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20 June 2020, Volume 34 Issue 3 Previous Issue    Next Issue

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Application of CFG Column Method in Collapsible Loess Improvement MAN Chaohui, YANG Lina, ZHANG Xiaohui 2020, 34 (3):  265-268.  Abstract ( 620 )   Save The treatment of collapsible loess foundation has always been an engineering challenge. The working mechanism of the Cement Flyash Gravel (CFG) column composite foundation for the ground improvement of collapsible loess is demonstrated by the brief discussion of the role of CFG columns strengthening the collapsible loess. This paper also presents a case history of installing CFG column in collapsible loess soils using a long flight auger. The installation methods are discussed with problem solving on the site-specific subsurface conditions. Both laboratory and the field quality assurance test results indicate that the bearing capacity and the deformation are met the design requirements. The CFG column is a cost-effective solution in the ground improvement of collapsible loess soils. Related Articles | Metrics

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Engineering Geology Characteristics of Baozi Creek Ecological Scenery Corridor DENG Qingjun, LIU Yazhou, ZHU Fanji, WANG Xiandeng 2020, 34 (3):  269-272.  Abstract ( 441 )   Save With the large-scale urban underground space development, the storage of the wasted soil from these developments has created a series of increased social economic and environmental concerns. It is of great significance to the ecological management, redevelopment of the waste soil storage sites and other areas to enhance the image, to convert them into an ecological friendly and sustainable development modern city. This paper presents a case history of the construction project of Wuhan Baozi Creek ecological scenery corridor. Based on the site exploration, sampling, evaluation and analysis of geological environment of the existing site, geological environmental aspects of the site were severely damaged by the large amount of waste soil storage. The engineering concerns were included: slope stability on the nonengineered high random fills; ground subsidence induced by the waste soil fills; hydrological and groundwater condition changes; engineering considerations on these random high waste soil fills. These concerns are discussed in the paper and recommendation of the redevelopment are also proposed. Related Articles | Metrics

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Application of BIM in Tunnel Engineering ZHOU Junfa, WANG Yutian, LIU Guannan, WANG Ning 2020, 34 (3):  273-276.  Abstract ( 744 )   Save The tunnel engineering has some unique characteristic; such as large concealment, complicated construction techniques, complex geological conditions and long construction period. It is therefore reasonable to apply the Building Information Modeling (BIM) tools in the tunnel excavation. The stateoftheart applications of BIM in the tunneling are demonstrated throughout an extensive literature review. The visualization modeling in the tunneling engineering, simulation of tunneling excavation process and construction safety monitoring applications are also reviewed. Recommendations of the improvement of BIM technique in the tunneling are also provided. Related Articles | Metrics

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Analyses and Remediations of the Collapse of a Deep Excavation Support in Soft Soils YANG Peng, ZHANG Shihua 2020, 34 (3):  277-280.  Abstract ( 459 )   Save This paper analyzes the collapse of a deep excavation support structure in soft soils. Factors that might contributed to the failure of the supporting structure are evaluated. These factors include, selecting of the typical analytical section; selecting of supporting structure; analysis of most unfavorable working assumptions; reinforcement connections in the supporting structures; protecting the adjacent utilities; construction monitoring data; selection of threshold values for the alarming conditions. This paper also provides recommendations for the equality control in the construction, improvement in the supporting structure design and construction monitoring. Related Articles | Metrics

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Construction of Large Diameter Cast-In-Place Reinforce Concrete Piles with Enlarged Base LIAO Kunyang, HUANG Xiaosong 2020, 34 (3):  281-284.  Abstract ( 441 )   Save 〖WT〗 Cast-in-place concrete pile by using deep well injection method was originated in the U.S. The injection method was used for the treatment of wasted materials from the petroleum generation process by injecting the waste material into the deep rock fissures through the deep wells. Currently, this injection method has been widely used in the deep and large diameter castinplace reinforced concrete pile installations. This paper presents a case history of the technique and quality control aspects of constructing of the large diameter castinplace reinforced concrete piles. Related Articles | Metrics

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Construction Aspects of Deep Excavation Around a Reserved Building WANG Yixuan 2020, 34 (3):  285-288.  Abstract ( 395 )   Save With the urbanization and the diversified development of underground space, the protective requirements of surrounding reserved buildings in ht edeep excavation construction become more and more popular and comprehensive. Based on the project case history at the westside of the Liuhu Road and the north side of the Huancheng Road in Juyuan New Development, Jiading District, Shanghai, this paper studies the key aspects of the deep excavation around a water tower that to be reserved. The projective requirements of supporting this structure were evaluated and the concept of reinforced concrete ring beam plus prestressed steel strand was proposed. This measure ensured the uniform settlement of the building and resolved the problem of unbalanced force during the excavation adjacent to the tower. Throughout the finite element numerical simulation, the deformation pattern of the reserved structure was able to be predicted. Related Articles | Metrics

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Installation of Cast-In-Place Reinforced Concrete Piles in Deeply Embedded Karst Terrain MOU Dapeng, WU Canxin 2020, 34 (3):  289-291.  Abstract ( 371 )   Save Some of the construction sites in Hangzhou have limestone deposits, karst is generally developed. The embedment depth of the karstic bedrock is generally large, and it is difficult to completely characterize the degree of development rock cavities and their connectivity. In large construction projects, the karst site is a vital part of the pile foundation safe installations. However, the experience of pile installations in karst formations is relatively rare in Hangzhou area. As a result, it is important to summarize the lessons learned in the pile installations in karst. This paper presents a project case history. The subsurface geotechnical investigation and karst rock cavity treatment during the construction are also introduced. Related Articles | Metrics

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Remediation of the Collapse at the Urgency Stopping Zone of a Deeply Embedded Tunnel LIU Xiaowei 2020, 34 (3):  292-295.  Abstract ( 302 )   Save The collapse hazards are frequently encountered in the tunnel excavations, especially, in the emergency stopping zone. The economical and life loss induced by these failures are often huge and the even uncountable. This paper presents a case history of remediation of the collapse at Yangbajing No. 1 Tunnel on December 4th, 2018. The reinforcement method was able to be proposed based on the collapse and geotechnical and geological information at the site. The following measures were used during the remediation: the ground penetrating radar was used to control the quality of the construction in the collapsed zone so that the following collapses were avoided. Related Articles | Metrics

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Impact of Regional Ground Subsidence on the Zhengxu Passenger Rail Line NI Yueyan 2020, 34 (3):  296-300.  Abstract ( 367 )   Save The comprehensive investigations indicate that a largescale regional ground subsidence is developing along the Zhengxu Passenger Rail Line induced by the excessive groundwater extraction. These ground subsidence cones are formed centered at the urban area. The geological and hydrogeological characteristics of the soil strata along the rail alignment, groundwater extraction conditions, change of seepage boundary conditions due to the groundwater extracting are evaluated. The groundwater level change was simulated by using Visual Modflow software so that the groundwater seepage field, limits of the settlement cone induced by the groundwater level changes could be obtained. Based on the simulation results, areas with severe ground subsidence potential were instrumented and monitored to provide long term data for the safe operation of the passenger rails. Related Articles | Metrics

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Factors that Affecting the Formation of High-Risk Rock Fall Hazard and Their Preventions YANG Chaofa 2020, 34 (3):  301-303.  Abstract ( 511 )   Save Guizhou is in a typical mountain terrain. There are many highrisk rock fall bodies in and surrounding the urban area of the city. With the increase quality of life, the instability induced by these highrisk rock falling bodies has drawn more and more attentions by the public and governmental agencies. This paper presents the investigation and remediation of rock fall hazards in Guiyang City. Factors, such as; topographical conditions, geological conditions od bedrock, tectonic structures, degree of weathering and unloading effect on the rock outcrops, role of surface and groundwater, vegetation and human activities; that might attribute to the rock falls have evaluated. The remediation measures are also proposed in the paper. Related Articles | Metrics

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Deformation Monitoring on a Soil Mixing Wall as Deep Excavation Supporting Structure WANG Tao 2020, 34 (3):  304-307.  Abstract ( 458 )   Save Due to the complication and variation of geomaterials and the limitation of various prediction models, it is very difficult to accurately predict the impact of deep excavation on the adjacent ground, utilities and buildings based only on theoretical and empirical approaches. This paper presents a case history of the comparative studies on the deep excavation supporting structure between the theoretical analysis and construction monitoring data. The soil mixing wall (SMW) supporting structure in the deep excavation process was simulated by the commercial geotechnical software Lizheng version 7.0PB1, the simulated data then were compared with the construction instrumentation data. It is therefore verified that the SMW could be adequately used as the supporting structure for the deep excavation. Related Articles | Metrics

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Stress Analysis of Elliptical Ring Supporting Structure in the Deep Excavation in the Nearshore Reclaimed Area ZHOU Xueliang, JIAN Wancheng 2020, 34 (3):  308-312.  Abstract ( 574 )   Save The elliptical internal supporting structure is a typical compressive element and the material properties of reinforced concrete can be fully utilized. However, under the uneven loading conditions, large bending moments and excessive deformation might be generated so that the application of this supporting type has many limitations. Currently, the elliptical supporting structure is rarely used in deep excavations with depth greater than 20 meters in nearshore reclaimed areas. This paper presents the application of reinforced concrete elliptical structure as the supporting structure for a 27 meters deep excavation in the reclaimed area. The threedimensional numerical analysis was used to simulate the performance of elliptical supporting structure with various aspect ratio. The deformation and stress conditions in the internal supporting structures are also investigated. The results indicate that, under the uneven loading conditions, with the increase of aspect ratio, large deformation and stress are observed in the supporting structure. Increase the cross strut supporting in the short direction can effectively reduce the deformation and bending moment. Related Articles | Metrics

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Stability Analysis of a Soil Slope Landslide and Parameter Selections DENG Junjun 2020, 34 (3):  313-315.  Abstract ( 410 )   Save This paper presents the stability analysis results of a landslide in a soil slope in Liuzhou City. The mineral component at the slip surface were tested and factors that might contribute to the slope instability were evaluated. The landslide body was investigated by field and laboratory tests, back analysis and geological analogical methods. The factors of safety under normal and heavy rainfall conditions were able to be determined by using transfer coefficient method. Both the analysis and site reconnaissance results indicate that, the slope was stable under normal condition and was not stable under the heavy condition. Under continuous precipitation condition, the rate of slip would be accelerated. Related Articles | Metrics

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Numerical Analysis Influence of Metro Tunnel Excavation by Perorated Pipe Grouting Method on the Adjacent Pile Supported Canopy Station Structure HU Dawei 2020, 34 (3):  316-320.  Abstract ( 387 )   Save The Yingze Underpass Tunnel in Taiyuan City was excavated by using perforated pipe jacking and grouting method. It had the characteristics of large span, shallow embedment depth and restrictive settlement control. The construction process such as, steel pipe jacking, cutting, concrete pouring and earthwork excavation, were numerically simulated. The settlement of the adjacent pile supported canopy station induced by the tunnel excavation was also evaluated. The allowable settlement value for the canopy structure was recommended. The following conclusions can be obtained: 1) during the tunnel excavation using perorated pipe jacking and grouting method, the adjacent pile supported canopy station structure was adversely affected since both vertical and horizontal deflections were observed. 2) The horizontal deflections at the canopy structure were mainly occurred during the pipe jacking and cutting stages. The earthwork stage had a relatively small impact on the horizontal deflection of the canopy structure. 3) After the construction, the maximum horizontal deflection at the canopy foundation level was 1.18 mm and the maximum vertical settlement was 4.59 mm and both values met the allowable settlement requirements. Related Articles | Metrics

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Study on Stability Analysis and Control Measures of anIncline Bedding Slope JIANG Fasen 2020, 34 (3):  321-325.  Abstract ( 422 )   Save The stability of a highway roadside incline slope was evaluated by using the combination of geological information, stereographic projection and plane slide methods in this paper. The results show that the stability of this incline bedding slope was mainly controlled by the bedding plane; the slope is stable under natural conditions and is in instable state under the rainstorm conditions. In the stability mitigation design, the prestressed ground anchor cable frame assisted with anchor rod was used. Related Articles | Metrics

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Relations Between the Index Properties and Compressibility of Hangzhou Structured Soft Clay CHEN Liping, GAO Yanmiao, JIA Haidong 2020, 34 (3):  326-328.  Abstract ( 377 )   Save The soft clay of marine originis widely deposited in Hangzhou area. The marine clay is characterized as high compressibility, poor permeability, low bearing capacity, and specific structural properties. The soft clay depositions are adversely affected theengineering construction, so that it is necessary to study engineering properties of this type of soil. This paper first summarizes the microstructure and chemical compositions of type of soil, then a series of laboratory onedimensional consolidation tests were performed on undisturbed soil samples from Xiaoshan District of Hangzhou City. Other index properties of this type of soft soils were also tested and the relationship between the compressibility and index properties were statistically established, especially, the relationship between liquid index and the compressibility. Related Articles | Metrics

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Stratified Earthwork Estimation of a Large Embedded Box Culvert GAO Hongwei, XIAO Guiqing, ZHANG Jiafeng 2020, 34 (3):  329-330.  Abstract ( 526 )   Save This paper presents a case history of earthwork quantities estimation for the construction of a large embedded box culvert in a Meishan wastewater treatment plant by using commercial software for earthwork estimation FastTFT. Based on the required excavation depth for the box culvert and the geotechnical investigation information, the earthwork for each soil stratum can be accurately estimated. The required excavation quantities of the following soil layers are estimated: topsoil, silty clay, clay, fine sandy gravel and gravel. The subsurface soil profiles and the location of culvert bottom slab can be generated based on these accurate estimations. The earthwork quantity estimation can be used for the cost estimation and for the optimization design of the box culvert locations. Related Articles | Metrics

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Impact of Shielded Tunnel Excavation on the River Levees Crossing XIAO Zhaoyang, LI Yi, ZOU Qi, YANG Ming 2020, 34 (3):  331-334.  Abstract ( 406 )   Save Shielded tunnel excavations often encounter the situation of under crossing the river leveesin the urban metro construction. The soil movement induced by the shielded tunnel excavation might have adverse impact on the river levee above so that it is necessary to evaluate the potential influence of tunnel excavation on the safety of levees. This paper presents a case history of a metro tunnel excavation. The influence of shielded tunnel excavation on the south side of the river levee above was simulated by a commercial finite element analysis software FLAC3D. The results indicate that the maximum settlement induced by the tunnel excavation is 4.94 mm and this value is less than the allowable value of 15 mm defined in the design code. The river levee is determined to be safe. To improve the construction quality and to reduce tunnel excavation risk, the excavation penetration rate is optimized based on the tunnel design plan. At the same time, the grouting while excavation and after excavation are also planned so that potential soil disturbance induced by the construction and be reduced. Related Articles | Metrics

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Pile Soil Interaction Parameters from Flat Dilatometer and Cone Penetration Tests#br# RAN Menghui 2020, 34 (3):  335-338.  Abstract ( 382 )   Save The bearing capacity and deformation behavior of piles are directly related to the geotechnical parameters of surrounding soil. Extensive reliable insitu test parameters of soil are provided by the flat dilatation test (DMT) and cone penetration test (CPT) devices for the pilesoil interaction analysis. The diameter of 0.4 meters and 12 meters long castinplace concrete pile installed by the long flight auger method was statically load tested for the axial compressive capacity. The load test results were then compared with the threedimensional numerical analysis results using parameters developed from DMT and CPT. The results indicated that, in both axial resistance and the settlement predictions in the numerical analysis, the discrepancies are existed. The parameters using DMT results are closer to the actual test results. The CPT parameters, however, over predict. Related Articles | Metrics

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Effect of Moisture Content on the Shear Strength and the Creep Properties of Jingyang Q2 Loess LI Kai 2020, 34 (3):  339-341.  Abstract ( 367 )   Save The issue of loess intensity has always been a hot topic in the study of geotechnical scholars. The shear strength and loess creep caused by the change of water content are closely related to the stability of loess slope. Through direct shear and creep tests, the effects of water content, dry density and normal pressure on shear strength,and long-term strength of unsaturated Q2 loess are studied. The results show that compared with the strength of loess with 10% and 18% moisture content under different dry densities, 18% shear strength weakens more than 20% compared with 10%；The increase of water content also has a weakening effect on the viscous force, and there is a more serious tendency to weaken with the increase of dry density；The creep will be caused by the decrease of water content and the increase of dry density； By fitting, it is found that the creep of loess conforms to the law of logarithmic function curve. Related Articles | Metrics

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Research on the Development Law of Negative Friction Resistance of Pile Foundation in Dredger Filling Area LIU Jiaxin, ZHANG Yutian 2020, 34 (3):  342-344.  Abstract ( 381 )   Save In order to explore the influence of the settlement of the surrounding soils on the pile negative side friction and to investigate methods reducing the potential impact, the numerical simulations were performed on development of the negative side friction in piles under loading conditions by using commercial software ABAQUS based on the field pile static loading test results. The long term loading condition of piles in recent fills are also demonstrated. Related Articles | Metrics

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Analysis of the Influence of Cracks in Different Distribution Areas on Slope Stability LUO Chongmu 2020, 34 (3):  345-347.  Abstract ( 605 )   Save The field investigation observed that there are a large number of cracks on the surface of a slope. The presence of these fractures is adversely affecting the stability of the slope, especially under seismic conditions. Therefore, the study on the stability of the cracked slope is particularly important. Using the conventional limit equilibrium upper limit analysis method, combined with the strength reduction and the quasi-static methods, factor of safety of the fractured slope at different zones is then derived and the influence of earthquakes and presence of fractures on the stability of slope are investigated. The results show that the presence of fissures will reduce the factor of safety of slopes by up to more than 20%, and the earthquakes also significantly affect the slope stability can be as much as more than 20%. The location of the fractures is also important, fractures that away from the slope have little impact on the stability. Related Articles | Metrics

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Numerical Analysis of the Influence of Deep Excavation on Adjacent Buildings ZOU Yuqiang, LIU Chao, WANG Xingyun 2020, 34 (3):  348-350.  Abstract ( 444 )   Save Thispaper presents the numerical studies using commercial software MIDASGTS on the deep excavation on the adjacent structures. The rntire deep excavation process was considered in the threedimensional numerical model by considering the spatial effect so that the impact of the excavation on the adjacent building structures. The deformation of the supporting structure and the risk assessment are evaluated in accordance with the current design code. The numerical analysis results indicate that the deformation of the supporting structure are within the acceptable range. Related Articles | Metrics

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Three-Dimensional Expansion Rate Test of Grey-White Expansive Soils in Nanning LI Yaqi, TAN Bo, XU Liang 2020, 34 (3):  351-354.  Abstract ( 407 )   Save It is very important to study the threedimensional expansion characteristics of expansive soils for the stability analysis of slopes with expansive soils. In this experiment, an inhouse developed three-dimensional expansion testing device was used to test the three-dimensional expansion rate in the laboratory conditions of the grey-white expansive soil samples in Nanning. The results show that:  after soaking, the expansion rate of expansive soil samples can be divided into three stages: the rapid expansion, the slow expansion and stabilization phases. The 80%~90% of the entire expansion process can be completed within three hours, and the overall expansion can be generally completed in six hours. The vertical expansion rate of the sample is larger than the lateral expansion rate, and the lateral expansion rates in two different directions are roughly equivalent. The ratio R0 of expansion rate to vertical expansion rate varies with the initial dry density, ranging from 0.61 to 0.82. Under the same initial moisture content condition, R0 increases with the increase of dry density, which indicates that the greater the dry density of expansive soil, the weaker the anisotropy of the sample. Under the same initial moisture content condition, the expansion rate increases with the increase of dry density of soil sample, and the higher the moisture content, the smaller the change rate of vertical expansion rate with the initial dry density; Under the same initial dry density, the expansion rate decreases with the increase of initial water content, and the higher the dry density, the higher the vertical expansion rate with the initial water content. Related Articles | Metrics

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Comparative Study on Pile Static Axial Compressive Loading Test Between US and Chinese Standards ZHANG Kaiwei, LI Hui, YANG Lingjie, ZHAO Haichao, ZHI Zhenghua 2020, 34 (3):  355-360.  Abstract ( 950 )   Save This paper compares the five aspects of the static axial compressive loading test between the ASTM《D 1143M-07 Standard Test Methods for Deep Foundations under Static Axial Compressive Load》(2013) and the Chinese Standard “Technical Code for Testing of Piles for Building Foundations (JGJ106-2014); the applicable range, purpose of testing, test methods, test equipment and test procedures. The similarity and different aspects of two different test procedures and data process methods are studied. Throughout the comparative study, the Chinese test procedure was adopted by the foreign owner as well as the technical staff. Related Articles | Metrics

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Construction Monitoring and Analysis of a Deep Excavation of a Ventilation Shaft of Shaoxing Metro REN Cheng, HUANG Rui, 2020, 34 (3):  361-365.  Abstract ( 412 )   Save This paper presents a case history of construction monitoring of the deep excavation for the ventilation shaft of Shaoxing Metro. The lateral deflections of the supporting structure as well as soil mass, settlement of adjacent soils as well as nearby highway and the axial force in the supporting structure were monitored. The results indicate that, the deflection curves measured in the supporting structures using slope inclinometer are similar to those observed in the adjacent soils and the maximum lateral deflections occurred at the bottom of the excavation. Spatial effect was observed in settlement in the adjacent soils and the bowlshaped settlement pattern was measured at each side. The magnitude of the settlement was not only related to the lateral deflections of the supporting structures, but also was affected by the near be surcharge and the bottom heave of the excavated area. On the adjacent express highway, maximum settlement was measured at locations close to the excavated area, he frequency of the construction monitoring should be increased to ensure that the construction disturbance can be minimized. The axial force in the supporting structure increased rapidly during the initial excavation stage and became stable afterwards. Related Articles | Metrics

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Application of Borehole Imaging Technology in the Determining the Thickness of Drilling Debris SUN Yugang, BAO Fubo, LV Yingming, ZHENG Yong, 2020, 34 (3):  366-368.  Abstract ( 518 )   Save A new method for the determining the thickness of drilling debris at the bottom of the cast-in-place reinforced concrete pile boreholes is proposed combined with testing practice in this paper. Based on the borehole drilling inspection, this device can visually reproduce the interface conditions of the “pile-end concrete-drilling debris layer of rock or soil” at the bottom of the borehole by using borehole imaging technology. Thus, image analysis technique can be applied to accurately measure the drilling debris thickness at the bottom of the drilled pile. Through expanding the cylindrical imaging of the borehole to a panoramic plane, the operator can directly measure the drilling debris thickness under the side wall corresponding to various azimuth angles. “N equal-point average” and “integral average” algorithms are recommended to achieve the representative drilling debris thicknessat pile bottom, which can be used to evaluate whether it meets the design requirement.According to on-site tests of 10 large-diameter rock-socketed cast-in-place piles form different projects, the drilling debris thicknessobtained by this new method is proved to have the advantages ofaccurate,reliable and simple operated. Related Articles | Metrics

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Soil Classification Based on Material Index from the Flat Dilatometer Test TANG Feiyue 2020, 34 (3):  369-371.  Abstract ( 445 )   Save This paper introduces the geotechnical material classifications from the engineering explorations. Because of the complexity and variety origination of different soils, their physical and mechanical properties are usually different and demonstrate strong locality. The classification of the geotechnical material by the flat dilatometer test (DMT) requires the establishment of a classification system for geotechnical parameters. Based on laboratory test data and DMT results and the formula of material index proposed by the current national code, this paper summarizes the classification method and the correlation of rock and soil types in Wuhan area. Related Articles | Metrics

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Static Load Test and Numerical Analysis of Composite Foundation of CFG columns in Soft Soil Area LI Xike 2020, 34 (3):  372-375.  Abstract ( 449 )   Save Both the static loading test ingle Cement-Fly-ash and Gravel (CFG) column and the numerical analysis of the composite foundations formed by the CFG columns are performed in order to evaluate the soil improvement results using CFG columns. Three CFG columns were statically loading tested and the results were used to calibrate the numerical analysis results. The calibrated parameters were used in the numerical analysis by using FLAC3D finite different analysis commercial software on an area of 20 by 20 meters. The numerical analysis simulated ground settlement of ground with and without CFG columns. The results indicated that both the settlement and the stress distributions in the composite ground with CFG columns are significantly different. The CFG columns share the portion of the stress and improve the soft soils. Related Articles | Metrics

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Comparative In-Situ Study of Soft Soil in Dongting Lake#br# ZHANG Peng, MA Deqing, WU Yuanming 2020, 34 (3):  376-379.  Abstract ( 416 )   Save In situ test methods have advantages in testing different soil parameters of soft soils. The accuracy and effectiveness of these in-situ testing methods are related to their structural characteristics; geological conditions, and testing experience of the operator. In Dongting Lake soft soil area, the insitu testing methods are very important tools for the soil property characterization, and it is also equally important to select the appropriate testing device for the certain soil parameter. This paper presents the comparative study results of wo soft soil with different deposition origin using different insitu testing devices. The results indicate that, the cone penetration test (CPT) results are repetitive and more accurate. Diverse results are obtained in using vane shear testing device; the empirical formula for flat dilatometer in Dongting soft soil has scattered results and are not reliable. It is concluded that the CPT should be mainly used for the soft soil characterization and compensated by vane shear device. Plat dilatometer should be used for the purpose of experience accumulation. Related Articles | Metrics

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Experimental Study on Application of Artificial in Situ Hard Crust in Sea Highway GAO Dawei, GAO Shihu, YUAN Guohui, XU Huimin 2020, 34 (3):  380-384.  Abstract ( 403 )   Save Considering the fact of no hard crust existed in the highway along coastal soft soils that can be used, this paper proposes the conventional surcharge method to create an artificial hard crust layer using manmade drainage measures based on the laboratory model test and numerical simulation results. Compared with the original soil layer, the improved soil reduces the deformation the vertical settlement at top of embankment by 20% and reduces the horizontal deflection at the toe of the embankment. In addition, the numerical analysis indicates that the differential settlement of the roadway surface in the manmade hard crust layer can also effectively be reduced compared with the original soft soils. With the special conditions in the coastal soft soil area, the other strengthening methods can also be introduced to improve the surface soil layer for the long term stability of highway embankment. Related Articles | Metrics

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Deformation Monitoring and Back Analysis of Soil Parameters in the Cut and Cover Installation of Taihu Tunnel GAO Defeng, ZHOU Ao, FENG Yateng, WANG Haixiao, XIA Wenjun 2020, 34 (3):  385-390.  Abstract ( 423 )   Save It is of great significance to obtain appropriate soil parameters for efficient engineering design and safe construction in soft soils. However, different degrees of disturbance are inevitably induced in the soft soil samples in the sampling and test process due to the soft soil properties so that the accuracy of soil properties is affected. The back analysis of soil parameters from a large amount of construction monitoring data can effectively optimize and compensate the soil parameters obtained from the laboratory and in-situ testing. This paper presents the back-analysis results of soft soil parameters from the construction monitoring of a cut and cover tunnel in Taihu Lake by using the BP neurol network analysis method. The results indicates that, based on the back analysis obtained soil parameters, the deformation of the supporting structure could be accurately simulated and consistent with the monitored data. Related Articles | Metrics