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30 June 2024, Volume 38 Issue 3 Previous Issue    Next Issue

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Analysis of Seepage Stability and Dewatering Effect on the Suspended Impervious Curtain in the Deep Excavation for a Vertical Shaft in a Highly Permeable Stratum HE Wei, HAI Han, ZHAN Yuan, CHEN Xiaoxiang, GONG Jianwu, LI Yijiang 2024, 38 (3):  181-185.  Abstract ( 9 )   Save This paper presents a case history of a cut-and-cover deep excavation for a DN3500 power project in Xi’an where the pipe jacking initiation working shaft. Through theoretical analysis, the influence of the suspended impervious curtain on the seepage stability in the sandy soil and other highly permeable strata is evaluated. And then, the influence of different groundwater control options, such as, water collection and open drainage, dewatering of pipe well points in the pit and dewatering of tube wells outside, on the deformation of the soldier pile in the deep excavation and the soil outside the excavation area are studied. The lateral earth pressure of the soldier pile can improve the safety of the excavation, but compared with the dewatering inside the excavated area, the use of the dewatering outside the pit will significantly increase the settlement of the surface outside the well. Risk control measures related to “requiring dewatering” provide a basis for the pipe jacking project’s construction and a reference for the construction of related projects. Related Articles | Metrics

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Stability Analysis and Evaluation of a Landslide by Using Transfer Coefficient Method NIE Bingqi, JIA Xiangxin, MAO Yuchao, ZHANG Yi, SHAO Shan, LI Yunjie 2024, 38 (3):  369-372.  Abstract ( 125 )   Save This paper selects a typical landslide site and investigates the basic conditions of the landslide. The triggering mechanism of the landslide is analyzed qualitatively from four aspects: the landslide structure, the weak plane, the groundwater infiltration, and the weakening of the rock and soil mass. The traditional classical transfer coefficient method is then used to quantitatively evaluate the stability of the landslide under the natural, the rainstorm and the earthquake conditions. The body is unstable, the factor of safety under the earthquake conditions is 1.017, and therefore is marginally stable condition. The stability analysis results of the landslide are basically consistent with the deformation history and qualitative analysis results. The qualitative and quantitative evaluation results confirm each other, which validates the accuracy of the evaluation results and provides a strong basis for the landslide mitigation and prevention measures. Related Articles | Metrics

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Analysis of the Interactions Between the Deep Excavation of a Subway Station and Adjacent Buildings LIU Zhe 2024, 38 (3):  373-377.  Abstract ( 126 )   Save In order to study the influence of buildings on the deformation characteristics and mechanical behavior of the retaining structures during the excavation of the deep foundation pit of the adjacent subway station, and the interaction characteristics of the retaining structures, soil and the adjacent buildings during the excavation of the foundation site, this paper provides on  the background of the deep excavation project of Nanchang Metro Line 2 subway station passing through the adjacent high-rise buildings. The finite element analysis software MIDASGTSNX is used to establish a three-dimensional simulation model of the deep excavation construction of the subway station and the adjacent buildings. The horizontal displacement and stress characteristics of the underground diaphragm wall, the stress characteristics of the internal support, the surface settlement of the surrounding soil and the stress characteristics of the adjacent building structures under different construction conditions are simulated and analyzed. The results are compared with the simulations results without buildings. The mechanical behavior characteristics of the interaction between the deep excavation of the subway station and the adjacent building structures are obtained. The comparative study results can provide a reference for the design and construction of the deep foundation pit of the subway station. Related Articles | Metrics

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Foundation Settlement Analysis and Foundation Reinforcement with Micropiles LI Qingkai, XIANG Jihui, QIN Meng, ZHANG Xiaoyu 2024, 38 (3):  378-382.  Abstract ( 157 )   Save The characteristics of collapsible loess in northwest China often induce the phenomenon of the foundation subsidence after the completion of the projects. It is of the great practical significance to deal with such hazards on time. This paper presents a case history of the ground improvement work for an alumina factory reconstruction project. The causes of differential settlement of the sediment tank system were analyzed. The geotechnical properties of the site and the bearing capacity of the foundation soil were identified through the supplementary geotechnical engineering investigation. The design problems and defects existing in the foundation treatment of the original lime soil cushion were reviewed. The reliability of the foundation treatment strengthened by micropiles was demonstrated in accordance with the design principle of “settlement reduction pile”; In addition, according to the construction specifications and engineering experience, construction details and corresponding parameters in the construction process of micropile were provided. It showed that reinforcing of the existing foundation with micropile can effectively mitigate the differential settlement issues of sediment tank foundation. Related Articles | Metrics

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Case History of a Seepage Stoppage Method for a Deep Excavation Project HUANG Zhenbo 2024, 38 (3):  382-386.  Abstract ( 118 )   Save To protect the groundwater resources and prevent the impact of the dewatering inside the excavated area on the surrounding environment, most the deep excavation support projects need to setup the groundwater stop curtains, which are mainly in the form of cement mixed soil system, such as soil-cement mixed columns; jet grouting columns, etc. The groundwater curtain stopping leakage is the main hazardous source of deep excavation projects, which will have a great impact on the project and the surrounding environment. Combined with the leakage hazards of a deep excavation project, this paper focuses on the plugging method and the implementation effect adopted in the mitigation process of the excavation. Facts have proved that for the minor seepage of the groundwater stop curtain of the excavation system, the treatment method of “internal drainage and internal plugging” can be adopted; For more serious seepage, the treatment method of “external stopping and internal plugging” should be adopted, and the method of “external stopping” should be selected in accordance with the local conditions to highlight mitigation process. Related Articles | Metrics

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Study on Application Effect of Energy-Accumulating Hydraulic Blasting in Fractured Rock Mass of Long Tunnel with Thick Overburden REN Shifang, YU Tanqiu, ZHANG Huanyu, GUO Zhiwei 2024, 38 (3):  387-393.  Abstract ( 159 )   Save To solve blasting effect of a long tunnel with thick overburden in the fractured rock mass, the Bashkorgan No.2 tunnel of Xinjiang Urumqi-Yuli Highway PPP Project is presented as the research object. The energy-accumulating hydraulic blasting method which is based on the principles of the cumulative effect were used to overcome difficulties and challenges during the fractured rock mass tunneling. The blasting parameters and the production process of the energy-accumulating tube were determined. The effects of the dust reduction, the transverse section shaping, the surrounding rock disturbance, the cost reduction and benefit enhancement are studied by using the method of the field measurement. The results show that, compared with the smooth blasting method, the peak value of the dust concentration produced by the energy-accumulating hydraulic blasting method is about 11.23mg/m3, and the time of ventilation and dust removal is saved by 50%. As far as the Class III surrounding rock is concerned, both blasting methods are applicable. The advantages of the energy-accumulating hydraulic blasting method smooth effect are not obvious; For the Class IV surrounding rock (abundant joint fissure) and the Class IV surrounding rock (f80 fault), the maximum overbreak value of the energy-accumulating hydraulic blasting method is controlled at 7cm and 9cm, respectively. The overbreak and underbreak values are significantly improved. The use of the energy-accumulating hydraulic blasting method can effectively reduce the blasting vibration and the disturbance of surrounding rock. The maximum vibration speed is 0.78cm/s. The cost saving of the single tunnel can be 9.1216 million yuan. Related Articles | Metrics

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Comparative Analysis of the Effect of Fully Buried Rigid Frame Pile and Single Row Anti Slide Pile on Slope Reinforcement XU Xiang, LI Jiaqing, HUANG Jianbin, ZHONG Hua, XU Xutang 2024, 38 (3):  394-398.  Abstract ( 125 )   Save This paper presents a case history of the comparative study of a single row of anti-slide pile used in a practical slope reinforcement project is equivalent to a fully buried rigid frame piles by from the principle of the equal concrete consumption. The three-dimensional finite element model of the fully buried rigid frame piles and a single row of anti-slide pile for slope reinforcement is established by using the finite element analysis software ABAQUS. The factor of safety, horizontal displacement, internal force and displacement distribution of the two types of piles are obtained. From the quantitative point of view, the differences of the effect and stress between the rigid frame pile and the single row pile are compared intuitively to discuss the advantages of the rigid frame pile in slope reinforcement. Comparing with single row anti-slide pile, the results show that, the bending moment distribution of single row anti slide piles is a “bow” shape, while that fully embedded rigid frame piles is an “S” shape. Due to the connections of the continuous waler, the fully buried rigid frame pile bears less internal force. The displacement of the slope strengthened by the fully buried rigid frame pile is smaller, the factor of safety is larger, and the slope is therefore safer. Related Articles | Metrics

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Safety Control of a Subway Station Deep Excavation Construction HUANG Zhenke, CAO Ke, XIE Jun 2024, 38 (3):  399-403.  Abstract ( 122 )   Save This paper presents a case history of the safety control of a deep excavation of a subway station in the saturated gravel stratum. Based to the pre-reinforcement ideas for the entire process of the new structures, the rock and soil mass between the new structures and the existing structures, the existing structures involved in the adjacent construction and the targeted reinforcement measures are adopted to minimize the influence of the adjacent deep excavation construction on the surrounding environment: 1) The new subway foundation excavation supporting system adopts the “diaphragm wall + internal support” retaining structure system and the groundwater control measures of sealing the bottom with the Sleeve Valve Pipe Grouting Method; 2) The municipal viaduct pile foundation near the subway station is pre-extended, the grouting pipe is reserved around the pile cap and the jet grouting isolation pile is applied between the piles and the cut and cover foundation; 3) bored cast-in-place concrete piles are installed between the subway excavated area and the adjacent area. The results of deep excavation supporting system show that the method used, and the pre-reinforced measures are effective and achieve a good safety control effect. The project can provide a reference for the similar projects of the future deep excavation construction. Related Articles | Metrics

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Analysis on Key Construction Details of a Slope with the Inclined Drainage Hole  YU Jin, YANG Zhao, XIONG Qihuan, TONG Defu, ZHANG Ziping 2024, 38 (3):  404-408.  Abstract ( 346 )   Save The inclined drain hole is an economical and effective measure to drain the groundwater from slopes. However, the effect is often poor, and the phenomena of no groundwater flowing through, and fast siltation is very common. To further solve these issues, this paper analyzes and discusses the technical methods and principles in the design and construction of the inclined drainage holes in detail based on a rich waterside slope of an expressway. Otherwise, it also explained the design parameters, drainage hole construction requirements. Finally, the two batches of drainage holes were compared in terms of borehole parameters, spatial locations and actual drainage effect. The results show that the hole length and the spatial position of inclined drainage holes are key factors that influencing the drainage effect. Therefore, when designing the drilling parameters, the bore hole position should be arranged in the low elevation position such as the slope toe in combination with the geological investigation data, and the drilling should be extended below the groundwater level or into the aquifer. Related Articles | Metrics

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Treatment Measures and Deformation Analysis on Some High Sensitivity Formation Deep Excavation in Xichang ZHANG Ning, MENG Baohua, DENG Yu 2024, 38 (3):  409-414.  Abstract ( 95 )   Save A deep excavation project was in the highly sensitive soil layer area in Xichang, which is about 12m deep. Excessive lateral deformations in the supporting system were observed three meters after the excavation. Evaluations are performed on the adjacent environments and deformations, poor geological conditions, precipitations and the space effect of the deep excavation are the potential main factors of these serious deformations. Throughout the back analysis, the shear strength parameter of the soil mass after the excavation deformation hazard was only 1/3 of that presented in the geotechnical investigation report. According to the load test of the ground anchor, the standard value of axial pull-out force per meter within the bond length was about 28.27kN. A third-party expert panel discussion based on these results suggested that mitigation methods of “ground anchor with expanded angle jet grouting” and “corner supporting” be used to control the deformations. These measures mitigated deformation effectively and the safety and smooth construction of the project were ensured. Related Articles | Metrics

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Application of Rigid Inclusion Composite Foundation of High-Raised Buildings in Soft Soils HU Xuebo, WANG Zhengan 2024, 38 (3):  415-418.  Abstract ( 152 )   Save The rigid pile composite foundation is widely used in soft soils as the foundation of various buildings and highways. But in high-rise buildings, the load acting on the foundation is large, and when the local stratum is too weak, considering the complexity of the composite foundation interaction, the bearing capacity of composite foundation is usually having problems. This paper presents a case history of the application of rigid inclusion composite soil as the foundation for a high-raised building by using the relevant tests and the numerical analysis methods. The bearing capacity of the composite foundation under different soil layers and the soil load acting on the single pile and among piles are obtained. At the same time, considering that the construction of rigid inclusion in soft soil layer is usually have different quality problems, which requires a high level of experience of construction personnel and is difficult to deal with quality defects. It is not recommended to use rigid inclusion composite foundation as the foundation for the high-raised buildings in the too weak soil strata. Related Articles | Metrics

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Design and Practice of the Entire Process Deformation Control of a Deep Excavation Under Complex Environments LIAO Zhijian, ZHU Huogen, TANG Junwu 2024, 38 (3):  419-426.  Abstract ( 149 )   Save Shanghai is a rapidly growing city with densely distributed buildings, numerous underground utilities, and crisscross viaducts and tunnels in urban areas. With the great demand of the underground engineering development, the construction difficulty of the deep excavation is getting more and more demanding. The design and construction of the deep excavation supporting system under complex environments has changed from the conventional strength control to the deformation control. Based on the deep excavation project of a hotel located in the center of Shanghai, this paper introduces the entire process deformation control idea of the deep excavation supporting system by integrating investigation, design monitoring and construction under complex environmental conditions. In the investigation phase, accurately obtain design parameters. In the design phase, investigate surrounding environment in detail and adopt targeted support design method. In the construction stage, use effective dewatering schemes and dredging measures, timely adjust the construction scheme according to the monitoring data and control the deformation of the supporting system in the entire process to protect the surrounding environment. The results of the implementation and the monitoring show that the design and the entire implementation process achieved the expected goal, which can provide a reference for the similar deep excavation supporting system deformation control. Related Articles | Metrics

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Deformation Characteristics of Laterally Loaded Piles in Deep Silty and Peaty Strata CHEN Xiaoxuan 2024, 38 (3):  427-431.  Abstract ( 100 )   Save In this paper, based on the conditions of the thick silt and peaty soil strata in a highway in Guangdong Province, the formation parameters were obtained through field tests, and a numerical model calibrated with the in-situ mechanical characteristics was established. The accuracy of the numerical analysis was verified by using the field measured data. At the same time, the distribution pattern of the displacement and the bending moment of the pile under the lateral loads is analyzed by using numerical modeling evaluation. The specific conclusions are as follows: 1. Under the condition of the thick silty and peaty soil formation, piles demonstrate large deformation under the lateral loads. 2. The near-surface soil layer is greatly affected by the laterally loaded pile, and the deformation effect of changing the thickness of the silty and peaty layer on the pile is not obvious. 3. The transmission of the pile displacement and the bending moment is mainly distributed in the silty and peaty layer, and the transmission range of the lateral displacement and the bending moment is only carried out in a small range on the pile side. Related Articles | Metrics

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Practice of Dewatering for a Riverside Cofferdam with High Permeability and Strong Recharge in Overseas GUO Shengqiang 2024, 38 (3):  432-436.  Abstract ( 117 )   Save With the extensive increasing involvement of domestic enterprises in the construction of “the Belt and Road Initiative” projects, domestic enterprises need to face new standards and new environments overseas. Consequently, they need to select appropriate engineering design, construction and management methods that are tailored to local conditions. Due to the high permeability of soil strata, abundant groundwater recharge, and difficulties in local groundwater slurry wall construction, an overseas riverside and seaside pit project encounters an extremely large challenge in dewatering inside the foundation pit. The success or failure of dewatering the excavated area affects the project schedule and cost. This article discusses a deep excavation dewatering project to introduce the problems encountered in the hydrogeological investigation, design, and construction process of the deep excavation dewatering engineering. The experiences gained from projects involving large groundwater volume, strong recharge, and intense corrosion groundwater challenges, and puts forth specific solutions. The objective is to serve as a reference for the construction of similar projects. Related Articles | Metrics

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Analysis of Deformation Characteristics of Double Diaphragm Walls under the Dewatering for a Deep Excavation Project YANG Jinjian 2024, 38 (3):  437-442.  Abstract ( 112 )   Save The rapid development of cities has made the surface construction space increasingly limited, and the requirements for the development and construction of underground space are gradually increasing. Dewatering is a necessary measure to ensure the smooth excavation of foundation pits, and it is also an important reason for the deformation of retaining structures. Based on the deep foundation pit of Suzhou River’s deep drainage and storage pipeline in Shanghai, the deformation characteristics of the dewatering in the “double water-resisting system” of double diaphragm walls were analyzed. The results showed that the diaphragm wall showed a “bulge-shaped” deformation towards the foundation pit with the excavation and dewatering, and local displacement peaks appeared within the depth range of the filter pipe in the well. The depth of maximum displacement was mostly concentrated in the range of 55-66m, and the maximum displacement was only 7.9mm. The vertical displacement of the surface at the edge of the pit showed a decreasing trend away from the foundation pit and stabilized at about 30 meters. The surface within 10 meters of the edge of the foundation pit was in a raised state. The peak displacement of the second diaphragm wall was within the depth range of 8-24m, and the deformation was less directly affected by the dewatering in the pit. Related Articles | Metrics

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Discussion on the Design Buoyancy Groundwater Level in Dingtailu Area of Jinan HE Zhaoyu, SONG Zhigang 2024, 38 (3):  443-448.  Abstract ( 199 )   Save With the continuous development of the urban underground spaces in our country, more and more buildings are constructed closer to the river, the site coefficient of permeability is large, the groundwater level is shallow, and the impact of river water level changes is significant. The buoyancy problem faced by the underground structure is increasingly prominent. Therefore, this paper presents a case history of design groundwater lever in Dingtailu area on the south bank of the Yellow River. Based on the analysis of natural factors such as groundwater conditions, climate characteristics, groundwater exploitation, water resources utilization and other factors in this area, the paper adopts Mann-Kendall trend analysis method to predict and analyze the dynamic changes of groundwater, proposes the scientific and reasonable buoyancy groundwater level recommendations. The buoyancy groundwater levels of the different zone within the site are analyzed. It provides a reference for the future construction planning, design and construction. Related Articles | Metrics

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Dynamic Response of a Shielded Tunnel Structure under Eccentric Blast Loads TANG Xiongjun, FENG Kun, XIAO Mingqing, ZHZANG Jingxuan 2024, 38 (3):  449-452.  Abstract ( 131 )   Save This paper presents a case history of Jintang Subsea Tunnel of Yongzhou Railway. The commercial software ANSYS/LS-DYNA is used to establish the finite element model by using the dynamic response of the lining structure under the eccentric explosion. The stress and displacement response of the segment lining, secondary lining and lane plate are also evaluated. The results show that the eccentric explosion of a 40kg TNT bomb mainly affects the safety of the local components, and the main countermeasures are to perform the local repair of the tunnel lining and the internal structure in time. The structure displacement caused by the eccentric explosion of a 40kg TNT bomb 14m away from the initiation section is small. The displacement of the lining nodes rapidly increases to the maximum value in a very short time, and then gradually decreases with a variation pattern close to the sinusoidal pulse, and the time of the peak displacement gradually moves backward with the increase of longitudinal distance. Related Articles | Metrics

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Advances in the Pile-Soil Interactions XIAO He, FENG Jianxue, MA Xiuru, ZHANG Xiaoyong, WANG Linjun, HUANG Baotao 2024, 38 (3):  453-458.  Abstract ( 143 )   Save The pile foundation is widely used in the engineering construction because of its high axial capacity and the small settlement. The mechanical properties of the pile-soil interface are the key factors affecting the axial capacity and the settlement deformation of the pile foundation. In engineering practice, the unsaturated soil is widely distributed, and the settlement prediction and the axial capacity prediction of the pile foundation are often far from the theory. The theoretical research on the interaction between the unsaturated soil and the pile is far behind the engineering practice requirements. This paper summarizes the research on the mechanical properties and failure mechanism of the pilesoil interface, the pattern of the pile-soil load transfer and the consolidation theory of the soil around the pile foundation, to provide a reference for the relevant research. Related Articles | Metrics

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Finite Element Simulation of the Sand Internal Erosion Considering Erosion-Mechanical Coupling WANG Zhi, WU Yang, ZHU Xianfa, Li Yingjie, ZHAO Sensen 2024, 38 (3):  459-464.  Abstract ( 153 )   Save Based on the basic internal erosion control equation and the soil mechanical constitutive model, a coupled internal erosion and mechanics model is proposed in this paper. The model can reflect the dynamic changes of the soil physical and mechanical properties such as the fine grain particle content, the porosity and the pore water pressure during the internal erosion. The model is simulated by finite element method to reveal the mechanism of internal erosion, describe the characteristics of internal erosion in the process of occurrence, development and stability, and explore the change law of physical and mechanical properties in the process of sand internal erosion. The erosion process can be divided into three stages: the initial erosion stage, the erosion process just began to develop slowly; the steady erosion stage and the erosion rapid development stage; In the erosion equilibrium stage, the sedimentation rate and the loss rate of fine grain particles gradually reached the same, and finally the erosion stopped. The internal erosion changes the physical and mechanical properties of the soil and redistributes the soil pressure, which leads to the surface settlement. The magnitude of settlement is positively correlated with the degree of erosion, and it has a great influence over the drain hole. Related Articles | Metrics

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Issues Frequently Encountered in the Investigation of Artificial Fill Soils MA Jian 2024, 38 (3):  465-468.  Abstract ( 124 )   Save With the increasing demand of building functions, there are more and more projects for installing elevators in existing buildings. This paper presents a case history of an existing building with elevator foundation investigation project. The engineering geological conditions of the project site, the composition, engineering characteristics and distribution of the artificial fill are analyzed and evaluated. Feasible foundation options are provided by means of the field exploration and existing building data collection. The geotechnical investigation around the existing buildings should focus on the investigation of the spatial distribution of backfill soil, and fully identify the composition, engineering characteristics and distribution of the backfill soils; For possible underground structures, it is necessary to focus on the collecting construction drawings of existing buildings and relevant surrounding buildings. This paper describes the issues that are frequently encountered in the investigation of the artificial fill foundation and the appropriate foundation options. The relevant methods can be used for a reference in similar projects in the future. Related Articles | Metrics

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Spatial Variability and Physical-Mechanical Indexes Regularity of Structural Clays in Zhanjiang ZENG Yue, HU Jin, GUAN Shenggong, LV Guisheng 2024, 38 (3):  469-472.  Abstract ( 96 )   Save Based on the geotechnical investigation results of a super large Zhanjiang steel factory site, and on the basis of the large amount of data obtained, this paper analyzes the horizontal and vertical variabilities of the structural clay of Zhanjiang Formation. Two typical geomorphic units are selected and analyzed for the variation of the physical and mechanical indexes of the clay of Zhanjiang Formation. The results indicate that: (1) the top surface of the clay layer in Zhanjiang Formation is generally distributed in a wavy shape in space, with the irregular spatial distribution and significant differences. (2) From the top to the bottom, the number of standard penetration tests (SPT) increases with depth in Zhanjiang Formation clay, following a linear variation pattern. (3) The particle size distribution and material source of Zhanjiang Formation clay with different embedment depths and plane positions are relatively stable, with the high liquid limits and the high plasticity. There are significant differences in other physical and mechanical indicators, but there is a linear variation pattern with the depth. These investigations provide a basis for the selection of geotechnical design parameters, and adds value to the design and construction projects. Related Articles | Metrics

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Numerical Study on the Influence of Lining Cracking on the Tunnel Lining YANG Feiyi, JIANG Kai, 2024, 38 (3):  473-478.  Abstract ( 112 )   Save This paper presents a case history of the second-west Xiamen subway project of the upper-span Subway Line No. 1. A three-dimensional numerical model of the lining structure with cracks is established by using the FLAC3D finite difference software and the displacement method in the structural mechanics. The development of the lining crack width in the tunnel deformation modes is simulated. The feasibility of the simulation method is verified by comparing with the measured data. At the same time, numerical experiments are designed to study the influence of the different crack depth and the circumferential length on the lining section. The results show that, compared with the measured results, the numerical results are larger, but their changing rules are consistent, which basically verifies the feasibility of the analytical model and the simulation method. The increase of the cracking depth and the circumferential length will lead to the increase of the cumulative variation of the cracking width in tensile strain zone, and lead to the increase of axial stress at the crack section and the axial stress of reinforcement, in which the effect of cracking depth is more significant. Related Articles | Metrics

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Effect of Alkali Liquid (NaOH) on the Aeolian Sand Strength and Its Microscopic Mechanism ZHANG Zhongzhong, ZHANG Ning, CHEN Jun, CHEN Taixu, CHANG Qiang 2024, 38 (3):  479-484.  Abstract ( 211 )   Save In response to the problem of the insufficient strength of the aeolian sand in engineering, an alkaline solution (NaOH) is used to treat the aeolian sand. To verify whether the strength of the aeolian sand has changed, a direct shear test is used to determine the appropriate alkali concentration. To study the micro mechanism of the alkali solution in strengthening the aeolian sand, the microstructure of the aeolian sand was observed by using the electron microscopy scanning. The micro images of the aeolian sand were processed by using the IPP (Image Pro Plus) image analysis software and the PCAS software to extract micro parameters. The results indicate that: (1) the addition of the alkaline solution can significantly improve the strength of the aeolian sand, but the additional addition of Ca2+ will not result in a more effective improvement in the soil strength; (2) An increase in the alkali concentration will enhance the shear strength of the soil, but there is an optimal content range. Excessive alkali concentration will not significantly improve the shear strength; (3) There is a certain relationship between the changes in the strength of the aeolian sand after the alkali solution reinforcement and the changes in the pore microstructure; (4) In terms of the microscopic mechanism, the NaOH interacts with the soil to produce the sheet-like polymers to fill soil pores and adhere to the surface of particles, enveloping soil particles, and improving the soil strength. Related Articles | Metrics

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Numerical Simulation of Deformation Control of Small Clearance Shielded Tunnel Excavation XIONG Hao, DONG Yabo, LUO Mingfu, JIN Xiaojun, TANG Xinke 2024, 38 (3):  485-489.  Abstract ( 134 )   Save The small clearance shielded tunnelling can cause a large change in the stress state in the soil mass and deformation of the ground, which can affect the safety of the tunnel structure and existing buildings when the deformation is excessive. However, the existing studies on the shielded tunnel reinforcement control measures for the small clearance shielded tunnel excavation are relatively insufficient, especially in the deformation control methods for the small clearance shielded tunnel excavation. In this paper, based on a smallclearance tunnel construction section in Xiong’an New Area, a numerical model of the deformation control measures for the small clearance shielded tunnel excavation is established, and the effects of different reinforcement schemes are discussed in depth. The results show that the grouting reinforcement is the most effective control measure for the small clearance overlapping shielded tunnel excavation, which can significantly reduce the surface settlement and ensure the stability and safety of the project. This study provides a strong theoretical support for the implementation of related projects. Related Articles | Metrics

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Pore Structure and Energy Evolution of Sandstone with Different Particle Sizes under Unilateral Wet and Dry Cycle MA Jiabao, BI Jing 2024, 38 (3):  490-495.  Abstract ( 119 )   Save To study the effect of the unilateral wet and dry cycle on the sandstone with different particle sizes, the red sandstone and the gray sandstone samples were used in the study. The nuclear magnetic resonance method was used to test the saturated sandstone under different wet-dry cycle times and the water-soaked sandstone samples at different time periods to study the pore structure characteristics and the permeability. Through the uniaxial compression tests, the mechanical properties and the energy evolution of the two sandstone samples are discussed. The results show that with the increase of the dry and wet cycles, the gray sandstone samples under different time of water immersion reaches saturation first than the red sandstone samples and have a better permeability. When the dry-wet cycle reaches 60 times, the results of the NMR imaging show that both sandstone samples have directional damage accumulation, and the damage accumulation degree of the gray sandstone samples is greater than that of the red sandstone samples. In the uniaxial compression tests, the uniaxial compressive strength and the total deterioration degree of the elastic modulus of the gray sandstone samples are larger than that of the red sandstone samples. Related Articles | Metrics

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Study on Dynamic Stability of a Colluvial Slope under Reservoir Pooling Water Level Varation and Earthquake TANG Hongbo, WANG Liwei, JIANG Wenpeng, LUO Li, WANG Xing, 2024, 38 (3):  496-502.  Abstract ( 125 )   Save The colluvial slopes are widely distributed in southwestern China, and the reservoir pooling water level variation and earthquakes are the main factors inducing the stability issues in colluvial slopes. Studying the stability of colluvial slopes under the effects of earthquakes and reservoir pooling water level fluctuations is of the great engineering significance. The stability evaluation of a typical bank slope of the Jinji Dadan River Bridge in Yunnan Province in presented in this paper. Based on the coupling theory of the stress and seepage, the stability of a colluvial slope under 10 different conditions of the reservoir pooling water level variations is evaluated in the paper. Based on the theory of equivalent linear analysis, the dynamic response of the water reservoir slopes under different seismic loads are studied by using the finite element and limit equilibrium M-P methods. The dynamic stability evaluation of slopes is performed from two aspects: the factor of safety and the permanent displacement, respectively. The results indicate that the factor of safety of the slope is greater than the critical value during the change of reservoir pooling water level, and the possibility of the slope instability is small; When subjected to a VIII degree earthquake, the dynamic factor of safety and the permanent displacement of the slope indicate a very high risk of instability. The investigation results can provide a technical support for the safety assessment of slopes similar to the bank deposits under the variations in reservoir pooling water level and seismic action. Related Articles | Metrics

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Improvement Method of Displacement Monitoring Device in the Static Load Test ZHANG Zhaobin, HAN Wenyong, ZHI Zhenghua, GU Zhichao, LIU Qingyu, WU Yuanping 2024, 38 (3):  503-506.  Abstract ( 116 )   Save The “fixed position”, the “high efficiency” and the “reduced error” are used as the research objectives of this paper. A new displacement monitoring method in the foundation inspection is proposed. By using the repeated observation method, the improved monitoring device can reduce the system error, improve the precision of the monitoring displacement data and improve the monitoring efficiency. Combined with the actual data analysis and the displacement of the beam adjustment method and double system vibration displacement method, can be relatively accurate correction based on top of the vertical displacement, is given priority to with the first set of monitoring system in the process of data collection. A second system is complementary, monitoring at the same time, mutual correction, improve the test accuracy, reduce the influence of the error of the results. The improved monitoring device can accurately and quickly monitored the variation characteristics of the settlement and the fluctuation of the soil surrounding the pile, evaluate and analyze the influence range of the soil changes surrounding the pile on the benchmark pile, and provide a reasonable erection distance for the benchmark beam. Related Articles | Metrics

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Experimental Study on the Dynamic Characteristics of a Coastal Silty Fine Sand with a Narrow Grain Size Distribution Using the Resonance Column System ZHANG Huayu, ZHOU Bin, ZHU Fangcai, ZHOU Junjie, WANG Jie, LIU Pengfei, ZHOU Zhengmao 2024, 38 (3):  507-511.  Abstract ( 121 )   Save The subgrade backfill material characteristics of a tourist highway surrounding the Hainan Island is presented as an engineering case history. The dynamic characteristics of a narrowly graded fine sand as the subgrade backfill material were studied in the paper. The gradation curve of the narrowly graded fine sand is obtained throughout the laboratory sieve analyses, with curvature coefficient of 1.0 and the non-uniformity coefficient of 2.0. The GDSRCA resonant column test system is used for the experimental study. Based on the Hardin Drnevich model, the characteristics of the dynamic shear modulus and the damping ratio variation with the dry density and the confining pressure under the same water content are analyzed. The dynamic shear modulus of the sand sample decreases with the increase of the dynamic shear strain and increases with the increase of the consolidation confining pressure and the dry density. When the dry density is the same, the dynamic shear modulus ratio of the sample increases with the increase of the confining pressure, and the damping ratio decreases. At the same confining pressure, the dynamic shear modulus ratio of the sample increases with the increase of the dry density, and the damping ratio increases.  ratio is reduced.  The dynamic shear modulus ratio and the damping ratio have a certain discreteness, and the discrete degree of damping ratio is higher than that of the dynamic shear modulus ratio. Related Articles | Metrics

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The Study of Crack Development and Shear Strength Deterioration of Red Clay Soil Under Dry and Wet Cycles YANG Huihong, ZHANG Zhiwei 2024, 38 (3):  512-515.  Abstract ( 182 )   Save The problem of the crack development and the shear strength deterioration of the red clay soil under the dry and wet cycles has gained widely attention. The crack development and the shear strength deterioration of the red clay soil with the change of the degree of compaction, water content and times of dry and wet cycles has been studied by the laboratory test in this paper. The results show that the moisture content of the red clay soil with the same degree of compaction has significant effect on the crack development. The grid cracks develop in the red clay soil with the low water content, while the long and wide strip cracks develop in the red clay soil with high water content. It is also found that the crack ratio and the crack length ratio raise with the times of dry and wet cycles. the higher the water content and the low density of the red clay, the greater the crack ratio and the crack length ratio and the higher the crack development degrees. The cohesion and the internal friction angel of the red clay soil with different water content decrease rapidly at the first and then gradually stabilize. The higher the degree of compaction of the red clay soil with same water content, the faster the decay ratio of the cohesion and the internal friction angel of the red clay soil. Moreover, the results also show that the decrement of the cohesion and the internal friction angel of the red clay soil with 4 times of the dry and wet cycles can be ignored and the average decay ratio of the cohesion and the internal friction angel with the different degree of compaction can obtained which indicate that dry and wet cycles has more significant effect on the cohesion than the internal friction angel. Related Articles | Metrics

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Two-Point Method of Liquid and Plastic Limit Water Content Joint Measurement WANG Juanhua, WANG Jun, YANG Fuqiang, LAN Hongzhu 2024, 38 (3):  516-519.  Abstract ( 415 )   Save The principle of liquid and plastic limits water content joint measurement method is that the depth measured by a cone penetration of a cohesive soil is linear with its water content in the double logarithmic coordinate system. In order to ensure the accuracy of these results or to judge abnormalities, it is needed to measure three different depths of one uniform cohesive soil samples in different water contents to calculate the liquid limit water content and the plastic limit water content. The author’s years’ experience in the liquid and the plastic limits analysis has shown that most types of soil have excellent linearity. Based on the mathematical theorem that two points determine the line, any two points can obtain the line. Further study of the two-point method, the ideal depth range was found. It is shown that the two-point method can ensure the quality better and the lower out-of-tolerance rate by the repeated test to three-point method. In this paper, ideal depth range of the two-point method is obtained by the theoretical deduction and is verified by experiments. Related Articles | Metrics

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Application of High-Density Electrical Method in the Detection of Fracture Zone in the North Extension Channel Project Area of Qiaocheng East Road ZHANG Yuxue 2024, 38 (3):  520-524.  Abstract ( 176 )   Save To solve the problem of the refined detection of the fracture zone under the complex geological conditions, a case history project of north extension of Qiaocheng East Road in Shenzhen City is presented in this paper. Throughout the analyzing the engineering geological conditions of the site, the high-resolution resistivity distribution image of the site is obtained by using the high-density electrical method. The position and trend of the fracture zone are inferred. The results show that there are four faults within the project limits that have a greater impact on the alignment. The tectonite in the fracture zone is mostly squeezed, with poor rock fracture development and integrity, poor rock structure, rock mineral alteration and cementation, which results in low strength of the tectonite, which is relatively soft rock and soft rock. The geophysical exploration indicates that there are three abnormal areas, all of which are characterized by the low resistivity anomalies. Their resistivity is significantly different from that of the fully weathered granite and the moderately weathered granite layers, which indicating relatively low resistivity. The interface between the geoelectric layers is well defined, and the resistivity of the abnormal area is roughly the same as that of the Quaternary soil layer, with a resistivity range of less than 30 Ω· m, while the resistivity range of the fully weathered granite is 30-50 Ω· m. The resistivity of the moderately weathered granite layer is greater than 50 Ω· m. The interpretation results of the high-density electrical method are consistent with the results revealed by the geological drilling, indicating that the high-density electrical method has the characteristics of high accuracy, high efficiency, and visualization. Related Articles | Metrics

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Case History of a Large Tonnage Pile Static Load Tests JIANG Wei 2024, 38 (3):  525-529.  Abstract ( 201 )   Save The static load test is still the most intuitive and reliable method for determining the axial capacity of foundation piles. With the development of the economy, science and technology, the experience of engineering designers is becoming increasingly rich, and the axial capacity of the pile foundation design is also gradually increasing. High axial capacity piles pose great challenges to the testing work, and more attention should be paid to the safety, accuracy, and efficiency of the large tonnage tests. Given that the requirements for the large tonnage static load testing equipment and testing risks are much higher than those for the small tonnage, there are many safety hazards and difficulties in the testing process. Therefore, engineering inspectors must comprehensively consider a prudent treatment plan. The key points of the experiment were introduced in detail from the aspects of the equipment installation selection, axial capacity and deformation verification, and safety issues during the experiment. Solutions were explored, and relevant selection calculation methods were provided. A comprehensive analysis was conducted on each step based on engineering examples. Results show that this test method is stable and reliable and can accumulate experience and provide a useful reference for the large tonnage static load tests. Related Articles | Metrics

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Study on Mechanical and Microscopic Properties of Solidified Soil-cement YIN Wenhao, ZHANG Jianbiao, WANG Xiaolong, CHEN Zhe 2024, 38 (3):  530-534.  Abstract ( 135 )   Save The use of curing additives and the cement to solidify the plain soil can make the full use of the abandoned soil of the project, reduce the cost of sand and gravel, reduce the use of cement and protect the ecological environment. The unconfined compressive strength test, splitting tensile strength test, and scanning electron microscope test were utilized to investigate the mechanical properties and the microscopic features of soilcement after the solidification. The mechanical test shows that the unconfined compressive strength and the splitting tensile strength of the solidified soil-cement can be enhanced by the extension of curing age, the increase of cement content and the addition of curing agent. The specimen containing 0.04% curing agent and 10% cement content exhibits greater strength compared to the specimen without curing agent but with 10% cement content and is nearly equivalent to the strength of the specimen without curing agent but with 12% cement content. The microscopic examination reveals that the introduction of a curing agent and an increase in cement content result in improved hydration reaction, elevated levels of hydration products, as well as reduced surface porosity and pore diameter of the sample at 28 days old. The results show that the road performance of solidified soil-cement is better than that of soil-cement, which meets the needs of road engineering. Related Articles | Metrics

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Field Vane Shear Strength Tests in Marsh Peat Soils DUAN Yongkai, ZHANG Ruiqi 2024, 38 (3):  535-538.  Abstract ( 127 )   Save To evaluate the stability of the high embankment over marsh peat soils, this paper presents a case history of a high fill airport runway project in peaty soils. The physical and mechanical property laboratory tests and in-situ vane shear test were performed. The engineering characteristics of peaty soils of tidal marsh phase in this region were analyzed. The similarities and differences of the shear strength index correction methods of the vane shear test between China and the United States were compared and evaluated, to demonstrate the variation of the vane shear strength along the depth and the heterogeneous of the peat soil deposition, as well as to linearly regress the relationship between the vane shear strength index and the shear strength index of the soil mass. Different shear strength indexes are used to evaluate the factor of safety of the peaty soil embankments. The principle of the high fill embankment stability evaluation is proposed, which is of reference significance for the construction of similar projects in the region. Related Articles | Metrics

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Experimental Study on the Dynamic Characteristics of Ningbo Saturated Clay under Different Drainage Conditions WANG Hongchao, HUANG Juehao, 2024, 38 (3):  539-543.  Abstract ( 106 )   Save The effect of drainage conditions on the accumulated axial strain and pore pressure of the soft clay under traffic load are investigated by using the GCTS true triaxial system. A series of cyclic triaxial tests are conducted on the undisturbed Ningbo soft clay under the undrained and partially-drained conditions with different cyclic stress ratio. The results show that accumulated axial strain of the clay increases with cycles during loading. Regardless of the drainage conditions, axial strain gradually grows with vibration times and tends to be stable under a particular cyclic stress ratio that is the critical cyclic stress ratio and equals 0.25~0.30. Under different drainage conditions, the pore pressure has different development patterns. With the increasing number of cycles, the pore pressure firstly increases and then decreases with a peak under the partially drainage condition, however, the pore pressure increases gradually with cycles and tends to be stable under undrained condition. Based on the test results, the empirical equation between accumulated axial strain and vibration times is obtained. No matter how drainage conditions, the variation of fitting parameter with the cyclic stress ratio match the linear functions. Related Articles | Metrics

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Shear Tests on Soft and Hard Materials in Rock Joints and Damage Characterization LONG Guangyu, WANG Hong, SHAO Peng 2024, 38 (3):  543-546.  Abstract ( 333 )   Save There are soft and hard materials in the rock joints composed of different infill stiffness in nature. The investigation into the shear properties of these rock joints has substantial relevance for the stability of the intertwined roughness. Shear tests are conducted to investigate the shear strength and failure characteristics of the soft and hard rock joints under various conditions of joint roughness coefficient and normal stresses where in the failure characteristics are quantified based on the area of the failure surface post-shearing of the joint surface. The results indicate that both the shear strength and the area of the shear failure surface escalate with an increase in joint roughness coefficient and normal stress. A larger difference in the hardness of the rock joint walls leads to a more pronounced difference in the degree of shear failure on either side with the softer joint surface exhibiting a larger failure surface area compared to the harder joint surface. A distinct correlation is observed between the shear test strength and the hardness of the joint walls with the shear strength of a joint wall being inferior to that of a joint wall with increased hardness on one side. This investigation elucidates the shear behavior of rock joints in intertwined roughness, which will help in the prevention of landslide hazards on this type of slopes. Related Articles | Metrics

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Experimental Study on the Bearing Capacity of Red Clay under Water Action CHEN Daosong, WU Liyan, CUI Wei 2024, 38 (3):  547-551.  Abstract ( 192 )   Save This paper presents the study results on the red clay in Chongzuo area. The results show that after the evaporation and the migration of water in the red clay soil samples, cracks appear on the surface of the soil and inside the soil mass. The cracks on the surface are in a circular and irregular shape, and the cracks on the crosssection are in a wide upper and a narrow lower shape. After encountering the water, the water seeps into the soil along the cracks, causing the soil on the crack surface to collapse and fill the cracks with the water, resulting in soil softening and reducing the bearing capacity, which affects the normal use of the building structures. By studying the changes in the bearing capacity of the red clay samples under the natural moisture content and the soaking for 10 hours using the lightweight dynamic penetration testing and the plate load tests, it was found that the estimated bearing capacity based on the number of dynamic penetration tests is basically consistent with the reduction in the bearing capacity determined by the plates load tests. If the foundation excavation encounters the water during the construction, a light dynamic penetration test can be used to determine its degree of softening and to guide the construction, which has good reference value for the practical engineering. Related Articles | Metrics

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Model Tests on Surface Deformation Pattern of Colluvial Landslide in Reservoir Area YU Miao 2024, 38 (3):  552-556.  Abstract ( 114 )   Save Affected by the fluctuation of reservoir pooling water level, the movement of a colluvial landslide in the Three Gorges reservoir area exhibits the non-uniform behavior and the distinct zoning characteristics. The conventional deformation monitoring means (such as total station, GPS, GNSS, etc.) can only achieve limited point data collection at important locations on the landslide mass and cannot detect deformation in unmonitored areas. Based on the physical model test, a three-dimensional laser scanning technology and the geographical and temporal weighted regression model (GTWR) are used to study the surface deformation pattern of the colluvial landslide at different pooling water storage levels. The results show that the laser point cloud of the slope surface deformation can present the characteristics and the overall deformation trend of the landslide intuitively and find the deformation phenomenon that is difficult to be identified by the naked eye or outside the monitored area, which can be an important supplement for point monitoring. The GTWR performs well in fitting the surface deformation of the landslide slope for considering the non-stationarity of space and time. Related Articles | Metrics

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Experimental Study on the Shear Characteristics of a Mechanical Bolt-Surrounding Rock Interface GAO Wenda, CHEN Hang, CHENG Yonghui, JIANG Jiwei, HE Yilin, LI Jingxi 2024, 38 (3):  557-561.  Abstract ( 166 )   Save The mechanical anchor is a type of commonly used ground anchor in the rock and soil anchoring engineering. It can obtain the required anchoring force in a short time mainly through the mutual extrusion friction between the metal anchor head and the rock and soil mass. The surface morphology of the metal anchor head is one of the important factors that affecting the interaction between the mechanical anchor and the rock and soil mass. In the practical applications, a form is often set up according to experience, and the pull-out test is used to verify whether the anchoring force meets the requirements. There is no targeted research on the shear performance of the rock-soil interface. To solve this issue, the spatial problem of the anchor-rock interaction is transformed into a plane problem. The direct shear test method is used to study the relationship between the shear stress and the shear displacement at the interface between the anchor head metal block with different surface morphology and the simulated surrounding rock, as well as the maximum shear stress under different normal stress, so as to obtain the shear strength of the anchor-rock interface. The results show that the cohesion of the pointed tooth shape is significantly larger than that of the smooth surface and the flat tooth shear contact surface. The internal friction angle of the shear contact surface also increases gradually in the order of smooth surface, flat tooth shape and pointed tooth shape, but the amplitude is not obvious. The internal friction angle is between 30° and 40°.  Related Articles | Metrics

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Study on Acoustic Emission of the Fractal Characteristics of the Stratified Shale Under Uniaxial Compression TIAN Geng, WANG Chaolin, ZHENG Kun, TANG Wei 2024, 38 (3):  562-566.  Abstract ( 155 )   Save It is of great significance to study the mechanical characteristics of the stratified shale from different angles and detect the fracture instability process of the stratified shale through the reasonable monitoring technology to ensure the production efficiency of the shale gas and the stability of drilling operations. In this paper, the shale samples with different bedding angles were tested by the uniaxial compression, and the fracture process was recorded by the acoustic emission monitoring method. The experimental results show that the uniaxial compressive strength of the stratified shale has strong anisotropy characteristics. With the increase of the bedding angle, the uniaxial compressive strength decreases first and then increases. The uniaxial failure types of the bedding shale at different angles are obviously different. The failure types are mainly tensile failure at 0° and 90°, and shear failure at 30° and 60°. The correlation dimension D of the acoustic emission time series based on the fractal theory can well characterize the development and evolution law of damage and the failure inside the stratified shale. The fluctuation of the correlation dimension D at a high value indicates that the microcracks are mainly formed inside the stratified shale, while the sharp decline of correlation dimension D indicates the occurrence of large-size cracks. That is, the sharp decline of the correlation dimension D can be used as the early warning information of the imminent instability failure of bedding shale. Related Articles | Metrics