bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of complex geological conditions on the in situ stress field of the SK Hydropower Station in Pakistan
Authors: Zhang Xinhui , Ai Kai , Yin Jianmin , Xu Chunmin 
Published: November 2020

Abstract
The Suki–Kinari hydropower station is situated in a landform with high mountains and deep valleys in northwest Pakistan. Affected by some geological conditions such as topography and faults, the in situ stress distribution of the project area is highly complex. To determine the in situ stress associated with this project, hydraulic fracturing in situ stress tests are conducted in four representative boreholes. Generally, the relation of the three principal stresses is σ
H
> σ
z
> σ
h
. However, the measured stress directions associated with the headrace tunnel and the powerhouse area are clearly different. The direction of the maximum horizontal principal stress of the headrace tunnel is NNE–NEE, whereas that of the underground powerhouse area is NNW–NWW. To identify the mechanism responsible for this difference, the present study simulates the stress field in the project area based on the three-dimensional finite element regression analysis method. Two theories are proposed on the basis of the numerical simulation results. On the one hand, the direction of the maximum horizontal principal stress in the rock mass above the valley elevation is controlled mainly by topography. On the other hand, the fault will disturb the stress field, causing noticeable changes in the stress direction and value of the fault-affected zone. By comparing the characteristics of the stress direction distribution at three elevations, the direction of maximum horizontal principal stress of the shallow strata is determined to be affected mainly by the topography and faults, and topography may be the most important factor. Moreover, with an increase in strata depth, the influence of the topography and faults on the stress direction decreases gradually. After reaching a particular strata depth, the direction of maximum horizontal principal stress tends to be the same as that of the regional tectonic stress, i.e., NNE.
Semi-automatic terrain slope unit division method based on human–computer interaction
Authors: Fang Hao , Tong Bin , Du Xianxiang , Li Yuan , Yang Xudong 
Published: November 2020

Abstract
A slope is the fundamental element of a landslide. Conducting a high-precision geohazard survey and a slope-based evaluation is important for geohazard prevention and mitigation and useful for governments in terms of improving the precision and the efficiency of geohazard management. The efficient and accurate division of slope units is the precondition of improving the accuracy and automation of a slope-based geohazard evaluation. This study introduces a semi-automatic slope unit division method that mainly includes automatic division using the geographic information system technology, followed by the revision and refinement of results by experienced professionals. Three major steps are involved in this method: 1) searching and eliminating the disturbing effect areas that could result from the disturbance of the micro-landform during the automatic division process; 2) determining the slope unit density by disclosing the relationship between the valley length and the threshold by fitting the trend with the power function; and 3) experienced professionals would perform the revision and refinement of the results generated from the previous steps to ensure that the slope unit division results meet the requirements of the slope-based evaluation. The field verification indicates that the slope units generated by the presented method are sufficient to support a slope-based evaluation on a scale of 1:10,000. The method can save considerable time and effort, which could, otherwise, be consumed during the conventional slope unit division process.
Formation setting and karst development characteristics of red beds in Wuhan, Hubei Province, China
Authors: Yin Xiansong , Luo Xiaojie , Zhang Sanding , Gao Jian 
Published: November 2020

Abstract
The red beds in Wuhan are mainly Cretaceous–Paleogene Donghu Group (K-Edn) strata, and the main lithologies are purplish red semi-cemented and weakly cemented mudstone, sandstone, and conglomerate. The formation setting of the red beds in Wuhan is analyzed from the regional tectonic movement and sedimentary environment. In addition, the karst development characteristics of red beds in Wuhan are studied on the basis of a large number of karst borehole data. The results show that the karst development of red beds in Wuhan is mainly controlled by the tectonic position and stratigraphic lithology. The soluble rock in the red beds of Wuhan is a calcareous cemented conglomerate, and the gravel component of conglomerate is mainly limestone. The karst phenomena in the red beds are mainly karst caves and karst fissures, while the surface karst phenomena, such as karst ditch and karst trough, are not prominent. The karstification is mainly weakly developed, and the degree of karstification positively correlates with that of the underlying karstification belt. When the lithology of the underlying formation of the red beds is carbonatite, the red bed karst is developed; by contrast, when the lithology of the underlying formation is insoluble clasolite, the red bed karst is not developed. The filling mode of the karst cave in the red beds may also be from top to bottom. The filling material mainly comes from the disintegration of the red beds themselves, and part of them comes from the overlying Quaternary strata.
Mixed Hardening Characteristics of the Anisotropic Coal under Cyclic Loading
Authors: Huang Bingxiang , Xing Yuekun , Jin Feng , Zhao Long 
Published: November 2020

AbstractPulse fracturing has been used to increase permeability and weaken the strength of the coal seam, making the coal fracture under cyclic loading. During the cyclic loading, the rock-like materials tend to present mixed hardening (mixed mode of isotropic and kinematic hardening) from initial yielding to failure (critical yielding). At present, understanding of the mixed hardening characteristics in anisotropic coal involving massive cleats remains challenging and crucial. In this paper, the cylinder specimens (diameter: 50 mm; length: 100 mm) of the coal were tested under cyclic uniaxial loading (loading rate: 900 N/s), and acoustic emission (AE) was employed to characterize the hardening process. The samples were drilled at the angle (α) of 0°, 45° and 90° with the coal surface cleat respectively. The upper-stress limit (Pmax) increases by 2 kN at each loading cycle, and the lower-stress limit (Pmin) was kept at 1 kN. Several findings were obtained based on the experimental results. (1) Uniaxial compression strength and the cyclic number increase with α, presenting isotropy. (2) The remarkable accumulation of AE energy is the feature of identifying plastic hardening. Both the isotropic and kinematic hardening processes are significant for the specimen with α dip angle (α) of 90°, validated by the dramatically increased isotropic and kinematic hardening indexes. However, the coal presents a slight isotropic and kinematic hardening, with a ranging from 0° to 45°. (3) The remarkably mixed hardening (α=90°) corresponding to a complex fragmentation of the coal, which is supposed to be caused by the continuous weakening of coal matrix (including the butt cleat). In contrast, at α of 0° and 45°, the mixed hardening characteristics are slight. Accordingly, the final fracture surfaces of coal tend to be relatively single, roughly along with the surface cleats. Thus, we can infer that the slightly mixed hardening is due to the weakening of surface cleats. Based on the mixed hardening characteristics of anisotropic coals, conducting pulse fracturing to apply cyclic loading perpendicular to the cleat surface is supposed to be beneficial for generating more complex fractures, to improve coal permeability.
Investigation of the fractal characteristics of cumulative damage to tunnel surrounding rock under blasting vibration
Authors: Xiaolong SONG , Wenxue GAO , Jinming JI , Mingban YE , Dengjie ZHANG 
Published: November 2020

Abstract
In this work, the cumulative damage effect of tunneling and blasting on the rock surrounding a tunnel is studied. Ground penetrating radar (GPR) is used to detect the damage of tunnel surrounding rock during blasting. and EEMD–HHT transform is used to process the obtained radar signals to obtain an intuitive representation of the damage. The relative relationship between fractal dimension and degree of damage is established to analyze the damage evolution of the tunnel surrounding rock quantitatively. The results show that the instantaneous amplitude parameter obtained by the EEMD–HHT transform could reflect the damage characteristics of the original signal and analyze the characteristics of damage evolution quantitatively. The effect of cyclic blasting causes a great direct disturbance to the area near the blast source and generates new fissures, which could aggravate the damage. The impact of blasting on areas located far from the blast source is mostly manifested as the expansion and penetration of existing cracks. The fractal dimension of the damage area is closely related to the damage evolution of the rock mass; the greater the change in fractal dimension, the more intense the damage expansion and evolution. This study quantitatively analyzes changes in the damage of tunnel surrounding rock through fractal dimensions, enriches the theoretical system of damage evolution in rock masses, and explores a new strategy to study blasting disturbances in tunnel surrounding rock.
Experimental study on seepage characteristics of coal under truly triaxial loading and unloading based on different minimum principal stress properties
Authors: Liu Zhiyuan , Wang Gang , Cheng Weimin , Qin Xiangjie , Han Dongyang 
Published: November 2020

Abstract
China’s coal-mining industry has developed from shallow mining to deep mining. Consequently, coal under unloading conditions is becoming increasingly complicated. In this study, seepage experiments are conducted for different minimum principal stress properties and levels of coal using a self-developed truly triaxial fluid–solid coupling seepage experimental system. In the experiment, the maximum and intermediate principal stresses correspond to the rigid stress and the minimum principal stress corresponds to the flexible stress. Experimental results show that the flexible minimum principal stress is conducive to coal deformation during axial compressive loading, whereas the rigid confining pressure inhibits coal deformation. For coal under stress unloading, the deformation and permeability of coal show a recovery change. In the initial stage of unloading, the permeability of coal shows a relatively large increase; this increase is evident in the unloading tests for rigid minimum principal stress. However, the level of the minimum principal stress is not related to the unloading effect. The findings of this study aid the prevention and control of dynamic disasters caused by coalbed gas in deep coal mining.
Quantitative study of the influence of organic-rich and natural fracture-rich regions on shale gas production
Authors: Wei S M , Jin Y , Xia Y , Zhang Y Q 
Published: November 2020

Abstract
Natural fractures and organic matter are randomly and unevenly distributed in shale gas reservoirs. The presence of organic-rich and natural fracture-rich regions causes the simulation results of the multi-continuum model to exhibit deviations from the real gas flow process. This paper presents a multi-continuum, discrete fracture model that captures the discontinuous nature of kerogen and natural fractures. The mathematical model describes the collision-weighted gas flow in organic matrix pores, inorganic matrix pores, and natural fractures by use of the unified flow model. The influence of organic matter and natural fractures on shale gas production is then quantitatively investigated. We find that Knudsen diffusion plays a more important role in shale gas flow than the viscous flow mechanism. Good communication between hydraulic fractures and natural fracture-rich regions can greatly improve gas production.
A new early-warning technology based on microseism and deep sliding force comprehensive monitoring for high-steep slope landslide disaster
Authors: Hui Cao , Zhigang TAO , Xiushan Qin , He Wang , Hu Ji 
Published: November 2020

Abstract
The accurate and efficient identification of potential slip surfaces of high-steep slopes, monitoring of deep sliding forces, and multi-source monitoring information fusion analysis and processing are the key technical problems of slope monitoring and early-warning. A new method for accurately and efficiently identifying the potential slip surfaces of high-steep slopes was proposed to solve these problems. A refined high-constant resistance energy-absorption anchor cable monitoring device was also developed, and multi-source monitoring and early-warning information fusion discrimination criteria were established. A set of new early-warning technology for open-pit slope landslide disasters based on the combination of microseism and deep sliding force monitoring was formed. This technology was used to successfully warn about landslide disasters twice or three days in advance in the demonstration mine, which effectively guided the safety management and emergency decision making. The successful development and application of this new early-warning technology provide a new idea for the safety monitoring and control technology of high-steep slopes in China.
Study on Comprehensive Treatment Technology of High-speed Railway Passing Through Giant Karst Tunnel
Authors: Wang Jun , Gu Xueqing , Liu Tongjiang , Yu Mingyang 
Published: November 2020

Abstract
In the mountainous areas of Southwest China, a karst landscape is well developed. There, exposed giant karst caves in the construction of high-speed railway tunnels cause great construction difficulties and safety risks for the tunnel crossing. In this paper, the study object is the project on giant karst cave of the Qianjiang–Changde railway high-mountain tunnel. After the karst cave was revealed, unmanned aerial vehicle detection, three-dimensional laser scanning, and blasting vibration monitoring were used to study the stability of the karst cave. It was found that the karst cave has a higher risk of falling rocks. On the basis of careful consideration of construction, operation safety, and economy, the “backfill cave ballast + grouting to reinforce on the upper part” scheme was determined for the treatment of the karst cave. During the process of disposal, the surface and layered settlement of backfill were monitored, in which it showed that the surface settlement control was reasonable, and the settlement mainly came from the bottom of the grouting layer, the top of non-grouting backfill, and original accumulation. To prevent the risk of falling rocks, we performed permanent safety protection of the wall and the roof for the karst cave and temporary safety protection of the mobile scaffold. Finally, the backfill treatment of the giant karst cave of high-mountain tunnel was smooth, the settlement after construction was controllable, and it met the design requirements.
Dynamics superposition mechanism analysis of the overlapped tunnel groups during the shield tunnel undercrossing
Authors: Zeng Qinghe , Ming Weihua , Luo Jin , Zhou Cuiying , Liu Zhen 
Published: November 2020

Abstract
Studies on superposition mechanism analysis of the old-new overlapped tunnel systems during the undercrossing process are still exploratory. Based on the viscoelastic-plastic theory of the underground structure and nonlinear evolution model of tunnel deformation and instability, the nonlinear dynamic evolution model, energy evolution model, and failure criterion of the three-dimensional (3D) tunnel system are established. The temporal and spatial superposition mechanism of the old-new overlapped tunnel system during the undercrossing process is quantitatively analyzed. The spatial expansibility and temporal continuity of the superposition mechanism are also verified. The intersecting line formula and its expansion formula of the cylinder and cone calculate the position, boundary, and volume of the superposition area. Based on the disturbed state concept theory, the disturbed function during the new shield tunnel undercrossing is theoretically derived. This study is significant for the quantitative analysis and control of the overlapped tunnel stability during the undercrossing process.
Study on the preloading effect of grouting on the tunnel lining
Authors: Xing Zhanqing , Li Jinlin , Fu Ping , Wu Xueqian , Huang Liwei 
Published: November 2020

Abstract
Grouting can effectively improve the stress state of the tunnel lining tensile areas under high external water pressure. To determine the relation between the permanent preloading effect and the post-grouting preloading effect on tunnel linings, several groups of grouting experiments were conducted using a grouting simulation test device developed in this research. Theoretical analysis was then performed on the basis of the experiments. Results showed that the preloading effect was severely affected by microcracks in the grouting area, although the effect gradually decreased after grouting. The ratio of the permanent effects against the post-grouting effects was shown to be a function of the drainage volume and deformation of the grouted rock mass.
Study on the Creep Characteristics of Gentle Dip Red Bed Mudstone of the Surrounding Rock Tunnel
Authors: Tang Yin , Yu Yu , Zheng Changqing , Lu Junfu 
Published: November 2020

Abstract
Red bed soft rock exhibits poor physical and mechanical properties and certain creep characteristics, which cause continuous deformation of tunnels and underground engineering structures during operation. The rock mass at the bottom of a railway tunnel in Sichuan Province is mudstone of the Penglaizhen Formation of the Upper Jurassic. It has a thin to medium-thick layered structure. Moreover, the rock formation is nearly horizontal. In this paper, the shear creep test and deep learning are employed to study the creep characteristics of gentle dip red bed mudstone.The results indicate that the red bed mudstone in the tunnel site exhibits medium-low creep characteristics. When the stress level is relatively low, the rate of the creep deformation gradually reduces with time, and when it reaches a certain time, the deformation no longer increases, and the final deformation tends to a stable value. Conversely, when the stress level is relatively high, although the rate of the creep deformation gradually reduces as the time increases, it remains unchanged when it reduces to a certain value. At the initial stage of creep, the deformation of each grade is evident; at the middle stage, the deformation is slow; and at the later stage, the deformation remains unchanged, that is, it enters the stable creep stage after a rapid decay in creep rate. The long-term strength of red bed mudstone in the tunnel site is low, which easily causes continuous deformation of the surrounding rock of tunnels under the action of high ground stress. According to the long-term deformation monitoring data at the bottom of the tunnel, combined with 20 groups of red bed mudstone creep parameter samples and the upper arch deformation data of the tunnel numerical model, the deep learning inverse analysis model of the creep parameter of rock mass is established based on the deep learning algorithm. Finally, we obtain the creep parameter of the red bed mudstone via inverse analysis. The research results provide a basis for engineering structure design and long-term deformation prediction of red bed mudstone strata in this area.
Comparative Analysis and Research on Electromagnetic Detection Technology of Tunnel Groundwater
Authors: Cao Guicai , Gao Guangyi , Nie Lichao 
Published: November 2020

Abstract
The electrical method is a sensitive technique for groundwater detection. As the tunnel develops in a deep direction, the groundwater problem becomes prominent. Thus, tunnel groundwater forecasting is particularly important. Through the advanced water exploration prediction practice in the complex geology of Gaoligongshan Tunnel, the water detection sensitivity of the complex frequency conductance (CFC) technology and the time-domain transient electromagnetic method (TEM) are compared. The advantages and disadvantages of the two methods are discussed, and the CFC technology is obtained. In accordance with the conditions of use of the time-domain transient electromagnetic method, the processing data of the CFC and the TEM method are compared with the actual excavation to reveal the groundwater development and establish a correlation.
Numerical Simulation Study of the Load Sharing of an Arched Micropile Group in the Tizicao High-Position Landslide, China
Authors: Wang Wenpei , Yin Yueping , Li Dehua , Meng Minghui , Luo Gang , Zhang Zhihua 
Published: November 2020

Abstract
This study presents a combined anti-sliding structural system of micropile groups, with an arched shape on the plane and cement paste between the micropiles, in the Tizicao high-position landslide study conducted in the Wenchuan seismic area, China. Improvements in the landslide’s stability as a result of the embedded micropile groups alone and in combination with long prestressed anchor cables are studied using FD-SRM and FOS contour analysis methods, respectively. The soil arching effect and the load sharing of the arched micropile group are analyzed using the numerical simulation method. Findings show that the arching effect is due to arc-shaped arrangements of the micropile groups. The design scheme of the embedded micropile groups improves the stability of this kind of thickly layered, high-position landslide. Moreover, its construction is convenient and the mechanism is clear, making it a good engineering reference for the treatment of similar landslides. The improvement in the landslide’s stability is even better than that achieved by the combination of micropile groups and long prestressed anchor cables. Furthermore, the arching effect of multiple rows of micropile groups is significant and can effectively block the movement of the sliding body. The load transfer involved in the micropile–soil interaction process is a new type of two-part load sharing pattern. The soil arching behind the micropile groups takes more than 80% of the total load. A tangential tension zone appeared along the top of the pile–group arc crown when the arch protruded upward, and a related structural performance design should be considered in the future.