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Numerical Modeling in Civil and Mining Geotechnical Engineering
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Numerical Modeling in Civil and Mining Geotechnical Engineering

A special issue of Processes (ISSN 2227-9717). This special issue belongs to the section "Advanced Digital and Other Processes".

Deadline for manuscript submissions: closed (30 April 2022) | Viewed by 27921

Printed Edition Available!
A printed edition of this Special Issue is available here.

Special Issue Editor

Prof. Dr. Li Li

E-Mail Website
Guest Editor
Department of Civil, Geological and Mining Engineering, Polytechnique Montreal, Montreal, QC H3T 1J4, Canada
Interests: numerical modeling; mining backfill; backfilling of openings (trenches, silos, mine stopes); stability analysis; soil mechanics; rock mechanics; barricades
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Numerical modeling is largely used in geotechnical engineering to understand the responses of infrastructures in civil and mining engineering. Many homemade or commercialized numerical codes are available to handle with different geotechnical problems. For some, numerical modeling can be used as a useful tool to obtain qualitative results, showing some general idea or trend. For some others, numerical models are considered as reliable only if the numerical results are validated by experimental results (without worrying much about the reliability of experimental results). The calibration process of numerical models through adjustment of model parameters to obtain good agreements between numerical and experimental results is very often called “validation” or “prediction”. This process is in fact to test the applicability of the used numerical model. The numerical model along with the calibrated model parameters should be called a “calibrated numerical model”. Its predictability needs to be verified against more data obtained under different conditions.

In this Special Issue, we collect some high-quality articles that present original and novel contributions to civil and mining geotechnical engineering. The reliability of numerical results will be a critical concern. The physical and numerical models should be detailed enough to allow readers to reproduce the published results. Validation or verification of the used numerical code as well as domain and mesh sensitivity analyses of numerical models should be shown in appendices. Comparisons between numerical and experimental results will be advantageous, but not mandatory. The topics of articles include the application of numerical modeling to analyze the hydrogeotechnical behavior of:

  • Interaction between surface structures and soil/rock foundations;
  • Shallow and deep foundations;
  • Railway and road foundations;
  • Dams for reservoirs, sludge or mine tailings;
  • Landslide;
  • Slope stability of open pit mines;
  • Trenches;
  • Subsidence associated with underground activities (mines, subway, conduits, etc.);
  • Underground spaces in soils or rocks (tunnels, cavities, mine stopes);
  • Backfilling of openings (trenches, silos, mine stope, open pits.

Prof. Dr. Li Li
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Processes is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • stability
  • bearing capacity
  • failure
  • stress
  • displacement
  • pore water pressure
  • liquefaction
  • dynamic
  • soil
  • backfill
  • sludge
  • tailings
  • rock
  • foundation
  • road
  • dam
  • slope
  • landslide
  • trench
  • silo
  • subsidence
  • cavity
  • tunnel
  • mine stope

Published Papers (15 papers)

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Editorial

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5 pages, 195 KiB  
Editorial
Special Issue on Numerical Modeling in Civil and Mining Geotechnical Engineering
by Li Li
Processes 2022, 10(8), 1571; https://doi.org/10.3390/pr10081571 - 11 Aug 2022
Cited by 2 | Viewed by 1331
Abstract
Numerical modeling is a widely used method in geotechnical engineering to understand the interactive responses of infrastructures with soils or/and rocks in both civil and mining engineering [...] Full article
(This article belongs to the Special Issue Numerical Modeling in Civil and Mining Geotechnical Engineering)

Research

Jump to: Editorial

20 pages, 5467 KiB  
Article
Unsaturated Hydraulic Conductivity Estimation—A Case Study Modelling the Soil-Atmospheric Boundary Interaction
by Md Rajibul Karim, David Hughes and Md Mizanur Rahman
Processes 2022, 10(7), 1306; https://doi.org/10.3390/pr10071306 - 01 Jul 2022
Cited by 6 | Viewed by 1451
Abstract
Pore water pressure changes due to soil-atmospheric boundary interaction can significantly influence soil behaviour and can negatively affect the safety and stability of geotechnical structures. For example, prolonged rainfall events can lead to increased pore water pressure and lower strength; repeated cycles of [...] Read more.
Pore water pressure changes due to soil-atmospheric boundary interaction can significantly influence soil behaviour and can negatively affect the safety and stability of geotechnical structures. For example, prolonged rainfall events can lead to increased pore water pressure and lower strength; repeated cycles of pore water pressure changes can lead to degradation of strength. These effects are likely to become more severe in the future due to climate change in many parts of the world. To analyse the behaviour of soil subjected to atmospheric boundary interactions, several parameters are needed, and hydraulic conductivity is one of the more important and is difficult to determine. Hydraulic conductivity deduced from laboratory tests are often different from those from the field tests, sometimes by orders of magnitude. The problem becomes even more complicated when the soil state is unsaturated, where the hydraulic conductivity varies with the soil’s state of saturation. In this paper, a relatively simple alternative approach is presented for the estimation of the hydraulic conductivity of unsaturated soils. The method involved a systematic re-analysis of observed pore water pressure response in the field. Using a finite element software, the soil-atmospheric boundary interaction and related saturated/unsaturated seepage of an instrumented slope have been analysed, and results are compared with field measurements. The numerical model could capture the development of suction, positive pore water pressure and changes in water content with reasonable accuracy and demonstrated the usefulness of the hydraulic conductivity estimation method discussed in this paper. Full article
(This article belongs to the Special Issue Numerical Modeling in Civil and Mining Geotechnical Engineering)
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22 pages, 12627 KiB  
Article
Implementation of the Non-Associated Elastoplastic MSDPu Model in FLAC3D and Application for Stress Analysis of Backfilled Stopes
by Feitao Zeng, Li Li, Michel Aubertin and Richard Simon
Processes 2022, 10(6), 1130; https://doi.org/10.3390/pr10061130 - 05 Jun 2022
Cited by 1 | Viewed by 1732
Abstract
The multiaxial Mises-Schleicher and Drucker-Prager unified (MSDPu) criterion has been shown to exhibit several specific features compared to other yield and failure criteria, including a nonlinear mean stress dependency, influence of the Lode angle, use of independent uniaxial compressive and tensile [...] Read more.
The multiaxial Mises-Schleicher and Drucker-Prager unified (MSDPu) criterion has been shown to exhibit several specific features compared to other yield and failure criteria, including a nonlinear mean stress dependency, influence of the Lode angle, use of independent uniaxial compressive and tensile strength values and absence of an apex (singularity) on the envelope surface in the negative stress quadrant. However, MSDPu has been seldom used in practice to solve geotechnical and geomechanical engineering problems mainly because it had not yet been fully implemented into three-dimensional (3D) numerical codes. To fill this gap, a 3D elastoplastic MSDPu formulation is developed and implemented into FLAC3D. The proposed MSDPu elastic-perfectly plastic (EPP) constitutive model is then validated against existing analytical solutions developed for calculating the stress and displacement distributions around cylindrical openings. The FLAC3D MSDPu-EPP model is then applied to evaluate the vertical and horizontal stress distributions in a three-dimensional vertical backfilled stope. The numerical results obtained with the MSDPu-EPP model are compared with those obtained with the Mohr-Coulomb EPP model, to highlight key features of the new formulation. Full article
(This article belongs to the Special Issue Numerical Modeling in Civil and Mining Geotechnical Engineering)
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19 pages, 6342 KiB  
Article
Numerical Investigation on the Impact of Tailings Slurry on Catch Dams Built at the Downstream of a Breached Tailings Pond
by Shitong Zhou and Li Li
Processes 2022, 10(5), 898; https://doi.org/10.3390/pr10050898 - 02 May 2022
Cited by 2 | Viewed by 1916
Abstract
Tailings storage facilities (TSFs) are known as a time-bomb. The numerous failures of TSFs and the heavy catastrophic consequences associated with each failure of TSFs indicate that preventing measures are necessary for existing TSFs. One of the preventing measures is to construct catch [...] Read more.
Tailings storage facilities (TSFs) are known as a time-bomb. The numerous failures of TSFs and the heavy catastrophic consequences associated with each failure of TSFs indicate that preventing measures are necessary for existing TSFs. One of the preventing measures is to construct catch dams along the downstream near TSFs. The design of catch dams requires a good understanding of the dynamic interaction between the tailings slurry flow and the catch dams. There are, however, very few studies on this aspect. In this study, a numerical code, named LS-DYNA, that is based on a combination of smoothed particle hydrodynamics and a finite element method, was used. The numerical modeling shows that the tailings slurry flow can generally be divided into four stages. In terms of stability analysis, a catch dam should be built either very close to or very far from the TSF. When the catch dam with an upstream slope of a very small inclination angle is too close to the tailings pond, it can be necessary to build a very high catch dam or a secondary catch dam. As the impacting force can increase and decrease with the fluctuations back-and-forth of the tailings slurry flow, the ideal inclination angle of the upstream slope of the catch dam is between 30° and 37.5°, while the construction of a catch dam with a vertical upstream slope should be avoided. However, a catch dam with steeper upstream slopes seems to be more efficient in intercepting tailings flow and allowing the people downstream to have more time for evacuation. All these aspects need to be considered to optimize the design of catch dams. Full article
(This article belongs to the Special Issue Numerical Modeling in Civil and Mining Geotechnical Engineering)
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19 pages, 6856 KiB  
Article
Analysis on Water Inrush Prevention Mechanism of Paste-Filled Floor above Confined Water
by Qingliang Chang, Xingjie Yao, Jianzhuang Qin, Mengda Li, Yizhe Wang, Huaqiang Zhou, Ying Xu and Yuantian Sun
Processes 2022, 10(2), 274; https://doi.org/10.3390/pr10020274 - 29 Jan 2022
Cited by 1 | Viewed by 1692
Abstract
To study the influence of filling step and advancing distance on the deformation and failure of a working face floor, a mechanical model based on elastic foundation beam theory is established. The deflection and bending moment curves of the floor under different filling [...] Read more.
To study the influence of filling step and advancing distance on the deformation and failure of a working face floor, a mechanical model based on elastic foundation beam theory is established. The deflection and bending moment curves of the floor under different filling steps and advancing distance are obtained by Maple. Then, a fluid–solid coupling model of paste-filling mining on confined water is established by FLAC3D. The effects of different filling steps and advancing distance on the floor displacement, stress, and plastic zone of the floor are analyzed. The results show that there is a “concave” quadratic relationship between the filling step and the maximum displacement of the floor, and there is a “convex” quadratic relationship between the advancing distance and the maximum displacement of the floor. The maximum stress of the floor increases linearly with the increase in filling distance and tends to be stable with the increase in advancing distance. Moreover, the increase in filling steps will lead to the continuous increase in longitudinal failure. This study could guide paste-filling mining above confined water. Full article
(This article belongs to the Special Issue Numerical Modeling in Civil and Mining Geotechnical Engineering)
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21 pages, 12087 KiB  
Article
Influence of Yield Pillar Width on Coal Mine Roadway Stability in Western China: A Case Study
by Qingwei Wang, Hao Feng, Peng Tang, Yuting Peng, Chunang Li, Lishuai Jiang and Hani S. Mitri
Processes 2022, 10(2), 251; https://doi.org/10.3390/pr10020251 - 27 Jan 2022
Cited by 7 | Viewed by 2124
Abstract
Roadway excavation technology in underground coal mines has an important impact on mining efficiency and production safety. High-efficiency and rapid excavation of underground roadways in coal mines are important means to improve the production efficiency of coal mines. To tackle the problems of [...] Read more.
Roadway excavation technology in underground coal mines has an important impact on mining efficiency and production safety. High-efficiency and rapid excavation of underground roadways in coal mines are important means to improve the production efficiency of coal mines. To tackle the problems of instability of roadway and support difficulties, the tail entry of panel 3105 in Mataihao Mine was used as the case study. The methods of underground investigation, theoretical analysis, and FLAC3D numerical simulation were used to analyze the stability of the surrounding rock under different yield pillar widths. Through the stress field, displacement field, and plastic zone of roadway surrounding rock, the stability of the rock surrounding the roadway under different yield pillar widths (4 m, 6 m, and 8 m) was analyzed. The results show that, with the increase in the yield pillar width, the plastic zone failure and displacement of the roadway surrounding rock are mainly manifested in the narrow pillar rib, seam rib, roof, and floor. The plastic zone distribution changes slightly; the roadway displacement exhibits basic symmetry. The vertical stress and the displacement of the two sides increase with the increase in the yield pillar width, and the roof displacement and the ratio of tensile failure of the surrounding rock decrease with the increase in the yield pillar width. According to the dynamic evolution law of the rock surrounding the roadway along the goaf side, the effect of the yield pillar size is revealed, and a reasonable yield pillar width is determined. When the yield pillar width is 6 m, the plastic zone failure of the surrounding rock and the displacement of the two sides of the roof are the most balanced among the three schemes. This provides a reference for the selection of the narrow yield pillar size in coal mines under the same geological conditions. Full article
(This article belongs to the Special Issue Numerical Modeling in Civil and Mining Geotechnical Engineering)
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12 pages, 2413 KiB  
Article
Incompatible Deformation Model of Rocks with Defects around a Thick-Walled Cylinder
by Yingji Bao and Binsong Jiang
Processes 2021, 9(12), 2215; https://doi.org/10.3390/pr9122215 - 08 Dec 2021
Cited by 3 | Viewed by 1820
Abstract
Before the excavation of underground engineering, joints, fissures, and voids already exist in the rock—that is, there are defects in the rock. Due to the existence of these defects, the rock produces plastic deformation, which can lead to incompatible deformation. Therefore, the classic [...] Read more.
Before the excavation of underground engineering, joints, fissures, and voids already exist in the rock—that is, there are defects in the rock. Due to the existence of these defects, the rock produces plastic deformation, which can lead to incompatible deformation. Therefore, the classic continuum theory cannot accurately describe the deformation of the rock. In this paper, a relationship between the strain tensor and metric tensor was studied by analyzing the three states of elastic plastic deformation, and the elasto-plastic incompatible model was built. Additionally, the stress and deformation of a thick-walled cylinder under hydrostatic pressure was investigated by using a finite element program written in the FORTRAN language. The results show that the plastic strain is associated with not only deviator stress but also the distribution of defects (represented by the incompatible parameter R). With the value of R increasing, the defects in the rock increased, but the elastic plastic stiffness matrix decreased. Thus, as more rock enters the plastic state, the deformation of the surrounding rock is enlarged. Full article
(This article belongs to the Special Issue Numerical Modeling in Civil and Mining Geotechnical Engineering)
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11 pages, 2448 KiB  
Article
Precomputation of Critical State Soil Plastic Models
by Vicente Navarro, Virginia Cabrera, Gema De la Morena, Daniel González, Laura Asensio and Ángel Yustres
Processes 2021, 9(12), 2142; https://doi.org/10.3390/pr9122142 - 27 Nov 2021
Cited by 1 | Viewed by 1379
Abstract
In this paper, a simple precomputing procedure is proposed to improve the numerical performance of the technological application of critical state soil models. In these models, if associated plasticity is assumed, the normalization of the stress space allows both the yield surface and [...] Read more.
In this paper, a simple precomputing procedure is proposed to improve the numerical performance of the technological application of critical state soil models. In these models, if associated plasticity is assumed, the normalization of the stress space allows both the yield surface and the plastic components of the elastoplastic matrix to be defined as a function of a single variable. This approach facilitates their parameterization and precomputation, preventing the repetition of calculations when the boundary value problems appear at the yield surface with the calculation of plastic strain. To illustrate the scope of the procedure, its application on a modified Cam Clay model is analysed, which shows that the method allows a significant reduction of about 50% (as compared with the conventional explicit integration algorithm) in the computational time without reducing the precision. Although it is intended for critical state models in soils, the approach can be applied to other materials and types of constitutive models provided that parameterization is possible. It is therefore a methodology of practical interest, especially when a large volume of calculations is required, for example when studying large-scale engineering systems, performing sensitivity analysis, or solving optimization problems. Full article
(This article belongs to the Special Issue Numerical Modeling in Civil and Mining Geotechnical Engineering)
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30 pages, 9939 KiB  
Article
Applicability of Constitutive Models to Describing the Compressibility of Mining Backfill: A Comparative Study
by Ruofan Wang, Feitao Zeng and Li Li
Processes 2021, 9(12), 2139; https://doi.org/10.3390/pr9122139 - 26 Nov 2021
Cited by 7 | Viewed by 2015
Abstract
The compressibility of mining backfill governs its resistance to the closure of surrounding rock mass, which should be well reflected in numerical modeling. In most numerical simulations of backfill, the Mohr–Coulomb elasto-plastic model is used, but is constantly criticized for its poor representativeness [...] Read more.
The compressibility of mining backfill governs its resistance to the closure of surrounding rock mass, which should be well reflected in numerical modeling. In most numerical simulations of backfill, the Mohr–Coulomb elasto-plastic model is used, but is constantly criticized for its poor representativeness to the mechanical response of geomaterials. Finding an appropriate constitutive model to better represent the compressibility of mining backfill is critical and necessary. In this paper, Mohr–Coulomb elasto-plastic model, double-yield model, and Soft Soil model are briefly recalled. Their applicability to describing the backfill compressibility is then assessed by comparing numerical and experimental results of one-dimensional consolidation and consolidated drained triaxial compression tests made on lowly cemented backfills available in the literature. The comparisons show that the Soft Soil model can be used to properly describe the experimental results while the application of the Mohr–Coulomb model and double-yield model shows poor description on the compressibility of the backfill submitted to large and cycle loading. A further application of the Soft Soil model to the case of a backfilled stope overlying a sill mat shows stress distributions close to those obtained by applying the Mohr–Coulomb model when rock wall closure is absent. After excavating the underlying stope, rock wall closure is generated and exercises compression on the overlying backfill. Compared to the results obtained by applying the Soft Soil model, an application of the Mohr–Coulomb model tends to overestimate the stresses in the backfill when the mine depth is small and underestimate the stresses when the mine depth is large due to the poor description of fill compressibility. The Soft Soil model is recommended to describe the compressibility of uncemented or lightly cemented backfill with small cohesions under external compressions associated with rock wall closure. Full article
(This article belongs to the Special Issue Numerical Modeling in Civil and Mining Geotechnical Engineering)
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17 pages, 3450 KiB  
Article
Modeling the Effects of Seasonal Weathering on Centrifuged Oil Sands Tailings
by Umme Salma Rima, Nicholas Beier and Ahlam Abdulnabi
Processes 2021, 9(11), 1906; https://doi.org/10.3390/pr9111906 - 26 Oct 2021
Cited by 1 | Viewed by 1872
Abstract
The oil sands industry employs different technologies at pilot and commercial demonstration scales in order to improve the dewatering rate of fluid fine tailings. Of these technologies, centrifugation has advanced to the commercial scale and is playing a major role in the fluid [...] Read more.
The oil sands industry employs different technologies at pilot and commercial demonstration scales in order to improve the dewatering rate of fluid fine tailings. Of these technologies, centrifugation has advanced to the commercial scale and is playing a major role in the fluid fine tailings management strategy. However, centrifuge technology on its own may not develop the required strength to ensure fine tailings can be incorporated into dry landform reclamation, which requires water contents close to their plastic limit. Hence, it is paramount to combine more than one technology to maximize post-depositional dewatering. Management of the tailings deposit to promote seasonal weathering (freeze–thaw, evaporation and self-weight consolidation) can promote further dewatering. Properly assessing the contributions of the seasonal weathering components is vital to optimizing this strategy. Using the geotechnical properties of centrifuged tailings, the effects of seasonal weathering on tailings were modeled under two different freezing temperature gradients. A coupled analysis combining FSConsol and Unsatcon was used to simulate the deposition scenario similar to the laboratory. The modeling results were found to match the laboratory response reasonably well, indicating the coupled approach proposed in this manuscript is valid and helps to predict the seasonal weathering effects on dewatering. Full article
(This article belongs to the Special Issue Numerical Modeling in Civil and Mining Geotechnical Engineering)
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27 pages, 10640 KiB  
Article
Practice-Oriented Validation of Embedded Beam Formulations in Geotechnical Engineering
by Andreas-Nizar Granitzer and Franz Tschuchnigg
Processes 2021, 9(10), 1739; https://doi.org/10.3390/pr9101739 - 28 Sep 2021
Cited by 6 | Viewed by 3310
Abstract
The numerical analysis of many geotechnical problems involves a high number of structural elements, leading to extensive modelling and computational effort. Due to its exceptional ability to circumvent these obstacles, the embedded beam element (EB), though originally intended for the modelling of micropiles, [...] Read more.
The numerical analysis of many geotechnical problems involves a high number of structural elements, leading to extensive modelling and computational effort. Due to its exceptional ability to circumvent these obstacles, the embedded beam element (EB), though originally intended for the modelling of micropiles, has become increasingly popular in computational geotechnics. Recent research effort has paved the way to the embedded beam element with interaction surface (EB-I), an extension of the EB. The EB-I renders soil–structure interaction along an interaction surface rather than the centreline, making it theoretically applicable to any engineering application where beam-type elements interact with solid elements. At present, in-depth knowledge about relative merits, compared to the EB, is still in demand. Subsequently, numerical analysis are carried out using both embedded beam formulations to model deep foundation elements. The credibility of predicted results is assessed based on a comprehensive comparison with the well-established standard FE approach. In all cases considered, the EB-I proves clearly superior in terms of mesh sensitivity, mobilization of skin-resistance, and predicted soil displacements. Special care must be taken when using embedded beam formulations for the modelling of composite structures. Full article
(This article belongs to the Special Issue Numerical Modeling in Civil and Mining Geotechnical Engineering)
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15 pages, 4892 KiB  
Article
The Long-Term Mitigating Effect of Horizontal Ground-Source Heat Exchangers on Permafrost Thaw Settlement
by Amir Fatollahzadeh Gheisari, Pooneh Maghoul, Hartmut M. Holländer, Rob Kenyon, Rob Sinclair and Maryam Saaly
Processes 2021, 9(9), 1636; https://doi.org/10.3390/pr9091636 - 10 Sep 2021
Cited by 1 | Viewed by 1560
Abstract
This study investigated the long-term effect of horizontal Ground-Source Heat Exchangers (GSHEs) on mitigating permafrost thaw settlement. In the conceptual system, a fan coil was used to chill the recirculating fluid in the linear High-Density Polyethylene (HDPE) ground loop system. A fully coupled [...] Read more.
This study investigated the long-term effect of horizontal Ground-Source Heat Exchangers (GSHEs) on mitigating permafrost thaw settlement. In the conceptual system, a fan coil was used to chill the recirculating fluid in the linear High-Density Polyethylene (HDPE) ground loop system. A fully coupled thermo-hydro-mechanical finite element framework was employed to analyze multiphysics processes involved in the thaw settlement phenomenon. To investigate the sustainability of the system, a period of 50 years was simulated. Two operational modes were defined: one without and the other with HDPE. Different heat carrier velocities and inlet temperatures, and heat exchanger depths were examined to explore their effects on the thaw settlement rate. It was concluded that the proposed system can effectively alleviate the predicted permafrost thaw settlement over the study period. Moreover, the heat carrier temperature was found to have a prominent impact on the thaw settlement rate amongst other parameters. Full article
(This article belongs to the Special Issue Numerical Modeling in Civil and Mining Geotechnical Engineering)
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23 pages, 6166 KiB  
Article
A Parametric Numerical Study for Diagnosing the Failure of Large Diameter Bored Piles Using Supervised Machine Learning Approach
by Mohamed E. Al-Atroush, Ashraf M. Hefny and Tamer M. Sorour
Processes 2021, 9(8), 1411; https://doi.org/10.3390/pr9081411 - 16 Aug 2021
Cited by 6 | Viewed by 2658
Abstract
The full-scale static pile loading test is without question the most reliable methodology for estimating the ultimate capacity of large diameter bored piles (LDBP). However, in most cases, the obtained load-settlement curves from LDBP loading tests tend to increase without reaching the failure [...] Read more.
The full-scale static pile loading test is without question the most reliable methodology for estimating the ultimate capacity of large diameter bored piles (LDBP). However, in most cases, the obtained load-settlement curves from LDBP loading tests tend to increase without reaching the failure point or an asymptote. Loading an LDBP until reaching apparent failure is seldom practical because of the significant amount of settlement usually required for the full shaft and base mobilizations. With that in mind, the supervised learning algorithm requires a huge labeled data set to train the machine properly, which makes it ideal for sensitivity analysis, forecasting, and predictions, among other unsupervised algorithms. However, providing such a huge dataset of LDBP loaded to failure tests might be very complicated. In this paper, a novel practice has been proposed to establish a labeled dataset needed to train supervised machine learning algorithms on accurately predicting the ultimate capacity of an LDBP. A comprehensive numerical parametric study was carried out to investigate the effect of both pile geometrical and soil geotechnical parameters on both the ultimate capacity and settlement of an LDBP. This study was based on field measurements of loaded to failure LDBP tests. Results of the 29 applied models were compared with the calibrated model results, and the variation in LDBP behavior due to change in any of the hyperparameters was discussed. Accordingly, three primary characteristics were identified to diagnose the failure of LDBPs. Those characteristics were utilized to establish a decision tree of a supervised machine learning algorithm that can be used to predict the ultimate capacity of an LDBP. Full article
(This article belongs to the Special Issue Numerical Modeling in Civil and Mining Geotechnical Engineering)
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17 pages, 9241 KiB  
Article
Impact of Ballast Fouling on the Mechanical Properties of Railway Ballast: Insights from Discrete Element Analysis
by Luyu Wang, Mohamed Meguid and Hani S. Mitri
Processes 2021, 9(8), 1331; https://doi.org/10.3390/pr9081331 - 30 Jul 2021
Cited by 6 | Viewed by 2458
Abstract
Ballast fouling is a major factor that contributes to the reduction of shear strength of railway ballast, which can further affect the stability of railway supporting structure. The major sources of ballast fouling include infiltration of foreign fines into the ballast material and [...] Read more.
Ballast fouling is a major factor that contributes to the reduction of shear strength of railway ballast, which can further affect the stability of railway supporting structure. The major sources of ballast fouling include infiltration of foreign fines into the ballast material and ballast degradation induced by train movement on the supported tracks. In this paper, a discrete element model is developed and used to simulate the shear stress–strain response of fouled ballast assembly subjected to direct shear loading. A simplified computational approach is then proposed to model the induced ballast fouling and capture the mechanical response of the ballast at various levels of contamination. The approach is based on the assumption that fine particles comprising the fouling material will not only change the interparticle friction angle, but also the contact stiffness between the ballast particles. Therefore, both the interparticle friction coefficient and effective modulus are adjusted based on a fouled ballast model that is validated using experimental results. The effect of ballast degradation is also investigated by gradually changing the particle size distribution of the ballast assembly in the discrete element model to account for the increased range of particle sizes. Using the developed model, the effect of ballast degradation on the shear strength is then evaluated. Conclusions are made to highlight the suitability of these approximate approaches in efficiently modeling ballast assemblies under shear loading conditions. Full article
(This article belongs to the Special Issue Numerical Modeling in Civil and Mining Geotechnical Engineering)
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22 pages, 30383 KiB  
Article
Analysis of the Surface Subsidence Induced by Mining Near-Surface Thick Lead-Zinc Deposit Based on Numerical Simulation
by Yifan Zhao, Xingdong Zhao, Jiajia Dai and Wenlong Yu
Processes 2021, 9(4), 717; https://doi.org/10.3390/pr9040717 - 19 Apr 2021
Cited by 2 | Viewed by 2371
Abstract
This paper describes a case study of surface subsidence in the Hongling Lead-Zinc Mine. Hongling Lead-Zinc Mine is located in Inner Mongolia, China, about 240 km away from the border between China and Mongolia. There is a batch of outcrops of the near-surface [...] Read more.
This paper describes a case study of surface subsidence in the Hongling Lead-Zinc Mine. Hongling Lead-Zinc Mine is located in Inner Mongolia, China, about 240 km away from the border between China and Mongolia. There is a batch of outcrops of the near-surface thick steep-dip metamorphic orebody. The large-scale surface subsidence induced by underground excavation has brought some impact on the safety of herdsmen and their daily husbandry activities nearby. The requirements of reclamation for subsidence areas in the relevant laws and regulations, raise enormous pressure and risk on safe and economic operation. In this paper, a 3D numerical model of this mine was built by 3DMine and FLAC3D to analyse the excavation procedure and mechanism. The results of the simulation were in good agreement with the field subsidence data collected by satellites and unmanned aerial vehicles from 2009 to 2019. The analysis showed that the current mining method—an integrated underground method of stoping and caving—accelerated the surface subsidence, and some measures of monitoring, controlling and management were expected to take in order to improve economic and ecological benefits. Full article
(This article belongs to the Special Issue Numerical Modeling in Civil and Mining Geotechnical Engineering)
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