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23 April 2021, Volume 35 Issue 2 Previous Issue    Next Issue

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Groundwater Seepage and Deformation of Diaphragm Wall Supported Excavations of a Subway Station LIU Houcheng, GUO Qijun 2021, 35 (2):  91-95.  Abstract ( 465 )   Save This paper presents a case history of three-dimensional groundwater seepage simulation by commercial software Visual MODFLOW for the Lvshuiwan Station of No. 11 Line in Nanjing. The numerical groundwater seepage model of the diaphragm wall supported deep excavation considered the type of deep excavation, geological and hydrological conditions at the project site. The influence of various embedment depths of diaphragm wall into the bedrock on the groundwater seepage field inside and outside of the excavation as well as the deformation induced by the watering operation was investigated. The results indicate: The argillaceous silty sandstone bedrock embedment has an obvious groundwater retardation effect. With the increase of embedment depth, the groundwater table outside the excavated area decreases, but the height of water table decrease is relatively small. It is not cost effective of minimizing the groundwater reducing by only increase the bedrock embedment depth of the diaphragm wall. However, adequate bedrock embedment can effectively increase the time of groundwater water drop as the result of dewatering inside the excavated area, so that the ground subsidence induced by the rapid groundwater drop can be positively delayed. The required bedrock embedment depth can be determined by considering the adjacent environment, stability of the deep excavation, construction cost and other constructability. Related Articles | Metrics

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AutoCAD User Denvelopment Methods in Deep Excavation Applications ZHU Jia 2021, 35 (2):  96-100.  Abstract ( 340 )   Save This paper introduces the evolution of the user development and its major methods of using the user development platform based on the characterization construction drawings and the feasibility and practical needs of automatic drafting. The details of VBA based plug-in environment are also presented. Procedures that can automatically draft the construction drawings for the deep excavation are provided: instructions of the AutoCAD objects, performance functions and properties; VBA operation with Word and Excel files that can automatically read the design calculations and data from the user defined excel files. The automatically drafting procedures were satisfactorily applied in a deep excavation design project.  Related Articles | Metrics

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A Case Study of the Application of OU-CSP in a Deep Excavation of Underpass HE Qiming, LAI Yunjin 2021, 35 (2):  101-105.  Abstract ( 627 )   Save The proposed deep excavation for a highway underpass site in Zhujiajian of Zhoushan was 450m in length and its excavated depth varied from 0 to 8 meters. A combined sheet pile system with steel pipe piles and Usection sheet piles (OUCSP), in which the Usection piles are 12m long and the steel pipe piles are 15m or 18m long, respectively, has been used as the supporting structure with two layers of steel pipe struts for the excavation of the underpass structure in areas with the excavation depths less than 5 meters. The deep excavation site is located in peaty soft soils and was improved with deep mixing cement-soil columns. This application shows that OU-CSP has the advantages of cost effective, short construction schedule and much higher stiffness over other types of supporting structures such as SMW retaining wall. Due to above advantages, OU-CSP is feasible to the construction of long, narrow, and deep excavation such as that of highway underpass. Related Articles | Metrics

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Optimization of Design Parameters of Dynamic Compaction and Replacement Method in High Fill Soils WU Qitai 2021, 35 (2):  106-110.  Abstract ( 457 )   Save In the construction of large petroleum product storage tank farm project, the dynamic compaction and replacement method was used in the improvement of high fill soils for the first time. To validate the design parameters, a trial test area was selected for application of the dynamic compaction and replacement method. The construction procedures, test results, construction monitoring data and the site quality assurance testing data before and after the improvement were evaluated for the optimization of the design parameters for the soil improvement procedures to be applied in larger areas. The post construction settlement observation data for the petroleum product storage tank water filling test as well as in the operation of the storage tanks were also presented in the paper. The results indicated the dynamic compaction and replacement method is suitable for the improvement of high fill soils. Related Articles | Metrics

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Local Hazards and Stability Analyses of High Mountain Slope Under Precipitations FENG Tao 2021, 35 (2):  111-115.  Abstract ( 384 )   Save This paper presents a case history results of evaluating the stability of high mountain slopes after the soaking of rainfall waters, and the hazards of localized storm water accumulation induced by the blocking of drainage ditches by tree leaves on the slope stability. A case history of a building near the high mountain slope was numerically analyzed by using commercial finite element analysis software PHASE2. The numerical slope stability model of the soaked soil with rainfall accumulated at the toe of the slope was established by using the strength reduction method. The results indicate that, the controlling factor of the slope stability is governed by the properties of at the interface of the red clay and the highly weathered bedrock. Under the soaking of rainfall water, the stability of the slope reduces significantly, under this condition, the stability of the slope is controlled jointly be the soaking line and the above-mentioned interface. When the soaking line is close to the interface between the red clay and the highly weathered bedrock, the global stability of the mountainous slope reduces significantly, and even causes slope instability. Related Articles | Metrics

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Influence of Red Clay Lens on the Stability of Deep Excavation LI Xia 2021, 35 (2):  116-119.  Abstract ( 335 )   Save With the progressive of urbanization and the available land for the development becomes less and less. It is necessary to study the deformation of the deep excavation supporting structures in the complicated geotechnical conditions. This paper presents the evaluation results of the geotechnical and geological conditions for a deep excavation site in Sichuan. The process of the deep excavation supporting system was numerically analyzed. The results indicate that, before the excavation, the deformation of soils adjacent to the excavated area is mainly in the vertical direction under the gravity load. In the red clay lenses, horizontal deformation can be observed but the magnitude of the horizontal deformation is small. With the progress of the excavation, the horizontal deformation magnitude increases in at the excavation supporting structure, and the shear deformation along the red clay lenses increases. With squeezing of the weak red clay soil from the supporting structure and causes the instability of the supporting structure. Construction recommendations were also proposed based on the numerical evaluation results in the paper. Related Articles | Metrics

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Application and Numerical Simulations of Composited Retaining Structures in High Fill Slopes ZHAO Yejiang, CHEN Xu, CHEN Wang 2021, 35 (2):  120-123.  Abstract ( 331 )   Save Various supporting and retaining structures have been used in the landslide remediations. The engineering practice indicating that the single structure type could not meet the requirements in all projects. As a new retaining structure, the piled composited retaining structures, which combine the advantages of sliding resisting caissons and the conventional retaining walls, have been widely used in the slope stability remediation projects. This paper presents a case history of a high fill slope stability project in Guizhou Province. The finite element model was established, and the results were compared with the design values. Related Articles | Metrics

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Remediation of Collapse Induced by Groundwater Gushing in Pingtian Tunnel Excavation Crossing an F2 Fault Zone GAO Kang 2021, 35 (2):  124-129.  Abstract ( 501 )   Save The remediation of the highway tunnel excavation collapse induced by the groundwater gushing in the Pingtian Tunnel crossing an F2 faulted fracture zone in the Dapu Expressway project is introduced in this paper. Factors that caused the accident were evaluated and investigated in depth. The remediation plan was proposed based on the thorough investigations and was effectively implemented in the construction. Both the inflow of the groundwater into the excavated area and the deformations of the supporting structures were under the control.  Related Articles | Metrics

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Effect of Different CFG Column Installation Methods on the Adjacent Deep Excavation Support Structures LI Mingchao, YU Jianmin, WANG Rongyan 2021, 35 (2):  130-134.  Abstract ( 426 )   Save The compressive strength increase of the cement-fly ash-gravel (CFG) columns after the installation is positively related to the age of the concrete in the CFG column. During the CFG column installation, the passive soil zone inside the excavated area is disturbed and has minimal strength. Further, the strength of the CFG column at its early age is low. These adverse factors induce negative impacts on the supporting structures and their adjacent environment. The different CFG column installation sequences along the deep excavation supporting structures, which are column installed one next to the previous column along the longer supporting side and the column installed by skip one column along the shorter supporting side, are simulated by the commercial finite element software MIDAS GTS/NX. The results indicate that, the CFG column installed by skip location along the shorter side has less horizontal deflection in the supporting structure and less ground subsidence behind the excavated area. Further, the skip column location installation has only one day loner than the other method, but it is more reliable and less disturbance to the adjacent environment. Therefore, the skip column location method was recommended as the actual construction installation plan. Related Articles | Metrics

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Design of Varying CFG Column Length in Beijing Changxindian Area LI Yanhua , SUN Yanlin 2021, 35 (2):  135-138.  Abstract ( 315 )   Save The composite ground formed by the cement-fly ash-gravel (CFG) columns has the advantage of fast construction, short installation period, easy to control the quality and lost construction. This method has widely used as the foundation that supporting the high-raised residential buildings in Beijing. The Changxindian area is located in the west rolling area of Beijing. The shallow deposited bedrock consists of highly weathered to moderately weathered breccia, and soft rock such as mudstone. This paper presents a case history of design of CFG columns as the composited ground in Changxindian area in the shallow bedrock geological formations. The design applied varying CFG column lengths by socked the CFG columns of 0.5 to 1.0 meters into the strongly weathered bedrock. The paper also presents the preliminary design analyses and the ground improvement related column diameters, column length, center-to-center spacing, replacement ratio, column material composition and cushion zone thickness. Related Articles | Metrics

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Estimation of Improvement Zone of Launching End of Tunnel Boring Machine Excavations in Soft Soils MA Gaofeng, ZHU Jinxian, CAO Bingbing, WU Xiangtai 2021, 35 (2):  139-143.  Abstract ( 546 )   Save This paper presents a case history of estimating the soil improvement zone for the launching end of the Tunnel Boring Machine excavation method in soft soil in Shaoxing Transit Line No. 1. The improvement zone is estimated by three different approaches: namely, elastic plate theory, static approach and sliding instability theory. Numerical analysis of soil deformation and strain at various location of the soil improvement zone was performed by finite element software ABAQUS. The analytical results were compared with the construction monitoring data. The results show that: an improvement zone with a length of 6 meters in the longitudinal direction and a width of 3 meters in transverse direction is appropriate for the launching end of the TBM excavation. The longitudinal length of the improvement zone estimated by elastic plate theory is close to the results of numerical and monitored data. Therefore, the elastic plate theory should be applied in this project. Related Articles | Metrics

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Stability Analysis of Cut Slope Improved by Anti-Sliding Caissons MA Ning 2021, 35 (2):  144-147.  Abstract ( 305 )   Save A typical cut slope stabilized by antislide caisson in Guizhou was analyzed by both the code method and the finite element methods for the factor of safety of the slope. The numerical analysis results indicate that, when the cut slope is stabilized by the caisson and the retaining wall, the potential sliding plane is first developed in soil zone. With the increase of strength reduction, the deformation at the top of slope increases, and a circular sliding surface can be observed. When the factory of safety of the improved slope is between 1.1 and 1.2, the improved slope is stable and the deflection in the caisson is small and meets the code requirements. When the effective length of the anti-slide caisson is 29 meters, the anchoring depth is 19 meters. When the caisson length is 19 meters with anchoring depth is 7 meters, rotational tilting of the caisson is observed so that the ground anchor should be used in the caisson system. Related Articles | Metrics

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Case History of a Piping Remediation in a Pipe Jacking Pit Site in Yangtze River Floodplains YAO Yueliang, ZHANG Jie 2021, 35 (2):  148-150.  Abstract ( 763 )   Save During the deep excavations in the high groundwater area, the piping hazards are frequently encountered due to the inadequate dewatering measured or inappropriate supporting structure. If these piping hazards are not promptly remediated or inappropriately treated, the safety of the deep excavation will be jeopardized and excessive deformation the supporting structure might affect the stability of adjacent buildings and other structures and even induces the loss of properties and human life. This paper presents a groundwater piping within a pipe jacking pit. Factors that might induce the piping were evaluated and the emergency response program was developed with structural supporting, dewatering and the construction monitoring program. The results indicate that these measures were effective. Related Articles | Metrics

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Remediation of the Crest Collapse at a Shallow Buried Two-Lane Highway Tunnel ZHAO Liang 2021, 35 (2):  151.  Abstract ( 333 )   Save The shallow burred and unsymmetrical pressured highway tunnels have more safety hazards than other tunnels during the construction. A two-lane high tunnel experienced a crest collapse and the cracking in the initial supporting structures towards the shallow buried exit. The geotechnical, hydrological investigations indicated that the loose gravelly and boulderlike soils, which are difficult in the forming of the arching effect, are deposited at the collapsed area. The heavy precipitation was a majoring triggering factor to the crest collapse and the cracking in the tunnel supporting structure. The remediation measures included: backfilling of the collapsed area, ground backfill and improvement; installation of the perforated grouting steel pipes; installation of the pilot radial grouting pipes, installation of the pipe roof, installation of first immediately followed by the  secondary lining as well as construction monitoring. Related Articles | Metrics

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State-of-the-Art Review of Lignin and Its Derivatives on the Soil Properties Modification CHEN Xuejun, DING Xiang, XU Keyu, 2021, 35 (2):  156-160.  Abstract ( 745 )   Save Lignin is an organic polymer compound and it is most abundant renewable energy material on earth. Researches on the lignin and its derivative as the additives for the soil improvement are still at the beginning stage. The paper provides a state-of-the-art review of the application of the lignin and its derivatives as the soil improvement. Structure characteristics of the lignin, types and non-degradability are introduced in the paper. The influence of different contents of lignin and its derivatives in soil samples on the compressive strength are summarized. Effects of water stability, thermal conductivity, electrical conductivity, and pH values after mixing are comprehensively reviewed. Further studies are concentrated on the application of lignin in improving the heavy metal contaminated ionic soils. The various interactions between lignin and the soil particles are also evaluated. Related Articles | Metrics

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Effect of Basalt Fibers on the Abrasion Resistance of Concrete with Coral Reef Sand QIN Qinglong, MENG Qingshan, QIN Donglai, HUANG Xiaofang, 2021, 35 (2):  161-163.  Abstract ( 284 )   Save In the complex marine environments, the erosion and abrasion of concrete structures with coral reef sand such as breakwaters are frequently occurred. In order to improve the abrasion performance of coral reef sand concrete and the durability of breakwaters, basalt fibers with different content are mixed into the coral reef sand concrete samples. The basalt improved coral reef sand concrete samples were laboratory tested with uniaxial compressive strength, splitting tensile and abrasion resistance tests. The influence of the basalt fiber content on the mechanical properties of coral reef sand concrete were investigated. The results indicate that, the compressive strength of the basalt fiber improve coral reef sand concrete increases with the increase of curing age, but the content of basalt fiber has limited impact on the compressive strength. The split tensile strength of the sample can be improved by the basalt fiber content. When the basalt fiber content is 0.10% of the sample volume, the abrasion resistance reaches the maximum. Related Articles | Metrics

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Influence of Soft Soil Marine Layer on the Peak Ground Acceleration and Seismic Response Spectrum Using FLAC3D SONG Xing, WANG Ting, ZHANG Zhuangzhuang 2021, 35 (2):  164-167.  Abstract ( 442 )   Save The study of the seismic performance of marine soft soil sites becomes increasingly necessary with more and more near shore projects development in recent years. Numerical models for Both the nearshore and onshore sites with and without soft soil lenses were established by the commercial finite difference software FLAC3D. Different seismic waves, El Centro Wave and Kobe Wave, were input horizontally into the numerical models for the peak ground acceleration and seismic response spectrum in different soil sites and their differences. The results indicate that, the onshore site without soft soil, near shore without soft soil, onshore site with soft soil have significant difference in the magnitude of peak ground acceleration and the shape of the seismic response spectrum. At the low and medium frequency area, the response spectrum in the soft soil site is obviously higher than that of in other sites. The presence of the soft soil lens will magnify the acceleration. The soft soil lens in marine site has larger magnify effect than onshore site. Compared with other sites, the peak ground acceleration response spectrum of marine soft soil site has a lapse in the response. Related Articles | Metrics

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Stability Analysis of Fissured Slope Considering the Effects of Hydrostatic Pressure WANG Fan 2021, 35 (2):  168-170.  Abstract ( 342 )   Save Hydrostatic pressure can trigger the slope instability, especially for slopes with a large number fissures at top. However, the current slope stability analysis practice rarely considers the adverse effects of joint actions of fissures and the hydrostatic pressure. This paper presents the slope stability analysis results using upper bound limit analysis (UAM) and strength reduction methods on the fissured slopes. Slopes with various angles (30°~80°), various internal friction angles (10°~30°) and various amount of hydrostatic pressure in the fissures were analyzed and the factor of the safeties were reported. The results indicate that the hydrostatic pressure in the fissures can results in a large stability reduction in the slope and up to 30% of the reduction was reported. The critical location of the slip plane are similar in all instable slopes.  Related Articles | Metrics

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Mechanical Properties of Cement-Modified Collapsible Loess in Western Henan HAN Shuang, BI Qingtao, GAO Yujia, FENG Qiaoyun, MA Jiabing 2021, 35 (2):  171-174.  Abstract ( 324 )   Save The engineering properties of loess soils are characterized by their regional and location specific. In order to study the influence of the cement content on the mechanical properties of the collapsible loess in the western Henan Province, extensive laboratory tests were performed on treated collapsible loess soil samples. The test items are: Atterberg Limits, collapsible soil compression tests, unconfined compression tests with various cement content and curing ages. The results indicate that, the mixing of cement into the collapsible loess soils could change the grain size distribution of the soil so that the physical properties of the loess soils could be improved; then, the mixing of cement could significantly reduce the collapsibility of the loess soils. With the increasing of the cement content in the soil and curing age, the unconfined compressive strength of the modified loess has an obvious increase and the sensitivity to the water has significantly decreased. It is suggested that, due to the collapsibility and water sensitivities of the collapsible loess, a cement content of 4% should be applied in the loess soils for embankment and subgrade soils.  Related Articles | Metrics

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Influence of Deep Excavation Construction on the Deformation of Nearby Subway Tunnel ZHOU Xinyu, YUAN Jia 2021, 35 (2):  175-178.  Abstract ( 296 )   Save In the construction of a deep excavation project, the nearby subway tunnels, station halls, passages gallery and ventilation structure were monitored during the excavation. Base on the construction monitoring data analysis and evaluation, the following conclusions are obtained: Within the excavation depth between 5 meters and 10 meters, large horizontal deflection was observed the subway tunnel structures but the observed vertical settlement was small. It is suggested the segmental tunnel excavation method should be used, and the strength of the supporting structure or large supporting structure sizes should be used, along with a closer construction monitoring plan with focus on the horizontal deformation monitoring. Within the excavation depth between 10 meters and 16 meters, larger vertical settlement values were monitored at the subway tunnel with a small horizontal deflection. It is suggested that the construction monitoring program should be focused on the vertical settlement monitoring. Supporting structure reinforcement should be applied at larger deformation areas in the subway tunnel. Related Articles | Metrics

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Parametric Study of Stress Release Method in Tilting Correction by Using Circular Hole Expansion Theory XU Pengjing, LIAO Hongxuan 2021, 35 (2):  179-183.  Abstract ( 472 )   Save In building and other structure tilting correction projects, the soil extraction from a vertical hole is usually used to release the stress of the foundation soil, which causes the foundation soil to flow directionally into this vertical hole for the soil extraction to achieve desired tilt correction. Based on the mechanical analysis of the circular hole expansion theory, soil plastic zone of induced by the soil extraction was formulated. Using engineering case histories, a parametric study was performed on related soil extraction parameters such as the depth, spacing, and diameter of soil extraction holes, and suggested values for the related vertical soil extraction hole design parameters were proposed. Studies have shown that: as the depth increases, the extent of the plastic zone gradually decreases, and the larger the hole diameter, the larger the extent of the soil plastic zone around the hole; for high-rise buildings, the depth of stress relief holes can be appropriately increased; while for lowrise buildings, shallow holes should be the main focus. Deep soil extraction hole will increase the project cost, but the effect of the tilt correction is limited.  Related Articles | Metrics

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Numerical Simulations of Tunnel Construction Underneath an Active High-Pressure Natural Gas Pipeline ZHU Hongxi, CHEN Zhiyong, KE Wenhui, ZHONG Yu, YI Shun, HUANG Juehao, 2021, 35 (2):  184-188.  Abstract ( 444 )   Save Large size municipal stormwater discharge sewer pipes are frequently installed in urban area of coastal cities and cities near the river. These large size sewer pipe installations will un-inevitably affect the adjacent environment. This paper presents a case history of a storm water discharge sewer pipe project at Guanggu 1st Road and Gaoxin 4th Road interchange. In this project, an underground tunneling excavation of a large diameter sewer pipe was utilized to pass underneath an active high-pressure natural gas pipeline with a diameter of 720 mm. The numerical simulation was performed on the tunnel excavation with double-side pilot tunnel method by using commercial software Plaxis. The results indicate that, the ground subsidence value and area of ground subsidence increase with the progressive of the tunneling; the settlement along the cross section of the tunneling could be predicted by the Peck curve. The location of the maximum ground settlement is above the center of the sewer pipe and the observed ground settlement value is 24.76 mm, which was less than the settlement control value setup for the project. Related Articles | Metrics

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Index Parameters for Expansive Rock Identification and Its Applicability GENG Yun 2021, 35 (2):  189-193.  Abstract ( 430 )   Save The existing expansive rock identification index parameters can be classified into three types: rock material indices, rock powder material indices and comprehensive indices. The essential differences between the expansive soil and expansive rock are the history in the deposition of expansive rock. Therefore, the effect of cementation in the deposition of expansive rock should be considered as the index parameter of the expansive rock identification. Based on the thorough understanding of both advantages and disadvantages of the rock material indices and rock powder indices methods, this paper presents a new set of expansive rock identification index parameters, free expansion ratio and dry rock saturation moisture content, for the engineering application. For large engineer application, the conventional parameters such as, expansive force, and expansive ratio, should be references for the reliable expansive rock classification result. The paper also presents the identification results for the expansive rock samples in a high-speed rail project. The results indicate that the recommended expansive rock identification index parameters are reliable in the expansive rock classification. Related Articles | Metrics

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Tunnel Collapse Hazards in Completely and Strongly Weathered Granite CHEN Dejin 2021, 35 (2):  194-198.  Abstract ( 724 )   Save Tunnel collapse hazards were frequently in the Luojiazhai highway tunnel that is shallow buried in the completely or strongly weathered granite rock mass. Factors that might induce these collapses were evaluated with the combination field investigation, laboratory testing and theoretical approach. The results indicate that, the characteristics of the completely and strongly weathered granite are strength softening, slaking and poor stability when water is encountered. The main factors that caused the collapses are: geotechnical subsurface conditions: characteristics of the completely and strongly weathered granite, heavy precipitation, rich groundwater supply, abundant groundwater conduits and depressed groundwater collection shape; tunnel excavation under inappropriate advanced supporting measures caused by the insufficient geotechnical investigation data and inaccurate geological condition predictions during the excavation. Under the combination of the construction disturbance and the infiltration of the groundwater, the tunnel excavation area had the slaking failure and then rapidly developed into the global stability failure of the entire excavated area. The tunnel is then collapsed, and the ground sinkhole expression was also presented. With the understanding of above potential factors, the tunnel excavation sequence and advanced supporting method were adjusted, and the collapse hazards were able to be eliminated during the tunnel excavation. Related Articles | Metrics

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Reconsolidation Volumetric Behavior of Coral Sand Sample after Liquefaction XI Fangchao, JIA Zhen, TANG Xiaoxin 2021, 35 (2):  199-202.  Abstract ( 282 )   Save As a strategic project of China’s “Maritime Silk Road”, the man-made structures on islands and reefs in the South China Sea have to resistance the cyclic environmental loads such as waves and earthquakes, as well as the ground subsidence induced by seismic events. In this paper, the volumetric strain in the reconsolidation induced by the dynamic loading liquefaction is evaluated by the GDS triaxial testing device. The results indicate that, the volumetric strain in the reconsolidation by the dynamic loading liquefaction increases with the confining pressure and mean grain size in the sample; while the effect of cyclic stress ratio on the volumetric strain in the reconsolidated coral sand samples is only related to the time of dynamic load applied after liquefaction, not the size of grains in the sample. Related Articles | Metrics

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Experimental Study on Static Steel Chisel Sounding in Subsurface Investigation ZHAO Huahong, CHEN Xing, WANG Husheng, CHU Hao, LI Jinhua 2021, 35 (2):  203-206.  Abstract ( 327 )   Save The static steel chisel sounding is a new portable subsurface exploration device. This device has the functions of classifying the soil stratigraphy and measure the subgrade reaction. This paper presents a case history of comparison between the static steel chisel sounding (SSCS) penetration and penetration resistance obtained by cone penetration test (CPT) and their relationships in a highway project in Wuwei City. The subsurface investigation results obtained by SSCS, CPT, special disturbed soil sampler and laboratory test are evaluated; the tip resistance with depth curves and stratigraphy obtained by SSCS and CPT are compared; the reliability of the SSCS is discussed in this paper.  Related Articles | Metrics

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Study on Triaxial Test Deformation Measurement by Photogrammetry MU Chunmei, ZHOU Ziliang 2021, 35 (2):  207-211.  Abstract ( 326 )   Save In order to accurately measure the sample deformation in the triaxial shear tests, this paper presents a deformation measurement by using photogrammetry method. The image data acquisition was performed by an IPhone 6 cell phone on the RDA codes on the triaxial shear soil samples. The sample deformation model was established through the camera calibration, image processing and three-dimensional deformation reconstruction so that the sample deformation could be obtained. The results indicate that this method is feasible and effective and the advantages of using IPhone 6 cell phone for the image acquisition are easy to use and save both time and cost. Related Articles | Metrics

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Application of AccuPycⅡ1340 in the Specific Gravity Testing on Calcareous Sand Samples XIAN Quanzhen, LONG Shengjun, WANG Xueqing, HUO Yulong, WANG Yikun, 2021, 35 (2):  212-217.  Abstract ( 391 )   Save With properties significantly different from quartz sand of land origin, the calcareous sand of marine origin has irregular in grain shape, fragile and porous with both inter-connected and inner pores. Due to the inner porosity of the calcareous sand, the tested specific gravity values might be slightly different from different testing methods. Three different specific gravity testing methods: Pycnometer Method, Suspended Weighing Method and AccuPycII 1340 True Density Meter Method, are used to test the specific gravity values of both calcareous sand and quartz sand samples. The results are also evaluated. The “true density” values and the inner porosity of calcareous sand samples were tested by the AccuPycII 134 True Density Meter before and after the grain grinding. The results indicate that the tested specific gravity values were different with different testing methods. Smaller differences on values tested by Pycnometer Method and True Density Meter Method, comparing with the values tested by Suspended Weighing Method and True Density Meter Method. The inner porosity values on different grain size samples are different. A specific gravity value of 2.81 is suggested for the calcareous sand samples. From the testing time, testing accuracy and easiness points of view, AccuPycII 1340 True Density Meter Method is appropriate for the specific gravity testing on calcareous sand samples with various grain sizes. Related Articles | Metrics

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Application and Analysis of Borehole Magnetic Logging Method in Detecting the Reinforcement Cage Length in Bored Piles ZHU Zheng 2021, 35 (2):  218-221.  Abstract ( 884 )   Save The reinforcement cage length in bored piles in several projects was detected by the magnetic logging method and the magnetic logging curves were evaluated. The test results show that the magnetic logging method is an effective and reliable method for detecting the reinforcement cage length in bored piles. For piles with suspected total length and defects, the length of the reinforcement cage is an important factor for evaluating the quality of the bored concrete piles. When the number of longitudinal reinforcement bars change, the amplitude of the magnetic gradient curve-depth is lower in the area with fewer reinforcement bars. When the distance between the surface of the pile shaft and the borehole for magnetic logging is too large, the curve characteristics to be used for determining the bottom of the reinforcement cage and the reinforcement splice locations are becoming not obvious. As a result, the reinforcement bar cage length might not be accurate. Related Articles | Metrics

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Application of Comprehensive In-Situ Testing Methods in the Sandy Soil Liquefaction Evaluation GAO Qingcai, ZHANG Guochao 2021, 35 (2):  222-227.  Abstract ( 640 )   Save Although the sandy soil liquefaction under a seismic event is one of the major hazards in the geotechnical engineering, the soil liquefaction evaluation and prediction of the potential are difficult, and the in-situ testing evaluation methods are usually used. This paper presents various sandy soil seismic liquefaction evaluation methods by using in-situ testing methods. Earthquake damage of sands liquefaction is one of the most serious engineering disasters in geotechnical engineering. In situ test methods are often used to evaluate liquefaction because of the liquefaction evaluation and prediction is difficulty. Relying on the Chibi Yangtze River Highway Bridge Project, we analysis the domestic code methods and Seed simplified methods, and the engineering characteristics of each sands, then liquefaction evaluation of each sand layer is carried out by using shear wave test and standard penetration test respectively. The research results show that: the discrimination depth of “code for Investigation of Geotechnical Engineering” and “Code For Seismic Design Of Building” is relatively shallow, within the range of 20m, and the former is conservative for the use of SPT blow to discriminate sands liquefaction; compared with the code methods, seed simplified methods provide various calculation formulas, and can provide further discrimination for deep sands liquefaction, the discrimination results can be used as a supplement to the cod methods; the comprehensive comparison and analysis of various insitu testing methods are helpful to improve the accuracy of sand liquefaction identification. Related Articles | Metrics

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Effect of Saturation Methods on the Mechanical Properties of Coral Sands WANG Yikun, XIE Lin, WANG Xing, ZHOU Xueyou 2021, 35 (2):  228-233.  Abstract ( 303 )   Save Due to its special deposition environments, the coral sand has the characteristics of high voids with inner porous, low individual grain strength and prone to grain breakage. The high porosity of coral sand sample is difficult to reach high degrees of saturation in the sample preparations for the laboratory tests. This paper presents the triaxial test results on samples under different degree of saturations. The test results indicate that, the tested peak strength and the internal friction angle reach the maximum on sample saturation prepared by vacuum method followed by the submerging saturation method, and the back pressure saturated samples have the minimum peak strength and internal friction angle. With the increasing of confining pressure, the internal friction angle differences on samples prepared by different saturation methods are smaller. The grain breakage during the sample preparation by different methods has obvious difference with submerging method having the maximum amount of grain breakage and vacuum method having minimum amount of grain breakage. It is also concluded that the grain breakage is an important factor that affecting the peak oblique stress value. Since part of the grain breakage occur during the sample preparation, the amount of total grain breakage cannot completely be associated with the peak oblique stress value. It is necessary to conduct microscopic study on the samples and comparing the differences induced by different saturation methods so that the impact of the sample saturation methods on the shear strength properties of the coral sand samples can be evaluated.  Related Articles | Metrics

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Direct Shear Tests on A Pakistan Rock Salt XUE Bing, LIN Jiawei, LIU Jicheng, LIU Huachao 2021, 35 (2):  234-237.  Abstract ( 410 )   Save Direct shear tests on a high purity Pakistan rock salt samples were performed by using a YZW100 direct shear testing device. The shear strength, shear deformation and failure mode of rock salt samples were analyzed. The results show that the shear failure mode of the salt rock is a ductile failure, and the shear stressdisplacement curve is in a gentle change with high residual stress which indicating the strong frictional resistance in the sample tested. Both the shear strength and the residual strength of rock salt samples increase with the increase of normal force applied. The tested cohesion of the Pakistan rock salt samples is 7.41MP with an internal friction angle of 44.1° while the tested residual cohesion is 0.16MPa, and the residual internal friction angle is 47.1°. Comparing with domestic stratified rock salt samples, the high purity Pakistani rock salt samples have similar internal friction angle, but higher cohesion and therefore a stronger shear strength. The shear failure plane of rock salt samples is not smooth and there are obvious local scratches observed, which is similar to the “furrow effect”. The test results have the reference value for the further understanding the failure mechanism of salt rock as well as the stability of the underground gas storage facilities. Related Articles | Metrics

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Development and Application of a Combined Testing Device for SmallStrain Parameters of Soil ZHAO Kelie, ZHENG Hongjian, LI Jian, YANG Zhiyong 2021, 35 (2):  238-242.  Abstract ( 324 )   Save Resonance column and bender element are the two most promising methods for obtaining the dynamic small-strain parameters of soils in the laboratory conditions. However, as they are independent systems, tests that combining with their complementary functions have not been reported. This paper presents a new development of using commercial Stokoe type resonance column instrument by GDS (Geotechnical Digital Systems) Company and the implementation of the bender element system into the resonance column test system. The improved device could perform the combined tests on a soil sample. In order to test the reliability of the improved system, the small strain tests on silty sand samples from the Hangzhou Bay were conducted to measure the dynamic modulus. Results show that the device combines advantages of both the resonance column system and the bender element system; for the same sample, the calibration on bender elements can be achieved by the resonance column system, which effectively overcomes the problem of shear wave propagation time determination during the bending element test. There are significant dispersion properties in the bending element tests of the dry sand; when the bending element excitation frequency can satisfy the condition, 2<ξ<7, the influence of the near-field effect can be weakened, and a stable and clear shear wave receiving signal can be obtained. Related Articles | Metrics