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30 August 2022, Volume 36 Issue 4 Previous Issue    Next Issue

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Rotary Drilling Method in Bored Pile at an Ancient Yangtze Riverbeds in Southern Sichuan WANG Yingfei, MENG Baohua, DENG Yu, GUAN Qianyuan, JIANG Lu 2022, 36 (4):  501-504.  Abstract ( 227 )   Save This paper presents a case history of a deep foundation installation in Yibin City of southern Sichuan Province. The bored pile installation techniques, such as, rotary drilling of the bored concrete pile under wet conditions, slurry method and long casing method for the maintenance of the borehole stability are introduced in the paper. Then the optimum mud-water ratio was selected, bentonite slurry borehole stability technology was utilized to minimize the probability of borehole caving. The use of long casing effectively resolved defects in the bored pile installations, such as, connecting of adjacent bored piles, difficulties of slurry circulation return, and dirty concrete at the pile head so that the strength of the concrete at pile head lower than the required. The paper also proposes some bored pile installation suggestions such as, pile head treatment, difficulties encountered in the long casing withdrew. The improved pile head treatment methods, such as, temporary cofferdam and/or splitable short casing at bored pile head are proposed for the low pile head issues and improved the bored pile head installation quality.  Related Articles | Metrics

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Numerical Analysis on the Influence of Deep Excavation of an Underground Garage on the Adjacent Nanjing Metro Tunnel GUO Manyi 2022, 36 (4):  505-507.  Abstract ( 227 )   Save This paper presents a case history of a new underground garage deep foundation excavation project near an existing subway in Nanjing. The three-dimensional numerical simulation was used in the modelling, analyzing and predicting the deformation and internal force of the adjacent subway station and its adjacent tunnel structures induced by the entire construction process of the garage deep excavation by using the MIDAS-GTS commercial software. The safety of the existing structures/utilities as well as the structures that are under construction are evaluated based on the analytical results. As a results of the numerical analysis, the design and construction procedures could be adjusted and optimized. The deformation analysis results are also compared with the deformation criteria for the safe operation of the adjacent subway structures. It is concluded that the settlement and the horizontal displacement of stations and other subway elements meet the requirements of subway protection, and the structures are under the safe operation conditions. The tunnel deformation criteria should be based on the requirements of the national standard and Jiangsu provincial standard. The reinforcement depth of the diaphragm wall of the deep excavation needs to penetrate into the medium dense silty sand layer. The MJS construction method is recommended for the joint sealing of the diaphragm wall construction. Related Articles | Metrics

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Stability Evaluation and Mitigation Measures of Rockfall Hazards in Guilin LIU Yang 2022, 36 (4):  508-513.  Abstract ( 264 )   Save This paper presents a case history of a rockfall mitigation project in Guilin City. Based on the careful study of the natural geographical conditions of the treatment area, this paper utilizes the stereographic projection analysis method as the qualitative analysis on the stability of ten potential rockfall locations. At the same time, the limit equilibrium method is selected for the quantitative evaluation and analysis on the stability of three typical rockfall hazard locations under two preset working conditions. Based on the analytical results and comparative studies, the rockfall mitigation plan with a guideline of “eliminating hidden danger + comprehensive treatment” is implemented. The results show that: (1) the three typical potential rockfall locations in the study area are basically stable; (2) the factor of safety for the toppling failure mode for W1 and W2 is 0.93 ~ 0.96 under the simulated precipitation conditions, which is very easy to lose the stability; (3) the comprehensive treatment method of “static blasting and removal + passive protective net + ecological vegetation” is adopted in the study area, which has a good feasibility as well as a good result. The research conclusions in this paper are expected to provide some references for the relevant hazard prevention and mitigation projects. Related Articles | Metrics

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Application of a Combined and Weighted Gray-Trend Optimal Model in Prediction of Landslide Deformation LI Shigui, YAN Tao 2022, 36 (4):  514-517.  Abstract ( 178 )   Save The effective prediction of the landslide deformation plays a key role in the prevention and formulation safety measures of engineering projects. The landslide hazards are frequently encountered, and the triggering mechanism is extremely complex, therefore, the time of landslide occurrence is difficult to predict. In the view of the shortcomings of the current single deformation prediction model, this paper proposes a combined and weight gray-trend optimal model GM (2,1) for the landslide prediction based on the accumulate deformation data of Shuping Landslide from June 2004 to June 2013. The results show that the combination forecasting method has the highest prediction accuracy and adaptability and is closest to the actual monitoring results. Therefore, the combined prediction model is stable and reasonable, it can be used to predict the landslide deformation in the reservoir area and even other areas. Related Articles | Metrics

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Stability Analysis of An Expressway Landslide LI Fengmin 2022, 36 (4):  518-522.  Abstract ( 219 )   Save A significant amount of soft and hard interbedded rock slopes is existed in Guizhou Province. Affected by the difference in lithology, the difference in degrees of weathering of the soft and hard interbedded slopes is obvious. In addition to the complex structural geological conditions and other factors, weak structural planes are formed in the soft rock strata which resulting in a rockfall collapse or a landslide. A landslide occurred during the excavation and construction of the H ramp HK0 + 200 ～HK0 + 300 section of an expressway in Zunyi City, Guizhou Province. Throughout the geological mapping and exploration, it was found that one of the main causes of the landslide was the soft and hard interbedded slopes in marl and shale bedrocks. In the interbed, long-term rainfall infiltration causes the shale to soften and form a weak plane, which becomes the sliding surface of the landslide. After determining the shape and nature of the landslide and the scope of the landslide, the transfer coefficient method is used to establish a geological model, and the landslide stability safety factor and landslide thrust in the natural state and in the saturated state is calculated respectively, which provides a basis for landslide treatment. Related Articles | Metrics

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Stability Analysis of an Urban Roadway Cut Slope in Guizhou TANG Xu, ZHANG Tianyu, FANG Zhengfeng 2022, 36 (4):  523-527.  Abstract ( 187 )   Save The topographical conditions of Guizhou mountainous area are complicated, and it is inevitably affected by topography and geological conditions in the construction of urban roadways. As a result, cut slopes are becoming more and more common in urban roadways projects in Guizhou. The stability of cut slopes is the key to the effective control of roadway engineering hazards. Therefore, it is necessary to attach great importance to the investigation and evaluation of the stability of the cut slope in the construction of urban roadways. This paper takes an urban cut slope in Guizhou Province as the research object and carries out a detailed on-site survey of the cut slope. The method has been used to conduct the geophysical prospecting methods such as core-drilling sampling method, borehole television imaging method, and rock mass acoustic wave test, combined with theoretical analysis, numerical calculation and other studies analyzed the stability of the cutting slope, and the proposed corresponding treatment suggestions, in order to provide a certain reference for the urban road slope stability research and engineering application. Related Articles | Metrics

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Design and Construction of a Deep Excavations under Complex Urban Environment YU Dunmeng 2022, 36 (4):  528-532.  Abstract ( 192 )   Save Based on the project of Shanghai Arc de Triomphe, the basic theory and the key construction technology of the deep excavation is introduced. Combining the theoretical analysis and field monitoring, the key technologies of the deep excavation dewatering, bracing system and foundation excavation are presented respectively. The supporting system of the concrete bracing and the steel bracing is used to support the foundation excavations, to reasonably control the earth excavation construction, so as to support with excavation, the critical embedment depth of the soldier pile is determined from the horizontal displacement of the pile and ensure the stability and safety in the process of foundation excavation and construction. The vertical settlement and the horizontal displacement of soldier pile and soil are monitored, and the monitoring data are compared with the standard early warning value to ensure the safety of foundation construction. Through the systematic research, it provides references for the design and construction of similar deep foundation pit engineering. Related Articles | Metrics

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Ground Improvement Method Applied in the Integrated Zouma Lake Watershed Treatment Project YUAN Jiebin, GUO Pengjie, ZHANG Shutao, FU Hui 2022, 36 (4):  533-536.  Abstract ( 271 )   Save The integrated Zouma lake watershed treatment project is a pilot project of Ezhou Huahu airport project. The major work in this project is the ground improvement of soft cohesive soils and earthwork in the lake area. Large area of soft soils with an average thickness of about 7 to 8 meters and a maximum thickness up to 15 meters are deposited in the lake area. The post construction total settlement and differential settlement requirement criteria for the airport runway area are very strictive. Considering the construction cost and design requirements, the prefabricated vertical drains plus surcharging method was adopted as the ground improvement method. With the surcharge ratio between 1.35 and 1.45, the duration of surcharging was between six and ten months for achieving a degree of consolidation of 90% and a final rate of settlement less than 0.33 mm/day. The entire ground improvement duration was 33 months. Related Articles | Metrics

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Analytical Method and Application of Improved Multi-Row Micropiles in Shallow Landslide Mitigations NIU Yan, ZHANG Liangfa 2022, 36 (4):  537-540.  Abstract ( 283 )   Save As a small and light weight retention structure, the micropile has been widely used in the slope reinforcement engineering for its convenient in the construction, small disturbance to slope and large lateral stiffness. Due to the complex structure, of the multi-row anti slide micropiles, a unified analytical theory has not been formed, and its load carrying capacity is even more complicated. Based on the equivalent stiffness replacement method, the multi-row micropiles are equivalent to the single row micropiles. An improved evaluation process of the load carrying capacity of the multi-row micropiles is proposed in this paper. On the basis of ensuring the accuracy of the evaluation results, the proposed evaluation method greatly reduces the analytical procedures and associated complexity and has advantages of simple operation and the strong adaptability. Combined with the widely used practical steel pipe pile applications, the verification method of strengthening shallow landslide in alluvium soils with multi-rows of micropiles is also proposed in the paper, which provides a reference for the analysis and the application of micropiles in the shallow landslide mitigations. Related Articles | Metrics

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Triggering Mechanism and Stability Analysis of the Bizhong Landslide in Panzhou Area LIAO Dewu, CHEN Shouxi, , ZHENG Bing, ZHANG Junkai, DU Yansong, LAN Zhongxiao 2022, 36 (4):  541-546.  Abstract ( 206 )   Save This paper presents the case history of the Bizhong landslide in Panzhou area. The geological conditions and characteristics of the landslide are discussed, and the triggering mechanism and stability aspects of the landslide are analyzed. Based on the analysis of the landform and geomorphology, soil and rock characteristics, precipitation conditions and adverse human activities, the results show that the back side of the creeping body pushes the middle and front portion of the soil mass, forms the translation-compression failure mode; On the basis of qualitative evaluation, the factor of safety of the landslide is quantitatively evaluated. The results show that the landslide is basically stable under the natural condition and becomes unstable under the rainstorm condition. The precipitation is the main factor that influences the landslide, and rainfall is the main factor that triggering the landslide. Related Articles | Metrics

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Deformation Response Analysis of Deep Foundation Pit Steel Sheet Pile Enclosures Adjacent to Highways YE Kezhi 2022, 36 (4):  547-550.  Abstract ( 321 )   Save In order to provide guidance for the deep excavation and support construction for an underground comprehensive utility box culvert, a finite element three-dimensional numerical model was established to simulate the construction process of the deep excavation adjacent to a highway. In the establishment of the numerical model, the vehicle load on the adjacent road is simplified as a sinusoidal loading pattern, then the box culvert site is excavated in lifts, and the data for the excavation supporting structure and the deformation of the adjacent road surface are obtained. The results show that the maximum horizontal displacement of the supporting structure induced by the excavation of the proposed box culvert adjacent to the highway occurs after construction with a maximum value of 4.62mm. The lateral deformation meets the current code safety requirements. In addition, the deep excavation leads to the release of soil stress. The excavation induces a maximum upward displacement of 25.6 mm at the bottom of the excavation and the maximum observed settlement of the adjacent roadways is 25.2mm. This paper also discusses the effect of vehicle speed of the adjacent roadway and the relationship between steel sheet piles embedment depth on the deformation of the excavation supporting structures. The vehicle speed has little effect on the deformation of the excavation supporting structure. Whereas the steel sheet pile embedment depth has a greater impact on the deformation of the excavation supporting structure and the optimum embedment depth for the steel sheet pile is 12 m. Related Articles | Metrics

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Ground Deformation Induced by the Parallel Rectangular Tube Jacking CHEN Xuehua, ZHOU Lihong, WU Qixing, YE Zhongshuai, LIU Guodong, AO Xiang, WANG Xingxing 2022, 36 (4):  551-558.  Abstract ( 174 )   Save This paper presents a case history of twin parallel rectangular tubes jacking in Xingye Express Line Project. The ground deformation induced by the tube jacking was monitored and the monitored data were compared with the numerical analysis results. The conclusions are as follows: (1) the ground deformation can be effectively controlled by the soil improvement at the end of the launching pit and the micro undercutting of the machine head during the starting and jacking of pipe jacking to ensure the safety of the rectangular tube jacking; (2) During the normal jacking, the shape of the surface cross sectional settlement is consistent with the Peck curve, and the width of settlement trough is 2-3 times of the tube width; (3) The surface horizontal settlement caused by the single line tube jacking is V-shaped, and the surface horizontal settlement caused by the double line tube jacking is W-shaped. The width of the surface settlement groove is 3 times the width of the tube. The surface settlement caused by the construction of the front tube is about 2mm than that of rare pipe tube; (4) The numerical simulation shows that when the twin tubes were jacked to 65m and 60m respectively, the maximum surface settlement caused by the front pipe jacking is 13mm, and the maximum surface settlement caused by the rare tube is 10mm, and the surface within 5m in front of the machine head shows settlement deformation. Related Articles | Metrics

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Stability Analysis of a Large Diameter Shielded Tunnel Excavation in Karstic Cavity Rock Mass XU Chen, 2022, 36 (4):  559-563.  Abstract ( 201 )   Save This paper presents a case history of a larger diameter tunnel excavation of South extension of Heping Boulevard (Zhongshan Road to Zhang Zhidong Road) in Wuhan. The stress-strain characteristics of tunnel and its surrounding karstic cavity rock mass are analyzed by the finite element analysis software. The impact of the soil strata loss on the stability of the karstic rock cavity and the surround rock mass are evaluated, The results indicate that, when the size of the rock cavity is relatively large, the deformation of the tunnel is towards to the cavity and the stress in the tunnel structure is larger than that of in other locations. The rock cavity above the tunnel will induce a larger ground subsidence and even induce the sinkhole collapse on the ground surface. In the tunnel excavation, preventive measures should be applied to minimize the soil strata loss since the larger soil loss will induced the excessive ground subsidence. Related Articles | Metrics

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Strength Analysis of Grouting Sleeve and Internal Grouting Defect Using ABAQUS Software Yang Yizhou, ZHAO Jun, 2022, 36 (4):  564-567.  Abstract ( 271 )   Save The grouting induced defects are frequently encountered in prefabricated building projects. This paper presents the finite element analysis results on the grouting sleeve with a diameter of 40 mm for connecting the reinforcement bars. The finite element analysis software ABAQUS was used to establish the numerical grouting sleeve model with internal grouting defects. In the contact properties between the reinforcement and the grouting material, the bond slip parameters were modified to conduct unidirectional tensile simulation analysis. The analytical results show that the reduction coefficient of bond strength between the reinforcement and the grouting material is 0.84 with grouting defects inside the sleeve. The failure mode resulted from the numerical analysis is consistent with the test results. The ultimate bearing capacity is accurate, and the load-displacement curve demonstrates a good agreement with the test results. The stress concentration area of the grouting material model is basically the same as the failure area of the grouting material in the test. The stress distribution pattern is reasonable, which would provide a reference for similar engineering practice. Related Articles | Metrics

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Numerical Simulation of a Diaphragm Wall as the Deep Excavation Supporting Structure DU Zhenxi 2022, 36 (4):  568-570.  Abstract ( 209 )   Save With the development of high-rise buildings and the underground space domestically and abroad, the deep excavation engineering is developing towards the larger and deeper direction. At present, one of the many supporting (or retaining) structures of deep excavations is the underground diaphragm wall as the supporting structure, which has been widely used in engineering projects. The application of diaphragm wall solves the problems of “retaining soil” and “stopping water” in the deep excavation projects and plays an important role in ensuring the safety of the deep excavation engineering. Based on a project case history, this paper uses FLAC3D numerical analysis software to simulate and analyze the displacement and deformation of soil in the process of excavation and support of the underground diaphragm wall. The research has practical value and theoretical significance. Secondly, the ratio between the design value and the actual project monitoring value is evaluated by the same software, and then analyzed. The correctness of the model is established and verified, which has a special reference role and obvious significance for a better understanding of the interaction mechanism of the diaphragm wall. Related Articles | Metrics

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Rebound Deformation of a Deep Excavation in Soft Soils LU Shanjia, CHEN Xiangqiao, WANG Wei, WU Shaozhen 2022, 36 (4):  571-575.  Abstract ( 371 )   Save In deep excavation projects in the soft soil area, the deep foundation subsoil often demonstrates the rebound deformation. The bottom heaving deformation of the soil has a large effect on the stability of the excavated foundation soils. Based on some current analysis methods for the rebound deformation of the foundation soils, this paper combines two practical engineering case histories to estimate the rebound values at the excavated bottom. The estimated values are compared with the measured data in terms of the excavation footprint dimensions, depth, and soil properties of the deep excavations. Finally, it is concluded that the self-weight stress offset method is closer to the measured data, which can accurately estimate the rebound deformation value at the bottom of the excavated soils in soft soil area. The results provide some reference value for the future deep excavation supporting design and foundation deformation prediction. Related Articles | Metrics

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Water Jetting in the New TBM Combined Rock Breaking Feasibility Study QIU Haoquan, 2022, 36 (4):  576-581.  Abstract ( 286 )   Save The tunnel boring machine (TBM) has been developed for more than 100 years. With the changes in the excavation environment, the tunneling efficiency of TBM, which uses traditional tools as the main form of rock breaking, has become increasingly difficult to meet the requirements. Due to increasingly high construction requirements, a new combined rock breaking method is proposed, that is, a mechanical-hydraulic combined rock breaking method. This article is mainly from the approach of experiments. First, this paper studies the depth of grooves that can be formed by water jetting in cutting different rock types under different cutting parameters. Then, based on this experimental rule, the proposed water jetting adopts the method of repeatedly cutting in the same slot to increase the cutting depth. The experimental results show that: ①The higher the water jetting pressure, the slower the cutting speed and the greater the cutting depth. When cutting softer rock types, the target distance has a certain influence on the cutting depth. When cutting harder rock types, the target distance has a certain effect on the cutting depth. The impact is small. ②The repetitive cutting can effectively increase the cutting depth, but the increase in the cutting depth is related to the cutting parameters. The greater the water jetting pressure, the slower the cutting speed, the smaller the target distance, the greater the increase in the cutting depth. The experimental results have an important reference value for guiding the improvement of TBM and improving the tunneling efficiency. Related Articles | Metrics

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Effect of Temperature on Pore Water State in Cohesive Soil WU Jiangpeng 2022, 36 (4):  582-584.  Abstract ( 202 )   Save The variation of transverse relaxation time of three types of saturated compacted cohesive soil samples with temperature from 18 ℃ to 75 ℃ was measured by the nuclear magnetic resonance (NMR). The apparent activation energy ΔE of pore water in three types of cohesive soil samples was measured. The soil sample A with the largest specific surface area and the cation exchange capacity has the largest ΔE. For the soil samples B and C, ΔE < 0. This abnormal phenomenon may be due to the high content of kaolinite and illite in the clay minerals of these two cohesive soil samples, and the high adsorption energy of water molecules on the surface of these two minerals. Finally, the change of permeability coefficient of different types of cohesive soil samples with temperature is qualitatively analyzed. The positive ΔE indicates that the permeability coefficient of soil sample A increases with the increase of temperature; Negative ΔE indicates that the permeability coefficient of soil samples B and C decreases with the increase of temperature. Related Articles | Metrics

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Feasibility Study of Marble Waste as Highway Subgrade Material NIU Yong, CHAI Yuan, WANG Yong, TUO Jianbo 2022, 36 (4):  585-587.  Abstract ( 229 )   Save Based on the distribution of marble resources in China and the utilization of marble waste in Hezhou City, this paper analyzes the state-of-the-art marble waste resource re-utilization development in China and the existing waste accumulation issue in the current stone industry development process. In the view of effective utilization of the waste material, this paper analyzes the situation of marble waste reuse in the engineering applications domestically and overseas and proposes a suitable way for waste disposal in the Hezhou City. Throughout the basic material tests and subgrade bearing ratio tests, it is proved that the marble waste powder can be used as the highway subrade material under certain conditions. This conclusion can provide new ideas and references for the construction of roadway projects. Related Articles | Metrics

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Three-Dimensional Slope Stability Analysis Considering Spatial Variability of Fractured Zones WU Jing, XIA Yuxiang, LIU Yong 2022, 36 (4):  588-593.  Abstract ( 201 )   Save To truly reflect the instability process and failure mechanism of slopes within fractured zones, this paper presents the evaluation results of slopes in Gangtou Tunnel. The main water conveyance structure in the middle route of the South-to-North Water Transfer Project was studied in the paper to study the stability of the three-dimensional effect of slopes. Due to the complexity of the slope in the study area with an alternate deposition of soft and hard rock strata, the fractured zones are introduced in the 3D numerical model to simulate the actual dispositions of bedrock and overburden soil. Based on the strength reduction method, the influence of the fractured zones on the slope stability was studied. The failure mechanism of the fracture zones, as well as the sensitivity of the cohesion and internal friction angle of the bedrock and soil mass of the slope to its stability were analyzed. The results show that the strength properties at the fractured zones are significantly reduced, which leads to large displacements at the upper layers of the project site, which greatly reduces the factor of safety of the target slope. If the other conditions remain unchanged, the cohesion and the internal friction angle of the soil have an approximately linear relationship with the factor of safety of the target slope. Therefore, combined with the principles of the sensitivity analysis, the sensitivity to effectively identify the internal friction angle and cohesive force is high, which can improve the efficiency of slope reliability analysis. Related Articles | Metrics

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Discussions On the Theoretical Value of Bearing Capacity of Deep Excavations GU Shaofeng 2022, 36 (4):  594-597.  Abstract ( 408 )   Save With the development of city modernization, deeper and larger foundation excavations are rapidly increasing. The challenge of determining the bearing capacity of such excavated foundation soils is ever becoming urgent. The estimation formula for the deep foundation bearing capacity defined by the current code is a semi-empirical approach which is established based on the Prandtl foundation bearing capacity model and modified by the Reissner approach. However, the current formula ignores the shear strength of soils above the excavated area. This paper starts from the principles of Prandtl foundation bearing capacity model, then deduces theoretically the value of the foundation soil bearing capacity of deep foundations. This paper also presents a case history of the theoretical bearing capacity value in a cut and cover highway tunnel in Guangdong Province. These analytical results are compared with the value derived from the current code. The results show that the proposed theoretical formula is more comprehensive and intuitive, and it also provides a reference in determining the bearing capacity of deep excavation soils. Related Articles | Metrics

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Deformation Characteristics and Stability Analysis of Landslide in Expansive Soils in Yichang City DENG Yonghuang, TONG Shian, DONG Zhihong 2022, 36 (4):  598-601.  Abstract ( 274 )   Save In the process of construction in the center city of Yichang, geological hazards caused by expansive soils have been accompanied by the engineering construction, among which the landslide hazards induced by the expansive soil is more prominent. These hazards constitute a certain level of threat to the safety concerns in the urban engineering construction and engineering operation, which might cause significant economic and life losses. This paper presents the Zhangjiawan landslide as an example. On the basis of revealing the material characteristics and combining with the deformation characteristics of landslide bodies, this paper analyzes the stability and proposes the corresponding hazards prevention and comprehensive mitigation measures. This study has contributed in the geo-hazard prevention and mitigation of the urban construction in the center city of Yichang and has provided guidance for the construction planning of Yichang center city and promoting the economic development of the urban area. Related Articles | Metrics

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Evaluation of Geological Hazard Sensitivity in Tongliang District, Chongqing Using GIS XIE Xiaoyi, ZENG Yan, PENG Yun, ZHOU Tao, ZHANG Xingchong 2022, 36 (4):  602-606.  Abstract ( 263 )   Save In this paper, the GIS is as the major visualization evaluation tool for the geological hazard sensitivities in Tongliang District, Chongqing City. Six (6) factors, namely, slope of the topography, bedrock inclinations (incline or anticline), bedrock stratigraphy, distance to the waterway system, distance to the active structural tectonics and precipitations, are considered in the evaluation. The results show that: (1)the geological hazards in the study area are mostly occurred in the area with a topographical slope between 10° and 30°, the bedrock inclination direction towards southeast and south, and the bedrock stratigraphy formation of Middle Jurassic Upper Shaximiao Formation; Geological hazards are prone to occur in areas less than 200m away from the waterway system. The probability of the geological hazards is significantly higher in the area with monthly accumulated precipitation greater than 80mm than in the area with rainfall less than 80mm. (2)The existing geological hazard points are mainly distributed in the northeast and south of the study area, and they are concentrated and banded; (3)The area of high sensitivity and sensitive area accounted for 49.22% of the total area; The number of geological hazards in high sensitivity and sensitive area accounts for 90.74% of the total number of existing geological hazards. Related Articles | Metrics

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Influence of Spherical Weathering and Engineering Disturbance on the Stability of Completely or Highly Weathered Granite Slopes FAN Xiaogang, LI Yong, CHEN Weilong, ZHOU Chunmei, YAN Song, 2022, 36 (4):  607-611.  Abstract ( 372 )   Save In order to accurately analyze the stability of spherical weathered mixed granite slope, this paper uses the traditional limit equilibrium method and the finite element strength reduction method to study the influence of boulder content and excavation effect on the stability of mixed granite slope by using commercial numerical analysis software GeoStudio and PLAXIS, respectively. The results show that, when the content of spherical weathering material between 5% and 20%, with 5% of sphere weathering content, the slope stability factor of safety increases by 9.6%; the most dangerous sliding of the slope develops towards the deeper depth; When the content of spherical weathered material exceeds 20%, the slope factor of safety increases slowly; The engineering disturbance affects slope stability. With the increase of engineering disturbance, the slope stability decreases. Finally, a reliable slope treatment method is proposed through the numerical simulation. The research results can provide a theoretical reference for the design and stability analysis of mixed granite slope.  Related Articles | Metrics

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Influence of Shear Strength Parameters on the Slope Stability Analysis Results KANG Jingyu 2022, 36 (4):  612-616.  Abstract ( 252 )   Save The slope stability analysis methods can be divided into two parts: the total strength method and the effective strength method according to the different shear strength parameters selected. Since the pore water pressure is often unknown or difficult to obtain in the engineering practice, the total strength method is therefore widely used. When the total strength method is used, the result of the slope stability analysis is often erroneous due to the confusing in the actual shear strength and shear strength parameters of the soil. This paper utilizes the circular arc sliding method as an example to illustrate the relationship between the shear strength and the undrained strength of the potential sliding surface and the effective internal friction angle and the total internal friction angle. The basic reason for the difference between the effective strength method and the total strength method in the safety factor is proposed. Basic on this, a method for correctly evaluating the factor of safety of the slope stability is proposed when the pore pressure is unknown or difficult to obtain in an actual slope. At the same time, the slope stability analysis method proposed in this paper is verified by an example by using MATLAB software. Related Articles | Metrics

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Stability of Surrounding Rock Mass at the Exit Portal of Heiyakou Tunnel AO Guobi 2022, 36 (4):  617-620.  Abstract ( 167 )   Save In the tunnel excavations, especially in the construction of the portal segment, various hazards such as water inrush, mud inrush, tunnel roof collapse, and floor failure due to the adverse geological conditions, are frequently encountered due to the instability of surrounding rock mass. The factors affecting the stability of surrounding rock are complex, including physical and mechanical properties of bedrock, integrity of rock mass, structural characteristics of rock mass, geological structure, groundwater conditions, construction conditions, etc. these influencing factors often are often coupled with each other, and the superposition to a certain extent would aggravate the evolution of instability state of surrounding rock mass. This paper presents the Heiyakou tunnel as an example and combines with the previous research results. The engineering geological and hydrogeological conditions of the exit segment of the tunnel portal are presented. The paper analyzes and discusses the integrity and stability of the tunnel surrounding rock mass, in order to provide reference experience for the stability research of similar surrounding rock mass. Related Articles | Metrics

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The Highway Slope Stability Study Using Coupling Analysis of Multi-Source Automatic Data Acquisition System TANG Luosheng, YUE Min, WANG Yunan, DENG Changqing, HUANG Yuqun 2022, 36 (4):  621-625.  Abstract ( 285 )   Save The slope monitoring results are affected by many factors such as monitoring accuracy and human data collection error. These adverse factors might result in the actual slope deformation information could not be obtained in a single monitoring method, and the slope stability state cannot therefore be accurately justified. This paper presents a case history of an expressway embankment slope in Shiyan of Hubei Province. Several different automatic monitoring methods including automatic video surveillance, automatic crack monitoring, surface displacement automatic monitoring and deep displacement automatic monitoring for the slope were used in the target slopes for the deformation characteristics. The stability of the slope was evaluated comprehensively by the coupling and comparison analysis of the monitoring data in the real time dimension based on the analysis of different automatic monitoring data, combined with artificial inspection. The results show that the entire embankment slope was in a stable state, and there is a local surficial deformation near the top of the slope. Related Articles | Metrics

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Reliability Analysis of the Slope Stability of the Soil Disposal Area in a Mountainous Highway Construction AN Zhengming, FANG Zhengfeng, ZHOU Xingtong, LIU Zhiguo, PENG Kunjie 2022, 36 (4):  626-629.  Abstract ( 679 )   Save The waste soil disposal area in a mountainous highway construction has the characteristics of complex disposal material sources and large compactive effort differences, and its geotechnical mechanical parameters are random, which leads to a greater uncertainty in the slope stability in the waste soil disposal area. The study on the reliability of the slope stability of the waste soil disposal area has a strong engineering practical significance for the reasonable evaluation of the stability of the waste soil disposal area. The Monte-Carlo method is used to establish the reliability analysis model of the slope stability of the waste soil disposal area, and the stability and reliability at the 140m soil disposal area on the right side of K89+250 of Liupanshui-Weining Expressway in Guizhou Province are studied. The results show that the geotechnical mechanical parameters of the soil disposal area have obvious distribution characteristics, the slope stability coefficient of the residues disposal area is greater than he allowable safety coefficient, and the failure probability of the slope in an unstable state is 15.8%, which is a low-risk state. Therefore, the slope of the waste soil disposal area meets the requirements of stability and safety. The calculated safety factor and instability probability analysis of the slope stability of the soil disposal area can reflect the stability of the waste soil disposal area, which can provide a guarantee for the long-term safe operation of the soil disposal site. Related Articles | Metrics

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Experimental Study on the Influence of Particle Shape on the Compressive Characteristics of Sand JIANG Kaifang, ZHU Changqi, MA Chenghao, YI Mingxing, HUO Yulong, 2022, 36 (4):  630-634.  Abstract ( 207 )   Save The shape of particles reflects the history of particle formation and is one of the main control indices that determine the strength characteristics of cohesionless soils. To study the influence of the particle shape on the mechanical properties of sandy soils, A total of six (6) types of sand samples with different average particle sizes as well as different shapes are selected as the research object. The digital image of the particles is obtained by using the dynamic image capture technology, and the two-dimensional data are extracted by the computer digital image processing system and processed to quantify the shape parameter. A new shape factor (ρ) index from the particle sphericity and roundness indices to describe the shape of aggregate particles is proposed. The results show that the boundary void ratio and compressibility index (Cc) of the sample increase as (ρ) decreases. The rebound index (Cs) decreases with the decrease of (ρ); the experimental results also show that the number of particles breakage increases with the decrease of (ρ) and the sample develops from the poorly graded to the direction of well-graded. Related Articles | Metrics

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Experimental Study on Micro Mechanics and Features of Karst Ground Subsidence in Wuhan Subway Tunnel Crossing Area QU Ruofeng, PENG Shenggang, ZHOU Zhipeng 2022, 36 (4):  635-639.  Abstract ( 242 )   Save The ground subsidence induced by the subway tunnel crossing the karst terrain in Wuhan City is becoming an imperative issue to be resolved in the tunnel engineering practice. This paper presents the research results of the process and mechanical features of the ground subsidence in the karst terrain under different geological conditions. The following topics have been evaluated and studied: 1): a new visualization experimental device was developed to investigate the micro-mechanics under different geological and hydrodynamic conditions. 2): Development process of the ground subsidence over karst terrain under the four typical geological structure conditions was performed based on the PFC-CFD method. 3): Utilizing the pure sand collapse model as the research object, the development of pore water pressure and porosity under different vibration frequency and amplitude was studied, and the comparative analysis was performed by laboratory experiments.  Related Articles | Metrics

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Application of GPR and Monitoring Measurement in Inclined Shaft Tunnel ZHAO Wuyang, REN Shijun, XIANG Feifei, LI Jinrui, ZHANG Lewen 2022, 36 (4):  640-644.  Abstract ( 228 )   Save Inclined shaft tunnels have higher requirements for the stability of the surrounding rock mass, and at the same time, more accurate information is required at the supported excavations. The use of a single ground penetrating radar (GPR) will have certain deficiencies in the accuracy and effectiveness of the geological information prediction. Conventional radar data analysis includes time-depth conversion, but in the inclined tunnel, the face and the tunnel remain non-orthogonal. In the analysis, the depth after the time-depth conversion needs to be converted twice. In the Xianglushan inclined shaft tunnel project, through analyzing the rock mass instability and failure mechanism, this paper presents the results of using the combination of geological analysis and ground penetrating radar technology, as well as comprehensive advanced geological prediction analysis with complementary physical parameters, combined with the monitoring measurement in the inclined shaft tunnel. The monitored data were regression analyzed and a comprehensive data analysis for the stability of the surrounding rock mass was performed. Thee analyses provide background ground information for the design and construction of the inclined shaft tunnel. Related Articles | Metrics

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Compression Characteristics of a Calcareous Sand#br# SUN Liuliu, TANG Xiaoxin 2022, 36 (4):  645-648.  Abstract ( 262 )   Save A total of 10 series of calcareous sand compression tests with different average particle size, water content and relative density were performed for one dimensional compression tests. The particle size distribution analyses before and after the compression test were also performed to analyze the particle crushing characteristics and the change trend of the particle group during compression. The results show that the calcareous sand is a low compressibility soil, and the compression deformation is mainly plastic deformation; the average particle size has a linear relationship with the particle crushing rate. The larger the particle size, the more obvious the crushing of the particles leads to the greater the compression deformation; The water content can improve the compression performance of coral sand to a certain level. The fine-grained calcareous sand only produces limited particle fragmentation. The difference in the particle fragmentation caused by changes in water content is not the main reason for its compression characteristics; reducing the initial void ratio can effectively control the compression deformation caused by external force; 0.25mm can be used as the limit particle size to control the crushing of coral sand particles. Related Articles | Metrics

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Research Progress of a New Photogrammetry Method in Triaxial Tests HUANG Shaoran, MU Chunmei, 2022, 36 (4):  649-652.  Abstract ( 194 )   Save The photogrammetry method was applied to the triaxial tests of saturated soil and unsaturated soil in order to overcome the traditional triaxial experiment in volume measurement difficulties and obtain a three-dimensional model of the soil sample, but it is still a relatively new method with many difficulties. Throughout the literature review, new photogrammetry methods are introduced from the aspects of image information acquisition, soil sample 3D model establishment, data post-processing and application analysis. This paper summarizes the advantages, current difficulties and research progress of the new photogrammetry methods. The research of the new photogrammetry method is still in the early stage, but it has a great development future. It has less application in unsaturated soils, and further research is necessary. Related Articles | Metrics

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Experimental Study on Coastal Structural Soft Soils under Principal Stress Axis Rotation CHEN Kaiwen 2022, 36 (4):  653-656.  Abstract ( 208 )   Save The existing hollow cylindrical sample preparation technology has been improved to solve the problems of large disturbance and cumbersome steps in the original sample preparation method. The hollow torsion shear apparatus is used as the test equipment, with different frequencies and different dynamic stress amplitudes. For the influencing factors, the influence on the axial cumulative strain and softening index of Zijingang soft clay is analyzed. Under the rotation of the principal stress axis, there is an obvious critical cyclic stress value for coastal structural soft soils. When the frequency changes within the range of 0.1 Hz to 1 Hz, the number of cycles required for the hollow cylindrical specimen to reach the failure state under the action of the 0.1 Hz cyclic load. At the same time, frequency and cyclic stress ratio have a significant influence on the softening characteristics of coastal structural soft soils, and the effects of frequency and dynamic stress ratio on the axial cumulative strain and softening index are mutually coupled and mutually influencing, not alone exist. Related Articles | Metrics

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Application of TEM and GPR in the Geological Advanced Detection of Tunnel in Fractured Rock Mass with Soft Mudstone Lenses LAI Dayong, MO Qingwen, WU Shitao 2022, 36 (4):  657-659.  Abstract ( 325 )   Save This paper presents a case history of the advanced detection of hazards in the tunnel excavations in potential adverse geological conditions of surrounding mas of Enshi, Hubei Province. A typical fractured surrounding rock mass with soft mudstone strata section of tunnel between stations YK30 + 890 and 790 was used as an study example, the actual locations karst rock cavities in this range were predicted by using the combination of transient electromagnetic and geological radar. Firstly, the low electrical resistance anomalous zone was identified using the transient electromagnetic method, and the exact range was detected using the ground penetrating radar. During the tunnel excavation process, a deeper borehole was used to verify the broken rock mass zone. The surrounding rock geology exposed by the tunnel site excavation validated the correctness of the advance geological prediction results. Based on the advance geological prediction results, short footage method and weak blasting construction technical measures ensured the stability of the surrounding rock mass, and the research results can provide reference for the construction of similar tunnels with unfavorable geology.  Related Articles | Metrics

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Monitoring a Non-Load-Bearing Wrapped Geosynthetics Reinforced Soil Abutment CHENG Gang, LI Haoyu, WANG Qingming 2022, 36 (4):  660-664.  Abstract ( 264 )   Save Compared with the traditional abutments, the mixed abutment has the advantages of reducing the span length of the bridge superstructure, improving the backfill performance, rapid construction and improving the bridge esthetics. The structure has very good applications and promotion values under the current background of land shortage, assembly construction and ecological carbon reduction. Based on the monitoring practice of the wrapped non-load-bearing reinforced soil abutments in Mingguang to Chaohu Expressway Project, this paper introduces the details of monitoring purpose, content and selection of monitoring components of the project, also summarizes the implementation and potential critical aspects for the field monitoring. The field monitoring is of great significance to the study of working mechanism and service performance of the wrapped geosynthetic reinforced soil abutment.  Related Articles | Metrics

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Deformation Monitoring of an Expressway Lightweight Fill Embankment WU Xiaofang, JIANG Fenglin, LIU Xianwang, 2022, 36 (4):  665-669.  Abstract ( 211 )   Save This paper presents a case history of the post construction deformation monitoring results of a geofoam filled embankment in Changbao Expressway Project in Baoshan City. The project is located in high slope mountainous area with high seismic intensity area in southwest of Yunnan Province with a maximum embankment height of 15 meters. The deformation in the geofoam embankment was monitored and the post construction deformation is presented in the paper. The results and conclusions are the monitored settlement data at highway subgrade, lateral deflection at slope surface and lateral deflections at 0.5 meters and 3.8 meters below the toe of embankment slope. The maximum post construction settlement at highway embankment is 39.87 mm under an embankment height of 13.5 meters. The lateral deflection at slope surface is 8.12 mm and the lateral deflections at 0.5 m and 3.8 m below tow of embankment slope are 2.46 and 3.67 mm, respectively. Related Articles | Metrics

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Deformation Stability Analysis of a Tunnel Using Monitored Data GUO Ying, WANG Min, LENG Xianlun, 2022, 36 (4):  670-674.  Abstract ( 185 )   Save A tunnel in the construction process will inevitably cause disturbance to the stability of the rock mass, and further affect the original rock stress state and stability, so the surface settlement, the crest subsidence of the tunnel surrounding rock mass convergence have much restrictive requirements. In order to ensure the safety of tunnel construction, this paper takes Guangxi Ganglingpo double cell tunnel of an expressway tunnel monitoring measurement as the research object and choose the appropriate mathematical methods for the analysis of the monitored data. The results of the analyses can predict the final displacement of the surrounding rock and the ground surface subsidence. The rate of the displacement at the tunnel aprons can be used to determine the stability of stability the surround rock mass and the three-dimensional space-time effect of tunnel excavation. Related Articles | Metrics

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Experimental Study on in Situ Scouring of Slopes of Clay Gravel Layer LIU Yajian 2022, 36 (4):  675-678.  Abstract ( 204 )   Save The clayey gravel layer of the Anqing Formation is a special geological body composed of gravelly pebbles and clay. Its cementation force will be greatly reduced by the influence of rainfall, causing slope instability and damaging surrounding farmland and public facilities. Therefore, in this paper, the slope rainfall erosion experiment was carried out at the site to study the failure pattern and instability mechanism of slopes with different slope angles in the process of rainfall. The results show that the formation of slope ditches in the process of rain erosion of clayey gravel layer is roughly divided into the following three stages: surface erosion stage, fine trench formation stage and gullage network formation stage. At the same time, the larger the slope of the slope, the more conducive it is to the formation and widening of the slope ditch, which is not conducive to the stability of the slope. At the same time, whether the gravel on the slope of clayey gravel rolls down depends mainly on the slope ratio. The research results can provide a reference for the protection and treatment of local slopes.  Related Articles | Metrics

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Analysis of Unloading Ratio Rebound Modulus of Soil Samples in the Compression Rebound Test WANG Bo, YI Yuelin, LI Shichang, 2022, 36 (4):  679-682.  Abstract ( 211 )   Save The regional excavation project of Fuhe river channel is an early key project of the construction of the Yangtze River new city. In this project, the rebound deformation of the lower stratum caused by the widening and deepening of the river will affect the safe operation of the high-speed railway bridge. In this paper, the laboratory compression rebound tests of the silty clay and the muddy silty clay were performed for the main excavated strata, and the effects of unloading ratio and unloading stress level on the rebound modulus and rate of rebound of soil are discussed. The test results show that the lateral compression modulus and rebound modulus of the soil vary nonlinearly with the overburden pressure, and both of them increase with the increase of overburden pressure; the rebound modulus and rebound of soil decrease with the increase of unloading ratio; with the increase of unloading stress level, the rebound modulus increases and the rebound decreases. Related Articles | Metrics