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02 March 2019, Volume 33 Issue 1 Previous Issue    Next Issue

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Mitigation and Deformation Analysis of a Deep Excavation in Chengdu Expansive Soils ZHANG Ning1, DENG Yu1, MENG Baohua2, MA Jun2, LIANG Yao2 2019, 33 (1):  1-6.  Abstract ( 586 )   Save A deep excavation site in Chengdu City is located in expansive soils and large deformations were occurred in the norther supporting structures. Based on the analysis of the shape of the large deformation and the adjacent environment of the excavation site, it was concluded that the insufficient geotechnical investigation data, lack of layered and segmental excavations, presence of welldeveloped expansive soils and seepage of groundwater were the major causes. The mitigation measures should consider the safety as well as performance of adjacent building structures. One option included unloading soils, displacement micropiles plus daylighting weep holes and another option was corner and raking supporting plus daylighting weep holes. The monitoring data indicated that the excavation induced deformation was successfully controlled. Related Articles | Metrics

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Influence of Subway Foundation Excavation on Adjacent Buildings and Structures HU Zhengbo 2019, 33 (1):  7-10.  Abstract ( 591 )   Save The subway stations are usually located at the densely populated urban area with closely spaced buildings and other structures. As a result, deformation of the supporting structures for the station foundation excavation on the adjacent buildings and structures becomes more and more practically important. This paper presents a case history of subway station foundation excavation in Nanchang City. The deformation of the supporting structure was comparatively evaluated by analytical method using Lizheng software and numerical analysis using PLAXIS finite element method with Hardening Soil (HS) constitutive model. The results indicate that the numerical analysis using HS soil model resulted in closer deformations with the monitoring data. The deformation isolation walls constructed by castinsitu reinforced concrete piles and slurry wall between the excavated area and the adjacent buildings and structures were compared. This paper also summarized main aspects of deep excavation near building structures. Related Articles | Metrics

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Numerical Analysis of Deep Excavation Support in Thick Silty Soils in Wuhan East Lake WU Yungang1, ZHOU Miao1, GAO Zhenyu1，XIA Shuijiang1 , XU Dexin2 2019, 33 (1):  11-14.  Abstract ( 541 )   Save The thick and soft silty soils segment between stations DHTDK2+900 and DHTDK3+120 of Wuhan East Lake Passage Project were used for the study in this paper. The methods for the support of deep excavation in soft soils were compared and it was concluded that the pile frame support with internal support was the optimum supporting method. In order to identify the key factors that affecting the effectiveness of excavation support, the supporting structure was numerically simulated by using three dimensional ABAQUS finite element method. The results indicated that the diameter of the supporting pile was the key factor that affecting the lateral deflection of the supporting structure. The cost of the supporting structure can be minimized by optimizing the diameter of supporting piles. Related Articles | Metrics

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Application of High Energy Dynamic Compaction Replacement Method in Soil Improvement of Storage Tank Farms ZHANG Xuan, CHEN Jianyu 2019, 33 (1):  15-18.  Abstract ( 494 )   Save In recent years, more and more storage tank farms are constructed in the coastal reclamation area with usually soft soil strata. As a result, the soil improvement for the proposed construction becomes more and more imperative. This paper presents a case history of soil improvement for a storage tank farm of a petroleum factory pier. High energy dynamic compaction replacement with gravel column was used for the foundations of the storage tanks. The results of the soil improvement were examined by various methods at locations inside the gravel columns and soil inbetween columns. The testing methods included standard penetration tests, heavy dynamic cone penetration tests and plate loading tests. The results indicated that the gravel columns formed by the high energy dynamic compaction method could be form with a long column with higher capacity and the soils between columns were also improved. It is also concluded that the high energy dynamic compaction replacement method is a viable method for the soil improvement for the soft storage tank farm soils. Related Articles | Metrics

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Influence of Deep Excavation on the Adjacent Existing Shielded Subway Tunnels WANG Hang 2019, 33 (1):  19-22.  Abstract ( 532 )   Save Case history of a deep excavation project for a building construction at the north side of Suzhou Subway No. 4 Line is presented in this paper. The impact of the deep excavation process on the shielded subway tunnels was numerically simulated by using Midas GTS finite element method. The results indicated that: the maximum lateral deflection on the supporting structure of the deep excavation on the shielded subway tunnel was observed when the foundation excavation reached its maximum depth, and the lateral deflections on the supporting structures were gradually reduced during the backfill operation of the excavated area. The maximum vertical settlement in the shielded subway tunnel was 1.51 mm with a maximum lateral deflection in the tunnel was 6.32 mm; the maximum ground subsidence observed the deep excavation was 2.5 mm and the maximum ground heave at the bottom of the excavated area was 20.3 mm. The deformation and the stress within the supporting structures were satisfactory. Related Articles | Metrics

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Application of Grouting Technology in a Karstic SinkholeTreatment Project XIONG Bo 2019, 33 (1):  23-26.  Abstract ( 573 )   Save Karstic sinkhole will cause huge potential safety hazards to surrounding structures, and grouting technology is a very effective mitigation method. When a single collapse is encountered, the construction operations should be stopped immediately, and the collapse site should be backfilled with clay. Then the scope and nature of sinkhole should be analyzed, the original design should be modified accordingly. Then the collapse site should be grouted. Several key technoogies for grouting treatment of collapse are as follows: first, grouting pressure should not be too high; secondly, grouting should follow the principle of surrounding first and then center area; finally, the standard of grouting final hole should be controlled according to grouting test condition and grouting rate. In this paper, the application of grouting technology in a karstic sinkhole treatment project is studied, which provides a good reference for similar projects. Related Articles | Metrics

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Application of Compaction Sand Columns in Liquefaction Mitigation for Vertical Revetment Structures WU Jiawu 2019, 33 (1):  27-30.  Abstract ( 649 )   Save This paper presents a case history of the liquefaction potential mitigation for vertical revetment structures in port construction by using compacted sand column method. The paper introduces the principles of the compacted sand column, design approach and key aspects of construction. The geotechnical testing results after the compacted sand column installations indicate that, when the appropriate replacement ratio and the reasonable construction quality control, the density and the shear strength of sandy soils can be enhanced to resist the seismic shaking.The analysis and summary of the antiliquefaction of compacted sand piles can be used for reference in similar projects. Related Articles | Metrics

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Engineering and Geological Characteristics of Qinhuai East River Sandstone of Huangmaqing Formation ZHANG Liping1, XU Baotian2, QIU Dejun1, SHAN Taisong2 2019, 33 (1):  31-34.  Abstract ( 663 )   Save Field reconnaissance and engineering test results indicate that the properties of Qinghuai East River sandstone of Huangmaqing Formation (T2h) are critical to the stability of the proposed high cut rock slopes. The Xray Diffraction (XRD) tests indicates that high clay mineral contents exist in sandstone so that the rock will likely be softened when absorbing the water. Rock mass fractures could also be developed after the water infiltrating and connecting the microcracks. The targeted sandstone was categorized as soft rock by the unconfined compressive strength tests on intact rock samples. When exposed in the ambient atmosphere, the soft rock will be softened. The evaluation results indicate that the rock mass integrity index determined from the shear wave velocity is less than that of determined from the volumetric joint methods. It is also concluded that the water is a critical factor affecting the rock mass properties and the stability issue of the proposed slope excavation should pay attention to the effect of water. Related Articles | Metrics

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Loess Highway Slope Stability Analysis Using the Theory of Unsaturated Soil Mechanics WU Shuangzhao, YANG Jingyuan, ZHOU Wuyi 2019, 33 (1):  35-38.  Abstract ( 567 )   Save This paper presents evaluation of the slope stability in loess soils in a mountain highway project in west Henan Province by using unsaturated soil mechanics theory. Based on the laboratory tested mechanical and physical properties of loess soils and tested soilwater characteristics curve, potential affecting factors for the loess slope stability, such as, ratio of slope, height of slope and climate, are numerically investigated for the effect of moisture content and pore pressure fields. The loess slope stability analysis results under various working conditions are also provided. Related Articles | Metrics

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Effect of Coarse Aggregate Group on Mechanical Properties of the Fine-Grained Soil Mixtures ZHANG Yunyi1,2, WU Yupeng1,2, ZHANG Keneng1,2, XUE Yanqi1,2, QIN Libin3， LIAO Yang1,2 2019, 33 (1):  39-43.  Abstract ( 476 )   Save The content of coarse grained soils and their grain sizes have an important influence on the stressstrain characteristics of fined grained soil mixtures. This paper presents the valuation influence of coarse grain content on the geotechnical properties of fine grained soil mixtures throughout large scale insitu direct shear tests. After each test, the grain size distribution of each serious of sample were laboratory tested. The results indicate that: The peak shear strength value is proportional to the content of coarse grained materials. When the grain size range D60 is limited within 0.02 to 0.05 mm, both the shear strength and internal friction angle increase with the increase of grain size; when the grain size D60 is greater than 0.05mm, with the increase of grain size, both the rate of internal friction angle increase and the apparent cohesion reduction rate increase. Related Articles | Metrics

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The Influence of Geomechanical Environment on the Stability of Underground Rock Caverns WU Kai1, YANG Xuelian1, LI Jia2 2019, 33 (1):  44-48.  Abstract ( 554 )   Save The stability of underground rock caverns is affected by the geomechanical properties their surrounding rock mass. This paper presents a stability evaluation of an underground rock cavern during the rock excavation for a hydropower generation station in western China. The evaluation considered various combination of structural geological conditions, rock mass property as well as initial geostress field conditions by using elastoplastic finite element analysis for different rock excavation sequences. The influence of different geological faults, rock properties and initial stress conditions on the deformation, stress and plastic zones in the cavern are discussed. The results can be used for the design and construction of underground rock cavern under similar conditions. Related Articles | Metrics

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Numerical Simulation of Rock-Soil Aggregate Mixture -Throughout Digital Image Processing YANG Chenggang 2019, 33 (1):  49-53.  Abstract ( 538 )   Save The digital image information of soilrock aggregate mixtures of a target slope was collected by using digital image processing technique. Factors that might adversely affect the quality of digital image were filtered through the preprocessing of the digital photos. The dimensions, grain size distribution and other characteristics of the soilrock aggregate were obtained through gray scale, binary processing, and domain threshold adjustment.  The image pixel coordinates of the soilrock aggregates were converted the numerical identification that could be recognized by Particle Flow Code 2D (PFC2D) software and the numerical identification information in the software can be restored into digital image. The digital direct shear test results were also compared with the large scale direct shear test results on soilrock aggregate samples. Related Articles | Metrics

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Settlement Analysis of Geocell Reinforced Soils Using Asymptotic Homogenization Method PAN Ting, YIN Changjun, XIAO Peng 2019, 33 (1):  54-57.  Abstract ( 485 )   Save As a threedimensional reinforced material, geocell has been widely used in many engineering projects such as residential and industrial buildings, highways and ports.Under the external loading, the geocell reinforced soils will subject to stress and will induce settlement. It is necessary to analysis the performance of the geocell reinforced soils and to estimate the foundation settlement value to ensure the project quality. The equivalent elastic modulus and other mechanical parameters of the geocellreinforcement are analyzed by the asymptotic homogenization method. The results indicate that the geocellreinforcement is an isotropic negative Poisson's ratio material in the transverse and longitudinal directions.Using the asymptotic homogenization method derived mechanical parameters for the settlement analysis of the reinforced soils with different geocell embedment. Both the numerical analysis and the field test results demonstrated that deeper geocell embedment would induce larger settlement.  Related Articles | Metrics

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Construction Monitoring and Evaluation of Adjacent Structures Using Defect Characterization and Finite Element Analysis YAO Jing, WANG Pengpeng 2019, 33 (1):  58-61.  Abstract ( 421 )   Save Adverse deformation and damage at the existing highway bridge piers were observed, and it was concluded that these deformations were induced by the adjacent construction. These excessive deformations and damages might affect the safe operation of the highway and even result in serious traffic accident. The damages on the bridge piers were numerically analyzed by commercial software FLAC3D. The stress and strain fields of the piers were evaluated, and the construction monitoring program was established from the numerical analysis results. Based on the monitoring results, bridge management decision could therefore be made. Related Articles | Metrics

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Stability Risk Assessment of Ground Above Abandoned Mines by FLAC3D LI Jianhong1, HUANG Xin2, MA Anfeng3, XU Rui4 2019, 33 (1):  62-65.  Abstract ( 435 )   Save The stability risk hazard assessment of the ground surface above the abandoned mine is complicated and factors might result in the collapse. In this paper, the collapse process is numerically simulated by a commercial software FLAC and the probability of collapse of the ground is predicted using comprehensive analytical methods. Mitigation methods of the collapsed ground are also proposed in the paper. The results indicate that the collapse hazard of ground above the abandoned mines is mainly contributed by the mining methods. The stability risk evaluation method proposed in the paper can provide a relatively accurate risk prediction for the remediation. Related Articles | Metrics

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Numerical Simulation and Monitoring of Surrounding Rock Mass Deformation Induced by the Subway Communication Gallery Construction TIAN Ye, YIN Changjun， CHEN Keyi 2019, 33 (1):  66-69.  Abstract ( 535 )   Save The excavation of the communication gallery is a key process in the construction of subway tunnels. This paper presents a case history of a communication gallery construction for a subway tunnel. The deformation of the rock mass surrounding the tunnel in the excavation process was numerically simulated by using Midas GTX NX software based on the actual construction sequence and calibrated with construction monitoring data. Based on the analytical and monitoring results, the following conclusions could be made: In the process of communication gallery excavation, because of stress concentration, maximum settlement could be observed at the joint of main tunnel and communication gallery. This area should be monitored. The joint between the longitudinal side of the pump house and the shielded tunnel supporting area is the main lateral deflection zone. Large surface subsidence will be occurred in area within 15 meters along the center alignment of the communication gallery. Related Articles | Metrics

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Factors Affecting Rock Mass Shear Strength Results from Single Point In-Situ Direct Shear Tests ZHENG Chaolin1, YUAN Conghua2, QIAO Wenhao2,3 2019, 33 (1):  70-74.  Abstract ( 724 )   Save Single Point Shear and MultiPoints Shear methods are common insitu direct shear tests for the rock mass shear strength measurement. While strength data from the multipoints shear test methods are usually more scatter than those from single point shear testing, the single point testing method has its own limitations. From the practical project point of view, this paper presents different methods of conducting single point insitu direct shear test and their characteristics. Factors affecting test results, testing conditions and testing methods are discussed and evaluated. The single point direct test data demonstrate the following conclusions: Although testing errors might exist in the shear strength results from the single point testing method, these errors still could be controlled within the acceptable range for the engineering applications if appropriate precautious measures can be applied in the testing process. Key procedures, controlling testing measures and data process aspects are also discussed in the paper. Related Articles | Metrics

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Experimental Study on the Dynamic Strength of Sandy GrainMucky Soil of Dongting Lake LI Yi1, NIE Shicheng2, FU Yu3, YANG Bai3 2019, 33 (1):  75-77.  Abstract ( 408 )   Save The sandy grainmucky soil is a special structured lacustrine deposited soil with fine sand lenses from Dongting Lake. The dynamic strength envelope of Dongting sandy grainmucky soi samples was experimental studied by using DDS70 dynamic triaxial testing device. The effect of confining pressure and applied cyclic axial frequency on the dynamic strength was evaluated. Throughout the investigation, the following conclusions are obtained: 1) The dynamic cohesion and dynamic internal friction angle values decrease the number of cyclic stress; 2) The sample strength decreases rapidly at the small number of cyclic stress and after the cyclic stress number reaches a certain value, dynamic strength decrease slowly with the increase of number of cycles; 3) under the same cyclic number, the higher the frequency and the confining pressure, the higher the dynamic cohesion and the dynamic internal friction angle. Related Articles | Metrics

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Model Study on the Uplift Capacity of Vertical Threaded Steel Pile in Sandy Soils DUAN Zixia, LEIZhen, QU Juntong, ZI Xiaolei,QU Linhe, ZHANG Yongzhao 2019, 33 (1):  78-82.  Abstract ( 845 )   Save According to the similarity theory of model test, sand soil was used to simulate the soil layer in the field. The comparative studies of the laboratory model show that the axial capacity of the threaded steel pile is 1.34~1.92 times those of the identical diameter pile without shreds. When the thread spacing was densified from 100 mm to 50mm, the uplift capacity was 1.1 times of that of 100 mm spacing. The soil pressures, skin friction and the axial capacity of threaded pile with thread spacings of 100 mm and 50mm were comparatively studied and it was concluded that spacing of 50mm threaded pile is a better product. The empirical formula for the axial uplift capacity is was also recommended based on the test results. Related Articles | Metrics

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Application of Diver Automatic Groundwater Level Monitoring Device in the Pump Test JIN Yongsheng 2019, 33 (1):  83-86.  Abstract ( 597 )   Save This paper introduces the principle, installation and operation aspects of the Diver automatic groundwater level monitoring device. The application of this device in a pump test in the Airport Road Station of Nanjing No. 5 Metro Line is also presented in this paper. The groundwater level and water temperature were automatically collected in the pump well and the water level in the observation well is collected using conventional method. Throughout comparison of data from automatic device and conventional data collection methods, it is evident that the automatic monitoring device has the advantage of groundwater level, temperature measurements and collecting time setting, data acquisition, data processing and labor cost. The results are more reliable and more timely results and cost effective. Related Articles | Metrics

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Monitoring and Analysis of the Corrosion of Steel Reinforcement Bars in Foundation of Power Transmission Towers YANG Mangsheng, LI Kaimin, GUO Zhaohua, MA Jian, AN Xiangyang 2019, 33 (1):  87-90.  Abstract ( 574 )   Save The corrosions of the steel reinforcement bars in foundation of power transmission tower structures is one of the key factors that affecting the safe operation of power transmission lines. Among many potential factors, electrochemical properties such as, pH value, Cl concentration and oxygen content are factors that might induce the corrosion of the steel reinforcement bars. This paper presents a case history of corrosion monitoring of the subsurface environmental conditions for the steel reinforcement bars in foundation of power transmission towers in Maoming area. The monitoring results indicated that, the power transmission towers are located in the coastal area so that the pH is slightly alkane and chloride content is high, corrosion of the steel reinforcement bars was observed under the oxygen rich environments. Related Articles | Metrics

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Engineering Geological Characteristics of Rock Mass Reinforced with Rock Anchors Through Comprehensive Investigation Methods YU Song, LI Guangyao 2019, 33 (1):  91-94.  Abstract ( 508 )   Save This paper presents a case study of a suspension bridge construction in karst terrain: ChinaMyanmar natural gas pipeline crossing the Lancang River Project. The comprehensive investigation methods for the rock anchorage zone design and construction. The engineering characteristics of rock anchorage zone were investigated by engineering geology survey, geotechnical borings, geophysical methods, crosshole electromagnetic wave CT, acoustic velocity measurement, borehole panoramic digital image and laboratory tests. The geological stratigraphy, distribution of karst caverns and rock pinnacles, integrity of karstic rock mass and hydrogeological aspects of rock anchorage zone were extensively evaluated. The design parameters for the construction were also recommended in the paper. Related Articles | Metrics

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Ultimate Axial Capacity of a Single Pile by Static Load Tests Using US and Chinese Procedures XU Qingwei， YU Feng， ZHU Xiaodan 2019, 33 (1):  95-98.  Abstract ( 576 )   Save The static load test is one of the important methods to determine the ultimate axial compressive capacity of a single pile with a relative high accuracy. The static loading test procedures for the axial compressive capacity of a single pile in US and Chinese code are different. This paper summarizes the similarities and differences between the static loading test procedures and methods to determine the ultimate axial capacity of single piles. This paper also compares the static loading test results on piles in a power plant in Indonesia using both US and Chinese test procedures. Related Articles | Metrics

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Measurement of Thermal Parameters of Geomaterials YANG Hongying 2019, 33 (1):  99-102.  Abstract ( 591 )   Save The thermal parameters are necessary in metro design and construction projects. The DRE2C thermal conductivity testing device has been widely and commercially used in consulting and testing firms. This paper presents the testing procedures of two thermal parameter testing devices: DRE2C thermal conductivity and BRR unit thermal capacity testing equipment. Related Articles | Metrics