bluuebunny/crossref_metadata_2025_split huggingface dataset:
Simulation of CO2 Injection into Fractured Coal Samples
Authors: Li Li , Liang Weiguo , Yang Jianfeng , Dusseault Maurice B. 
Published: November 2020

Abstract
Coal bed formation is widely considered a potential reservoir for CO2 geological storage. The injection of CO2 into coalbed formations is beneficial for reducing the CO2 concentration in the atmosphere and enhancing the recovery of coalbed methane, which is a clean fuel. Natural coal mass is a complex system comprising fractures and matrixes. However, fluid transportation in this system is complicated, and its study is challenging. In this study, a dual-permeability model is established to investigate gas transportation and storage in the coal mass during CO2 injection. Furthermore, the fluid transportation in the fracture and the matrix are studied, along with the mass transfer between them. The fully-coupled multiphysics model is solved using the finite element method. Besides, experiments on CO2 injection and storage in the large fractured coal sample are performed using a special apparatus designed by the Taiyuan University of Technology (TUT). Furthermore, the results of the laboratory experiments and those of the numerical simulation are compared, and the model is confirmed to have high reliability. The simulation results demonstrate that the gas transportation in the fracture is much faster than that in the matrix. The pressure difference and the mass transfer between the fracture and the matrix are the primary causes of pressure increase in the matrix. However, there is a time delay between the change in pressure difference and the mass transfer. During the gas injection process, the evolution of permeability is obvious because of a decrease in effective stress. Furthermore, various cases are simulated to explore the influence of matrix permeability on the results. The results show that higher matrix permeability triggers more mass transfer and that it takes less time to complete CO2 storage. The enhancement of coal matrix permeability can promote CO2 flow rate in the coalbed mass and improve CO2 injection efficiency.
Study on the characterization of rock heterogeneity and simulation of fracture process based on the mesoscopic structure
Authors: Yanbo ZHANG , Enyuan ZHANG , Xulong YAO , Peng LIANG , Baozhu TIAN , Lin SUN , Xiangxin LIU , Shuai WANG 
Published: November 2020

Abstract
This study aims to explore the effect of rock heterogeneity caused by meso-structure differences on the macro-mechanical properties and fracture evolution process. With the help of computed tomography, the meso-structure characteristics of coarse-grained red sandstone are obtained, starting from the meso-structure level. The digital characterization of heterogeneous rocks is completed with the use of image-processing methods, and a rock equivalent crystalline model is constructed. A numerical simulation study is performed with the particle flow PFC3D 5.0 program. The results show that (1) the main form of rock heterogeneity is a meso-structure difference, and this determines the rock’s macro-mechanical properties and failure characteristics. The meso-structure difference mainly plays a role in the post-peak damage weakening stage of rock, and the slight difference leads to damage in different development modes. (2) The crack initiation starts at the cemented and crystalline grid surfaces, which is randomly distributed. The crack evolution process is selective and affected by the types and distribution of the surrounding mineral particles. The development of cracks is dominated by secondary cracks, distributed in strips, in the area of mineral particles with strong mechanical properties. In contrast, cracks are densely developed and spread around in a cluster in the area of mineral particles with weak mechanical properties.
The Influence of the Variable Thickness of Prestressed Linings with Annular Anchors on its Mechanical Properties
Authors: Wang Yujie , Cao Ruilang , Shen Qiang , Zhao Yufei , Qi Wenbiao 
Published: November 2020

Abstract
By embedding annular anchors, prestressed linings with annular anchors provide active prestress, which can effectively resist the high internal water pressure in large-diameter hydraulic tunnels. The variable thickness of concrete liners along the circumference can significantly influence the mechanical properties of the lining. On the basis of the prestressed lining of a 6.8-m-diameter pressure tunnel in the Yinsong Diversion Project, we adopted a 3D numerical modeling method to study the influence of the average and local thicknesses of the lining on its mechanical properties. The results show that the prestress of the lining used in resisting the internal water pressure is ultimately derived from tensioning the annular anchors. The average thickness of the lining has little effect on its load-bearing capacity. In elliptical lining, an annulus of a slight tensile stress area appeared on the inner side of the lining, whereas the crown and invert sections will form the weak area because of structural bending moments.
Long-term stability of gravity anchorage with notched sill for suspension bridge on soft rock ground
Authors: Wu C J , Lai Y J , Cao X J , Yu J 
Published: November 2020

Abstract
The biaxial shear creep test was carried out to investigate the shear rheological characteristics and long-term shear strength on the cemented interface between concrete and bedrock and study the long-term stability of gravity anchorage with notched sill situated on soft rock. The shear rheological model was proposed and its corresponding parameters were identified. A numerical simulation of the shear test with thin-layer element was adopted to simulate the shear rheological behavior of the cemented interface, which was verified reasonably by test results. Further numerical simulation using the 3D viscoelastic–plastic model was implemented to study the long-term stability of gravity anchorage with notched sill. The shear creep test results showed that the Burges rheological constitutive model can fully reflect the shear rheological characteristics of the cemented interface; the long-term shear strength decreased markedly with time, especially cohesion. In addition, time-dependent numerical simulation on the stability of gravity anchorage with notched sill indicated that the displacement of the anchorage foundation of Ganjiang Bridge experienced a transient stage of creep decay and then quickly entered into stable state under the tension of the main cable. The anti-sliding effect of notched sill showed distinct time-dependent property. As the creep displacement increased, the resistance at the normal face of the notched sill functioned well and remained constant when the creep displacement was stable.
DEM simulation of internal erosion around a submerged defective pipe
Authors: Wu Binzhong , Yan Qiong , Wang Li , Chen Quansheng , Wang Tuo , Zhang Fengshou 
Published: November 2020

Abstract
Internal erosion caused by broken sewer pipes often leads to ground subsidence in urban area, which is a major risk to public safety and has caused substantial socioeconomic loss. In order to ensure the ground stabilization and the safety of buried pipelines, it is necessary to understand the process of internal erosion around a submerged defective pipe. In this paper, the Dynamic Fluid Mesh (DFM) is coupled with the three-dimensional discrete element method (DEM) to simulate internal erosion in gap-graded soils above a defective pipe. In this fluid-solid coupling scheme, the fluid mesh can be generated according to the soil skeleton formed by coarse particles and updated at regular intervals. Seepage forces are calculated and applied on solid particles in the DEM model. The approach accounts for permeability and porosity changes due to soil skeleton deformation and internal erosion. In this study, some gap-graded soils samples with different size ratio are established. A defective pipe is placed below the sample. After that, different hydraulic gradients are applied to the sample. Fine particles are washed away from the hole in the pipe. The results indicate that the erosion process can be divided into three stages according to changes in the erosion rate. In the initial stage, numerous fine particles are washed away, and the flow rate increases with the increase of eroded particles. Subsequently, the erosion rate decreases and the flow rate tends to reach a steady state. Finally, only a small proportion of particles fall down from the outlets and the erosion rate levels off to zero gradually. Parametric studies show that the increase of hydraulic gradient increase the eroded particle mass. The number of erosion particles from the bottom layer is much larger than those from the upper layers as more fine particles in the upper layers are locked.
Research on the Design of Landslide Anti-sliding Engineering Based on Inverse Parameter Calculation and the GEO-Slope Limit Equilibrium Method
Authors: Ma Xianjie , Liu Hongyu , Li Jian , Li Jiaming , Li Wei , Hou Lijie 
Published: November 2020

Abstract
Landslide is one of the most widely distributed and most severe geological hazards among the types of slope damage. China is among the countries most seriously affected by landslide disasters in the world. The unreasonable landslide anti-slide design will not only miss the best time for landslide treatment but also cause unnecessary engineering waste. Some may even worsen slope deformation and damage. Thus, reasonable slope protection and reinforcement and landslide anti-slide engineering design have become the current research fascination. This paper uses the Chengdu–Lanzhou Railway as the research object. This railway exhibits the typical characteristics of “four poles and three heights” in engineering geology. The main geological hazards and typical geological conditions of the Chengdu–Lanzhou Railway are systematically explained. The reasons for the determination of the principal axis section of the most unfavorable landslide and the basis for the determination of the sliding surface are summarized. Moreover, in this paper, a reasonable anti-slide engineering design is proposed. Finally, the friction coefficient of the main sliding section is calculated using the method of the coefficient of stability of the block, and the landslide thrust is calculated. Then, the stability coefficient of the landslide is verified using the GEO-Slope limit equilibrium method to determine whether the anti-slide engineering design is reasonable. This article provides a more scientific anti-skid engineering design idea and a scientific analysis method for the rationality of anti-skid engineering design.
Thermally induced failure process of brittle rocks based on a thermo-mechanical coupling model
Authors: Zhao H J , Ma F S , Guo J 
Published: November 2020

Abstract
The thermal expansion and the extraction characteristics of a rock are observed in a common phenomenon caused by the rock’s exposure to significant temperature differences. A thermally induced rock damage is a complex process full of uncertain physical and mechanical processes. Hence, investigating the mechanism of brittle materials is significant for both scientific and engineering applications. This study proposes a thermo-mechanical coupling model based on a continuous–discontinuous element method to simulate the thermal cracking processes in brittle rocks. In this micro-mechanical model, the rock matrix is simulated as an assembly of blocks bonded to each other. A spring model is employed to model the contacts in the blocks to simulate the mechanical deformation properties, while a thermal model is applied between their bonds to simulate heat conduction. The model validity is verified herein. Furthermore, the cracking process of brittle materials under the thermal stresses caused by the temperature gradient is studied using a thick-wall cylinder model. Consequently, the simulation results show that the microscopic crack initiation and propagation processes can be reasonably simulated at the cooling stage using the thermo-mechanical coupling model. Different geological and operation conditions are also further studied to reveal their effects on the patterns of induced fractures. This study provides a possible method for analyzing the thermal damage process and mechanism of brittle materials.
Slope failure mechanism affected by mining subsidence: a case study of highway slopes in Yangquan, Shanxi Province, China
Authors: Chao Zhang , Tiefeng Li , Xudong Han 
Published: November 2020

Abstract
This paper presents details of highway slopes affected by a mining subsidence event that occurred in the Yangquan coal mining area of China in 2016. To ascertain the developmental characteristics of surface deformation, a few methods were applied for investigation and monitoring, such as multiple field investigations, unmanned aerial vehicle measurements, and time-series interferometric synthetic-aperture radar techniques. An accurate numerical simulation was conducted on two slopes for stability analysis and mining subsidence prediction. Results show that the mining subsidence developed from south to north, which was consistent with the mining direction; two subsidence centers were distributed on the ground, and the north one was located in the southeast slope foot of the highway. The influence of the mining subsidence whose subsidence magnitude reached 4 m is obviously different on both sides of the highway. Although the rock and soil structure were damaged seriously, the northwest slope was completely unstable, whereas the southeast slope remained standing. The differences were studied to illuminate that slope instability is not only due to the mechanical properties of rock mass decrease dramatically but also relates to the direction of horizontal traction force, the spatial distribution of the working face, and the effective free surface of the slope. This paper presents a case of mining landslide failure for researchers.
Creep and swelling of bentonite for the safety of disposal pit in high-level radioactive waste repository
Authors: Liu Y M , Cao S F , Tong Q 
Published: November 2020

Abstract
Displacement of the canisters with high-level radioactive waste (HLW) could be induced by creep and swelling of buffer material bentonite in the disposal pit of HLW geological repository. The displacement of the canisters could lead to the safety of HLW repository decrease. Several large scale experiments with bentonite and heater which was only regarded as components that would simulate the reference canister with respect to dimensions, weight and thermal emission were conducted in situ and laboratory respectively. The evolution of displacement of the heater, RH and stress in the bentonite indicate that the displacements of the heater are controlled by consolidation and volumetric/deviatoric creep of the bentonite under the heater induced by weight of heater, thermal expansion of heater and bentonite with heating, as well as swelling process of bentonite with the hydration. The canisters could move upward slightly in disposal pit during the early phase of HLW disposal. With the saturation of bentonite and stress redistribution in bentonite, the canisters could remain steady and minor fluctuation. After the bentonite in the disposal pit saturated fully, the canisters might move downward due to the weight of canisters. The thickness of buffer material around HLW canister and long-term stability of HLW canister should be considered in the design of the HLW repository.The parameters and evaluation of THM processes taking place in the compacted bentonite-buffer during the early phase of HLW disposal can provide a reliable database for numerical modeling and further investigations of EBS, and the design of HLW repository.
Effect of stress condition on the creep behaviour of Beishan granite
Authors: Chunping Wang , Jianfeng Liu , Jian Liu 
Published: November 2020

Abstract
In China, a deep granite formation in Beishan area is currently considered as a potential host rock for high-level radioactive waste repositories. Creep tests were conducted by two modes, namely single step loading mode on several samples and multi-step loading mode on single sample. According to the experiment results, the granite specimens failed almost at the same axial strain and volumetric strain at a given confining pressure, despite of the differences in deviatoric stress, stress ratio or strain ratio. The increase in stress condition (deviatoric stress, stress ratio, or strain ratio) could accelerate the cracking process and creep strain rate, and consequently resulted in a shorter time to failure. The stress effect on the cracking process was also confirmed by the acoustic emission (AE) energy rate. Significant increases in AE energy rate and the percentage of AE events with high energy could be observed with the increase of deviatoric stress. It was indicated from the results that, the stress ratio and strain ratio were more reasonable when discussing the influence of stress condition, perhaps because they were defined by considering both the applied stress level and the mechanical properties of rock material.
Evolution of mechanical parameters of deep sandstone and its constitutive model under the condition of different stress paths
Authors: Zhang Junwen , Fan Wenbing , Song Zhixiang , Wang Shanyong 
Published: November 2020

Abstract
Using a multifunctional true triaxial fluid–solid coupling system, the mechanical properties of deep sandstone and its constitutive model were studied under the simulated depths 1000, 1500, and 2000 m and different stress paths. In stress path 1, σz
is increased while unloading along the x-axis (σx
decreased). Path 2 involves an increase in σz
with two-sided unloading. Path 3 involves an increase in σz
with one-sided unloading σx
and σy
true triaxial loading. In addition, the evolution law of the Poisson’s ratio μ and deformation modulus E of the deep sandstone under different stress paths and simulated depths were studied. The experimental results show that the following: (1) The μ–σz
curves of the sandstone at different simulated depths and the same stress path are similar. As σz
increases, the Poisson’s ratio first decreases and then increases to a maximum value, and subsequently, it abruptly decreases. On the other hand, the initial value of the deformation modulus E increases with an increase in the simulated depth. (2) Under the same simulated depth and different stress paths, the deformation trends of the E–σz
curves of the deep sandstone are quite different. Under the stress paths 1 and 2, the deformation modulus E of the deep sandstone first increases and then sharply decreases as σz
increases. On the other hand, it first decreases and then increases under the condition of stress path 3. (3) A constitutive model for the deep sandstone is proposed herein. The research results can provide some important references for deep rock mechanics.
Investigation on the evolution of shale mineral composition under the fluid–solid coupling
Authors: Cao Han , Chen Yu , Zhu Haolong , Zhao Yu 
Published: November 2020

Abstract
To understand the mechanism of the fluid–shale interaction that influences the physical properties of shale during fluid–solid coupling, in this study, we investigated the changes in the mineral composition of the shale and ion concentration of the fracturing fluid during the fluid–solid coupling at the Niutitang formation in Northwest Hunan, China. The results show that the shale contains more brittle minerals but fewer clay minerals and the mineral composition of the shale in weakly alkaline fracturing fluid changes obviously. Brittle minerals decrease initially and then increase afterward under the fluid–solid coupling, which is related to the pH value and ion concentration of the fracturing fluid. These new findings can provide technical support for the prediction of the physical parameters of shale after the fluid–solid coupling and for the design of a hydraulic fracturing scheme.
Damage Evolution Characteristics of Non-fractured Regions during the Rock Fracture Process of Cracked Chevron Notched Brazilian Disc Specimens with Different Water Contents
Authors: Zhao Kui , Yang Daoxue , Zeng Peng , Song Lin , Wang Jinjian 
Published: November 2020

Abstract
To investigate the influence of water content on crack evolution during the fracture process of the red sandstone rock material, the damage and mechanical properties of cracked chevron notched Brazilian disc red sandstone specimens, with different water contents, were experimentally investigated. Using a P-wave velocity meter, the damage information of red sandstone specimens with different water contents, in the non-fractured region, during the pure mode I and II fracture processes, was quantitatively analyzed. The experimental results show that the damage amount of the non-fractured region, during the pure mode I and II fracture processes, increases linearly with an increase in the internal water content of the red sandstone specimens. Thus, the results from this study can provide certain theoretical basis for studying the evolution mechanism of microcracks in the fracture process of CCNBD specimens with the disparate water contents.
Method for calculating the shear strength of rock masses with different combined structural planes based on the 3D printing technology
Authors: Feng Wenkai , Yin Yibo , Dong Shan , Dai Hongchuan , Hu Rui 
Published: November 2020

Abstract
The mechanical behavior of rock masses with different combined structural planes is poorly understood because of the difficulties associated with the performance of rock observations and analyses from the surface, collection of samples during field investigations, specimen preparation, and laboratory tests. The combination of rock mass structural planes has a significant effect on the rock mass mechanical properties. The three-dimensional (3D) printing technology can conveniently create 3D entities with complex structures, thereby providing an unprecedented opportunity to break through this bottleneck. In this study, model samples of structural surface models with different combinations are printed using the 3D printing technology, and a cement slurry with 3:1 water–cement ratio is used as the structural body to produce rock masses with different combined structural planes. The method replicates well the morphological features of natural joints. Moreover, the shear properties and the failure characteristics are stable and consistent. Direct shear tests are also performed on the rock masses of different combined structural planes from the intersection line parallel and perpendicular to the structural planes to obtain the relevant mechanical parameters and rock mass failure modes. The results prove the feasibility of the 3D printing technology in the experimental study of rock mass mechanics and show that the strength and failure modes of rock masses with different combined structural planes are different. A calculation method for the shear strength of rock masses with different combined structural planes is proposed herein based on the experimental data and the Mohr–Coulomb theory, and the method’s feasibility is verified by several examples.
Physical Characteristics of the Compressibility of Saturated Cohesive Soil
Authors: Xian-bin LIAO , Xin-jie ZHAO 
Published: November 2020

Abstract
Water content and liquid limit are basic physical properties in saturated cohesive soils. Through the statistical analysis of compression index and these two physical properties, trends showed that compression index increases with increasing water content and liquid limit. Very loose and soft saturated cohesive soils with high water content have high compressibility; however, very stiff and hard saturated cohesive soils have low compressibility. Based on these tests, the correlations of compression index and physical properties were established for soils in China. These correlations provide a good approach to predict compression index based on physical properties and can be used for geotechnical parameter analysis.