bluuebunny/crossref_metadata_2025_split huggingface dataset:
The effects of gas pressure and adsorption in coal permeability under uniaxial strain conditions
Authors: Zhu J , Zhang B , Tang J , Shao T S , Lin L 
Published: November 2020

Abstract
Coal permeability evolution related to gas pressure is important to coal mining and coalbed methane exploitation. To apply the exponential model of coal permeability, we simplified the stress of coal reservoirs to the uniaxial strain condition. To investigate the permeability of coal samples changed in gas pressure under strain-controlled conditions, we measured the strain and permeability of coal samples collected from 12-1# coal seam in Hongyang No. 3 Mine in Shenyang, China, during gas pressure reduction under strain-controlled and constant temperature conditions using the Gas seepage measurement system in State Key Laboratory of Coal Resources and Safe Mining of China University of Mining & Technology (Beijing). The permeability experiment was performed under uniaxial strain conditions using adsorptive gas (carbon dioxide) and non-adsorptive gas (helium). The experimental results show that with decrease in gas pressure, the permeability ratio, k/k
0, of coal samples with helium and carbon dioxide firstly changed slightly with gas pressure from 4.0 to 1.5 MPa and then increased sharply with a gas pressure of <1.5 MPa. Coal samples shrank with the reduction of gas pressure under the uniaxial strain condition. The gas pressure of 1.5 MPa can be considered as the turning point of the volumetric strain change. When gas pressure was <1.5 MPa, the volumetric strain of samples sharply changed because of carbon dioxide gas desorbed from coal when the outlet was open. As the gas pressure decreased, the radial stresses of coal samples with carbon dioxide were less than those of samples with helium. Therefore, coal matrix shrinkage because of gas desorption has an important influence on the radial stress of coal samples under the uniaxial strain condition.
Investigation of hydraulic fracturing mechanism by using a coupled continuous-discontinuous hydromechanical model
Authors: Zhao H J , Ma F S , Guo J 
Published: November 2020

AbstractFluid-induced fracture nucleation, propagation, and interaction are the essentials for a better understanding of the hydraulic fracturing process in unconventional reservoirs. In this study, a coupled continuous-discontinuous hydromechanical model was established to investigate the hydraulic fracturing propagation under varied conditions. The interactions between induced fractures and natural fractures are investigated and discussed by a series of hydraulic fracturing simulations. Also considered are the influences of bedding joints, in-situ stress ratios, and fluid injection rates on the patterns of hydraulic fractures and the stress field. It was found that hydraulic fracture propagation is controlled by both in-situ stress state and strength anisotropy of the reservoir rock. The simulations indicate that an increase in the fluid injection rate is favorable to the formation of a complex fracture network. More hydraulic fractures were developed when fracture fluids were injected into rock specimens with a faster pressurization rate than a quasi-static pressurization rate. However, higher fluid injection rates could result in higher breakdown pressures for fracture initiation and propagation. In addition, hydraulic fractures tend to extend along the direction of the maximum principal stress or approach this preferred path. Bedding joints are preferred locations and orientations for fracture initiation and propagation in laminated shale reservoirs.
Research on LiDAR technology in early identification of geo-hazards in alpine loess areas
Authors: Wang L C , Wang M , Hung X C , Feng Z 
Published: November 2020

Abstract
The early identification is a key topic in geo-hazards science in China. Methods including engineering geological analysis, optical RS, InSAR, field survey verification, have been used for early identification of geo-hazards. This paper presents the application of airborne LiDAR to data collection and landslide identification in alpine areas. High-resolution images and point clouds of several landslides were obtained. And the characteristics of landslides have been interpreted. The study of relationship between point clouds and vegetation removal model (VRM) showed that the density of point cloud had a great influence on VRM. The lusher the vegetation, the less point cloud could be collected, resulting in much less point cloud density and lower resolution of VRM. When the density of point cloud is greater than 15 points/m2, the hillshade map generated after vegetation removal was usable for landslide characteristics recognition. The boundaries, shape, zoning, and some micro-topography, such as cracks with a certain length and width, could be effectively identified. The hillshade map with different azimuth angles were able to visually display the micro-topography features from different orientations. The slope image and surface roughness image from airborne LiDAR provided quantitative topographic parameters for geo-hazards identification, boundaries delineation and volume assessment. In the end, this paper proposes a guidance of early identification of geo-hazards in alpine areas by using LiDAR Technology.
BIM-based Quantitative Assessment Method of Tunnel Collapse Risk in TBM Construction
Authors: Chengbin LI , Yadong XUE , Yongqiang FAN , Jiaxu WANG 
Published: November 2020

Abstract
Tunnel risk assessment plays an important role in tunnel design, construction and tunnel safety risk control. TBM method is more and more widely used because of its comprehensive advantages, especially in the diversion tunnel engineering. Because the geological conditions in the long tunnel are complex and changeable, TBM machines are extremely sensitive to the changing of geological conditions, various risks may occur during the TBM tunnel construction. But the risks are difficult to assess quantitatively. In this paper, an excavation model of diversion tunnel is established in ANSYS to analyze the deformation of surrounding rock, the instability probability of tunnel is obtained by Monte-Carlo method. Combined with BIM technology, the construction information model of TBM tunnel including personnel distribution, team cooperation, material transportation, structure layout and other engineering information is established. Based on combining surrounding rock information and TBM engineering information, the TBM tunnel is divided into several sections according to time and space by statistical method, the collapse risk of TBM tunnel during construction is quantitatively assessed by zoning to realize the visualization of risk class. The results can be used for TBM tunnel construction risk assessment, improving the efficiency of risk control.
Research on Critical Depth of Rock Burst in Coal Mines in China
Authors: Wen Jinglin , Li Husheng , Jiang Fuxing , Yu Zhengxing , Ma Haitao , Shu Couxian 
Published: November 2020

Abstract
With increasing coal mining depths in China, the number of mines experiencing rock burst is increasing. The conditions in which a mine can reach the critical impact-mining depth remain theoretically unknown, which hampers the determination of the depth at which rock burst prevention can begin in coal mines. Based on different mining boundary conditions of rock bursts occurring in coal mines, this study proposes the concepts and calculation methods of three critical depths of rock bursts in coal mining. The strength criterion for rock mass impact of medium–hard and hard coal is used to evaluate the failure strength and stress state of the coal rock mass under dynamic loading conditions. Then, the value of the dynamic stress coefficient of the coal rock mass is determined. The research team applied this method to numerous mines in China to test rock bursts under different types of working face conditions with a coincidence rate of 100%. Results verify the rationality of the calculation formula of the critical impact depth and the value of the dynamic stress coefficient. The findings of this research can provide a basis for evaluating rock bursts.
Study on the mechanism of crack formation and the behavior of crack propagation of directional tension blasting in deep and high stress coal mine
Authors: Xiaojie Yang , Di Yuan , Haojie Xue , Yubing Gao , Jindong Cao , Lin Hou 
Published: November 2020

Abstract
Roadway safety is related to the high productivity and efficiency of coal mining, roof cutting and pressure releasing technology is one of the effective measures for roadway stability control. Under deep mining conditions,the stress condition around the blasthole is complex, and the expansion of directional crack will be affected by high ground stress. In this paper, Based on the engineering background of the roof Cutting and Pressure Relief Technology of Non-pillar Automatic Roadway Formation in guotun coal mine, the crack propagation mechanism and propagation evolution of deep rock under directional tension blasting were investigated. Based on the stress model of blasthole under the deep condition, the mechanical conditions of crack propagation under the action of directional detonation wave and high surrounding rock binding force are obtained theoretically; The mechanical model of directional blasting under the condition of stress constraint is established by using LS-DYNA numerical calculation software, the evolution characteristics of effective stress and the law of crack growth are analyzed; Finally, through the drilling peep and other technical means, the field measurement of the presplitting effect is carried out, which verifies the previous research results and puts forward the appropriate roof presplitting scheme. The results show that when the deep roof strata of Guotun coal mine adopt four hole continuous blasting and per blasthole charge of 2800g, the roof strata can form a continuous seam, and the Roof presplitting effect is the best.
Effects of microwave irradiation on impact comminution and energy absorption of magnetite ore
Authors: Jiawang HAO , Qingwen LI , Lan QIAO , Naifu DENG 
Published: November 2020

Abstract
The severe mechanical wear and high-energy consumption in the comminution process of high hardness iron ore have always restricted the efficient and economic development of an enterprise. On the basis of the basic principle that microwave irradiation can induce rock damage, the magnetic ore specimens were subjected to microwave heating treatment with different heating paths and cooling paths; the uniaxial impact comminution test was conducted by the drop hammer impact equipment. This study analyzed the effect of the heating and cooling paths on the crack propagation process, dynamic mechanical strength, and energy consumption of magnetite ore. The results show that microwave irradiation causes obvious microwave-induced cracks in ore, and in the subsequent impact cracking process, the new cracks gradually penetrate the microwave-induced cracks and form the macroscopic fracture surface. With the increase of irradiation power and time, the ore dynamic strength decreased, and the absorption energy increased. Therefore, increasing the total output energy of microwave can effectively alleviate the mechanical wear and enhance the comminution effect of ores. Among the factors that affect the mechanical properties and absorption energy of ore, power has a higher priority than time. With the increase in the heat exchange rate between the ore and the external environment, the ore comminution becomes more intense, leading to the best comminution effect of ores. The research results have an important reference for the practical application of microwave irradiation technology in hard rock comminution.
Characteristics of stress and plastic zone of a deep shaft in a nonuniform stress field considering the bearing structure
Authors: Sun X M , Zhao C W , Zhang Y , Cui L , Wang J , Zhang S K , Shen Z H 
Published: November 2020

Abstract
The selection of support parameters for the shaft of a deep soft rock under a nonuniform stress field (NSF) is a technical challenge. In this study, the distribution characteristics of the maximum stress-bearing circle were investigated via a numerical simulation. Based on the characteristics of the shaft rock-bearing structure, the stress and plastic zone characteristics of deep shaft rock under NSF were investigated. The maximum stress-bearing circle expanded with depth and NSF coefficient under the no-support scheme, and the stress-bearing circle was circular when the NSF coefficient was 1. When the NSF coefficient was greater than 1, the stress-bearing circle began to show an elliptical nonuniform distribution characteristic along the long axis in the y-axis. As the NSF coefficient and depth further increased, the elliptical effect became more obvious. A constant resistance and large deformation (CRLD) cable was used to control the stability of the shaft under NSF. The stress-bearing circle and plastic zone under the CRLD cable-support scheme were smaller than those under the no-support scheme. Furthermore, the peak stress under the CRLD cable-support scheme was higher than that under the no-support scheme, which indicated that CRLD cable support could improve the bearing capability of the surrounding rock and reduce the plastic zone caused by the NSF coefficient. The findings of this study can provide reference for the supporting parameters for deep shafts.
Numerical Analysis of Anchor Bolt Pull-out Test by Cohesive Zone Model Combined with Finite Element Method
Authors: Li Erqiang , Feng Jili , Xie Hao , Zhang Hongchang 
Published: November 2020

Abstract
In this paper, to characterize the pull-out process of anchor in concrete, we combined the cohesive zone model and the finite element method. The embedding cohesive elements simulate the contact effect of the bolt interface. The results show that the numerical predictions are in good agreement with the experimental results. With the change of pull-out load, the shear stress of anchorage interface changes correspondingly until it is destroyed, which is consistent with the laboratory test. The strengths of the anchorage material and the concrete have a positive correlation with the bond strength of anchor bolt. The radial and lateral stresses acting along the bolt are similar. Therefore, in bolt anchorage, the bond strength increases as the radial (lateral) stresses increase.
New type of lightweight high-strength foamed concrete blocks
Authors: Zhou Bo , Zhao Yuhong , Li Zhe 
Published: November 2020

Abstract
Lightweight high-strength concrete materials have been paid increasing attention with the development of the civil engineering technology. This study tested the effects of the admixture ratio on the properties of lightweight high-strength foamed concrete (LWHSFC) samples in a laboratory. The results demonstrated that a type of foamed concrete with 1200 kg/m3 density and >15 MPa uniaxial compressive strength can be produced by chemical foaming and by adding three types of materials (i.e., silica fume, slag, and fly ash) to the cement–fine sand matrix at an optimized mix ratio. The laboratory tests also showed that the failure mechanism of the LWHSFC was similar to ordinary concrete (i.e., longitudinal splitting failure). The angle between the failure surface and the vertical load direction was 53°–76°, indicating the material’s brittleness. The decreasing order of the compressive strength of the LWHSFC with one type of mineral powder when tested 28 days after casting was: silica fume to slag to fly ash. Moreover, the decreasing order of the compressive strength of the LWHSFC with two types of mineral powder admixtures when tested 28 days after casting was silica fume + slag to silica fume + fly ash to slag + fly ash.
Influence of in-situ stress on rock fragmentation by TBM cutters and prediction of TBM performance for deep tunnels
Authors: Ma Hongsu , Yin Lijun , Gong Qiuming , Wang Ju , Chen Liang 
Published: November 2020

Abstract
In-situ stress is a significant factor influencing TBM tunneling for deep tunnels, especially for the construction of deep repository for radioactive waste disposal. Beishan area of Gansu Province is the first preferred area for high-level radioactive waste disposal repository in China, and the feasibility of using TBM technology in Beishan area is investigated in recent years. In this paper, six levels of in-situ stress related to different depths from ground to 500m at Beishan area were selected and the influence of in-situ stress on rock fragmentation was investigated by linear cutting test. The rock samples were collected from the Jijicao site in Beishan area, with uniaxial compressive strength of 105.6MPa. The test results show that: 1) there is a clear power function correlation between the penetration and the normal cutter force for each stressed condition, and the higher the confining stress, the smaller the gradient of the power function curve, which means slower increase of penetration rate under the same cutterhead thrust; 2) the required normal cutter force increases with the increase of overburden as the corresponding in-situ stress increases. Based on the laboratory testing, the Specific Rock Mass Boreability Index model was modified and further used in the prediction of TBM performance at different depths on Jijicao site. This paper helps better understanding of rock fragmentation mechanism in TBM tunneling in stressed ground, and also provides reference on parameter selection for TBM operation in deep tunnel tunnelling.
Numerical simulation on Time-dependent Behavior and Long-term Safety Analysis of Soft Rock Tunnel under Seepage Condition
Authors: Liu Shifan , Wang Wei , Gong Chuangen , Li Haifeng 
Published: November 2020

Abstract
This study investigates the time-dependent behavior of soft surrounding rocks of the Shanxi Panxiushan railroad tunnel. Based on the viscoelastic-plastic damage mechanics, the rheological problem, mechanical properties of degradation, and seepage problem of the soft rock tunnel are comprehensively considered. The time-dependent deformation and stress of the surrounding rock mass following excavation were simulated using the proposed model of finite-difference software FLAC3D. The stress distribution of the surrounding rock support and reinforcement after the excavation were obtained. The simulation results show that the rationality of the existing reinforcement scheme is verified and the final deformation stability time of the surrounding rock during the operational period is calculated. Furthermore, a novel damage-based long-term safety analysis method is proposed, providing theoretical guidance and technical support for the design and construction of soft rock tunnels. The factor of safety (FOS) of the surrounding rock during the excavation and operational period is analyzed using the proposed analysis method. These results could have reference value for the design and construction of similar soft rock tunnels.
Research on a visualized real-time monitoring system for the slurry chamber of a slurry shield
Authors: Li Dongli , Pu Xiaobo , Qi Baowei , Ma Lin 
Published: November 2020

Abstract
In this study, a visualized real-time monitoring system was established to monitor the working conditions of the slurry chamber and collect rotation situations of the cutter head, wear conditions of the disc cutters, image information of the excavated strata and flow characteristics of the slurry. The operating condition of the front-end equipment is shown on the upper computer, and the signal collected by the camera is transmitted to the video acquisition system in real-time. Hence, this paper presents solutions to the system with an emphasis on the system structure, hardware, and software design, and verification. The system verification was conducted through a field test in a project site, where the system could reliably monitor the slurry chamber.
Study on the construction mechanical response of the double-shield TBMs of a long diversion tunnel crossing a fault fracture zone
Authors: Xia Weiyang , Zhang Kangjian , Hong Runlin , Zhang Zhiqiang 
Published: November 2020

Abstract
The Bheri Babai Diversion Multipurpose Project (BBDMP) in Nepal is located in the southern foothills of the Himalayas. The tunnel of this project passes through the Siwalik rock stratum. In this paper, the mechanical numerical model of the double-shield tunnel boring machine (TBM) crossing the fault fracture zone is established based on the morphology of the developed joint in the Bheri fault zone of the BBDMP. By analyzing the influence of joint group on double-shield TBM tunneling, the variation rules of the surrounding rock displacement, plastic zone distribution, and internal force of TBM crossing the fault fracture zone are obtained. The results of the research demonstrate the following: (1) when the single-shield tunneling mode is used in the fault fracture zone, the surrounding rock displacement is larger than that in intact rock mass, and the dissymmetry of joint geometry leads to the dissymmetry of the displacement distribution. (2) The plastic zone of the surrounding rock is mainly distributed along the geometric plane of two joints. The maximum value appears in the area from the left arch waist to the left arch shoulder and from the right arch waist to the right foot of the wall. The joints at all the other sites reach the yield state, except for the area around the vault and inverted arch, with a range of about 0.3 times the tunnel diameter. (3) The existence of joint surface leads to the asymmetrical distribution of the internal force in the pipe segment. The minimum safety coefficient appears at the left shoulder and right foot of the wall.
Influencing factors of lining crack width in hydraulic tunnels under high internal water pressure
Authors: Cao Ruilang , Wang Yujie , Zheng Lifeng , Zhao Yufei 
Published: November 2020

Abstract
The crack width of reinforced concrete lining under complex working conditions is a key factor affecting the safety of high-pressure hydraulic tunnels. This research investigates the lining of a pumped storage power station under high internal water pressure of 8.0 MPa. Considering the constraint of reinforcement and the combined bearing of rock mass and lining, the effect of circumferential reinforcement ratio, reinforcement location, tunnel radius, and surrounding rock on crack width is analyzed. On this basis, the relationship between the random distribution of lining parameters and crack width is obtained by numerical calculation. The results show the importance of adjusting the reinforcement spacing and reinforcement ratio to achieve the optimal constraint on the lining crack width. When the parameters are randomly distributed, the cracks appear locally mutated, but still form a strip distribution, with no obvious change in the average crack width.
Three-Dimensional Mechanical Information Model and Its Application to Large Underground Water-Sealed Storage Caverns for Oil or Gas
Authors: ZOU Jing , Chen RuiJin 
Published: November 2020

Abstract
This work explores a three-dimensional (3D) mechanical information model for use in the design optimization of large underground water-sealed storage caverns. First, a 3D geological model is built on the basis of the exploration results obtained at the beginning of the exploration stage. Second, a 3D numerical calculation model is established with parameters integrated from various engineering data sources, especially from geophysical explorations and field tests. Finally, the results of the numerical calculation model are used to evaluate the stability and water seal effectiveness of the surrounding rocks. The subsequent analysis of two engineering cases shows the feasibility of the technical method for the design optimization of storage caverns. The method is expected to be improved in the practical construction process in the future.