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Keywords = hole-containing specimens

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23 pages, 10465 KiB  
Article
Dynamically Triggered Damage Around Rock Tunnels: An Experimental and Theoretical Investigation
by Wanlu Wang, Ming Tao, Wenjun Ding and Rui Zhao
Appl. Sci. 2025, 15(14), 7716; https://doi.org/10.3390/app15147716 - 9 Jul 2025
Viewed by 243
Abstract
Dynamic impact experiments based on high-speed photography and digital image correlation (DIC) techniques were carried out on sandstone specimens containing arched holes to investigate the effect of the incident angle. In addition, the complex function method based on conformal mapping was used to [...] Read more.
Dynamic impact experiments based on high-speed photography and digital image correlation (DIC) techniques were carried out on sandstone specimens containing arched holes to investigate the effect of the incident angle. In addition, the complex function method based on conformal mapping was used to theoretically calculate the transient dynamic stress distributions around the arched holes. The test results indicated that the strength and modulus of elasticity of the specimens under dynamic impact decreased and then increased with the increase of the inclination angle of the holes from 0 to 90° at intervals of 15°, reaching a minimum value at 60°, due to the large stress concentration at this angle leading to the shear failure of the specimen. During the experiment, rock debris ejections, spalling, and heaving were observed around the holes, and the rock debris ejections served as an indicator to identify the early fracture. The damage mechanism around the holes was revealed theoretically, i.e., the considerable compressive stress concentration in the perpendicular incidence direction around the arched hole and the tensile stress concentration on the incidence side led to the initiation of the damage around the cavity, and the theoretical results were in satisfactory agreement with the experimental results. In addition, the effect of the initial stress on the dynamic response of the arched tunnel was discussed. Full article
(This article belongs to the Special Issue Advances in Failure Mechanism and Numerical Methods for Geomaterials)
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16 pages, 8572 KiB  
Article
Fracture Behavior and Cracking Mechanism of Rock Materials Containing Fissure-Holes Under Brazilian Splitting Tests
by Hengjie Luan, Kun Liu, Decheng Ge, Wei Han, Yiran Zhou, Lujie Wang and Sunhao Zhang
Appl. Sci. 2025, 15(10), 5592; https://doi.org/10.3390/app15105592 - 16 May 2025
Viewed by 346
Abstract
Fractures and voids are widely distributed in slope rock masses. These defects promote crack initiation and propagation, ultimately leading to rock mass failure. Investigating their damage evolution mechanisms and strength characteristics is of significant importance for slope hazard prevention. A numerical simulation study [...] Read more.
Fractures and voids are widely distributed in slope rock masses. These defects promote crack initiation and propagation, ultimately leading to rock mass failure. Investigating their damage evolution mechanisms and strength characteristics is of significant importance for slope hazard prevention. A numerical simulation study of Brazilian splitting tests on disk samples containing prefabricated holes and fractures was conducted using the Finite Element Method with Cohesive Zone Modeling (FEM-CZM) in ABAQUS by embedding zero-thickness cohesive elements within the finite element model. This 2021 study analyzed the effects of fracture angle and length on tensile strength and crack propagation characteristics. The results revealed that when the fracture angle is small, cracks initiate near the fracture and propagate and intersect radially as the load increases, ultimately leading to specimen failure, with the crack coalescence pattern exhibiting local closure. As the fracture angle increases, the initiation location of the crack shifts. With an increase in fracture length, the crack initiation position may transfer to other parts of the fracture or near the hole, and longer fractures may result in more complex coalescence patterns and local closure phenomena. During the tensile and stable failure stages, the load–displacement curves of samples with different fracture angles and lengths exhibit similar trends. However, the fracture angle has a notable impact on the curve during the shear failure stage, while the fracture length significantly affects the peak value of the curve. Furthermore, as displacement increases, the proportion of tensile failure undergoes a process of rapid decline, slow rise, and then rapid decline again before stabilizing, with the fracture angle having a significant influence on the proportion of tensile failure. Lastly, as the fracture angle and length increase, the number of damaged cohesive elements shows an upward trend. This study provides novel perspectives on the tensile behavior of fractured rock masses through the FEM-CZM approach, contributing to a fundamental understanding of the strength characteristics and crack initiation mechanism of rocks under tensile loading conditions. Full article
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18 pages, 7522 KiB  
Article
Study on Influence of Grouting on Mechanical Characteristics and Stress Concentration in Hole-Containing Rock
by Yanshuang Yang, Zhaopeng Kang, Shili Qiu, Lei Yan and Jiancheng Peng
Appl. Sci. 2025, 15(10), 5245; https://doi.org/10.3390/app15105245 - 8 May 2025
Viewed by 365
Abstract
Grouting technology is a pivotal methodology for enhancing the mechanical properties of defective surrounding rock masses in tunnel engineering. Through uniaxial compression tests on intact, hole-containing, and grouted marble specimens, the influence of cement grout filling on the mechanical behavior of marble containing [...] Read more.
Grouting technology is a pivotal methodology for enhancing the mechanical properties of defective surrounding rock masses in tunnel engineering. Through uniaxial compression tests on intact, hole-containing, and grouted marble specimens, the influence of cement grout filling on the mechanical behavior of marble containing holes was investigated. Based on the experimental results, discrete element method (DEM) models were established for the three types of specimens, revealing the mesoscopic crack propagation mechanisms and stress distribution in potential stress concentration zones during failure. The experimental results demonstrated that the implementation of cement grouting enhanced the strength properties of the specimens by 22.38%. In terms of failure modes, the failure mode of the grouted specimens was similar to that of the intact specimens, and the filling material transformed the failure mode from tensile to shear failure. Numerical simulations revealed differences in microcrack evolution: cracks in the hole-containing specimens initiated near the upper and lower ends of the holes, while cracks in the grouted specimens originated around the filling material, with both types propagating axially. Microcracks in the grouted specimens initiated earlier, but the majority of microcracks in both types developed after peak stress and were predominantly tensile. The stress concentration coefficients for the intact, grouted, and hole-containing specimens were approximately 0.84, 2.25, and 2.96, respectively. The grouted specimens shortened the duration and alleviated the degree of stress concentration in the defect zones. This study elucidates the grouting reinforcement mechanisms in defective tunnel surrounding rock through a multiscale approach, providing theoretical underpinnings for optimizing tunnel support systems and preventing engineering hazards including collapse and rockburst. Full article
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12 pages, 14963 KiB  
Article
Isothermal Oxidation Behavior of Nickel Base Single Crystal DD6 Film-Cooling Blades at 1050 °C
by Chunyan Hu, Xinling Liu, Changkui Liu, Weikang Sun and Chunhu Tao
Materials 2025, 18(7), 1498; https://doi.org/10.3390/ma18071498 - 27 Mar 2025
Viewed by 377
Abstract
The isothermal oxidation behavior of single crystal DD6 film-cooling blades was investigated. The isothermal oxidation tests were conducted at 1050 °C, and the phase analysis was performed by XRD, while SEM (EDS) was employed to observe the material. In addition to experimental studies, [...] Read more.
The isothermal oxidation behavior of single crystal DD6 film-cooling blades was investigated. The isothermal oxidation tests were conducted at 1050 °C, and the phase analysis was performed by XRD, while SEM (EDS) was employed to observe the material. In addition to experimental studies, a numerical simulation using three-dimensional finite element analysis based on Abaqus software (Version 6.13) was implemented to model the growth stress in specimens during the isothermal test. The obtained results showed that the average oxidation rate of specimens rose with increments in film hole spacing, up to a maximum value at a film hole spacing of 0.75 mm, and then fell, which could be interpreted with the concepts of the oxidation-affected zone and the growth stress. The results obtained from the numerical simulation of the growth stress agreed with the experimental results of the average oxidation rate. The oxide scale of film-cooling specimens mainly consisted of three layers, the NiO outer layer, the spinel sublayer containing cracks, and the non-continuous thin Al2O3 inner layer. The surface of the oxide scale commonly underwent spallation of the NiO outer layer, and the exposed sublayer could grow new NiO particles. The size of the NiO particles on the edge of the film holes was larger than those on the walls of the film holes. SEM images clearly showed that electro-hydraulic beam drilling on DD6 superalloy specimens could erode the γ phase in the γ/γ′ two-phase matrix, thereby inducing damages in regions near film holes. Full article
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19 pages, 13172 KiB  
Article
Design Study of Hole Types for Improved Cooling of Experimental Heatsinks Manufactured by SLM Technology Using an AlSi10Mg Alloy
by Rudolf Madaj, Robert Kohar, Frantisek Brumercik and Matus Veres
Appl. Sci. 2025, 15(4), 2118; https://doi.org/10.3390/app15042118 - 17 Feb 2025
Cited by 1 | Viewed by 590
Abstract
The purpose of this article is to inform the reader about the results of an experimental investigation into the appropriate manifold geometry for an air-cooled inverter, which is manufactured from an AlSi10Mg powder material using SLM technology. The best approach is to optimize [...] Read more.
The purpose of this article is to inform the reader about the results of an experimental investigation into the appropriate manifold geometry for an air-cooled inverter, which is manufactured from an AlSi10Mg powder material using SLM technology. The best approach is to optimize the part geometry for SLM technology so that the placement of support structures required for model fabrication is eliminated as much as possible. A suitable solution was selected based on the design of the most appropriate cross-sectional shape of the openings with the smallest dimensional accuracy deviation and shape deformation. In the experiment, three test specimens were designed; each of them contained eight holes of different shapes, particularly square, rhombic, and circular, with a given range of sizes. The results of the experimental study can help designers select the optimal design of vents and cavities for the chosen AM technology, e.g., for conformal cooling systems. Full article
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17 pages, 6521 KiB  
Article
Rational Fabrication of Ag2S/g-C3N4 Heterojunction for Photocatalytic Degradation of Rhodamine B Dye Under Natural Solar Radiation
by Ali Alsalme, Ahmed Najm, Nagy N. Mohammed, M. F. Abdel Messih, Ayman Sultan and Mohamed Abdelhay Ahmed
Catalysts 2024, 14(12), 914; https://doi.org/10.3390/catal14120914 - 11 Dec 2024
Cited by 1 | Viewed by 1410
Abstract
Near-infrared light-triggered photocatalytic water treatment has attracted significant attention in recent years. In this novel research, rational sonochemical fabrication of Ag2S/g-C3N4 nanocomposites with various compositions of Ag2S (0–25) wt% was carried out to eliminate hazardous rhodamine [...] Read more.
Near-infrared light-triggered photocatalytic water treatment has attracted significant attention in recent years. In this novel research, rational sonochemical fabrication of Ag2S/g-C3N4 nanocomposites with various compositions of Ag2S (0–25) wt% was carried out to eliminate hazardous rhodamine B dye in a cationic organic pollutant model. g-C3N4 sheets were synthesized via controlled thermal annealing of microcrystalline urea. However, black Ag2S nanoparticles were synthesized through a precipitation-assisted sonochemical route. The chemical interactions between various compositions of Ag2S and g-C3N4 were carried out in an ultrasonic bath with a power of 300 W. XRD, PL, DRS, SEM, HRTEM, mapping, BET, and SAED analysis were used to estimate the crystalline, optical, nanostructure, and textural properties of the solid specimens. The coexistence of the diffraction peaks of g-C3N4 and Ag2S implied the successful production of Ag2S/g-C3N4 heterojunctions. The band gap energy of g-C3N4 was exceptionally reduced from 2.81 to 1.5 eV with the introduction of 25 wt% of Ag2S nanoparticles, implying the strong absorbability of the nanocomposites to natural solar radiation. The PL signal intensity of Ag2S/g-C3N4 was reduced by 40% compared with pristine g-C3N4, implying that Ag2S enhanced the electron–hole transportation and separation. The rate of the photocatalytic degradation of rhodamine B molecules was gradually increased with the introduction of Ag2S on the g-C3N4 surface and reached a maximum for nanocomposites containing 25 wt% Ag2S. The radical trapping experiments demonstrated the principal importance of reactive oxygen species and hot holes in destroying rhodamine B under natural solar radiation. The charge transportation between Ag2S and g-C3N4 semiconductors proceeded through the type I straddling scheme. The enriched photocatalytic activity of Ag2S/g-C3N4 nanocomposites resulted from an exceptional reduction in band gap energy and controlling the electron–hole separation rate with the introduction of Ag2S as an efficient photothermal photocatalyst. The novel as-synthesized nanocomposites are considered a promising photocatalyst for destroying various types of organic pollutants under low-cost sunlight radiation. Full article
(This article belongs to the Section Photocatalysis)
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21 pages, 13864 KiB  
Article
Fracture Process of Rock Containing a Hole Before and After Reinforcement: Experimental Test and Numerical Simulation
by Linhai Zeng, Futian Zhang, Daobing Zhang, Jiahua Zhang and Huadong Yin
Buildings 2024, 14(12), 3864; https://doi.org/10.3390/buildings14123864 - 30 Nov 2024
Viewed by 1034
Abstract
A deeper understanding of the fracture evolution of hole-containing rocks is helpful for predicting the fracture of engineering rock mass. Based on this, uniaxial compression tests and two-dimensional numerical tests were conducted on red sandstone containing three different shapes of holes before and [...] Read more.
A deeper understanding of the fracture evolution of hole-containing rocks is helpful for predicting the fracture of engineering rock mass. Based on this, uniaxial compression tests and two-dimensional numerical tests were conducted on red sandstone containing three different shapes of holes before and after reinforcement. The mechanical properties, stress field evolution, and AE energy and AE events during the sample fracture process were studied. The conclusions are that: (1) The reinforced specimens exhibited a significant increase in Young’s modulus and strength compared to the unreinforced specimens (containing a semicircular arch hole). (2) The sample always cracks from the loaded axial direction of the hole, presenting as tensile cracks. Subsequently, stress concentration at the corners of the hole results in shear cracks. Finally, the cracks gradually expand and merge with the holes; there are obvious macroscopic cracks and fracture surfaces on the sample surface, which proves that the sample has been fractured. (3) The reinforcement of the hole-containing sandstone can effectively inhibit the expansion of cracks in the rock. (4) When the stress on the specimen is less than its peak stress, the accumulation of the AE energy and AE events in the reinforced sample are greater than those in the unreinforced sample. The specimen experiences more intense compression-induced fracturing and has a stronger load-bearing capacity. Full article
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22 pages, 9596 KiB  
Article
Damage and Crack Propagation Mechanism of Q345 Specimen Based on Peridynamics with Temperature and Bolt Holes
by Jinhai Zhao, Huanhuan Sun and Xinfeng Zhang
Buildings 2024, 14(10), 3220; https://doi.org/10.3390/buildings14103220 - 10 Oct 2024
Cited by 3 | Viewed by 892
Abstract
With the increasing demand for the performance and design refinement of steel structures (including houses, bridges, and infrastructure), many structures have adopted ultimate bearing capacity in service. The design service lives of steel building structures are generally more than 50 years, and most [...] Read more.
With the increasing demand for the performance and design refinement of steel structures (including houses, bridges, and infrastructure), many structures have adopted ultimate bearing capacity in service. The design service lives of steel building structures are generally more than 50 years, and most of them contain bolted connections, which suffer from extreme conditions such as fire (high temperature) during service. When the structure contains defects or cracks and bolt holes, it is easy to produce stress concentration at the defect location, which leads to crack nucleation and crack propagation, reduces the bearing capacity of the structure, and causes the collapse of the structure and causes disasters. In the process of structural damage and crack propagation, the traditional method has some disadvantages, such as stress singularity, the mesh needing to be redivided, and the crack being restricted to mesh; however, the integral method of peridynamics (PD) can completely avoid these problems. Therefore, in this paper, the constitutive equation of PD in high temperature is derived according to the variation law of steel material properties when changed by temperature increase and peridynamics parameters; the damage and crack expansion characteristics of Q345 steel specimens with bolt holes and a central double-crack at 20 °C, 200 °C, 400 °C, and 600 °C were analyzed to clarify the structural damage and failure mechanism. This study is helpful for providing theoretical support for the design of high-temperature steel structures, improving the stability of the structure, and ensuring the bearing capacity of the structure and the safety of people’s lives and property. Full article
(This article belongs to the Special Issue Low-Carbon and Green Materials in Construction—2nd Edition)
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21 pages, 97988 KiB  
Article
Study on Dynamic Loading Characteristics of Rock Containing Holes
by Chuanwei Zang, Qi Li, Miao Chen, Xiaoshan Wang, Can Xiao and Hongyuan Tu
Appl. Sci. 2024, 14(8), 3395; https://doi.org/10.3390/app14083395 - 17 Apr 2024
Cited by 1 | Viewed by 1276
Abstract
Accurately characterizing the mechanical behavior and fracture mechanisms of rock containing holes under dynamic loads is essential for ensuring the stability of underground rock structures. In this study, to enhance the understanding of the fracture processes in rock specimens with cavities subjected to [...] Read more.
Accurately characterizing the mechanical behavior and fracture mechanisms of rock containing holes under dynamic loads is essential for ensuring the stability of underground rock structures. In this study, to enhance the understanding of the fracture processes in rock specimens with cavities subjected to dynamic impacts, experimental and numerical studies focusing on the influence of borehole geometry and strain rate are conducted. The results reveal that the strain rate affects the specimens’ dynamic mechanical strength and peak strain. However, the degree of such influence diminishes as the borehole diameter increases in specimens containing two holes. Fractures that lead to failure are primarily initiated at the axial and radial edges of the holes, the specimen extremities, and around the rock bridges in specimens with dual cavities, indicating significant stress concentration zones within the stress field distribution for specimens with a single hole. Further analysis using displacement field diagrams confirms that shear-induced fractures are the predominant cause of failure across all specimens. These findings provide critical insights for developing borehole pressure relief technology to protect against the risks of deep dynamic impacts. Full article
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16 pages, 9785 KiB  
Article
Fracture Evolution and Mechanical Properties of Mortar Containing Different Inclusions
by Gang Yao, Guifeng Wang, Lihai Tan, Yinfeng Zhang, Ruizhi Wang and Xiaohan Yang
Appl. Sci. 2024, 14(8), 3166; https://doi.org/10.3390/app14083166 - 9 Apr 2024
Cited by 2 | Viewed by 1458
Abstract
To study the influence of inclusions on the fracture evolution and mechanical properties of mortar structures, a series of uniaxial compression tests for mortar samples containing cylinder inclusions of varying mechanical properties were conducted. The digital image correlation (DIC) technique was employed for [...] Read more.
To study the influence of inclusions on the fracture evolution and mechanical properties of mortar structures, a series of uniaxial compression tests for mortar samples containing cylinder inclusions of varying mechanical properties were conducted. The digital image correlation (DIC) technique was employed for the analysis of deformation characteristics. In addition, failure modes for each sample were determined using self-documenting code. The result shows that inclusions filled in holes significantly influence the mechanical properties and failure characteristics of mortar structures as they can change the stress distribution and cracking process. Cracks are typically initiated at the boundaries of the inclusions but will only extend into the inclusion if it is less robust than the surrounding matrix. Sample strength increases significantly with an increase in sample strength when the inclusion’s strength does not surpass that of the surrounding material. Once the inclusion’s strength exceeds that of the surrounding matrix, the strength of the specimen remains relatively unchanged. Full article
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28 pages, 38243 KiB  
Article
Analysis of Micro-Evolution Mechanism of 3D Crack Initiation in Brittle Materials with Hole under Uniaxial Compression
by Semaierjiang Maimaitiyusupu, Zhende Zhu, Xuhua Ren, Hui Zhang and Shu Zhu
Materials 2024, 17(4), 920; https://doi.org/10.3390/ma17040920 - 16 Feb 2024
Cited by 3 | Viewed by 1455
Abstract
This article investigates the microscopic mechanism of crack initiation and propagation in three-dimensional embedded cracks in brittle materials containing circular holes. First, a method for the development of transparent, brittle materials is proposed. Second, UCS tests were conducted on transparent, brittle materials containing [...] Read more.
This article investigates the microscopic mechanism of crack initiation and propagation in three-dimensional embedded cracks in brittle materials containing circular holes. First, a method for the development of transparent, brittle materials is proposed. Second, UCS tests were conducted on transparent, brittle materials containing circular holes and internally embedded three-dimensional cracks. Finally, a numerical model was established in PFC3D to analyze the crack initiation and propagation mechanism. The results show that when α = 0° (α refers to the pre-existing crack inclination), the upper tip of the pre-existing crack appears as a tensile wing crack, and the lower tip of the pre-existing crack appears as a tensile–shear mixed crack. When α = 30°, no wing crack appears, and the tensile crack on the fracture surface only appears after the hole cracks. When α = 60 and 90°, a tensile wing crack and an anti-wing tensile–shear mixed crack appear at the upper tip of the pre-existing crack. A tensile wing crack appears at the lower tip of the pre-existing crack and appears “self-limiting”. During the propagation of wing cracks to the surface of the specimen, the transition sequence of the crack propagation mechanism is tensile through failure—tension-shear mixed failure—tensile failure. It can be seen that the interaction between the crack and hole has an important influence on the evolution mechanism of the crack and the failure mode of the specimen. Full article
(This article belongs to the Section Mechanics of Materials)
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15 pages, 5680 KiB  
Article
Tribological Synergism of Anodic Aluminum Oxide Surface Containing Micro-Holes and Nanopores under Lubricated Reciprocation
by Minhaeng Cho
Lubricants 2023, 11(12), 533; https://doi.org/10.3390/lubricants11120533 - 15 Dec 2023
Cited by 1 | Viewed by 2148
Abstract
Micro-drilled aluminum surfaces containing micro-holes were anodized to produce nanopores over the machined and lapped surfaces. The anodized nanopores had an approximate diameter of 30–40 nm and a depth distribution of 20–30 μm from the surface. The diameter and depth of the machined [...] Read more.
Micro-drilled aluminum surfaces containing micro-holes were anodized to produce nanopores over the machined and lapped surfaces. The anodized nanopores had an approximate diameter of 30–40 nm and a depth distribution of 20–30 μm from the surface. The diameter and depth of the machined micro-holes were 125 μm and 300 μm, respectively. Anodization itself did not change the surface roughness because the nanopores were very small. Ball-on-disk reciprocating tests were performed under lubricated conditions for 2 h using a frequency of 2 Hz, a load of 2 N, and a travel distance of 5 mm. The results showed that both the micro-drilled and anodized surfaces greatly reduced the coefficient of friction compared with the lapped bare surface; however, the coefficient of friction of the hole-textured specimen was not maintained till the end. Contrary to expectations, the lubricant retention capability of the textured structure declined because of hole failure that occurred during oscillation. This gradually increased friction until the end of the reciprocating test. When the micro-drilled surface was anodized, the coefficient of friction decreased again, implying that non-anodized micro-holes alone were ineffective for reducing friction. The surface hardness of Al increased owing to anodization, and thus the micro-holes remained intact. Therefore, it is concluded in this study that a prerequisite for friction reduction in Al is to increase the hardness to minimize the failure of micro-holes, which can be achieved by anodization. The synergistic lubricant retention capability can be maintained by the presence of both nanopores and micro-holes. Full article
(This article belongs to the Special Issue Selected Papers from the K-TRIB2023)
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21 pages, 14699 KiB  
Article
Experimental Study on the Fracture Characteristics of Hole-Crack in Rock-like Material under Biaxial Compression
by Yuan Tian, Bangcheng Han, Xinyu Liu, Kai Shen and Jiangbo Li
Appl. Sci. 2023, 13(17), 9963; https://doi.org/10.3390/app13179963 - 4 Sep 2023
Cited by 2 | Viewed by 1438
Abstract
Using experimental methods to study the influence of hole and cracks on the mechanical properties and fracture characteristics of rock-like mortar materials under biaxial compression conditions. The double crack specimens with hole depths from 0–100 mm are prefabricated to study the strength and [...] Read more.
Using experimental methods to study the influence of hole and cracks on the mechanical properties and fracture characteristics of rock-like mortar materials under biaxial compression conditions. The double crack specimens with hole depths from 0–100 mm are prefabricated to study the strength and deformation characteristics of the specimens under different lateral loads σ2 = 0–6 MPa. The evolution process of secondary crack initiation, development, and connection of the hole-crack specimens are recorded. The results show that: (1) One type of rock mortar test material is prepared, and its main physical and mechanical parameters are all within the range of sandstone, which can effectively simulate the stress deformation characteristics of sandstone. (2) When the depth of the holes in cracked samples exceeds 50% of the length, the strength and deformation of the samples undergo a sudden change. When the depth of the hole in the crack specimen increases from 40 mm to 60 mm, the peak stress decreases most significantly. Moreover, the maximum values of the strain value at peak strength and lateral strain both occur at a hole depth of 60 mm. (3) When the cracked specimen contains through-holes, the failure mode is composite fracture and shear composite fracture. When the depth of the hole is different, the fracture forms include tension composite fracture, shear composite fracture, and composite fracture. Full article
(This article belongs to the Special Issue Rock-Like Material Characterization and Engineering Properties)
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16 pages, 18419 KiB  
Article
Numerical Analysis of Perforated Symmetric Fissures on Mechanical Properties of Hole-Containing Sandstone
by Hong Gou, Peng Shi, Zhijun Wan, Luchang Xiong, Bowen Fan and Zheng Zhen
Appl. Sci. 2023, 13(15), 8780; https://doi.org/10.3390/app13158780 - 29 Jul 2023
Cited by 3 | Viewed by 1235
Abstract
The symmetrical fissures located within the surrounding rock of the roadway (borehole) in tunnel engineering activities can easily induce damage and instability of the surrounding rock. Therefore, studying the impact of perforated symmetrical fissures on the mechanical properties of rock with a hole [...] Read more.
The symmetrical fissures located within the surrounding rock of the roadway (borehole) in tunnel engineering activities can easily induce damage and instability of the surrounding rock. Therefore, studying the impact of perforated symmetrical fissures on the mechanical properties of rock with a hole has significant practical significance. Based on indoor experimental results, conventional triaxial compression simulations were performed on symmetrical fissure-hole sandstone using PFC2D. The impact of the dip angle and length of symmetric fissures on the mechanical properties of the hole-containing sandstone was analyzed. Furthermore, the relationship between crack propagation and the macroscopic mechanical properties of the specimen was discussed. The results show that: (1) The deterioration effect of symmetric fissures on hole-containing sandstone can be controlled by increasing the fissure dip angle, suppressing the stress drop phenomenon. However, increasing the fissure length exacerbates the deterioration effect. (2) The effect of symmetrical fissure dip angle on the displacement field near the hole decreases with increasing dip angle while increasing fissure length exacerbates the effect of fissures on the displacement field. (3) As the angle between the fissure and the vertical principal stress increases, the degree of tensile failure weakens while the degree of shear failure increases. (4) During the crack development phase, the extension of the stress concentration zone drives rapid crack growth. It exhibits a stress drop in the macroscopic mechanical properties, followed by the evolution of the stress field with loading, allowing rapid expansion of the microcracks and eventually leading to rock destabilization damage. Full article
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26 pages, 7971 KiB  
Article
Stress Analysis and Spalling Failure Simulation on Surrounding Rock of Deep Arch Tunnel
by Kang Peng, Guansheng Yi, Song Luo and Xuefeng Si
Appl. Sci. 2023, 13(11), 6474; https://doi.org/10.3390/app13116474 - 25 May 2023
Cited by 10 | Viewed by 2440
Abstract
To study the stress distribution characteristics of surrounding rock and the spalling mechanism of deep hard rock tunnels with different arch heights, the complex variable function and angle-preserving transformation method in elasticity theory were applied to the analytic solution of tangential stress distribution [...] Read more.
To study the stress distribution characteristics of surrounding rock and the spalling mechanism of deep hard rock tunnels with different arch heights, the complex variable function and angle-preserving transformation method in elasticity theory were applied to the analytic solution of tangential stress distribution of arch tunnels during stress adjustment. In addition, true triaxial tests were conducted on granite cube specimens (100 mm × 100 mm × 100 mm) containing holes with three arch heights (including the 25 mm semi-circular arch, 16.7 mm three-centered arch, 12.5 mm three-centered arch) to simulate the spalling process under different initial ground stresses. The stress distribution solution and experimental results show that the initial failure stress of arch holes is 0.39–0.48 times the uniaxial compressive strength (UCS) of the rock. The initial failure location occurs at the arch foot, where tangential stress maximizes. When the lateral pressure coefficient is in the range of 0.38–0.50, the tangential stress is 3.2–3.5 times the UCS. The rock debris of the hole wall are in thin flake shapes. Symmetrical V-shaped or curved failure zones occurred on hole sidewalls. The stress distribution resolution of the surrounding rock of tunnels with different arch heights shows that with the increasing burial depth, the bearing performance of the semi-circular arch tunnel is optimal. In addition, the maximum tangential stress increases as the height of the arch decreases or the lateral stress increases, making it easier for the initial failure to occur at the foot of the arch. Full article
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