bluuebunny/crossref_metadata_2025 huggingface dataset:
Slurry Infiltration Column Tests on Saturated Sand
Authors: Zhuang X Y , Zhang Z X , Huang X , Yin T
Published: November 2020

Slurry infiltration process contributes to the stability of tunnel face significantly during slurry shield tunneling construction. The support pressure cannot be transmitted efficiently to the face unless a compact filter cake forms. This paper aims at investigating the formation of filter cake in saturated sand by slurry infiltration column tests. A series of tests were performed under different filtration pressures using three concentrations of slurry in four types of saturated sand stratums. In order to obtain the characters of the infiltration process and filter cake, pore pressure evolution was measured. Three types of filter cakes were observed in the tests, including external filter cake, external filter cake plus internal filter cake and deep infiltration. External filter cake transmits support pressure efficiently, while the other two types of filter cakes cannot provide sufficiently support pressure for the tunnel face. Especially, deep infiltration behaves no capacity of retaining pressure and should be avoided in engineering practice.
Experimental study on the prediction model of the cumulative strain of the soil–rock mixture backfill under metro train load
Authors: Zhong Z L , Xu Y W , Hu X X , Liu X R , Du L B
Published: November 2020

An indoor dynamic triaxial test was performed on the soil–rock mixture (SRM) backfill in Chongqing to study the cumulative strain characteristics of the SRM under the cyclic dynamic loading of the metro train. The effects of different consolidation degrees U, rock block contents P, and effective consolidation confining pressures

σ
3
′

were then analyzed. Results showed that when

σ
3
′

and P are the same, the lower the U, the faster will be the increase in cumulative strain. When U and P were the same, the lower the

σ
3
′

, the greater will be the increase in cumulative strain and the higher will be the cumulative strain stable value of the stability curve. When U and

σ
3
′

were the same, the lower the P, the faster will be the increase in cumulative strain. An empirical model of the cumulative strain of the SRM considering the influence of U, P, and

σ
3
′

was established on the basis of the results of the dynamic triaxial tests. The accuracy of the prediction model was verified against the actual test results. This study provides a theoretical basis for the settlement and deformation evaluation of SRM backfill subgrades under metro train cyclic loading.
Large physical simulation and optimum parameter determination of stimulated reservoir volume (SRV) of a tight reservoir in E’nan
Authors: Xiao Yang , Zhang Liying , Li Zhigang , He Wen , Liu Zilong , Liu Shouyu
Published: November 2020

Studies have demonstrated that the real hydrofracturing in fractured reservoirs will not all form symmetrical fracturing in classical theory; however, they will rather form a complex fracture network. The changes in geostress because of the existence of natural fractures are an important reason for this phenomenon. At present, there are systematic theories and methods for examining the extension of hydraulic fractures after intersecting with natural fractures. Moreover, there is little or no quantitative research on specific parameters reported in the literature. However, the results are not applicable to actual field exploitation. Based on previous studies, this study proposes an improved model for hydraulic fractures after intersecting with natural fractures. Using the Honghe 92 well area in E’nan reservoir as the test case, the intersection chart of the block was drawn to analyze the extended model of hydraulic fracture. In this study, the true triaxial physical simulation experiment is reported and a comparison was made to demonstrate the correctness of the intersection chart. The fracturing simulation of Honghe 92 well area in E’nan reservoir was conducted to optimize the construction parameters and construction suggestions were put forward for the well area. The research results provide a theoretical basis and parameter guidance for the actual exploitation design of the oilfield. Furthermore, the results obtained will be helpful in improving the effect of SRV and increase oilfield productivity.
In situ Stress Measurement in Kilometer-Deep Mine and Its Relationship with Minefield Fault Structure
Authors: Zhongcheng QIN , Wang NIE , Litian SUN , Bin CAO , Lining LIU , Dengyue LI
Published: November 2020

In view of the complicated geological stress structure and fuzzy distribution characteristics of a kilometer-deep mine, the KX-81 hollow inclusion stress relief method was used to test in situ stress in Shuanghe Coal Mine at the level of –1100. On the basis of the field test data, the 3D grid diagram of the principal stress distribution in the deep mining area of Shuanghe Coal Mine was drawn, and the relationship between the in situ stress distribution characteristics and the fault structure in wellfield was studied. Results showed that 1) the directions of σ1 and σ3 at each measurement point were horizontal, and the other principal stress σ2 was vertical. 2) The maximum principal stress value was 1.26–1.48 times of the self-weight stress value, indicating that the horizontal tectonic stress plays a leading role in the in situ stress of the mine. 3) The horizontal and vertical stresses at a depth of about 1090 m were estimated according to the theory. A comparison revealed that the theoretical values were lower than the field measured values. The area was found to be dominated by horizontal tectonic forces belonging to the dynamic stress field. 4) The direction of σ1 at each measurement point was 114.70°–124.72°, with an average of 120°. The direction was NWW-SEE. In accordance with the distribution law of the fault structure in the wellfield, the consistency between the wellfield geological structure and the measured direction of the maximum principal stress was analyzed and verified. The research results provide technical basis for deep well roadway layout and stability control and improve the scientific nature and reliability of surrounding rock control of high stress roadway in deep wells under complex geological structures.
Hydraulic characterization of fault F31 at the Xinchang underground research laboratory site for geological disposal of high-level radioactive waste
Authors: Ji Ruili , Su Rui , Zhang Ming , Zhao Jingbo , Zhou Zhichao , Li Jiebiao
Published: November 2020

As part of the suitability evaluation of the underground research laboratory (URL) candidate sites, the hydrogeological investigation activity was conducted at the Xinchang site in Beishan area from 2016 to 2019. A previous study discovered that the rock masses at the Xinchang URL site, which is surrounded by north–east trend and east–west faults, have low permeability and shortage of water-bearing structures. This article aimed to describe the hydraulic properties of fault F31, which is located on the west boundary of the Xinchang URL site, and evaluate the fault hydraulic characterization methodology for site characterization of the URL and repository sites.

The surface hydrology monitoring activity at the Xinchang site showed that the water flow occurring through the gully where fault F31 is located after precipitation is the main recharge resource of groundwater. Accompanied with hydraulic monitoring during the drilling period of inclined boreholes (BSQ04–BSQ06, BS35, and BS36) crossing fault F31, the survey revealed that groundwater was stored in the weathered zones of the middle and north parts along fault 31. Single-hole and interference tests were performed later with the Heavy-Duty Double Packer system. The hydraulic conductivity (K) and storativity (S) were interpreted from the test data using analytical solutions. Diagnostic plots were also used in determining the reliability of results and identifying the flow regime. By considering the interpretation of borehole acoustic television logging as reference, the spatial morphological statistics of the structures are mainly parallel with the fault plane, wherein K is lower than 1 × 10−9 m/s depth to −250 m below the surface. Thus, the strike-dip parameter of the water resistance structures can be roughly confirmed. Six sections were selected for the evaluation of the water-conductive structures; these sections exhibited depths of more than −250 m below the surface and K values of equal to or more than 1 × 10−9 m/s. After the structures with a strike-dip similar to that in the water-resistant sections were removed, the remaining structural planes were used to build a flow model path during the hydraulic test. Compared with flow regime derived from the diagnostic plots, the structural planes fitting the real flow regime were identified as water-conductive structures.

The results showed the following: (1) K and S increased from the south to the north in the shallow zone along fault F31, where water-conductive structures were surrounded by water-resistant structures; (2) the section located −250 m below the surface of F31 was water resistant, and no-flow channel existed in the deformation zone along fault F31; and (3) the fault hydraulic characterization methodology combining hydraulic test, hydrological survey, and geophysical logging is suitable for the site characterization of URL and repository.
Deep borehole in situ stress measurements by hydraulic fracturing method in Xuefengshan area
Authors: Yang Yuehui , Sun Dongsheng , Meng Wen , Li A-wei , Wang Bin , Chen Qunce
Published: November 2020

The in situ stress state is a key parameter for shale gas exploration and geodynamics. To obtain the ultra-depth stress state of the Xuefengshan area, the hydraulic fracturing in situ stress method was employed in this study to determine the stress state at a depth range of 170–2021 m. The test results, which are the first reported for borehole depth greater than 2000 m in China, show that the magnitude of the in situ stress increases with the depth of the borehole. At a depth of 2021 m, the measured maximum and minimum horizontal principal stresses were 66.31 MPa and 43.33 MPa, respectively. The linear fitting relationships between the maximum and minimum horizontal principal stresses with the depth of the test borehole were SH = 0.033999D + 5.9996 and Sh = 0.020729D + 4.8058, respectively. In the borehole depth range of 170–800 m, the relationships of the three principal stresses were SH > Sh > SV, which is favorable for reverse faulting. At borehole depths of 1000–2021 m, the relationships changed to SH > SV > Sh, which implies that the deep stress regime of this area is strike-slip faulting.
Liquid-filling auxiliary device for liquid-filled rock joints and its application
Authors: Huang J , Song D Q , Liu X L , Zhao J , Wang E Z , Wang S J
Published: November 2020

Filling joints are relatively common in rock mass-based geotechnical engineering. Presently, many researchers have concentrated on the analysis of filling joints with a solid or solid–liquid mixture as filling materials, while only few scholars have been investigating the filling conditions of liquid. In this study, a liquid-filling auxiliary device was developed. The primary test flow on a typical sample and its application in dynamic response to filling liquid were introduced. Granite and plexiglass were selected as test samples to emulate the structure of liquid-filled jointed rock mass, and a split Hopkinson pressure bar was employed for dynamic testing of the structure. The test results reveal that during data collection, pressure response of the filling liquid suddenly rises, experiences multiple fluctuations, and then gradually stabilizes. With an increase in the initial thickness of the filling liquid, peak value of the liquid pressure change exhibited an increasing trend. Further, dynamic response characteristics of filling liquid in liquid-filled jointed rock mass were analyzed. The outcomes provide a reference for the experimental study on the interaction mechanism between the stress wave and jointed rock mass and liquid.
SPH-FEM coupling simulation of rock blast damage based on the determination and optimization of the RHT model parameters
Authors: Wang Z L , Huang Y P , Li S Y , Xiong F
Published: November 2020

To improve the accuracy of the results of rock blast damage simulation, a numerical scheme of ascertaining and optimizing the Riedel–Hiermaier–Thoma (RHT) model parameters was developed. First, the RHT model was adopted to simulate limestone penetration experiments, and the 31 RHT model parameters were initially determined based on the published data and theoretical derivation. Subsequently, sensitivity analyses were conducted using the “controlled variable method” to optimally determine the parameters. Finally, the RHT model parameters and coupled smoothed-particle hydrodynamics (SPH)-finite element method (FEM) were employed to simulate the limestone blast damage. The results demonstrate that the relative sensitive parameters obtained by taking the penetration depth of the projectile as the investigation index are ρ
0, ρ
s, p
e, G, f
ϕ, B, M, and F
G. The proposed “constant-amplitude adjustment method” can guarantee the integrity of the parameter ascertainment to a certain extent. The blast simulations indicate that the RHT model parameters determined based on the penetration experiment have certain applicability for the blast simulation and that the coupled SPH-FEM algorithm has a great advantage over FEM or SPH and can realistically show the whole process of rock blasting.
Karst development characteristics and collapse risk assessment along Shaoxing metro line 1
Authors: Huang Jiandong , Xue Fei , Wang Tianzuo , Zhao Tongyang , Wang Xiaoyu
Published: November 2020

Urban subway construction in karst areas can be seriously threatened by geological disasters, which impact the safety of subway construction and operation. Given the effects of geological conditions and human engineering activities, it is necessary to comprehensively analyze the influence of various factors and then evaluate the risk of karst collapse. With the section between Yanghe road station and Jianhu town station of Shaoxing metro line 1 as an example, crosshole seismic wave computed tomography (CT) was employed to prospect the geometric characteristics and spatial distribution of karst caves. Based on the survey results, ten influencing factors were selected as evaluation indexes for karst collapse susceptibility. Then, an assessment system was established, and each index was quantitatively rated through three grades. The analytical hierarchy process was used to determine the weight of these indexes, and the fuzzy transform principle and maximum membership degree principle were applied to quantitatively and comprehensively evaluate the collapse risk level in the study area. Results showed that karst cave development mainly occurred in the bedrock surface under 11 m. The caves were mostly 2–5 m high, and most of them were filled. Approximately 70% of the studied section had a moderate or high risk of karst collapse. As the subway passes through the karst area, appropriate measures should be implemented for the different risk sections to ensure the safety of construction and operation.
Risk assessment of Sichuan–Tibet Highway susceptible to debris flows at Suotong Basin, southeastern Tibet
Authors: Hu Kaiheng , Wang Xiaodong , Liu Jinfeng , Wang Zhang , Tang Jinbo , Zhong Wei
Published: November 2020

The planned Sichuan–Tibet Highway will pass through many debris flow-prone areas. Suotong catchment with a drainage area of 38.03 km2, a tributary of Parlung Zangbo River in the Bomi County of Tibet, has not experienced large-scale debris flows since 1991. Field survey and image interpretation show that glacial till in the catchment has volume of approximately 160 mm3 and is the primary source of loose materials for debris-flow reoccurrence. Once large glacial debris flows occur, they will cause harm to the highway. A comprehensive method including engineering geology, hydraulics, and computational mathematics is developed to quantitatively assess the debris-flow risk to the highway. The magnitude and peak discharge of glacial debris flows of a 100 year return period are calculated using empirical relationships in this region. The peak velocity at the outlet can reach 6.75 m/s, and the peak discharge is 6238 m3/s for such a return period. The Saint–Venant equations governing debris-flow movements are numerically solved by finite difference method. The simulated results are close to those by empirical methods. The hazard value at the alluvial fan is as high as 24.7 according to the numerical simulation. Two routing schemes (one goes through the tunnel and other pass the bridge) are compared with each other. Although the bridge scheme is cheaper than the tunnel scheme, the bridge’s section cannot fully discharge debris flows within the 100-year return period. Therefore, the tunnel scheme is safer and more strongly recommended than the bridge scheme.
The development of China national geohazard information system
Authors: Tong Bin , Li Yuan , Yang Xudong , Yin Chunrong , Qu Xueyan , Fang Hao , Han Bing , Zhang Yanling
Published: November 2020

Geohazards caused significant damages to people and economical properties. The prevention and mitigation of geohazards in China is facing great challenges. To solve the problem, establishing a national geohazard information system is important in accessing the distribution of geohazards, optimizing the efforts of prevention and mitigation, and improving the public awareness and risk reduction capabilities. After two decades’ of development, China national geohazard information system have upgraded from client-server (C/S) to browser-server (BS) architecture, and now to the micro-service based architecture, more than 320 thousands of geohazards which were mainly collected through field surveys and the routine field inspections have been saved in the database; through the information system, data acquisition and integration, classified storage, efficient data processing, real-time statistics and data services have been achieved and standardized by numerous technical specifications. In this paper, the current status of China national geohazard information system, including the development progress, database architecture, system functionality and data applications are introduced, and expected to provide references of establishing an efficient and comprehensive geohazard information system to improve the geohazard risk reduction capabilities for the countries or regions suffering from geohazards.
Surrounding rock deformation and supporting measures on small structure in non-pillar mining with gob-side entry retaining
Authors: Yang Jun , Qiao Bowen , Gao Yubing , Zhang Jiabin , Wei Xingjian , Fu Qiang
Published: November 2020

This study proposes a “large and small structure” concept of cutting cantilever based on the technical principle of gob-side entry retaining in a non-pillar. A mechanical structure model of the “small structure” concept of cutting cantilever is established by analyzing the stress transfer mechanism of the overlying strata in the gob-side entry. The calculation formula of the roof sinking is derived. The deformation law of the surrounding rock and the roof subsidence characteristics in the small structure are studied using a numerical analysis method. Moreover, the surface displacement curve is obtained by combination with the field measurement. The results show that the cutting structural plane generated by pre-splitting blasting effectively changes the stress transfer between the roof of the gob-side entry and the working face, which is beneficial to the rapid formation of the large structure with a self-stabilization bearing. The deformation of the surrounding rock of a “small structure” roadway is significantly controlled and combined with the rigid support system comprising constant-resistance and large-deformation anchor cables, gangue prevention structures, and a pier-beam unit. The gangues in the goaf interact with the large and small structures formed by the surrounding rock of the gob-side entry retaining, thereby forming a synergistic support structure for effectively increasing roadway stability.
Improvement and application of drilling and blasting techniques of anchor net (cable) spraying in rock roadways
Authors: Wen Zhongyi
Published: November 2020

To overcome the shortcomings of the prior art of bolting net (cable) spraying technology in rock tunnels of mine engineering, based on the principle of the combined action of surrounding rock and support, improvement methods and technical requirements are formulated. Through roadway section optimization and support parameter design and improvement of technology, smooth blasting, initial shotcreting, and construction quality of the anchor net (cable) as well as controlled release of the surrounding rock stress and local reinforcement are improved, so that the surrounding rock and support can be carried out together. Finally, through thin shotcreting, the coupling effects of the anchor net (cable), shotcreting layer, and surrounding rock can be realized, and the bearing performance can be brought into play to achieve the best support effect and ensure that the net section meets the requirements with minimal investment. The test shows that the improved technology can effectively solve problems of large area cracking and convergence deformation; the effect is positive and highly recognized by the industry, and it has been popularized and applied in this area and brother units. Large economic and social benefits have also been obtained.
Presplitting cutting slots technique of roof cutting entry retaining and its impact on strata behavior law of workface in Baoshan coal mine
Authors: Jun YANG , Cheng Yu , Xingen MA , Zhang Jiabin , Kuikui Chen , Rundong Zhao
Published: November 2020

Presplitting cutting slots advance working face is the key technology of non—pillar gob—side entry retaining formed by roof cutting and pressure release. And the rationality of parameters not only affects the formation of the structural surface of joint-cutting, but also has a significant impact on the retaining roadway. In order to enrich and improve the system of presplitting cutting slots technology, this paper takes the 6302 working face in Baoshan Coal Mine as the research object to discuss the effect of presplitting cutting slots technology on the strata behavior law of the working face. Then the presplitting cutting height, cutting angle and the distance between blasting holes are determined as the key parameters based on theoretical calculation. And the working face hydraulic support monitoring data are analyzed statistically. The research shows that: when the cutting height, cutting angle and the distance between blasting holes is 5m, 15 °and 500 mm respectively, the structural surface of joint-cutting can form through cumulative blasting. The influence range of pre-splitting roof joint-cutting technology on underground pressure is 30m. Furthermore, the average holding power of the powered support decreased by 3.8mpa, and the first weighting interval and periodic weighting length of the roof respectively increased by 4m and 5.5m in the affected area.
Research on the Mining Effect of Floor Strata in Deep Coal Seam Mining: A Case Study of #7 Coal Seam at Chazhuang Coal Mine
Authors: Zhang Wenquan , Wu Xintao , Shao Jianli , Ren Yanghui , Wang Zaiyong
Published: November 2020

Studying the mining effect of floor strata in deep coal seam mining is beneficial for evaluating and relieving the risk of water inrush from the floor. In addition, such research forms the basis for ensuring the support and stability of roadways and chambers in the lower part of the coal seam. By considering the mining of #7 coal seam in the 7600 deep mining area of the Chazhuang coal mine in Feicheng coalfield as the engineering background, this study analyzes the distribution law of mining abutment pressure and the range of failure depth affected by mining using elastic theory. In addition, the stress, strain, and failure states of the floor rock mass affected by mining are comprehensively simulated and studied using the FLAC3D finite difference software combined with field measurement results of rock movement in the lower roadway of the #7 coal seam. The mining effect of the floor is further compared and studied, providing a scientific reference basis for realizing the safe mining of coal in confined water in the deep lower group of the Feicheng coalfield.
Stress-induced brittle failure of surrounding rock mass and its engineering countermeasures in the Baihetan underground powerhouse
Authors: Chen J L , Li L Q , Wan X B , Fang D , Buyue Y G
Published: November 2020

Stress-induced brittle failures, such as spalling, slabbing, and rockburst, are common failure modes of underground caverns in high-stress zones. In the Baihetan Hydropower Station, the brittle failures, embodied as spalling, rock fracturing, and time-dependent deformation, bring new challenges to the excavation and support system design of underground caverns. Based on the New Austrian Tunneling Method, the specific design principles for the underground caverns of Baihetan Hydropower Station are proposed, the keys of which are preconditioning surrounding rock mass, reducing the excavation damage, supporting quickly in the proper sequence, and controlling loosen zones. These principles are applied during construction, and a series of excavation and support methods are developed for the key parts of the powerhouse, such as the roof arch, the rock wall of rock-bolted crane girder, the high side wall, and the partition wall of the generator pit. Data obtained from visual appearance, displacement measurement, and acoustic testing show that the proposed design principles are appropriate and that the developed excavation and support methods can control the range and depth of stress-induced failure of the surrounding rock mass.
Interaction between soft rocks and water and its application to engineering
Authors: Zeng Qinghe , Ming Weihua , Wang Xiangdong , Liu Zhen , Tan Xiangshao , Zhou Cuiyng
Published: November 2020

The interaction between soft rocks and water is a frontal project in the field of geotechnical engineering. This study constructs a time-effect model on the interaction between soft rocks and water by experimenting on the interaction and physical-mechanic of soft rocks, such as silty mudstone, argillaceous siltstone, and carbonaceous mudstone, which are sampled from a water supply project in South China. It also investigates the chemical mechanism of softening when soft rocks interact with water. Thus, the study not only builds a foundation for the theme of water–rock interaction but also provides effective guidance for the construction of priority projects.
Research and microscopic analysis of seepage characteristics of sandstone under low-frequency cyclic loading
Authors: Chunde Ma , Shan Long , Xibing Li , Zelin Liu , Weibin Xie
Published: November 2020

The change of rock permeability properties under cyclic load is of great significance to the safety of underground engineering. However, there are few studies on triaxial seepage tests under different cyclic loads, and most of them have not carried out microscopic mechanism analysis. Therefore, in this paper, the seepage test of intact sandstone under different cyclic loads was carried out under low confining pressure. The test used sine waves to simulate low-frequency seismic waves, highlighting the permeability of underground water-bearing engineering rock mass with vibration frequency and amplitude under low-frequency source disturbance Variations and test results show that in the sandstone triaxial stress-strain curve, from the compacted section, the elastic section to the expansion section, the permeability of the rock gradually increases, and the sensitivity to cyclic load also increases. At the same time, the damage threshold of the rock gradually decreases, and the rock will break even in the elastic section. Under low confining pressure, the loading amplitude has a greater impact on rock permeability than the loading frequency under low-frequency cyclic loading. The loading frequency and loading amplitude can be comprehensively characterized by the average loading rate. Then, using nuclear magnetic imaging technology to change the microstructure of the rock sample before and after the test, the analysis shows that the effect of different cyclic load parameters on the permeability of the rock sample is actually obtained through the effect of force on pores and cracks. For dense rocks, The increase in permeability caused by cracks is even greater.
Research on the optimization of underground logistic paths based on the positive and negative bidirectional demand model
Authors: Xinyu Liu , Ai-lian Zhou
Published: November 2020

With the rapid development of e-commerce, urban ground distribution pressure is increasing daily with an increasing number of vehicles transporting goods and worsening urban traffic congestion. As an important public resource for urban transportation, the metro can effectively relieve the pressure on passenger transportation as well as become an active component of urban logistics and distribution operations. In this study, we establish a metro distribution model of urban underground logistics based on the positive and negative bidirectional demand model by exploring a new mode of urban underground logistics combining metro resources and urban logistics to achieve the lowest total cost. In the proposed model, we consider the positive and negative bidirectional logistic demands of each station and solve it using a genetic algorithm. Finally, by analyzing a case study, this paper demonstrates the feasibility and validity of the proposed model and algorithm.
Fortified length of the tunnel under the S-type fault displacement pattern
Authors: Guangxin ZHOU , Qian SHENG , Zhen CUI , Yalina MA , Tianqiang WANG
Published: November 2020

Many tunnels have been built in central and western China; these tunnels are facing serious damages of active faults. At present, the fortified length of tunnels remains to be solved under fault dislocation. To overcome this issue, a numerical calculation model is established on the basis of previous research on the numerical calculation and model test of tunnels across active faults, with Xiang Lushan tunnel project as the research background of the paper. The S-type fault displacement pattern is proposed, which is based on the deflection curve of the support of the fixed beam at both ends under the uneven settlement. The influence of S-type and linear fault displacement patterns on tunnel lining is investigated using the finite difference method. Meanwhile, through the orthogonal test of fault factors at different levels, the influence rule of the multi-factor combination of faults on the fortified length of the tunnel under the S-type fault displacement pattern is obtained. Results reveal that the S-type fault displacement pattern, compared with the linear displacement pattern, can eliminate the stress singularity at the boundary of the fault zone. Therefore, the S-type fault displacement pattern is more reasonable and can be used as the selection of fault displacement pattern. In addition, the fortified length of the tunnel ranges from 1.1 L to 2.0 L (L is the fault width), which is the result of the orthogonal test. The most influential factor for the fortified length of the tunnel is the angle between the fault strike and the tunnel axis, whereas the least influential factor is the fault dip angle. This research provides a reference for the fortified range of the tunnel crossing fault with certain practical significance.
New planning and design concept for urban underground spaces based on geo-environmental factors
Authors: Xu Hui , Li XiaoZhao , Fan XiaoQiu
Published: November 2020

As the urbanization in China advances, urban underground spaces are vigorously developed through large-scale projects. However, the development of underground spaces often proceeds without prior scientific planning and design. City planners who fail to consider geo-environmental factors tend to design nonholistic blueprints that may cause serious problems. The development of an underground space is irreversible because underground resources are currently deemed highly valuable. Therefore, scientific planning must be conducted before the construction and launch of underground space projects. This study adopts a new concept of underground space planning and design and analyzes unfavorable geo-environmental factors, such as sand liquefaction and soft soil, which affect the development of underground spaces. The development mode of the underground space suitable for the geological environment in the study area is proposed. Based on the new concept of planning and design, this work considers a case study in Guangdong Province as a reference for the development mode, depth, and function of underground space in the study area. The findings of this study provide some new planning and design ideas for the development and utilization of underground spaces.
Analysis of deformation characteristics of a tunnel in layered soft rocks with considering the effect of bedding
Authors: Ren Weitao , Qiang Sihan , Wang Xuehai , Tian Yun , Li Zhe
Published: November 2020

The layered soft rock tunnel is affected by the combination of layering and geostress, and it is easy to cause large deformation disaster. Based on the Weiwu high-speed Minxian tunnel, the influence of bedding on the stress and deformation characteristics of sandstone and carbon slate is studied in this paper. The calculation results show that the influence of bedding on the deformation of sandstone and carbonaceous slate is significant. If the influence of bedding is not considered in the process of tunnel deformation prediction, the deformation of surrounding rock will be seriously underestimated. The influence of bedding on the deformation distribution of surrounding rock is related to the strength of bedrock. For sandstone, the strength of bedrock is high, and the deformation and failure of surrounding rock is mainly caused by shear failure of layer, and its deformation distribution and magnitude It is obviously affected by the layered production. When the angle between the bedding and the maximum principal stress direction of the ground stress is 45°, the deformation amount reaches the maximum value. For the layered carbonaceous slate, due to the low strength of the bedrock, the surrounding rock has obvious crushing damage zone after the tunnel excavation, and the layered occurrence has little influence on the deformation value and distribution of the surrounding rock. The maximum deformation orientation of the surrounding rock is basically perpendicular to the direction of the maximum principal stress of the geostress.
Model experiment study on the stability mechanisms of box culvert excavation faces under the effect of pipe roof in a shallow bury
Authors: Xie X Y , Jiang C Z , Zhou B , Dai Q , Zhang Z , Liu F Z
Published: November 2020

The pipe roof box culvert construction method is widely used in short-distance crossing projects. The shallow buried tunnel can reduce the wiring length, thus saving on the project’s construction costs. However, if not handled properly, roof collapse may occur in the tunnel. In this study, we created a model experiment design based on the Tianlin Road pipe roof box culvert project and conducted an experiment involving a pipe roof box culvert excavation surface stability model under different bury depths and pipe roof stiffness levels as well as a support plate moving forward or backward. This was done to explore the process of the excavation face instability and the development mechanism of ground deformation. The excavation face support plate was moved during the experiment to simulate the failure process of the excavation face limit equilibrium state. The DIC binocular camera and the fiber Bragg grating fiber were used to monitor the surface deformation and pipe roof deformation, respectively. The experiment results reveal the environmental influence law of the supper shallow buried pipe roof box culvert construction method and the failure shape of the excavation surface. The results further indicate that the development of the surface deformation of the under-excavation gradually changes from “straight” to “parabolic” with the change of the stiffness of the pipe roof. Furthermore, without the pipe roof, both the deformation value and the ground deformation under the over-excavation do not exceed 63.4% and 20.6%, respectively. The maximum vertical deformation of the over-excavation pipe roof is located at about 1 H of the excavation surface, and the maximum deformation of the under-excavation occurs at a distance near 2 H. The results of the model experiment can provide guidance in the application of the pipe roof box culvert construction method under supper shallow buried conditions.
Study on upper limit solution and its application on bearing capacity of rock slope foundation
Authors: Li Shulin , Liu Yinchi , Tang Chao , Cao Yun , Zhang Jianlin , Peng Fuhua
Published: November 2020

The determination and analysis of the bearing capacity of a slope foundation has become an important research topic in foundation design theory. To explore the ultimate bearing capacity of the rock foundation adjacent to a slope on the basis of the shear failure mode of a rock foundation on a semi-infinite plane, the failure mode of the rock foundation near the slope was established by analyzing the failure mechanism of the Bell solution. The upper limit theorem of limit analysis was used to build a velocity field allowable for maneuvering. Using this method, the ultimate bearing capacity of the Sandaozhuang open-pit mine was analyzed and calculated. The results show that the foundation load of the mine is less than the allowable bearing capacity; hence, the building on the slope meets the requirements of foundation bearing capacity. At the same time, this paper uses this method and existing research methods to compare and analyze this project with others, proving the rationality and feasibility of the proposed method. This paper further explores factors affecting the ultimate bearing capacity, such as the horizontal setback distance of the footing from the edge of the slope and the dip angle. It is concluded that the ultimate bearing capacity increases with increases in the distance to the slope and decreases in slope angle. The study also shows that the calculations developed and proposed in this paper for the bearing capacity of the rock foundation adjacent to the slope are reasonable and feasible, can be applied to the calculations of the bearing capacity of rock foundations near the slope, and have guiding significance for the project.
Calculation Method for Unstable Rock Stability based on Dominant Fissure Model
Authors: Zhou Y T , Shi S W , Tang H M , Wang L F
Published: November 2020

In accordance with in-situ exploration and years of experience in unstable rock-related design, this paper states that the Mohr-Coulomb model is insufficient for the selection of the shear strength parameters of the dominant fissure of unstable rocks. Therefore, a JRC-JCS model of dominant fissure for three types of unstable rocks was established, which is more applicable to construction practice. Based on this model, calculation methods were obtained for the three types of unstable rocks, and the stability coefficient expressions of the unstable rocks were determined. The stability of five typical unstable rocks in Wanzhou District, Chongqing Municipality, China, namely, W12, W22, W59, W4, and W16, was calculated by these methods. As indicated by the calculation results, the unstable sliding rock W12, unstable toppling rock W22, and unstable falling rock W4 are stable, while the unstable toppling rock W59 and unstable falling rock W16 remain unstable and thus need reinforcing. These calculation results are relatively in line with the actual situation, according to a verification by in-situ monitoring from 2003 to 2013. This further verifies the practicality and applicability of the above calculation methods, which are based on the dominant fissure model. These methods also offer a theoretical basis for the amendment of the local standard, namely, Chongqing’s design specification for prevention and control projects of geological hazards (DB50/5029-2004), in terms of calculation methods for unstable rock stability.
Study on the deformation mechanism of abutment slope and its influence on the dam during the impoundment of high arch dam
Authors: Wang X W , Zhuang W Y , Liu Y R , Xue L J , Cheng L , Yang Q
Published: November 2020

The deformation of abutment slope during impoundment poses great challenges to the working behavior and long-term safety of the arch dam. According to the monitoring data of impoundment and slope, slope deformation, valley width change, and arch dam chord length change are systematically analyzed and studied. It is pointed out that the deformation of the dam body and foundation is an irreversible plastic deformation and is evidently correlated with impoundment. Based on the unsaturated effective stress principle of fractured rock mass and the action mode of the reservoir basin pressure, the deformation mechanism of abutment slope has been discussed. The large-scale 3D nonlinear finite element model is established based on numerical analysis, and the deformation mechanism during impoundment and the effect of the effective stress change on the displacement and stress of the dam body are analyzed. The results indicate that effective stress can elucidate the valley contraction to some extent and that the contribution of the reservoir basin pressure is small. Slope deformation is beneficial to the dam displacement to some extent. Moreover, it has a negligible influence on the dam surface stress. However, the junction of the dam and foundation needs to be given special attention.
GIS-based Analysis of Distribution and Development Characteristics of Landslide Hazards in the Bailong River Basin
Authors: Jiarui MAO , Tiefeng LI
Published: November 2020

The Bailong River Basin is one of the most landslide prone areas in China. Based on landslide interpretations from field investigations and high-precision remote sensing images, the influencing factors, distribution rules, and development characteristics of landslides in this region are examined using the powerful spatial analysis capability of the ArcGIS platform. This study identifies the following major influencing factors and provides corresponding conclusions. (1) Fault and tectonic activities: landslides in the study area are distributed mainly in the vicinity of the large and secondary fault zones (< 10 km) and in areas with high peak acceleration and seismic intensity (with a peak motion acceleration of 0.3 g and seismic intensity of a VIII-degree area). (2) Hydrological conditions: the closer to the river (an area of < 200 m), the higher the likelihood of a landslide to occur. Landslide density is highest in areas with substantial short-term rainfall (maximum rainfall amount within 30 min shows the highest correlation with landslides). (3) Topographic parameters of slopes: landslides are distributed mostly on sunny slopes (facing south, southwest, and southeast), gentle slopes (with an incline of approximately 15°–30°), and high mountain areas (with an elevation of approximately 1000–2000 m). (4) Vegetation: areas with low FC coverage (approximately 10%–45%) are prone to landslides, which are distributed mainly in grasslands and cultivated lands. (5) Human engineering activities: densely populated areas (urban areas) and both sides of roads (approximately 0–200 m from a road) are prone to landslides. Overall, landslides are sudden, periodic, synchronous, and occur in groups. The research results have certain reference value for hazard prevention and mitigation in the Bailong River Basin area.
A novel index to evaluate CO2-induced wellbore cement degradation in CO2 rich environment
Authors: Zhang L W , Miao X X , Wang Y , Cheng X W , Ellett K , Gan M G , Fu X J , Liu S N , Li X C
Published: November 2020

A new index named CT-derived carbonation index is proposed to evaluate CO2-induced cement degradation in CO2-rich corrosive environment. This index is obtained by conducting CT scanning of cement samples before and after exposure to CO2, calculating grayscale difference and applying an algorithm to correlate grayscale with CaCO3 content. To demonstrate how to calculate the carbonation index, a CO2-cement interaction experiment along with X-ray computed micro-tomography characterization of a cement sample before and after exposure to CO2 was carried out to investigate the degree of cement carbonation. CO2 was dissolved in 1 wt% NaCl solution under a CO2 partial pressure of 17 MPa and a temperature of 63 °C. The carbonate shell in the cement sample was segmented from the grayscale difference images and the average penetration depth of the carbonate shell was obtained. The carbonation index was then calculated as the ratio of the average penetration depth of the carbonate shell to the radius of the sample, divided by the reaction time. In this study, the carbonation index of the cement sample exposed to CO2 for 14 days was 0.01 day−1. Based on the results in this study and other studies, a carbonation index of 0.05 day−1 or above corresponds to heavy degradation of cement by CO2.
Anti-floatation design test and simulation study of large LNG underground storage tanks
Authors: Li K W , ZHOU B , Xie X Y , Ma X F , Jin G L
Published: November 2020

With the changes in China’s energy demand, the proportion of liquefied natural gas (LNG) is expected to account for 10% of the country’s total energy resources by 2020; thus, the demand for large storage tanks has become urgent. However, all LNG storage tanks in China are located aboveground, with no precedent set for fully- or semi-underground storage tank implementation. Therefore, the present study analyzes the displacement and pore water pressure characteristics of underground LNG storage tanks under anti-floatation conditions based on the construction of a 250,000 kL underground storage tank that is 91 m in diameter and 42 m in depth. Centrifuge tests were conducted to explore the development laws of displacement and pore water pressure of the bottom plate under different load conditions for fully- and semi-underground tanks. The displacement response of the tank under the flotage condition clearly exhibited three-stage characteristics, that is, the safe, dangerous, and failure stages. The development laws of each stage were then summarized, analyzed, and explained by numerical and analytical calculations to provide a theoretical basis for storage tank design and anti-floatation monitoring.