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31 August 2021, Volume 35 Issue 4 Previous Issue    Next Issue

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Application of PHC Pipe Piles in Tianjin Soft Mucky Soil ZHANG Qi, WANG Tianbao, HU Haijiang, 2021, 35 (4):  421-424.  Abstract ( 330 )   Save The main reinforcing bars of a pre-stressed high performance concrete pipe pile (PHC) are made of high-strength and low-relaxation steel bars, which have a high strength, good bending properties and cracking resistance. The concrete strength of the pile is high, and the structural capacity of a single pile is also high. The pile has a good corrosion resistant performance, so that it has a wide range of design and selection, suitable for a various of soils. This type of pile has the advantages of short construction period, and environmentally friendly. This paper presents an application of the PHC pipe pile in the soft mucky silty soft soil in Tianjin. Approaches of selecting appropriate pile type and length are provided. The soil plug effect of the pipe pile on the axial pile resistance is also considered in the pile. The static pile loading tests and the integrity testing have confirmed that the PHC installation was satisfactory. Related Articles | Metrics

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Measures Minimizing Bridge Foundation Construction Impact on the Nearby Existing Tunnel YANG Po, LIU He 2021, 35 (4):  425-428.  Abstract ( 308 )   Save Based on the hydrogeological conditions of Changzhou, this paper analyzes the sensitivity of subway tunnel to the geological condition of groundwater bearing sand layer. A case history of Xinqiaozhongqiao highway over existing Metro Line No.1 is presented. This paper also analyzes a series of protective measures for the subway construction near the bored pile and monitors the subway tunnel structure during the construction period. The monitoring results show that, in the project, the protection measures for the construction risk of cast-in-place bored pile are effective. During the whole pile foundation construction process, the changes of the subway tunnel are within the control range, and the tunnel structure is safe. The monitoring data also reflect that the pile foundation construction with a distance of more than 5m from the tunnel has a small impact on the tunnel. The deformation mainly occurs during the construction of the pile foundation in the middle of the two tunnels. The structure of the subway tunnel has a significant impact on the construction of the tunnel The external vibration load is relatively sensitive, so it is necessary to carefully consider the impact of vibration load on the deformation of track segment during construction; due to the impact of pile foundation density, the tunnel deformation in the forward projection area of the bridge is relatively large, gradually reducing to both sides, and the overall distribution is in the groove shape. The tunnel is basically unchanged about 10 m outside the projection. Related Articles | Metrics

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Evaluation of Deformation Management Levels of Large Deep Excavation Projects Considering the Deformation Control of Surrounding Buildings and Structures YANG Youjiang, HU Cai, XI Mingjun, ZHANG Jiaxin, HUA Zhijin, FAN Bo, XU Dingping, JIANG Quan 2021, 35 (4):  429-433.  Abstract ( 324 )   Save The excavation of a deep foundations surrounded by dense distributed tall buildings or close to underground utilities and ground transportation facilities will change the initial equilibrium of the soil. As a result, differential settlements of the nearby ground and soil deformation in the excavated area will be induced. If the deformation control is not effective, it will have adverse effects on the surrounding buildings and/or structures. This paper presents a case history of a deep excavation project in Wuhan City. The excavation project is close to a subway tunnel and is surrounded by deep foundation supported tall buildings. The construction monitoring location distribution were optimized by the numerical simulations under various loading combinations and construction conditions under densely distributed tall buildings and other structures. Different deformation criteria from various buildings, utilities and other structures were considered and their deformation management control levels were suggested. The results indicate that these deformation control measures were effective and satisfactory. Related Articles | Metrics

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Ground Improvement Design of a Large Fills DONG Pengcheng, TANG Wei, GUO Shengjuan 2021, 35 (4):  434-437.  Abstract ( 310 )   Save This project is located in Yunnan Province. The original site terrain has significant variation in elevations with well-developed erosion gullies with depth up to 20 meters deep. During the site preparation, the site fill height would vary from 10 to 35 meters. Due to the tight construction schedule, the site would be filled immediately after the site grading was completed. Since the project main structure construction and the roadway retaining wall were located in the fill area, so that that soil improvement for the post construction settlement mitigation were critical to the success of this project. After the feasibility and cost comparison of various soil improvement methodologies, dynamic compact method and the layer compaction plus geogrid reinforcement methods were finally selected. After the completion of the project, the settlement monitoring was lasted for four years and the results showed that the site initial settlement after construction was relatively small and meets the design and engineering requirements. Related Articles | Metrics

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Engineering Practice of Metro Tunnel Construction in Karst Area ZHANG Wei, 2021, 35 (4):  438-440.  Abstract ( 340 )   Save Long tunnels through the karst terrain are the challenge area in the railway and highway tunnel construction. To explore solutions for the tunnel through the well-developed karst area, this paper elects a case history of geotechnical investigation, design construction in karst terrain of a segment of the Shenzhen Metro Line No.16 project. Mitigation method was based on the site specific conditions, such as, horizontal and vertical distributions of karst rock cavities and their sizes, karst feature development as well as the characterization of the filling materials, and the compaction grouting method, permeating grouting and the combination of compaction grouting and filling grouting method were selected for the karst mitigation. The satisfactory mitigation results were verified by integrated geophysical methods as well as the coring method. Related Articles | Metrics

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Research and Practice of Composite Retaining System for Excavation Engineering ZHANG Hongtao, WANG Xi, LIU lijian, MA Tianyi, MA Sai 2021, 35 (4):  441-444.  Abstract ( 280 )   Save With the rapid development of urbanization, a variety of composite support methods have been received more and more applications in the excavation supports. This paper presents a case history of selecting the deep excavation supporting system in Beijing. Based on the project needs, a combination of several supporting systems, soil nail wall, soldier pile with ground anchor and gravity retaining wall were used. The construction monitoring data indicated that the results were satisfactory. Related Articles | Metrics

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Seepage Analysis of Deep Excavation Dewatering Induced Ground Subsidence—A Case History WEN Jiaming, LI Rongsheng, LI Hong, GAO Wei, XIONG Jian 2021, 35 (4):  445-448.  Abstract ( 319 )   Save In this paper, a case study of the seepage influence analysis is presented considering different cut-off wall depths at a subway deep excavation project in Shenzhen. The two dimensional numerical analysis results indicate that, the groundwater drawdown outside the excavation area depends on the permeability coefficient of the soil layers at the toe of the cut-off wall. The loss of groundwater could be minimized when the tow of the cut-off wall is penetrated into the impervious layers. Further assessment of the potential ground subsidence induced by the groundwater extraction could be referred as the early prediction and judgement for the deep excavation risk control. Related Articles | Metrics

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Numerical Simulation of a Deep Excavation in Weathered Slate Area Supported by Double-Row-Piles GUO Yonghui, LEI Jinshan, CHEN Fei, ZHANG Yuqing, FENG Zhihui 2021, 35 (4):  449-452.  Abstract ( 228 )   Save The deformation of a double-row-piles supported deep excavation project in the weathered slate area was numerically simulated by using finite element method. The ground subsidence surrounding the excavated area, lateral deflection as well as the stress in the supporting structure during the entire excavation process were evaluated and compared with the construction monitoring data in order to provide an optimized excavation sequence. The results indicate that, in the excavation process in the weathered slate area, the ground settlement within a distance of 6.5 to the excavated area and lateral deflection at the top of double-row piles should be monitored with more attentions; Further, large bending moments were observed in the front row piles 4.5 m from the top and the and 16 m from the pile top in piles in the rear row. Related Articles | Metrics

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Deformation and Stability of a Deep Excavation Supporting Structure LI Qugang, DAI Xianyao, ZOU Donglin, WANG Xinyi, HUANG Xin 2021, 35 (4):  453-455.  Abstract ( 341 )   Save The deformation and stability of an excavation support structure under an expressway bridge viaduct will like directly affect a safe operation of adjacent piers and other structures nearby. A box culvert to be construction would be very close to the bridge viaduct piers No.5 and No.6. This box culvert would be constructed in a complicated and constrained environment with small vertical clearance and it would affect the safety of the bridge if an appropriate protective measure was not implemented. The stress and deformation of the excavation supporting structure were analyzed through a commercial finite element method software MIDAS-GTS. Further, the deformation of the bridge pier during the entire excavation process was simulated by FLAC3D software after the supporting structure was installed. So that the role of supporting structure could be appropriately evaluated. Throughout the evaluation of the safety and the stability of the evaluation of the deep excavation supporting structure for the box culvert construction, the results and experience can provide an important theoretical support for the design and validation of the deformation and stability of deep excavation near the active under highway, and also provide reference for similar projects in the future. Related Articles | Metrics

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In-situ Solidification of Soft Mucky Cohesive Soils for a Highway Subgrade SHAN Huagang, FEI Weiquan, ZHU Guohua 2021, 35 (4):  456-458.  Abstract ( 590 )   Save This paper introduces a cost effective and environmental friendly in-situ solidification of soft mucky cohesive soil technique that replacing the conventional soil improvement method of removal and replacement for a highway project in an alluvial plain with well-developed rivers and creeks and hidden historical waterways. The construction techniques of the in-situ soft mucky cohesive soil are also briefly introduced and a case history of the project that applying this soil improvement method is presented in this paper. Further, the applicability as well as results of using this technique for strengthening of shallow deposited soft cohesive soils are evaluated. Related Articles | Metrics

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Stability Monitoring of Jiangzhao Expressway Overpass During the Construction of Chashan Highway XIONG Yi 2021, 35 (4):  459-462.  Abstract ( 335 )   Save The proposed Chashan Highway was designed as the First-Class Highway elements and considering the Urban Artery functions. It under crosses the Jiangzhao Expressway at K9+082 with an acute intersection angle 30 degrees on a gentle profile with an oval geometry. Piers of the Jiangzhao Expressway Overpass were located in the median area of divided Chashan Highway. In order to maintain a safe operation of Jiangzhao Expressway during the construction, a bridge stability monitoring system was established at the bridge piers with the active traffic above them. The monitoring results were analyzed for the stability evaluation of the existing bridge structures. The monitoring and evaluation results could also provide the basis for the design and construction of necessary stability mitigation measures. To ensure the safety of the construction activities and the safety of the traveling public, safety facilities, such as, reinforced concrete crash barriers, speed limit signs, deceleration markings, isolation barriers, were installed in the construction zone on the Jiangzhao Expressway Overpass. Related Articles | Metrics

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Numerical Simulation of Dewatering for an Underground Combined Utility Pipe Gallery Construction ZENG Fanfu 2021, 35 (4):  463-467.  Abstract ( 275 )   Save This paper presents a case history of dewatering of an underground combined utility pipe galley construction in Pingtan City. In order to evaluate the dewatering effect under different dewatering design parameters, a three-dimensional numerical model of dewatering during the excavation was established by using commercial finite element method software PLAXIS. In the numerical analysis, the groundwater pressure distribution with different dewatering well spacing, soil layer deformation, variation of groundwater extraction volume with time and dewatering well spacing, are investigated. The results indicate that, the mucky clay layer that lays four (4) meters below the bottom of the excavation serves as a good aquitard layer and the cut-off wall is penetrated into this soil layer so that the connectivity of groundwater between the excavated area and the surrounding area has been effectively reduced. Due to lacking of the groundwater recharging, the groundwater level inside the excavated area could be quickly reach the design groundwater level. The consolidation induced settlement in the cohesive layer inside the excavated area occurs during the dewatering process and the lateral deflection in the excavation supporting structures also occurs so that the ground subsidence behind the supporting structure also consequently induced; The groundwater extraction volume with time pattern shows that a large quantity initially and the extraction volume reduces with time. Under the constraint of the aquitard layer, the time required to reach the design groundwater level has a linear relationship with the pump well spacing. Related Articles | Metrics

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Effect of Trench Excavation on the Deformation of Adjacent Bridge Pile Foundations SHEN Jianfang, YANG Lanqiang, WANG Guoquan, SUN Baosheng, LI Jiaming 2021, 35 (4):  468-471.  Abstract ( 333 )   Save The deep excavation activities will induce the change of pore water pressure and earth pressure fields in the surrounding soils, which might lead to the deformation of the surrounding soil. Therefore, the excavation has a significant impact on the surrounding environment, which will induce the excessive tilting, cracking and even structural damage of the pile supported bridge foundations. Currently, the analytical method for the effect of trench excavation on the adjacent pile supported bridge foundations is not clearly defined so that data collection of the construction monitoring becomes important. This paper presents a case history of a trench excavation near the pile supported bridge foundations in Yincheng of Ningbo soft soils. The effect of the trench excavation on the adjacent bridge foundations was simulated by the three dimensional finite element method using MIDAS GTS NX software and the numerical results were compared with the construction monitoring data. The results indicated that, inserting a hot rolled steel H beams into the soil-cement mixed columns formed by the Metro Jetting System (MJS) plus one row of reinforced concrete waler beam has a good performance in controlling the lateral deflection of the supporting structure and minimizing deformation of the adjacent soils. With the appropriate soil constitutive model and other numerical parameters, using the three-dimensional finite element method for simulating the effect of trench excavation on the adjacent bride structure is effective. Related Articles | Metrics

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Landslide Along River Levee under Heavy Precipitations CAO Jinchun, MENG Lingfeng, ZHANG Benke 2021, 35 (4):  472-475.  Abstract ( 271 )   Save This paper presents the stability analysis of the landslide at a highway on top of the river levee. The effect heavy precipitation and the river water level fluctuations on the stability of the highway embankment are investigated through the numerically analysis and through the geological survey. The results indicate that the failure mode of the landslide belongs to the circular failure mode. The precipitation, flood erosion on the river bank and the rapid drawdown of the flood level are factors that might contribute to the occurrence of the landslide. Among these potential factors, the rapid drawdown of the flood level has the most influence on the embankment stability. This study could provide some references of stability of levees along the frequently flooded area. Related Articles | Metrics

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Fluid-Solid Coupling Analysis of Deep Excavation of a Cut and Cover Tunnel in a Lake LIN Lianquan, YE Daicheng 2021, 35 (4):  476-481.  Abstract ( 290 )   Save The fluid-solid coupling method was used in the finite element analysis of the effect of deep excavation dewatering on the deformation of the excavation supporting structures and the adjacent soils of a cut and cover tunnel in the lake in Xiamen City. The three-dimensional model was established by using commercial finite element method software PLAXIS and considering the site specific soil conditions. The entire installation of the supporting structure for the deep excavation, dewatering and excavation process are numerically simulated. The stress and deformation in each stage of the construction are evaluated. The results indicate that, under the fluid-solid coupling approach, no convergence could be obtained in the original design. As a result of the numerical analysis, the passive zone underneath the excavated area were improved by the deep mixing method. After the soil improvement in the passive soil zone, the deformation in the supporting structure and the settlement in the surrounding soils reduced. Along the longitudinal direction of the excavated area, the variation of the stress on the strut could be more than 100%. In the excavated area, the bottom deformation in the wider area had much larger deformation than other locations and the lateral movement and bending moment in the supporting structure were also improved. The results also showed that the fluid-solid coupling approach can improved the reliability of deep excavation supporting in complicated soil and spatial conditions. Related Articles | Metrics

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Diaphragm Wall Stability Based on Pressure Balance of Slurry LI Yiyang, LI Xinping, GUO Yunhua, WEI Gang, LI Dan 2021, 35 (4):  482-486.  Abstract ( 210 )   Save The stability and deformation control of the excavated side wall is an essential part of the construction quality control of the diaphragm wall. It is an important index of the construction quality control throughout the slurry preparation parameters. Since the mechanism and the role of slurry for the excavated wall stability are not well understood, the empirical method for the concentration of the slurry is still widely used in various projects. The active earth pressure at the excavated wall and the dynamic balance of the pressure of the slurry are illustrated in this paper. The stability criteria of the excavated wall are also presented. The results indicate that, the rate of the diaphragm wall excavation, viscosity of the slurry, depth of the excavation and the internal friction angle of the excavated soil are the factors that might affect the stability of the excavated wall. The potential instability zone is located 10 meters below the ground surface and 3 meters above the bottom of excavation. Related Articles | Metrics

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In-Situ Engineering Properties of Silty Fine Sand in Xiamen ZHUANG Shuyu 2021, 35 (4):  487-490.  Abstract ( 350 )   Save High-quality undisturbed samples for the silty fine sand soils are usually difficult to obtain, and the laboratory tests results are often unreliable due to the sample disturbance. A series of in-situ tests of the silty fine sand soils in Xiamen area were performed. These test included standard penetration tests, cone penetration test, seismic flat dilatometer test and cross-hole shear wave velocity test. The in-situ engineering properties such as horizontal stress, strength characteristics, over-consolidation ratio, stiffness characteristics, and degree of compaction in soil were systematically investigated using these in-situ testing methods. In addition, the soil stratigraphy and soil classification were independently estimated by using these methods. The results showed that the Xiamen silty fine sand is an over-consolidated soil with a static earth pressure coefficient between 0.52 and 0.70. With the increase of depth, the strength and stiffness of the soil gradually increase, but the density does not increase significantly. In contrast to the flat dilatometer test results, the seismic flat dilatometer test can obtain the maximum shear modulus and stiffness attenuation curve of the soils, the test strain range is wider, and the result is more reliable. This study can provide theoretical support for the foundation construction in the silty fine sand formations in Xiamen area. Related Articles | Metrics

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Stability Analysis of Siwan Village Landslide in Chengkou, Chongqing LONG Shengjun, WANG Xueqing, HUO Yulong, WANG Yikun 2021, 35 (4):  491-494.  Abstract ( 272 )   Save The Siwan Village Landslide locates on the northwest of Longtan River. The landslide seriously threatens the lives and property of the residents and the safety of pedestrians using the village roads. Based on the analysis of various conditions of the landslide body, the basic characteristics of the landslide, the potential influencing factors, the stability analysis of the landslide body and potential slip zone are discussed in this paper. The results show that the structural surface and cracks on the slope are well developed, and the structure of the soil layer of the slope is in loose state. Under the action of continuous rainfall, it eventually developed into a landslide. The stability analysis shows that the landslide body is in an unstable state under the condition that the rock and soil are saturated by rainfall, which is consistent with the actual situation. The potential slip zone on the right back side of the landslide body is in an unstable state under normal conditions, it is unstable under the condition of saturation and needs further mitigation and monitoring. Related Articles | Metrics

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Numerical Solution of Stress Singularity in Rectangular Piles WEN Guangjun, LI Fanfan, ZHAO Huahong, TAN Xianjun 2021, 35 (4):  495-499.  Abstract ( 446 )   Save Due to its non-smooth geometry, rectangular piles often demonstrate the stress singularity in the numerical analysis. Using rounded corners to smooth the corners of rectangular piles can eliminate the stress singularity, but the size of the rounded corners has some effects on the reliability of the approximate model results. In this paper, a numerical model single rectangular pile is established by a commercial finite element method software ANSYS, the degree of influence of the round size on the reality of the finite element approximation result is analyzed. When the size of the rounded corners is, the overall displacement calculation result of the structure is reliable; When the size of the rounded corners is, the overall stress analysis result of the structure is reliable; Finally, the deformation of the rectangular pile used as an actual deep excavation project is simulated, and the simulation results are compared with the construction monitoring results to validate numerical results. It is concluded that, in the numerical analysis, rounding corners can effectively minimize the non-convergence problem caused by stress singularity. At the same time, selecting the appropriate size of the rounded corners according to the results of this paper can not only satisfy the accuracy of numerical analysis but also reduce the number of meshes. Related Articles | Metrics

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Fractal Characteristics of a Landslide Movement Trajectory Under Precipitations ZHOU Qi, LI Huiqin, ZHU Haichao 2021, 35 (4):  500-503.  Abstract ( 180 )   Save This paper presents the dynamic landslide movement trajectory under the action of potential triggering factors. Based on fractal theory, the trajectory of the landslide displacements and its correlations with the precipitations are systematically evaluated. Firstly, the landslide deformation was analyzed with support of the observed sliding monitoring data; Secondly, the fractal dimensions of the deformation curve at each monitoring point of landslide were analyzed by using the boxcounting theorem of fractal dimensions. Lastly, the fractal characteristics of landslide movement trajectory were explored through the variation of fractal dimensions during the study period. The results show that, under the influence of the precipitation, the shear strength of landslide soil decreases and the deformation increases. The deformation trend of fractal dimensions of the landslide movement trajectory increases and the overall trend is increasing. Related Articles | Metrics

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Correlation Between Confining Pressure and Dynamic Shear Modulus and Damping Ratio of Calcareous Sand in South China Sea GAO Yangyang, ZHANG Zhuangzhuang, SONG Xing, WANG Ting, SONG Xijun 2021, 35 (4):  504-506.  Abstract ( 255 )   Save The consolidation undrained tests of calcareous sand samples from the South China Sea were conducted by using a GDS dynamic triaxial testing apparatus. The results show that the Hardin-Drnevich model can better simulate the G/Gmax~ dry density curve of the calcareous sand under complex stress conditions. The dynamic shear modulus value increases with the increase of the confining pressure, and the dynamic shear modulus ratio also increases, but the curve fitting rule of damping ratio is opposite to that of dynamic shear modulus. The maximum dynamic shear modulus value of the calcareous sand increases with the increase of the confining pressure. This relationship demonstrates a linear trend and could be fitted using Janbu Formula. Related Articles | Metrics

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Laboratory Investigation on Acoustic Emission Characteristic of Intact Rock Samples Under Uniaxial Compression Condition CHEN Xueping, GE Juan, CHEN Zhongqing, GAO Xin 2021, 35 (4):  507-509.  Abstract ( 220 )   Save A series of uniaxial compression tests were performed on four types of typical intact rock core samples (basalt, sandstone, limestone and tuff) in Zhejiang area to investigation the acoustic emission in the entire rock compression tests process. The results show that (1) the acoustic emission characteristics of limestone and sandstone under the uniaxial compression are similar, and a large number of acoustic emission events mainly occur when the rock is close to the failure, which is significantly different from the acoustic emission characteristics of tuff and basalt rock samples; (2) when the compressive stress of tuff is close to 0.4 times the peak compressive strength, the acoustic emission events increase more obviously, and occur in large amounts when the rock sample is close to failure; (3) a large number of acoustic emission events occur in the entire process before the failure of basalt, and a more obvious step-by-step progressive ascending change feature is shown. The research results can provide a reference for the acoustic emission monitoring and the early warning of rock landslides in Zhejiang area. Related Articles | Metrics

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In-Situ Groundwater Pumping Tests with Various Well Diameters in Hangzhou Asian Game Village Site XIONG Xing, CHEN Dazhou 2021, 35 (4):  510-513.  Abstract ( 209 )   Save In-situ hydrological test is a major method to obtain the hydrological design parameters. For the upper perched and the lower artesian groundwater parameters, large well diameter for pumping is usually required in order to minimize the testing error from the well installation. However, due to the site condition constraint in the preliminary investigation phase for the municipal projects, the well pump tests are performed with the relatively small well diameters. This paper presents a case history of the well pump test in Hangzhou Asian Game Village. In-situ tests were performed in the upper perched in silt and silty fine sand and lower artesian groundwater in rounded ground layers with various well diameters. The results were evaluated and the differences between the small and large well diameters were obtained. Related Articles | Metrics

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Bearing Capacity Testing on CFG Column Composite Ground CHENG Xunchao, FU Zhibin 2021, 35 (4):  514-517.  Abstract ( 639 )   Save This paper presents a case history of quality assurance and quality control testing of Cement-Fly Ash-Gravel (CFG) Column composite ground in Shangdong Wanhe Project and a soil improvement project in the eastern district of Zhangjiakou Bridge. The subsurface soil strata are introduced and the end bearing CFG column is located in the gravelly soil stratum. Then the low-strain integrity testing instrument equipment diagram, several frequently encountered integrity test results types, basic principles and the essential static loading test devices are introduced. The bearing capacity evaluation of the CFG columns in the Shangdong Wanhe No.7 Building is divided into two steps: the first step is the column integrity testing, the second step of is the static loading tests on the composite ground (including column and it surrounding soils) as well as on the single column. The testing results are evaluated. The column installation integrity as well as bearing capacity of the composite ground evaluated throughout the low-strain test results and load-settlement (Q~s) curve of static loading test results. The results are satisfactory. The results also indicate that the low-strain test technique is needed for the improvement. Related Articles | Metrics

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High-Density Resistivity Method the Regional Geological Hazard Survey in Rolling Hill Areas ZHAO Haichao, ZHANG Jianqiao, ZHANG Zhaobin, ZHANG Kaiwei, 2021, 35 (4):  518-521.  Abstract ( 296 )   Save In the rolling hill area under the strong precipitation, the geohazards, such as mud flows and landslides, are frequently occurred in the well-developed, fractured zones in the geological tectonic structures and these hazards have large potential threat to the life and property loss of the public. In order to evaluate these factors that might induce the geohazards, such as, natural environment, form conditions, characteristics of the hazard and its potential target, geophysical investigation methods are frequently applied. Among these investigation methods, the high density resistivity method has the advantage of one-time setting the probes and the fast data acquisition could be obtained by using digital scanning device through the “U” type exception method to identify the geologically fractured zone. Related Articles | Metrics

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Analysis of the Transmission Error in the Compressive Modulus Es LIU Dahai, 2021, 35 (4):  522-525.  Abstract ( 421 )   Save Compressive modulus Es is one of the physical and mechanical indices of the soil, and is also an important index in the foundation settlement estimation. In the consolidation test, it is difficult to minimize the measurement error of the applied pressure and deformation test indices. On the basis of establishing the spline function of test data (p, ln(h)) and applying the theory of error transmission, the error transmission of the measurement error of test index (p, h) to the compressive modulus is analyzed. The results show that the measurement error of the applied pressure and the deformation test index do not have significant effect on the error transmission of the compressive modulus, and its contribution to the error of compressive modulus are almost the same. The overall transmission error is generally less than 3%. Secondly, the ratio coefficient β>1 of the secant compressive modulus is less than 1.1 for the normal cohesive soil and 1.5～1.7 for the soft soil. The secant compressive modulus of the engineering strain is only suitable for the small deformation. When the tested modulus is applied to the settlement estimation of the soft soil with large deformation, the settlement is much smaller, which needs special attention. The results suggest that the secant compressive modulus determined by the true strain should be used in the revision of geotechnical test code. Related Articles | Metrics

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Triaxial Consolidated-Drained Compressive Shear Tests of a Wide Graded Gravelly Soil LI Fangzhen, 2021, 35 (4):  526-530.  Abstract ( 469 )   Save In this paper, a series of triaxial consolidated-drained compressive shear tests (CD-test) were performed on a wide graded gravelly soil sample. The shear strength, stress-stain properties and the nonlinear parameters of Duncan model of this wide graded gravelly soil sample under different gravel contents and dry densities were devaluated. The results indicate that the shear strength and the parameters of Duncan model of this wide graded gravelly soil sample exhibit correlations with various of gravel contents and dry densities. When the content of coarse gravelly grains increases, the angle of internal friction φ and φ0 also increases, the cohesion c increases initially then decreases. When the dry density increases, the angle of internal friction φ and φ0 and Δφ increases, the cohesion c increases initially then decreases. Related Articles | Metrics

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Monitoring and Analysis of Xi’an Metro Line No.2 Vibration Influence on Historical Buildings ZHANG Kai, LI Huan, LI Jiayi, WANG Long 2021, 35 (4):  531-534.  Abstract ( 422 )   Save This paper presents an engineering case history of constructing Xi’an Metro Line 2 crossing or detouring around the national key cultural relic protection unit. The vibration response levels at the tunnel during the operation and at the historical buildings have been obtained throughout the in-situ monitoring. Based on the monitored vibration data, the effect of vibration reduction of the floating steel spring plate placed underneath the track. The vibration levels of historical buildings under the subway with and without the operating traffic were also evaluated. The nine years of the vibration monitoring data were statistically analyzed and the following results are concluded: 1) The floating steel spring plate is suitable for the special vibration reduction need such as rail tracks near the historical buildings; 2) the vibration level of the building induced by the operative traffic is within the code tolerable range; 3) The speed of the subway train has limited effect on the vibration level of the historical building and these monitoring data provide useful references for the optimize the speed of the subway trains. Related Articles | Metrics

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Engineering Characteristics of Back Fill Materials for Xinjiang Daheyan Reservoir Dam YU Jishi 2021, 35 (4):  535-538.  Abstract ( 357 )   Save The dam of the Daheyan Reservoir was designed to be an asphalt concrete cored rock fill dam with a maximum height of 77.7 meters. The structural geological stability of the project area is classified as Poor, and the design seismic intensity belongs Zone Ⅶ. Therefore, it is necessary to conduct a comprehensive evaluation of the engineering characteristics of the dam back fill materials for the dam stability analyses. The results indicate that the coefficients of compressibility of the back fill material are between 0.036 and 0.06 MPa-1 under the pressure of 100~200 kPa, which indicating a low compressibility material property. The permeability coefficients of the tested materials are in the range of 3.8×10-2~4.5×10-2 cm·s-1, which means that the material is a free-drain back fill material. The tested internal friction angle of the material is nearly 42°, which illustrates a high shear strength property. The Duncan-Chang model could better describe the deviatoric stress-axial strain relationship. Whereas, the differences between the prediction model and tested data of the volume strain-axial strain relationship of the back fill materials are relatively large. Related Articles | Metrics