Underground Engineering: Excavation, Monitoring, and Control)

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14 pages, 2626 KiB

Open AccessArticle

Nitrogen Dioxide Gas Levels in TBM Tunnel Construction with Diesel Locomotives Based on Directive 2017/164/EU

by Hector Garcia-Gonzalez, Rafael Rodriguez and Marc Bascompta

Appl. Sci. 2023, 13(18), 10551; https://doi.org/10.3390/app131810551 - 21 Sep 2023

Cited by 1 | Viewed by 895

Abstract

Directive 2017/164/EU proposed a drastic reduction of nitrogen monoxide (NO) and nitrogen dioxide (NO₂) levels, thereby fortifying the health protection framework within the mining industry. Despite the commendable record of non-road emissions standards (Stage IV and V) in continuing to reduce [...] Read more.

Directive 2017/164/EU proposed a drastic reduction of nitrogen monoxide (NO) and nitrogen dioxide (NO₂) levels, thereby fortifying the health protection framework within the mining industry. Despite the commendable record of non-road emissions standards (Stage IV and V) in continuing to reduce NOx emissions, concerns remain about compliance with the directive’s strict limits, particularly in demanding tunnels and mining fields. To illustrate this problem, this study undertakes a comprehensive assessment of the practical feasibility surrounding the implementation of these proposed limits in a 6.2 internal diameter tunnel-boring machine (TBM) tunnel constructed with Stage III emission locomotives. The results cast light upon the formidable challenges entailed in achieving strict compliance with the envisioned limits, with a substantial number of measurements notably surpassing these thresholds, primarily concerning NO₂ emissions from Stage III engines. To address these challenges, this study highlights the key role of moving to Stage IV-V locomotives or introducing electric locomotives to effectively reduce NOx emissions, ensure compliance with the directive, and avoid delays in tunnel construction. Full article

(This article belongs to the Special Issue Urban Underground Engineering: Excavation, Monitoring, and Control)

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17 pages, 6951 KiB

Open AccessArticle

Full-Scale Model Test of Subway Contact Channel under Mechanical Construction

by Liping Fan, Xibo Sun, Xinfeng Ye, Shuai Niu, Zibo Dong, Yuebao Deng and Yaohong Zhu

Appl. Sci. 2023, 13(18), 10375; https://doi.org/10.3390/app131810375 - 16 Sep 2023

Cited by 1 | Viewed by 724

Abstract

The mechanical construction method for a subway contact channel has the advantages of a short construction period and high safety, and is more and more being applied in coastal soft-soil areas. In order to explore the suitability of this method in inland areas, [...] Read more.

The mechanical construction method for a subway contact channel has the advantages of a short construction period and high safety, and is more and more being applied in coastal soft-soil areas. In order to explore the suitability of this method in inland areas, a full-scale model test platform is used to simulate the shield-cutting construction process of the subway contact channel. The convergence deformation of the segments and the strain of the reinforcement and concrete are tested, so as to analyze the internal force and deformation law of the tunnel structure during cutting construction. The influence of the steel ring on the deformation of the subway contact channel is also studied. It is found that the segment convergence at the top is less than that at the waist position, and the convergence deformation of the waist is less than 30 mm; the internal force of the segment redistributes and the axial force mainly decreases during the cutting process; the stress state may change from compression to tension. The segment structure of the main tunnel, the supporting structure in the tunnel, and the stiffness of the steel-ring-lined composite pipe segment have little influence on the cutting force of the contact channel. The research results provide the corresponding technical indexes for the construction of a contact channel by the mechanical method, as well as a reference for the design and optimization of a steel-ring-lined composite pipe segment. Full article

(This article belongs to the Special Issue Urban Underground Engineering: Excavation, Monitoring, and Control)

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22 pages, 6926 KiB

Open AccessArticle

Vibration Characteristics Analysis of Immersed Tunnel Structures Based on a Viscoelastic Beam Model Embedded in a Fluid-Saturated Soil System Due to a Moving Load

by Hongyuan Huang, Yao Rong, Xiao Xiao and Bin Xu

Appl. Sci. 2023, 13(18), 10319; https://doi.org/10.3390/app131810319 - 14 Sep 2023

Viewed by 600

Abstract

This study aims to investigate the vibration responses on underwater immersed tunnels caused by moving loads, taking into account factors such as the viscoelastic characteristics of riverbed water, foundation soil, and the immersed tunnel itself. An ideal fluid medium is adopted to simulate [...] Read more.

This study aims to investigate the vibration responses on underwater immersed tunnels caused by moving loads, taking into account factors such as the viscoelastic characteristics of riverbed water, foundation soil, and the immersed tunnel itself. An ideal fluid medium is adopted to simulate the water, while a saturated porous medium is used to simulate the riverbed soil layer. The immersed tunnel structure is simplified as an infinitely long viscoelastic Euler beam, and the vibration effects are described by the theory of the standard linear solid model, taking into account structural damping. The coupled dynamic control equations were established by utilizing the displacement and stress conditions at the interface between the ideal fluid medium, the saturated porous medium, and the immersed tunnel structure. The equivalent stiffness of the riverbed water and site foundation was obtained. Furthermore, the numerical solutions of the tunnel displacement, internal forces, and pore pressure in the riverbed site were obtained in the time-space domain using the IFFT (Inverse Fast Fourier Transform) algorithm. The correctness of the model was validated by comparing the results with existing studies. The numerical results show that the riverbed water significantly reduces the Rayleigh wave velocity of the immersed tunnel structure in the riverbed-foundation system. Therefore, it is necessary to control the driving speed during high water levels. As the permeability of the saturated riverbed foundation increases, the vertical displacement, bending moment, and shear force of the beam in the immersed tunnel structure will increase. As the viscosity coefficient of the viscoelastic beam in the immersed tunnel structure increases, the vertical vibration amplitude of the beam will decrease, but further increasing the viscosity coefficient of the beam will have little effect on its vibration amplitude. Therefore, the standard solid model of the viscoelastic beam can effectively describe the creep and relaxation phenomena of materials and can objectively reflect the working conditions of the concrete structure of the immersed tunnel. Full article

(This article belongs to the Special Issue Urban Underground Engineering: Excavation, Monitoring, and Control)

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17 pages, 3604 KiB

Open AccessArticle

Ground Deformation Associated with Deep Excavations in Beijing, China

by Shu Li, Chenhe Ge, Pengfei Li and Meng Yang

Appl. Sci. 2023, 13(17), 9579; https://doi.org/10.3390/app13179579 - 24 Aug 2023

Cited by 1 | Viewed by 804

Abstract

A performance study is considered to be reliable method for comprehending deformations associated with deep excavation. To gain insight into the laws governing ground deformations that are associated with deep excavation, details of 88 cases were collected and analyzed in Beijing. The results [...] Read more.

A performance study is considered to be reliable method for comprehending deformations associated with deep excavation. To gain insight into the laws governing ground deformations that are associated with deep excavation, details of 88 cases were collected and analyzed in Beijing. The results were compared with worldwide case histories. Field data were selected to survey the ground behavior and to examine the correlation between deformation and excavation. The position and magnitude of the final ground deformation (δv), as well as the maximum deformation (δvm), the correlations between δvm and excavation depth (H), the length–width ratio, embedded depth ratio (EDR), and the stiffness of the support system, were assessed. The clear evolution process, influence zone, and final deformation pattern are illustrated. Our study revealed the following: (1) the groove pattern is detected in the final deformation of the ground surface, δvm occurred when positioned approximately 0.42H~0.62H off the wall, when the 1st~2nd supports on the bottom were removed; (2) δvm increases with an increase in H, and it ranges from 0.04% to 0.12% when H has an average value of approximately 0.089%; (3) EDR has an observable effect on reducing the δvm, as there a slight impact was observed until the ratios exceeded 0.4; (4) the deformation value of the 75% monitoring points ranged from −25 mm to 0 mm; (5) excavation could cause minor upheaval in some areas, but the upheaval reduces with increasing levels of excavation, so both deformation magnitude and the number of points are low; (6) deformation exhibits clear temporal–spatial characteristics, the settlement rate gradually increased over time, especially after drainage started or consolidation appeared, and when the internal structure is completed, δvm decreases with the rise in support system stiffness, ranging from 7000 to 11,000, and deformation becomes stable; and (7) transverse sections near the excavation center experienced larger deformations than others and the smallest deformations were near the corners, a significant increase occurs with the removal of the lowest 1–2 struts, particularly on the long side where ∆δv reaches 2.8 ± 0.75 mm, and the influence zones extend from approximately 2.5H to 3H beyond the excavated face. These findings have valuable implications for designing and constructing similar projects in Beijing and other regions, as they can help prevent accidents and minimize resource wastage. Full article

(This article belongs to the Special Issue Urban Underground Engineering: Excavation, Monitoring, and Control)

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15 pages, 5654 KiB

Open AccessArticle

Research on the Influence of Subway Tunnel Depth on Heat Storage Characteristics of the Surrounding Soil Mass

by Huaitao Song, Jingfen Li, Yueyang Yu and Qianlong Chen

Appl. Sci. 2023, 13(17), 9534; https://doi.org/10.3390/app13179534 - 23 Aug 2023

Viewed by 771

Abstract

With the long-term running of the subway, the soil layer around the tunnel takes on the thermal deposition effect, which can lead the air in the tunnel to heat up and pose a serious threat to the safety operation of trains. Through taking [...] Read more.

With the long-term running of the subway, the soil layer around the tunnel takes on the thermal deposition effect, which can lead the air in the tunnel to heat up and pose a serious threat to the safety operation of trains. Through taking some subway tunnels from typical zones as an example, the influence of tunnel depth on the heat storage characteristics of the surrounding soil mass was analyzed in the paper. The results indicate that the temperature field of the surrounding soil mass was thermally disturbed by both the ground air temperature and the tunnel air temperature, and there was a significant coupling point ‘O’ located at the center of the tunnel overburden. With the extension of the heat-exchange time, the shape of the cooling ring around the tunnel gradually changed from a circle to an oval. For the analysis of cases, from the space aspect, when the tunnel depth was less than 30 m, the wall temperature increased gradually with the increase of tunnel depth. From the time aspect, over time, the wall temperature gradually rose and finally reached a fixed value. From the region aspect, the heat absorption capacity of different areas decreased gradually with the increase of tunnel depth. When the depth exceeded 45 m, the heat absorption capacity of certain cities became negative. In addition, three typical boundaries were discussed, and the optimal method for evaluating the heat absorption capacity of the tunnel soil was ultimately determined. This study has important reference value for temperature control and positioning problems in the process of tunnel construction and operation. Full article

(This article belongs to the Special Issue Urban Underground Engineering: Excavation, Monitoring, and Control)

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21 pages, 12490 KiB

Open AccessArticle

Experimental Investigation on Deformation Characteristics of Strutted U-Shape Sheet Pile Flexible Retaining Structures in Excavations Using 3D Printing

by Jie Huang, Zeping Yang and Qinyue Lin

Appl. Sci. 2023, 13(14), 8163; https://doi.org/10.3390/app13148163 - 13 Jul 2023

Viewed by 905

Abstract

U-shape steel sheet piles are widely used in deep and large excavation engineering due to their excellent soil-retaining and water-stopping performances. To achieve deformation control in excavations, an experimental investigation on the deformation characteristics of a strutted U-shape sheet pile flexible retaining structure [...] Read more.

U-shape steel sheet piles are widely used in deep and large excavation engineering due to their excellent soil-retaining and water-stopping performances. To achieve deformation control in excavations, an experimental investigation on the deformation characteristics of a strutted U-shape sheet pile flexible retaining structure was conducted. Single-layer and double-layer strutted retaining structure excavation indoor model tests in sand, where U-shape sheet piles were formed by 3D printing, were successfully accomplished. Deformation was monitored in real time during the test. The results show that the lateral displacement mode of the retaining structure transformed with the change in excavation from the “cantilever” to the “bulge” and finally developed into an intricate “recurve bow”. The average maximum lateral displacement was 0.756% of the excavation depth. With a maximum settlement of 0.375% of the excavation depth on average, the distribution of ground settlement behind walls changed from “exponential” to “triangular” before ultimately transforming into “trough” or “trapezoid” mode. The maximum settlement to maximum lateral displacement ratio (s_max/δ_max) on average was 0.54; the maximum settlement deformation rate was always less than the maximum lateral displacement deformation rate. Full article

(This article belongs to the Special Issue Urban Underground Engineering: Excavation, Monitoring, and Control)

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19 pages, 4440 KiB

Open AccessArticle

Bearing Capacity of Karst Cave Roof under Pile Foundation Load Using Limit Analysis

by Ze Li, Kaiyu Lu, Wenlian Liu, Hebo Wang, Pu Peng and Hanhua Xu

Appl. Sci. 2023, 13(12), 7053; https://doi.org/10.3390/app13127053 - 12 Jun 2023

Viewed by 916

Abstract

Reducing the computational workload by simplifying the analysis of karst foundations into a plane strain problem can yield significant advantages. Yet, such an approach fails in reproducing the engineering situation in a rigorous manner. In this regard, this paper proposes an upper-bound method [...] Read more.

Reducing the computational workload by simplifying the analysis of karst foundations into a plane strain problem can yield significant advantages. Yet, such an approach fails in reproducing the engineering situation in a rigorous manner. In this regard, this paper proposes an upper-bound method that can effectively analyze the bearing capacity of three-dimensional karst foundations. This method is utilized to investigate the impact of various pile diameters, the ratio of roof thickness to pile diameter, and the ratio of cave width to pile diameter on the stability of karst foundations. The validity of this method is established through an illustrative example. The outcomes illustrate that when subjected to both tensile and compressive horizontal stresses if the maximum horizontal stress surpasses the tensile strength of the rock mass, the roof rock mass may suffer damage. Increasing the ratio of roof thickness to pile diameter can bring down the horizontal stress value. The stability factor is largely influenced by the ratio of roof thickness to pile diameter. The most prominent growth trend of the stability factor is observed when the ratio is less than 3. If the ratio of the roof thickness to pile diameter exceeds 3, the prediction of the bearing capacity estimation for the karst foundation in three-dimensional circumstances is more conservative than that in two-dimensional circumstances. Full article

(This article belongs to the Special Issue Urban Underground Engineering: Excavation, Monitoring, and Control)

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22 pages, 13437 KiB

Open AccessArticle

Study on Seismic Reduction Measures of a Diaphragm Wall—Underground Structure System

by Qi Zhang, Mi Zhao, Jingqi Huang and Zhidong Gao

Appl. Sci. 2023, 13(12), 6910; https://doi.org/10.3390/app13126910 - 7 Jun 2023

Cited by 1 | Viewed by 1032

Abstract

In this paper, the seismic reduction and isolation measures are first proposed by setting a segmented isolation layer between the diaphragm wall and the side wall of the station structure. Although the segmented isolation layer can effectively improve the stress state of the [...] Read more.

In this paper, the seismic reduction and isolation measures are first proposed by setting a segmented isolation layer between the diaphragm wall and the side wall of the station structure. Although the segmented isolation layer can effectively improve the stress state of the side wall and slabs, the seismic reduction effect of the middle column is not obvious. In order to improve the overall seismic performance of the station structure, the reduction measures by combining the segmented isolation layer and new type bearing of the middle column are then proposed. At the same time of inserting the isolation layer between the diaphragm wall and the structure, the sliding bearing at the top of the column is set up to reduce the vibration. The results show that the segmented isolation layer can significantly reduce the internal force and damage at the top, bottom and side wall joints. In addition, the combined measures of segmented isolation layer and sliding bearing at the top of the column can effectively reduce the seismic damage of the middle column. The damage of the connection between the top plate, the middle plate and the middle column can be significantly decreased. Full article

(This article belongs to the Special Issue Urban Underground Engineering: Excavation, Monitoring, and Control)

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17 pages, 7337 KiB

Open AccessArticle

Deformation Control of the Existing Medium-Low-Speed Maglev Metro Viaduct over a Double-Line Bored Tunnel

by Hua Peng, Zikai Wu, Xv Peng, Xiaoqi Xiao and Zichen Li

Appl. Sci. 2023, 13(11), 6659; https://doi.org/10.3390/app13116659 - 30 May 2023

Viewed by 824

Abstract

Taking a double-line underground excavation subway tunnel underneath the medium-low-speed Maglev bridge section of the Beijing S1 Metro line as a project reference, the deformation control index of the Maglev metro bridge and track panel was studied using numerical simulation and data monitoring, [...] Read more.

Taking a double-line underground excavation subway tunnel underneath the medium-low-speed Maglev bridge section of the Beijing S1 Metro line as a project reference, the deformation control index of the Maglev metro bridge and track panel was studied using numerical simulation and data monitoring, under the conditions of deep-hole grouting measures for the soil layer around the excavation tunnel and active lifting for the superstructure of the viaduct. The results of the numerical simulation show that the maximum deformation value of the pier is −1.73 mm and the maximum vertical deformation value of the Maglev rail track is −1.56 mm. Monitoring shows that the maximum vertical deformation value of the magnetic levitation rail is −1.25 mm and the deformation is within the allowable range. Both numerical simulation and field monitoring results reflect the deformation trend of existing structures; the deep-hole grouting measures taken to strengthen the soil layer around the tunnel and the upper structure of the active roof elevation frame can effectively control the deformation of the existing structure. The study can provide guidance and reference for similar projects. Full article

(This article belongs to the Special Issue Urban Underground Engineering: Excavation, Monitoring, and Control)

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17 pages, 6746 KiB

Open AccessArticle

Mechanical Properties of the Shield Tail Brush and Its Pressure Distribution Acting upon the Segment

by Wenqi Ding, Yanling Qiu, Yafei Qiao and Xiaoqing Chen

Appl. Sci. 2023, 13(11), 6451; https://doi.org/10.3390/app13116451 - 25 May 2023

Cited by 1 | Viewed by 861

Abstract

Shield tunnels are widely used in underground transportation. The shield tail brush is an important component of the shield machine, but also can exert an adverse influence on the segment as it can induce considerable and uneven pressure thereon. Therefore, it is necessary [...] Read more.

Shield tunnels are widely used in underground transportation. The shield tail brush is an important component of the shield machine, but also can exert an adverse influence on the segment as it can induce considerable and uneven pressure thereon. Therefore, it is necessary to consider the tail brush pressure in calculations on the segment. However, there are few studies on the calculation method of this pressure. As a consequence, this study carried out laboratory tests on the tail brush, and revealed the two-stage nature of its pressure-compression curve, which can be fitted well by a line together with a polynomial function. In addition, formulas describing the tail brush pressure distribution along the circumference were derived by theoretical analysis. Furthermore, by summarizing the distribution law, simplified formulas for the tail brush pressure acting upon the segment along the circumference and lengthwise due to vertical shield posture adjustment were established. The results can be used in calculations on the segment to improve the segment design and provide guidance for shield tunnel construction. Full article

(This article belongs to the Special Issue Urban Underground Engineering: Excavation, Monitoring, and Control)

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15 pages, 5288 KiB

Open AccessArticle

Stability Analysis of Box Tunnel Working Face under Non-Uniform Support Pressure

by Xuanyang Zhang, Miao Yu, Jiaxin Liang, Chao Yang and Wei Liu

Appl. Sci. 2023, 13(9), 5776; https://doi.org/10.3390/app13095776 - 8 May 2023

Cited by 1 | Viewed by 1304

Abstract

For rectangular section tunnel construction, soil bin pressure fluctuates under biaxial emergence conditions. Support pressure is difficult to uniformly distribute, and it can easily cause instability of the tunneling face. The Silo-wedge model is used to perform horizontal strip splitting of parts of [...] Read more.

For rectangular section tunnel construction, soil bin pressure fluctuates under biaxial emergence conditions. Support pressure is difficult to uniformly distribute, and it can easily cause instability of the tunneling face. The Silo-wedge model is used to perform horizontal strip splitting of parts of the soil at risk for instability under unsupported conditions. In the ultimate equilibrium analysis, the strength discounting method is introduced, a new expression for the safety factor is derived by combining the horizontal strip splitting equilibrium equations, and the safety factor is solved numerically. When the opening range is greater than 0.75 and the effective internal friction angle of the soil is less than 25°, the safety coefficient is less than 1, and destabilization damage is likely to occur. The field application of a box tunnel project in Suzhou demonstrates that the research results have good engineering applicability to the issue. Full article

(This article belongs to the Special Issue Urban Underground Engineering: Excavation, Monitoring, and Control)

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27 pages, 12073 KiB

Open AccessArticle

Mechanical Properties of Disconnectable Coupling Joints for Steel Bracing under Eccentric Load

by Zhitian Xie, Xiaokai Niu, Pengfei Li, Mingju Zhang and Xiao Liu

Appl. Sci. 2023, 13(9), 5596; https://doi.org/10.3390/app13095596 - 30 Apr 2023

Cited by 2 | Viewed by 1252

Abstract

Disconnectable coupling (DC) joints of steel bracing in foundation pit engineering are inevitably subjected to eccentric load, but their mechanical properties under eccentric load have not been thoroughly investigated. Based on full-scale test results of DC joints under axial compression, a validated finite [...] Read more.

Disconnectable coupling (DC) joints of steel bracing in foundation pit engineering are inevitably subjected to eccentric load, but their mechanical properties under eccentric load have not been thoroughly investigated. Based on full-scale test results of DC joints under axial compression, a validated finite element model was established. The bearing capacity and flexural performance of DC joints under eccentric load were studied systematically through a series of numerical simulations. These parameters included the length, width and height of the steel wedge; eccentricity; steel tube wall thickness; channel steel thickness and middle-rib plate height. Based on the numerical results, a modified moment–rotation model was established. The results obtained show that the numerical models accurately reflect the failure mode and the load-displacement curves revealed by the full-scale test. The bearing capacity and flexural performance of DC joints decreases with eccentricity, middle-rib plate height, and steel wedge height. The effect of eccentricity is the most significant. By contrast, the bearing capacity and flexural performance of DC joints increases with steel wedge length, steel wedge width, channel steel thickness and steel tube wall thickness. The modified moment–rotation model can describe the flexural performance of DC joints accurately under eccentric load. Full article

(This article belongs to the Special Issue Urban Underground Engineering: Excavation, Monitoring, and Control)

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16 pages, 7667 KiB

Open AccessArticle

Bearing Capacities and Failure Behaviors of F-Type Socket Joint in Rectangular Pipe Jacking Tunnel

by Youjun Xu, Zhengdong Huang, Chao Zhang, Yuekui Pang and Tianyu Liu

Appl. Sci. 2023, 13(9), 5442; https://doi.org/10.3390/app13095442 - 27 Apr 2023

Cited by 1 | Viewed by 1167

Abstract

The joint bending test was carried out to study the bending mechanical property and deformation characteristics of the F-type socket joint in rectangular pipe jacking tunnels under the conditions of foundation settlement, construction disturbance and different upper loads. The supporting function of soils [...] Read more.

The joint bending test was carried out to study the bending mechanical property and deformation characteristics of the F-type socket joint in rectangular pipe jacking tunnels under the conditions of foundation settlement, construction disturbance and different upper loads. The supporting function of soils under different geological conditions on the rectangular pipe jacking was simulated by arranging different numbers of equivalent foundation springs at the bottom of the pipe. The test results show that the greater the foundation stiffness is, the greater the joint bending moment will be at the same loading displacement, which leads to greater joint opening deformation. When the pipe joint itself produces large deformation, the change rate of joint opening slows down, and the slope of the bending stiffness curve of the joint increases. The bending bearing capacity of the joint is closely related to the foundation stiffness. The greater the foundation stiffness is, the higher the bending bearing capacity. Full article

(This article belongs to the Special Issue Urban Underground Engineering: Excavation, Monitoring, and Control)

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19 pages, 8416 KiB

Open AccessArticle

The Generalized Mohr-Coulomb Failure Criterion

by Dongshuai Tian and Hong Zheng

Appl. Sci. 2023, 13(9), 5405; https://doi.org/10.3390/app13095405 - 26 Apr 2023

Cited by 5 | Viewed by 5067

Abstract

With the construction of supertall buildings such as high earth dams, the linear envelope of the Mohr-Coulomb (M-C) failure criterion fitted to lower confined pressure would significantly underestimate the loading capacity of foundations, causing a huge increase in the amount of earthwork. Given [...] Read more.

With the construction of supertall buildings such as high earth dams, the linear envelope of the Mohr-Coulomb (M-C) failure criterion fitted to lower confined pressure would significantly underestimate the loading capacity of foundations, causing a huge increase in the amount of earthwork. Given that the M-C criterion has dominated in the stability analysis of geotechnical structures, it is proposed in this study that the M-C criterion remain invariant in form but the cohesion c and the frictional factor f be related to the coefficient of intermediate principal stress b, called the Generalized Mohr-Coulomb (GMC) criterion. In other words, c and f are both functions of b, written as c(b) and f(b). In the simplest way, the GMC criterion for soils, a true three-dimensional failure criterion, can be established by using a piece of conventional triaxial apparatus. The GMC has a non-smooth strength surface like its conventional version. However, we prove from true triaxial tests and the characteristic theory of stress tensors that the failure surfaces in the stress space should be non-smooth per se for b = 0 or 1. Comparisons with other prominent failure criteria indicate that the GMC fits the test data best. Full article

(This article belongs to the Special Issue Urban Underground Engineering: Excavation, Monitoring, and Control)

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20 pages, 6016 KiB

Open AccessArticle

Efficient Method for Calculating Slope Failure Risk Based on Element Failure Probability

by Pu Peng, Ze Li, Xiaoyan Zhang, Wei Zhang and Wushu Dong

Appl. Sci. 2023, 13(8), 4806; https://doi.org/10.3390/app13084806 - 11 Apr 2023

Cited by 4 | Viewed by 1443

Abstract

The finite element method (FEM) and the limit equilibrium method (LEM) are commonly used for calculating slope failure risk. However, the FEM needs to carry out post-processing to estimate slope sliding surface, while the LEM requires assumption of the shape and location of [...] Read more.

The finite element method (FEM) and the limit equilibrium method (LEM) are commonly used for calculating slope failure risk. However, the FEM needs to carry out post-processing to estimate slope sliding surface, while the LEM requires assumption of the shape and location of the sliding surface in advance. In this paper, an element failure risk method (EFR) for calculating soil slope failure risk is proposed based on element failure probability (EFP) acquired by plastic limit analysis. The proposed method does not require any assumptions about failure modes. Firstly, the non-common-node triangle element is used to discrete the slope then the random field is generated based on the Cholesky decomposition midpoint method. According to the reliability stochastic programming model and solution strategy, the external overload coefficient, bulk overload coefficient, slope stability coefficient and velocity field of the slope under each random field are obtained, according to which the failure of the element is judged and the failure risk of the slope is calculated. In order to verify the correctness of the proposed method, two classical slopes are systematically analyzed. The research shows that compared with the traditional slope failure risk analysis method, the greatest advantage of the proposed method is that it can capture all failure modes of the slope and greatly simplify the calculation of the slope failure consequences of each failure mode. An efficient upper bound method (UBM) parallel program is prepared, which greatly improves the calculation efficiency. Full article

(This article belongs to the Special Issue Urban Underground Engineering: Excavation, Monitoring, and Control)

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17 pages, 7281 KiB

Open AccessArticle

Parameter Analysis on Seismic Response of Long Lined Tunnel by 2.5D Substructure Method

by Qi Zhang, Mi Zhao, Jingqi Huang and Xiuli Du

Appl. Sci. 2023, 13(7), 4593; https://doi.org/10.3390/app13074593 - 5 Apr 2023

Viewed by 1329

Abstract

When the numerical analysis of a long lined tunnel is carried out, the calculation amount of the finite element model becomes restricted large-scale parameter analysis. In this paper, an efficient and high-precision 2.5-dimensional (2.5D) frequency-domain finite element method is used to simulate the [...] Read more.

When the numerical analysis of a long lined tunnel is carried out, the calculation amount of the finite element model becomes restricted large-scale parameter analysis. In this paper, an efficient and high-precision 2.5-dimensional (2.5D) frequency-domain finite element method is used to simulate the three-dimensional response of tunnels under the action of oblique incident plane seismic waves. This method can save calculations and avoid the boundary effect caused by the longitudinal truncation of the tunnel. The 2.5D zigzag-paraxial boundary is developed. The artificial boundary is attached to the structure’s surface. The substructure method for oblique plane seismic waves is established. Comparing the substructure method with the analytical solution, the correctness of the site response is verified first. The accuracy of the 2.5D finite element substructure method is further verified. The parameter analysis of different incident angles and conversion angles shows that the underground tunnel does not reach the maximum of structural seismic response when the seismic wave is vertically incident. The location of the soil–rock interface on the tunnel is further discussed. The results show that when the underground tunnel crosses the location of the soil–rock interface, the seismic response of the tunnel will be amplified. Full article

(This article belongs to the Special Issue Urban Underground Engineering: Excavation, Monitoring, and Control)

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19 pages, 4447 KiB

Open AccessArticle

Study of the Effect of Gas Baffles on the Prevention and Control of Gas Leakage and Explosion Hazards in aUtility Tunnel

by Baobin Gao, Wenjie Zhu, Chuangnan Ren, Shaopeng Song and Chenhui Geng

Appl. Sci. 2023, 13(7), 4264; https://doi.org/10.3390/app13074264 - 28 Mar 2023

Viewed by 1138

Abstract

This paper takes the gas cabin in the utility tunnel in the Xuwei District of Lianyungang as the study object. Based on the computational fluid dynamics (CFD) theory, a simulation model of the gas cabin in the utility tunnel is established. The propagation [...] Read more.

This paper takes the gas cabin in the utility tunnel in the Xuwei District of Lianyungang as the study object. Based on the computational fluid dynamics (CFD) theory, a simulation model of the gas cabin in the utility tunnel is established. The propagation law of methane leakage and diffusion and the characteristics of methane explosion shock wave propagation were simulated under different conditions of the gas cabin. These conditions are the presence or absence, spacing and height of the air baffle. The results show that: (1) the gas baffle can limit the propagation of methane at the top of the gas cabin and slow down the velocity of diffusion so as to increase the concentration of methane near the baffle and speed up the time for the monitor to reach the alarm concentration; (2) the first peak pressure and the second peak pressure generated in the middle of the gas cabin are smaller than that when the gas baffle is installed. The gas baffle has the function of blocking the propagation of shock waves. However, due to the installation of the gas baffle, the superposition of the shock wave will make the pressure surge at the gas baffle; and (3) combined with the simulation results, it is recommended that the gas baffle spacing is not less than 50 m and the height setting is not greater than 0.5 m. Full article

(This article belongs to the Special Issue Urban Underground Engineering: Excavation, Monitoring, and Control)

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17 pages, 3523 KiB

Open AccessArticle

Analysis on Bearing Behavior of Single Pile under Combined Action of Vertical Load and Torque in Expansive Soil

by Zhi Wang, Jie Jiang, Shunwei Wang, Chenzhi Fu and Di Yang

Appl. Sci. 2023, 13(7), 4133; https://doi.org/10.3390/app13074133 - 24 Mar 2023

Viewed by 1097

Abstract

To reasonably analyze the bearing characteristics of curved beam bridge pile foundation under the combined action of vertical force (V) and torque (T) in expansive soil, a method of determining T_u (limit torque) under the action of V [...] Read more.

To reasonably analyze the bearing characteristics of curved beam bridge pile foundation under the combined action of vertical force (V) and torque (T) in expansive soil, a method of determining T_u (limit torque) under the action of V is proposed. Considering the effects of expansive force and ground heave after immersion, the load transfer function at the pile–soil interface with positive and negative friction resistance is established. The nonlinear solution of a single pile under vertical load is achieved by the finite difference method. Subsequently, the circumferential limit friction resistance is modified, and a loop iteration program is compiled through MATLAB. Thus, the bearing capacity of single pile under the loading path of V→T is obtained. The corresponding failure envelope curve is drawn and verified by laboratory model tests. Based on the verified solution, the bearing capacity envelope curve and deformation characteristics of single pile are analyzed. The influence of the expansion rate on the bearing capacity envelope curve is discussed, and reasonable engineering suggestions are put forward. Full article

(This article belongs to the Special Issue Urban Underground Engineering: Excavation, Monitoring, and Control)

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17 pages, 3504 KiB

Open AccessArticle

A Data-Driven Indirect Approach for Predicting the Response of Existing Structures Induced by Adjacent Excavation

by Liyun Li, Qingxi Sun, Yichen Wang and Yunhao Gao

Appl. Sci. 2023, 13(6), 3826; https://doi.org/10.3390/app13063826 - 16 Mar 2023

Cited by 1 | Viewed by 1106

Abstract

A data-driven indirect approach for predicting the response of existing structures induced by excavation is hereby proposed based on making full use of monitoring data during excavation, which can predict the deformation history of the research object during excavation. In this article, a [...] Read more.

A data-driven indirect approach for predicting the response of existing structures induced by excavation is hereby proposed based on making full use of monitoring data during excavation, which can predict the deformation history of the research object during excavation. In this article, a machine-learning-based model framework for implementing the proposed approach is constructed and the treatment of key issues in the design and implementation of the proposed method is described in detail including the theoretical framework, the implementation mode of the method, the dimensionality reduction of the model parameters, and the normalization of data for model. On this basis, three models are provided to predict the settlement of buildings induced by adjacent excavation, namely the SVM model, BP model, and BP–SVM model. Relying on an excavation project for a subway in Xuzhou, Jiangsu Province, China, the proposed method is verified, and some conclusions are obtained. Full article

(This article belongs to the Special Issue Urban Underground Engineering: Excavation, Monitoring, and Control)

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20 pages, 6914 KiB

Open AccessArticle

Displacement Analyses of Main Structure of Parallel Pit Excavation and Analysis of Countermeasures

by Xiangyang Cui, Zhaoping Li, Fei Guo, Xuegang Han and Jianping Song

Appl. Sci. 2023, 13(6), 3706; https://doi.org/10.3390/app13063706 - 14 Mar 2023

Cited by 1 | Viewed by 1183

Abstract

To solve the impact on the pre-existing main structure due to the need for early traffic restoration of urban roads within the cross-hub and the difficulty of co-ordinating a construction plan among groups of pits, a construction method combining TD and BU was [...] Read more.

To solve the impact on the pre-existing main structure due to the need for early traffic restoration of urban roads within the cross-hub and the difficulty of co-ordinating a construction plan among groups of pits, a construction method combining TD and BU was proposed. By establishing a three-dimensional finite difference method (FDM) of parallel pit excavation considering the small strain constitutive model of the strata, the influence of four different excavation schemes on the pre-existing main structs is studied. The results of the study show that: (1) the asynchronous excavation of the pit on both sides of the cover excavation area causes additional deformation of the steel pipe structs; sequential excavation produces the greatest additional deformation of the steel tube columns, followed by staggered excavation and the least simultaneous excavation; (2) the middle 1 slab enhances the overall stiffness of the main structure in the cover excavation area, reducing the additional deformation caused by the unsynchronized excavation of the pit, with the maximum horizontal deformation of 5.8 mm, a reduction of 61%; (3) the greater the depth of excavation and the closer the distance from the pit, the more obvious the deformation of the steel pipe column; and (4) the function relationship between δ_hm/H and the relative stiffness coefficient R_d was obtained by fitting, and the maximum controlled mis-step spacing of the foundation excavation on both sides was 4.3 m when the middle 1 floor slab was cast. Full article

(This article belongs to the Special Issue Urban Underground Engineering: Excavation, Monitoring, and Control)

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19 pages, 14239 KiB

Open AccessArticle

Calculation Method of the Finite Soil Pressure for a New Foundation Pit Adjacent to an Existing Subway Station

by Zhenbo Zhang, Jiadi Zhou, Fei Xu, Zhichun Liu and Minglei Sun

Appl. Sci. 2023, 13(3), 1994; https://doi.org/10.3390/app13031994 - 3 Feb 2023

Cited by 1 | Viewed by 1859

Abstract

The study aimed at the simple prediction problem of finite soil pressure for a new foundation pit adjacent to an existing subway station. Failure modes of the finite soil were proposed. Considering the friction between the soil and the structural interface, the formulas [...] Read more.

The study aimed at the simple prediction problem of finite soil pressure for a new foundation pit adjacent to an existing subway station. Failure modes of the finite soil were proposed. Considering the friction between the soil and the structural interface, the formulas for calculating the finite soil pressure were derived with the horizontal differential element method, and the distribution was discussed. Furthermore, a simple calculation method for the resultant force of the finite soil pressure and the height of the action point was proposed with the principle of area equivalence. With the example and model tests, the rationality of the above method was verified. The influences of parameters on the resultant force of the soil pressure and the relative height of the resultant force were analyzed. The main conclusions are as follows: (1) The finite soil pressure has a nonlinear distribution and is lower than the conventional soil pressure. (2) Compared with other existing methods and model test results, the proposed finite soil pressure calculation method and simplified method are rational. (3) The finite soil pressure increases with the ground overload and soil weight and decreases with the internal friction angle and the structure-soil friction angle. (4) The relative height of the resultant force of the finite soil pressure increases with the structure-soil friction angle and decreases with the internal friction angle. (5) The proximity and covering soil thickness of the existing subway station have a lesser influence on the finite soil pressure, whereas the internal friction angle, weight, structure-soil friction angle and ground overload have a greater influence on the finite soil pressure. (6) The structure-soil friction angle has a greater influence on the height of the action point. The height of the resultant force is one-third of the enclosure structure depth if the structure-soil friction angle is 0. Full article

(This article belongs to the Special Issue Urban Underground Engineering: Excavation, Monitoring, and Control)

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21 pages, 9059 KiB

Open AccessArticle

Experimental Study on the Effect of Single Structural Plane on the Stability of Shallow Tunnel Surrounding Rock

by Zhijie Sun, Pengfei Li, Xiuli Du and Xuanyu Yang

Appl. Sci. 2023, 13(3), 1946; https://doi.org/10.3390/app13031946 - 2 Feb 2023

Cited by 1 | Viewed by 1481

Abstract

There are a large number of structural planes distributed in the surrounding rock of a tunnel, and this is one of the key factors causing a tunnel’s instability. Due to different geological and historical conditions, the distribution characteristics and the occurrence of structural [...] Read more.

There are a large number of structural planes distributed in the surrounding rock of a tunnel, and this is one of the key factors causing a tunnel’s instability. Due to different geological and historical conditions, the distribution characteristics and the occurrence of structural planes in the rock mass also have significant differences. In engineering, it is common to encounter structural planes that cut across the tunnel section and have a significant impact on the stability. The occurrence of structural planes is a key factor controlling the mechanical behavior of the surrounding rock. Based on this, laboratory uniaxial compression tests were carried out by constructing a small tunnel physical model with single structural planes of different inclination angles. A related numerical simulation analysis was also carried out. This research indicates that: (1) Under the influence of a single structural plane, the dip direction with 30°–60° is the most dangerous situation, and when the dip angle of the structural plane is between 38 and 88°, it will slip along the structural plane. (2) According to the mechanical mechanism, there are three types of cracks: tensile cracks, shear cracks, and tensile shear cracks. According to the deformation characteristics, there are four types: tension, friction, bending, and shear. (3) There is a certain correlation between the strength of a single discontinuity rock mass and that of a multi-jointed rock mass. When the dip angle of the joints’ combination is 45°+60°, the rock mass is in its weakest state. Full article

(This article belongs to the Special Issue Urban Underground Engineering: Excavation, Monitoring, and Control)

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21 pages, 19269 KiB

Open AccessArticle

Three-Dimensional Geological Modeling of the Shallow Subsurface and Its Application: A Case Study in Tongzhou District, Beijing, China

by Hanhan He, Jingze Xiao, Jing He, Bo Wei, Xiaogang Ma, Fan Huang, Xiangmin Cai, Yuanxin Zhou, Jingyi Bi, Yiting Zhao, Chunjun Wang and Jingran Wei

Appl. Sci. 2023, 13(3), 1932; https://doi.org/10.3390/app13031932 - 2 Feb 2023

Cited by 1 | Viewed by 1632

Abstract

Three-dimensional (3D) geological models are currently needed and used independently for urban development. The main difficulty in constructing a 3D geological model of a shallow subsurface is to determine the stratigraphic distribution. Highly variable properties and geometries of geological units beneath lead to [...] Read more.

Three-dimensional (3D) geological models are currently needed and used independently for urban development. The main difficulty in constructing a 3D geological model of a shallow subsurface is to determine the stratigraphic distribution. Highly variable properties and geometries of geological units beneath lead to difficulty. It is key to find a practicable and efficient way to construct a model in practical work. This study takes Tongzhou District (Beijing) as a case; 476 boreholes (40 newly drilled and 436 existing engineering boreholes) were utilized combined with the cross-section method to construct an integrated 3D geological model. The framework and analyses contributed to the following applications: (1) High-quality information from new boreholes and existing engineering boreholes were used to define stratigraphy and build cross-sections. (2) The resulting geological model (up to 50 m beneath Tongzhou area) shows many details of the shallow subsurface. This includes 10 major layers which were grouped into three cyclothems representing cyclic sequences of clay, interbedded silt, sand, and gravel with variable quantities of lenses. (3) The new model was used as a tool to visualize the depth and geometry variations below ground and to characterize a large variety of properties (for example, the compression modulus analyzed in this paper) that each unit contains, and then to evaluate the underground geological conditions. (4) An analysis of a dynamic monitoring model based on the resulting 3D model indicated that the geological units (sand and silty clay) at depths between 30 m and 40 m, with an average vertical deformation of 0.97 mm, from July 2019 to September 2020, are suitable for underground construction, from the perspective of vertical stability in the study area. Monitoring models that take time into consideration based on a 3D framework will be further explored. Full article

(This article belongs to the Special Issue Urban Underground Engineering: Excavation, Monitoring, and Control)

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16 pages, 7556 KiB

Open AccessArticle

Model Experiment Study on Vertical Bearing Characteristics of Large-Diameter Ring Piles

by Yingtao Sun, Aijun Yao, Lei Dong, Yanlin Li and Yifei Gong

Appl. Sci. 2022, 12(24), 13011; https://doi.org/10.3390/app122413011 - 18 Dec 2022

Viewed by 1268

Abstract

The hollow structure of large-diameter ring piles (LDRPs) reduces the amount of concrete used, is economically efficient, and reduces the weight of the pile. However, its bearing characteristics and safety performance are still not fully known. In this study, to determine the properties [...] Read more.

The hollow structure of large-diameter ring piles (LDRPs) reduces the amount of concrete used, is economically efficient, and reduces the weight of the pile. However, its bearing characteristics and safety performance are still not fully known. In this study, to determine the properties of the LDRP structure, a combination of the indoor scale model test and numerical simulations was used, and a new parameter, K, which is the thickness-to-diameter ratio, was introduced. A comparative study of LDRPs with different hollow ranges was conducted. The results show that for a value of K in the range of 0.2–1, the ultimate bearing capacity of LDRPs is not significantly different from that of large-diameter solid piles (LDSPs), and they can ensure sufficient safety reserves. Under ultimate bearing capacity, the strain on an LDRP is large, but it does not exceed its own material strength, and the strain variation law is similar to that of a solid pile. LDRPs show the characteristics of end-bearing piles, and concrete savings can reach up to 50% for K in the range of 0.2–1. Full article

(This article belongs to the Special Issue Urban Underground Engineering: Excavation, Monitoring, and Control)

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20 pages, 5795 KiB

Open AccessArticle

Lower Bound Limit Analysis of Non-Persistent Jointed Rock Masses Using Mixed Numerical Discretization

by Wenlian Liu, Hanhua Xu, Sugang Sui, Ze Li, Xiaoyan Zhang and Pu Peng

Appl. Sci. 2022, 12(24), 12945; https://doi.org/10.3390/app122412945 - 16 Dec 2022

Cited by 1 | Viewed by 1096

Abstract

The bearing capacity of a non-persistent jointed rock mass containing a rock bridge is investigated by combining the lower bound limit analysis theory, a mixed numerical discrete method, and linear mathematical programming. A mixed numerical discrete method is proposed to divide non-persistent jointed [...] Read more.

The bearing capacity of a non-persistent jointed rock mass containing a rock bridge is investigated by combining the lower bound limit analysis theory, a mixed numerical discrete method, and linear mathematical programming. A mixed numerical discrete method is proposed to divide non-persistent jointed rock masses in which rigid block elements are used to simulate the rock blocks, whereas the finite element method is used to simulate the intact rock bridges. A linear mathematical programming model for the ultimate bearing capacity is constructed and solved using the interior point algorithm. The proposed formulation is validated by application to three rock slopes. Full article

(This article belongs to the Special Issue Urban Underground Engineering: Excavation, Monitoring, and Control)

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19 pages, 15618 KiB

Open AccessArticle

Grouting Additives and Information-Based Construction of Jet Grouting in the Water-Rich Sand Stratum

by Xiaqing Qian, Peng Zhang, Shengnian Wang, Shuangfeng Guo and Xinyu Hou

Appl. Sci. 2022, 12(24), 12586; https://doi.org/10.3390/app122412586 - 8 Dec 2022

Cited by 3 | Viewed by 1827

Abstract

The dynamic action of groundwater in the water-rich sand stratum carries away injected cement slurry before it becomes solidified, which seriously affects the determination of the diameter and strength of the column. Grouting additives and information-based construction are two main actions to control [...] Read more.

The dynamic action of groundwater in the water-rich sand stratum carries away injected cement slurry before it becomes solidified, which seriously affects the determination of the diameter and strength of the column. Grouting additives and information-based construction are two main actions to control the quality of jet grouting construction. This study introduced a solution of grouting additives and information-based construction of jet grouting in the water-rich sand stratum. First, high-polymer cement grout (HPCG), red mud and phosphogypsum cement grout (RPCG) and metakaolin cement grout (MKCG) additives were screened with a series of laboratory tests on solidification time and permeability; moreover, the mix proportion of grouting fluids was developed in order to adapt for water-rich sand strata. Secondly, information-based construction of jet grouting was conducted to control grouting quantity with real-time monitoring of drill rotational velocity, drill lifting speed and injection pressure equipped with the monitoring system on the double fluid jet grouting systems. Lastly, the validity of grouting additives and information-based construction in the water-rich sand stratum was verified via a test pile in situ, and a series of material tests on drilling core samples on permeability with SEM observation. The results indicate that the high polymer is the preferred additive of grouting fluids because the solidification time can be controlled in the range of 10 min to 20 min; the permeability of drilling core samples can reach the order of 10⁻⁷, with the mix proportion being A:B = 2:1, high-polymer additive:water > 1:3, with a water-cement ratio of 0.8. The specifications of information-based construction are a drill rotational velocity of 10 r/min, a drill lifting speed of 0.2 m/min, an injection pressure of 20 MPa and a grouting quantity of 40 L/min. Full article

(This article belongs to the Special Issue Urban Underground Engineering: Excavation, Monitoring, and Control)

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17 pages, 30553 KiB

Open AccessArticle

Numerical Simulation Study on Ventilation Optimization Design of Extra-Long Double-Line Mountain Tunnels with Parallel Heading: A Case Study

by Weidong Guo, Lei Chen, Guoqiang Liu, Juntao Wang, Shaoshuai Shi and Lin Bu

Appl. Sci. 2022, 12(23), 12416; https://doi.org/10.3390/app122312416 - 4 Dec 2022

Viewed by 1573

Abstract

There are many issues affecting multi-hole parallel tunneling and long tunnel ventilation, such as insufficient fresh air supplied at the tunnel face, pollution by contaminated winds, and uncoordinated work among multiple fans. In view of these issues, this paper uses the numerical simulation [...] Read more.

There are many issues affecting multi-hole parallel tunneling and long tunnel ventilation, such as insufficient fresh air supplied at the tunnel face, pollution by contaminated winds, and uncoordinated work among multiple fans. In view of these issues, this paper uses the numerical simulation software Fluent combined with the orthogonal analysis test method, and, based on the actual working conditions of Yuelongmen Tunnel on the Chenglan Line, simulates the parameters of the duct, the installation position of the jet fan at the cross channel, and the combined operation status of multiple fans. The main conclusions are as follows: (1) the primary factor affecting the CO discharge from the tunnel face is the distance between the exit of the duct and the tunnel face, and the secondary factor is the diameter of the duct, while the position of the duct is the least influential factor; (2) the jet fan at the intersection of the cross channel should be set close to the pollution source in such a way as to prevent the jet from hitting the windward side of the cross channel and thereby avoid causing the contaminated wind to contaminate the adjacent tunnel; (3) in tunnels in which blasting operations do not occur, the simultaneous use of high-power air supplies and jet fans will reduce the air pressure in the tunnel, generate an air pressure difference with the adjacent tunnel, trap polluted air, and reduce the ventilation effect. Full article

(This article belongs to the Special Issue Urban Underground Engineering: Excavation, Monitoring, and Control)

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21 pages, 5820 KiB

Open AccessArticle

Working Face Stability of Box Shield Tunneling under Non-Uniform Support Pressure

by Miao Yu, Wei Liu, Ben Wu, Jiajia Yan and Penglu Gan

Appl. Sci. 2022, 12(23), 12360; https://doi.org/10.3390/app122312360 - 2 Dec 2022

Cited by 1 | Viewed by 1145

Abstract

This paper proposes a theoretical model for the stability analysis of a box tunnel face in non-cohesive soils considering the uneven distribution of support pressure caused by multiple cutter heads and screw conveyors. The support pressure distribution on the tunnel face is concave. [...] Read more.

This paper proposes a theoretical model for the stability analysis of a box tunnel face in non-cohesive soils considering the uneven distribution of support pressure caused by multiple cutter heads and screw conveyors. The support pressure distribution on the tunnel face is concave. Accordingly, the failure mechanism is composed of a prism and a wedge, both including three blocks. The relatively smaller support pressure acting on the middle blocks lead to the tendency of slide. Assuming that the support pressure acting on the side blocks is obtained using the active earth pressure coefficient, the support pressure acting on block II can be achieved by limit equilibrium analysis considering the interactions between the blocks. The influences of strength parameters and geometric parameters on the tunnel face stability are discussed in the parametric analysis. For comparison, numerical analysis is conducted in the commercial software OptumG3. It is found that the results given by the proposed model agree well with those from the numerical model. Therefore, the rationality of the proposed model in predicting the collapse geometry is verified. Full article

(This article belongs to the Special Issue Urban Underground Engineering: Excavation, Monitoring, and Control)

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18 pages, 2951 KiB

Open AccessArticle

An Established Theory of Digital Twin Model for Tunnel Construction Safety Assessment

by Yuhong Zhao, Naiqiang Wang and Zhansheng Liu

Appl. Sci. 2022, 12(23), 12256; https://doi.org/10.3390/app122312256 - 30 Nov 2022

Cited by 4 | Viewed by 1732

Abstract

In traditional construction safety assessment, it is difficult to describe the safety status of different construction stages. To solve this problem, this paper proposes a digital twin modeling theory for construction safety assessment. Firstly, this paper analyzes the requirements of a digital twin [...] Read more.

In traditional construction safety assessment, it is difficult to describe the safety status of different construction stages. To solve this problem, this paper proposes a digital twin modeling theory for construction safety assessment. Firstly, this paper analyzes the requirements of a digital twin model. Secondly, the required information is collected by IoT. Finally, the DT model is established based on the collected information. This DT model analyzes the collected information by ML, which aims to conducting the assessments of construction safety. To verify this method, this paper analyzes the vault settlement during tunnel construction. The analysis results show that the DT model can predict the settlement value with high accuracy. Moreover, the safety state is assessed dynamically based on the settlement value by DT. Full article

(This article belongs to the Special Issue Urban Underground Engineering: Excavation, Monitoring, and Control)

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20 pages, 137403 KiB

Open AccessArticle

Hybrid-Supervised-Learning-Based Automatic Image Segmentation for Water Leakage in Subway Tunnels

by Dongwei Qiu, Haorong Liang, Zhilin Wang, Yuci Tong and Shanshan Wan

Appl. Sci. 2022, 12(22), 11799; https://doi.org/10.3390/app122211799 - 20 Nov 2022

Cited by 2 | Viewed by 2056

Abstract

Quickly and accurately identifying water leakage is one of the important components of the health monitoring of subway tunnels. A mobile vision measurement system consisting of several high-resolution, industrial, charge-coupled device (CCD) cameras is placed on trains to implement structural health monitoring in [...] Read more.

Quickly and accurately identifying water leakage is one of the important components of the health monitoring of subway tunnels. A mobile vision measurement system consisting of several high-resolution, industrial, charge-coupled device (CCD) cameras is placed on trains to implement structural health monitoring in tunnels. Through the image processing technology proposed in this paper, water leakage areas in subway tunnels can be found and repaired in real time. A lightweight automatic segmentation approach to water leakage using hybrid-supervised-deep-learning technology is proposed. This approach consists of the weakly supervised learning Water Leakage-CAM and fully supervised learning WRDeepLabV3+. The Water Leakage-CAM is used for the automatic labeling of data. The WRDeepLabV3+ is used for the accurate identification of water leakage areas in subway tunnels. Compared with other end-to-end semantic segmentation networks, the hybrid-supervised learning approach can more completely segment the water leakage region when dealing with water leakage in complex environments. The hybrid-supervised-deep-learning approach proposed in this paper achieves the highest MIoU of 82.8% on the experimental dataset, which is 6.4% higher than the second. The efficiency is also 25% higher than the second and significantly outperforms other end-to-end deep learning approaches. Full article

(This article belongs to the Special Issue Urban Underground Engineering: Excavation, Monitoring, and Control)

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14 pages, 3560 KiB

Open AccessTechnical Note

Laboratory Tests on Swelling Properties of Field-Coring Gypsum Rock in Tunnels

by Chongbang Xu, Haoju Fan, Xu Zhao, Lifeng Fan and Peng Wang

Appl. Sci. 2023, 13(2), 719; https://doi.org/10.3390/app13020719 - 4 Jan 2023

Viewed by 1405

Abstract

The reaction between gypsum rock and water results in swelling deformation and swelling pressure. Swelling deformation and swelling pressure cause damage to underground engineering such as tunnels. It is of significance to study the swelling characteristics of gypsum rock. The variation in maximum [...] Read more.

The reaction between gypsum rock and water results in swelling deformation and swelling pressure. Swelling deformation and swelling pressure cause damage to underground engineering such as tunnels. It is of significance to study the swelling characteristics of gypsum rock. The variation in maximum radial free-swelling ratio, axial free-swelling ratio, lateral restricted-swelling ratio and lateral restricted-swelling pressure of gypsum rock with a water immersion time of 2880 min were investigated experimentally. The early swelling characteristics were further discussed and described by an S-shaped model. The results show that the swelling ratio and swelling pressure increase rapidly as the immersion time increases for the first 120 min. Subsequently, the swelling ratio and swelling pressure increase slowly and become stable as the immersion time further increases. At the 120th minute, the maximum radial free-swelling ratio, axial free-swelling ratio, lateral restricted-swelling ratio and lateral restricted-swelling pressure of gypsum rock reach more than 80% of their final values (2880 min in the present study). Based on the swelling characteristics of gypsum rock during the first 120 min, an S-shaped swelling-time model was introduced to describe the early swelling behavior of gypsum rock. Full article

(This article belongs to the Special Issue Urban Underground Engineering: Excavation, Monitoring, and Control)

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