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    25 June 2021, Volume 35 Issue 3 Previous Issue    Next Issue
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    Excel Programing for a Ground Improvement Design Application
    ZHU Jia
    2021, 35 (3):  243-246. 
    Abstract ( 407 )   Save
    This paper presents a solution for estimating the foundation settlement in the ground improvement design by using the VBA programing function in the Excel spreadsheet. The basic functions and operations in the Visual Basic developer tab are introduced and the feasibility of calculation of the key parameters in the foundation settlement formula using VBA programing are discussed. The method for the foundation settlement estimation programing is also presented. In the end, the settlement estimation method is used in a practical ground improvement project. The data processing techniques are also provided.
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    Discussions on the Drilling Debris Control in Rotary Drilling of Cast-In-Place Concrete Piles
    SUN Yugang,
    2021, 35 (3):  247-250. 
    Abstract ( 625 )   Save
    With a wide application of rotary drilling of cast-in-place concrete piles in the foundation construction projects, the insufficient axial capacity induced by the excessive deposition of drilling debris at the bottom of the borehole has attracted more and more attention. Based on the foundation construction inspection practice in Xiamen, this paper presents the drilling debris control method of rotary drilling of cast-in-place concrete pile from the following five aspects: application of casing for the borehole protection; borehole cleaning technology; tremie concrete pouring; postgrouting and quality control of site operation. By comparing the measured construction monitoring data, all the above measures are proved to be reliable and provide as references for future relevant projects.
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    Mitigation of Excessive Deformation in the Supporting Structure for a Deep Excavation
    ZHANG Qi, WANG Tianbao, FENG Keming, PENG Zhanliang,
    2021, 35 (3):  251-253. 
    Abstract ( 456 )   Save
    A Larson steel sheet pile system was used in a deep excavation supporting project. Due to the large difference between the actual excavation condition and the conditions assumed in the design, the partial deep excavation support system was observed to have an excessive lateral displacement and the deformation did not converge, which exceeds the deformation threshold value and even the control value of the design limit. After the field survey, factors that might induce the excessive deformation in the support system were analyzed. Mitigation measures of soil removal unloading at the outside of the support system, as well as the constructing soil berm inside the excavation side, were implemented so that the horizontal displacement of the deep excavation supporting system was effectively controlled. As a result, the overall excavation and foundation construction could be proceeded smoothly.

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    Results Comparisons in a Deep Excavation Case Histories Analyzed with Plaxis and Lizheng Software
    ZHOU Yi
    2021, 35 (3):  254-256. 
    Abstract ( 799 )   Save
    Lizheng commercial software is one of the most used analytical software in the geotechnical engineering projects. Plaxis is also a geotechnical specialty finite element software. This paper presents a case history of deep excavation supporting system design and analysis using both software. The results are the following: the maximum settlement of 14.0 mm and the maximum lateral deflection of 18.28 mm were obtained by Lizheng software, whereas, the maximum settlement of 15.81 mm and the maximum lateral deflection of 20.71 mm were obtained by Plaxis software. Using different software can improve the prediction results and help in selection the most appropriate software for the project.
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    Installation of Rammed Gravel Columns with Expanded Base in Alternating Cohesive and Liquefiable Sandy Soils
    HUANG Lianfen, HUANG Junxiong
    2021, 35 (3):  257-259. 
    Abstract ( 341 )   Save
    This paper presents a ground improvement case study of a pump station project with the alternating of cohesive and liquefiable sandy soils near the Central Business District. Based on the engineering and hydrological geologic conditions, the effect of the installation preparation, installation sequence and method on the rammed gravel column with expanded base is evaluated in detail through various trial tests. The installing the gravel column can be divided into five steps. The quantity of the gravel backfill at each time should be controlled with 0.3 cubic meters. Larger ramming energy should be used to compact the gravel and the energy should be reduced when the depth is less than two meters from the ground surface in order to minimize the ground heave. The rammed gravel column installation quality control criteria, testing items and design parameters in the alternating of cohesive and liquefiable sandy soils are discussed in this paper.
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    Application of AutoCAD Civil3D in Quantity Estimation of an Abandoned Mine Rehabilitation Project
    FAN Yali, PANG Jiawei, XIAO Fengrong
    2021, 35 (3):  260-262. 
    Abstract ( 523 )   Save
    In recent years, the rehabilitation of mine ecological environment projects has developed rapidly. Slope cutting, benching, soil or rock excavation and backfilling are common engineering measures that are frequently in the ecological environment control projects of abandoned mines. The accuracy of earthwork quantity estimation of slope cutting and backfilling is an important task to determine the construction schedule. The traditional earth work quantity estimation software, including South CASS and MAPGIS, has the disadvantages of complicated calculation process, long computation time and coupling parameters etc. Switching and conversion between software modules will also increase unnecessary computational work. This paper presents a case history of using Civil 3D software for the estimation of earth work quantity. The earthwork volume can be changed according to the change of design surface. The quantity estimation results are accurate, with less adjustment operation and have a real-time display of adjusted result. It can provide more direct and comprehensive visual display effect, optimize the design to the maximum extent and save project investment.
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    Analysis of Factors Affecting Backfill Settlement of a Cut and Cover Tunnel
    XI Lingzhi, YANG Yu, XIONG Song, XIN Weiming
    2021, 35 (3):  263-267. 
    Abstract ( 384 )   Save
    Large post construction settlement is usually observed at the excavated area of a cut and cover tunnel excavation area. This paper presents an excavation of a cut and cover tunnel in soft soil area. The effect of the shape of the tunnel cross section and the backfill material on the settlement of the excavated area and the structural deformation of the tunnel are numerical investigated by using MIDASGTS geotechnical commercial software. Results show that the ground settlement after the completion of backfilling is mainly affected by the compressibility of the backfill material itself, that is, the greater the compressibility of the backfill material, the greater the surface settlement. The main factors that affecting the settlement and deformation of the tunnel structure are the unit weight of the backfill material and the thickness of the weak stratum below the tunnel. Therefore, for the excavation of the cut and cover tunnel, it is necessary to select an appropriate method for the backfill soil in accordance with the allowable deformation criteria for backfill material and for the tunnel strucutre.
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    Optimization Design of Jet Grouted Ground Anchors in the Deep Excavation Supporting System
    XI Zaoyang, YANG Suxin, LI Yue
    2021, 35 (3):  268-271. 
    Abstract ( 397 )   Save
    In a deep excavation supporting system, conventional ground anchor design approach is usually used for the jet grouted ground anchor design. It is recognized that this approach results in the conservative design and waste in the material. This paper presents a numerical analysis using ABAQUS commercial software on the excavation process of a deep excavation project. In the analyses, the design parameters optimization of jet grouted ground anchor is also performed. The effect of the jet grouted ground anchor length, magnitude of prestress and anchor inclination angle of the global stability of the deep excavation is also studied in this paper. The optimized jet grouted ground anchors are as follow: first layer anchor: 13 meters and 12 meters for the second layer with a prestressed forced of 150 kN and inclination angle of 15 degrees. This evaluation provides a case history for the deep excavation supporting structure design in similar conditions.

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    Deformation Analysis and Mitigation of a Large Foundation Excavation for the Metro Station in a Saturated Soft Stratum
    HUA Zhigang, CAO Yilong
    2021, 35 (3):  272-275. 
    Abstract ( 385 )   Save
    This paper presents a case history of foundation excavation for Huashan Road Station of Suzhou Metro Line No. 3. The foundation excavation supporting design methods were selected and optimized based on the site engineering geology conditions, supporting structure performance and construction technique. Different stages of this wide and large sized deep excavation construction were monitored, and the data were analyzed. The conclusions can be made as follow: For deep excavation supporting for a wide metro station excavation in saturated soils, the concrete raker with horizontal waler supporting method have the following characteristics: difficult in the deflection control, solder pile heaving and large axial stress in the reinforced concrete rakers. During the construction, the earth removal pattern should be optimized and the installation of raker support should be accelerated. The bottom concrete slab of the foundation should be poured immediately after the completion of the excavation so that the supporting system deformation can be controlled. In the design the heave of the solder pile and the larger axial stress in the concrete raker.
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    Application of Sparsely Spaced Soldier Pile and Ground Anchor in Deep Excavation Support
    LIU Minghua
    2021, 35 (3):  276-280. 
    Abstract ( 309 )   Save
    With the developments of the urban projects, revitalization of the old cities and the popularity of skyscrapers, deep excavation supporting design methods become increasing diversified. Selection of a deep excavation supporting method that can minimize the impact on the adjacent environment and is also cost effective, is frequently encountered in the urban construction in the mountain area. This paper presents a case history of the deep excavation supporting design for an underground parking garage. The sparsely spaced soldier pile and ground anchor were used as the excavation supporting structure under the confined spacing and complicated adjacent environment. The application of the combined methods safeguards the excavation construction, minimizes the impact the nearby buildings and saves the cost and construction schedule.
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    Application of Central Island Excavation Method in Support of Deep Excavation in the Depressed Area with Uneven Excavation Depth
    DAI Bin, TAN Yongwei, ZAHO Sheng
    2021, 35 (3):  281-285. 
    Abstract ( 412 )   Save
    For large areas depressed farmlands, ditches and other uneven terrain with side slopes and adjacent roads, deep excavation projects in these areas will mainly face the situations which differ from conventional deep excavations in urban areas. These differences are in natural ground floor elevations surrounding the excavated area and the variation of excavation depths. When it is not eligible to install ground anchors for the supporting structure, double-row piles and other conventional supporting structures without internal support with the limitation by the cost and/or environmental constraints, the concern of the independent supporting structure for the side excavation with different excavation depths could be effectively resolved by using site specific conditions, which is a combination of the “central island” (central structure blocks) and diagonal support members. This arrangement could avoid fully installing the internal support in a large area, thus is cost effective and efficiency. Further, using the main structure as part of the support system is reliable in the overall stiffness, can better control the deformation of the supporting structure and protect the environment.
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    Optimization Design and Application of Support System in Foundation Pit in Soft Soil Area
    SHI Minjun
    2021, 35 (3):  286-289. 
    Abstract ( 297 )   Save
    The selection and layout of deep excavation support system in soft soil area should be determined by the plan dimensions and shape of the excavated area, the requirements of surrounding environmental protection, the geological conditions of the site and the requirements of the excavation depth. Generally, cast-in-place concrete structure is used as the support of excavation structure with restrictive requirements of surrounding environment or complicate shape for the supporting. Based on the complex shape of the deep excavation project of Zhuguang New City Phase III and the high requirements of the surrounding environment, this paper analyzes the design of the internal support method, introduces the design optimization of the project: from the preliminary reinforced concrete diagonal brace to the reinforced concrete horizontal brace, and further puts forward the optimization of the reinforced concrete horizontal brace to the steel brace, so as to realize the economic and engineering saving It is expected to achieve good results.
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    Impact Analysis of River Excavation on the Deformation of an Underlying Shielded Tunnel
    WANG Guoquan
    2021, 35 (3):  290-296. 
    Abstract ( 314 )   Save
    In Ningbo soft soil area, the problem of excessive deformation of shield section of the tunnel can be effectively solved by means of gate reinforcement, “tofu” block excavation and in-channel pressure. The Midas GTS NX finite element method was used to study the effect of river block excavation on the deformation of the shield section of Rail Transit Line No. 1 directly in the Ningbo soft soil area. Compared with the measured results, it is shown that with different construction conditions of the river excavation, the horizontal displacement of shielded tunneling interval increases gradually. The maximum horizontal and vertical displacements of the tunnel are in good agreement with the field measurement results during the excavation of the river channel. The deformation of shielded tunnel is in a low deformation level. The effect of soil reinforcement process should be considered for shield deformation. When the triaxial cement mixing pile is constructed, the cement is mixed into the soil body, which leads to the increase of the soil weight and the increase of the dead weight of the soil body, which leads to the sinking of the shield tunnel in the lower section. With the excavation of river channel, the uplift deformation of shield section increases gradually. The main characteristic is that the excavation of the river in the secondary affected area on both sides has a great influence on the uplift deformation of the interval shield tunnel, followed by the influence caused by the main affected area directly above the shield tunnel. When the river is open to water, the small settlement of the interval shield tunnel appears.
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    Safety Evaluation Method and Case Analysis of Soldier Pile and Ground Anchor Retaining Structure in the Extended Service
    TONG Yin, WANG Xin
    2021, 35 (3):  297-301. 
    Abstract ( 739 )   Save
    As a temporary retaining system, the design service life of the deep excavation support structure is generally 1~2 years, however, many excavation supporting projects often have undertaken the extended service. At present, there is no technical specification to determine how to define the safety of the supporting structure, how to determine the reinforcement scheme or the supporting structure sustained service life after the expiration date. Based on an actual overdue foundation pit project, from the perspective of supporting structure entity detection, identification and deformation monitoring data analysis, combined with supporting structure calculation and numerical simulation, this paper summarizes a set of ideas and methods suitable for overdue evaluation of pile anchor structure, which is intended to provide reference for similar projects.
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    Application of Dynamic-Rammed Gravel Columns in Ground Treatment
    ZENG Huajian, WU Xiangfei, PAN Chen, LIU Xuezhu, ZHENG Haibo
    2021, 35 (3):  302-306. 
    Abstract ( 397 )   Save
    With the rapid development of the logistics industry, logistics warehousing projects are gradually increasing, and the problem of soft ground treatment of large area building floor is also increasing. This paper presents a case history of ground treatment of a logistics center project in Qingdao, which involves poor geological conditions such as miscellaneous fill, soft clayey soil, plain fill, muddy soil and chemical white mud.  A variety of ground treatment methods are comprehensively evaluated under these site conditions. The dynamic-rammed gravel columns are used to strengthen the large area for the proposed storage floors and foundations, which are dominated by deformation coordination design to solve the concerns of soft soil settlement, insufficient bearing capacity and uneven settlement. This paper describes the design, construction technology and method of dynamic-ramming gravel piles in hole of soft soil foundation. Furthermore, the field test results of composite foundation are analyzed, the results show that the method has satisfactory treatment effect and the relevant conclusions can provide reference for similar projects.
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    Safety Hazards of Deep and Large Foundation Excavation Construction on the Adjacent Rail Transit Station
    GUO Xiang
    2021, 35 (3):  307-310. 
    Abstract ( 370 )   Save
    This paper presents a case history of a deep foundation project of SUDI 2012-G-17 block near Baodai Road Station of Suzhou Rail Transit Line No.3. Based on the relative location of the deep excavation to the station structure and the characteristics of rail transit structure, the safety hazards of deep foundation engineering were theoretically evaluated, and a three-dimensional simulation model was established to simulate and analyzed the construction process of the foundation excavation, backfilling, and the stress deformation of rail transit station. The results show that the deep and large foundation is excavated in different areas, and the influence of the construction method of “far first and then near” on the structure of rail transit station is within the control range of the specification. The deformation of adjacent rail transit structure mainly occurs in the excavation and back construction stage of foundation pit. The principle of “slotting support, supporting first and then excavation, layered excavation and over excavation” are followed in the excavation of foundation pit, which can effectively reduce the deformation and deformation of station structure Displacement to ensure the operation safety of the station.
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    Deformation Analysis of Deep and Large Foundation Excavation Support
    ZHOU Zhenhong, SUN Huabo, LV Guo, CAO Shichao, ZHOU Yanfu
    2021, 35 (3):  311-314. 
    Abstract ( 446 )   Save
    This paper presents a three-dimensional numerical modelling of the deep excavation supporting process. The monitored data of the lateral deflections in the soldier pile and ground anchor supporting structure, deep horizontal displacement in the soldier pile, soldier pile and ground anchor axial force changes under different conditions, different waler beam materials and different prestressing force are compared with the numerical analysis results. The results show as follow: the monitored values and numerical calculation data of the foundation excavation support structure are in good agreement, and the monitored values are far less than the warning values specified in the specification; in the process of foundation excavation and support structure construction, the maximum deformation of the pile occurs in the middle of the pile body, compared with the common Isteel waler beam, the concrete waler beam can better control the deformation of the excavated area, and the analysis shows that the design of the support structure selected for the foundation excavation.
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    Deformation Monitoring and Numerical Analysis of Deep Foundation in Soft Soil by Semi-Reverse Excavation Method
    WU Xubin, ZHANG Wei,
    2021, 35 (3):  315-318. 
    Abstract ( 326 )   Save
    In order to resolve the deep foundation excavation in soft soil area, the soil and the supporting structure deformation are usually large. This paper presents a case history of semi-reverse excavation method of deep excavation in saturated soft soils of the Pearl River Delta alluvial plain. The Midas GTS NT 3D modeling results were compared with the construction monitoring data. The following conclusions can be made: (1) after half the semi-reverse excavation in soft soil area, the lateral deformation of supporting structures has a convex in shape, the maximum average in 0.5H~0.6H (H) from excavation depth; (2) The main influence zone of ground settlement and deformation around the excavated area caused by semi-reverse excavation in soft soil area is 0~1.0H. (3) Through the study of this case history, it is shown that the application of the space-time effect theory of semi-inverse method in the deep excavation in saturated soft soils not only ensures the safety of excavation itself and the surrounding environment, but also reduces the construction duration and reduces the construction cost, which provides a reference for the design and construction of deep foundation pit in similar soft soil area.
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    Construction Safety Assessment on A New Urban Subway Tunnel Under-Passing An Existing Tunnel
    HU Min
    2021, 35 (3):  319-322. 
    Abstract ( 275 )   Save
    This paper presents a case history of the Line A section tunnel of an urban subway passing through the existing Line B train section. Throughout the field tests, the geological problems existing in the construction process are analyzed, and the engineering overview and potential geological risks of the construction are discussed. The safety assessment is performed at Line B. Reinforcement of the typical section plan is also presented. Results shows that in this project, the groundwater within the depth of impact of the project mainly consists of upper perched water and confined water; during the construction process, the fracture zone and sand liquefaction are ignored, but the release rate and volume of shallow toxic gas should be controlled.
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    Analysis and Integrated Mitigation of Water and Mud Inrushing Hazard in Anshi Tunnel Excavation
    CHEN Dejin
    2021, 35 (3):  323-328. 
    Abstract ( 658 )   Save
    During the excavation of Anshi Tunnel of Yunfeng Expressway Project, two large-scale water and mud inrush incidents occurred at the excavated and supported face of the tunnel (Station YK42+951.6), which was 614 m away from the exit apron of the right tunnel. Combined with engineering geology and hydrogeology conditions in the Anshi tunnel, the factors that might induce the hazards and integrated mitigation measures of water and mud inrush incidents are studied in this paper. The results show that the water inrush hazards occurred suddenly and had a strongly destructive influence with a high evolution rate. The main reason for the water inrush and mud hazard was that there was a hidden saturated fracture zone at the upper right of the right tunnel mileage post K42+955, which had not been accurately characterized during the subsurface investigation stage. The fracture zone was in the shape of an irregular weathering lens, only about 3 meters away from the tunnel arch. When the tunnel excavation face passed through the weathering rock lens, although the quartz schist of the tunnel vault was in a relatively intact state, there was no obvious sign of water inrush and mud inrush. The cracks caused by the passage of time and the disturbance of the tunnel construction gradually penetrated and the seepage channel expanded. When the strength of the surrounding rock of the tunnel vault reached the critical limit state, the first burst of water and followed the mud inrush. After the first water and mud inrush, a large number of debris material quickly accumulated in the excavated area, and the water and mud inrush could be stopped temporarily. With the continuous inflow and convergence of the supply groundwater, the potential energy increased sharply, and the pressure increased, resulting in the second water and mud inrush. After an comprehensive considering the tunnel excavation environment, an integrated mitigation system was implemented, and it was successfully applied to the practice of minimizing and controlling water inrush hazards in the hidden saturated fracture zone of the Anshi Tunnel, which can be used as a reference for similar tunnel projects.
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    Sensitivity Analysis of Geotechnical Parameters on the Steel Sheet Pile Deformation
    WANG Fan
    2021, 35 (3):  329-332. 
    Abstract ( 395 )   Save
    As a new type of deep excavation support structure, steel sheet piles have the advantages of fast construction and reusable as the support of shallow excavations. This type of supporting structure is irreplaceable in electricity pits and box utility culvert excavation projects. Based on a comprehensive utility culvert excavation support project, this paper utilizes the parameter sensitivity analysis method and numerical simulation by using MIDAS GTS commercial software to analyze the parameter sensitivity of the steel sheet pile support of excavation. The analysis results show that the deformation of the steel sheet pile supporting structure is most sensitive to the changes in the elastic modulus of the surrounding rock and soil, followed by the internal friction angle, again the cohesion, and finally the Poisson’s ratio. The analysis results provide references and suggestions for the design and construction of similar steel sheet pile supporting projects.
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    Pore Size Distribution of Soft Soil under External Loading
    XUE Xiaojie, CHEN Hongbin, LI Wenjie, SONG Xing
    2021, 35 (3):  333-337. 
    Abstract ( 280 )   Save
    To investigate the variation of the pore size distribution of soft soil under the external loading, one-dimensional consolidation tests on Zhanjiang soft soil samples under vertical pressure of 100~800 kPa were performed. The pore size distribution of soil samples under different loads was characterized by the mercury intrusion method, and the pore structure was further analyzed by the uniformity and typing characteristics. The results show that the pore size r=0.25 μm can be regarded as the critical pore size of the tested soft soil, which divides the soil pore into compressible pore sizes (r≥0.25 μm) and incompressible pore sizes (r<0.25 μm). As the load increases, the compressible pore size decreases linearly, and the incompressible pore size remains almost unchanged. The larger the external load, the better the uniformity of the pore size distribution, and the uniformity coefficient C of the pores increases, that is, the pore size distribution tends to concentrate from complexity. The pore size structures experiencing different external loads have good fractal characteristics, and the fractal dimension is between 2.98 and 2.94, and decreases with increasing of external load.
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    One-dimensional Soil Model Test and Numerical Simulation of Coupled Seepage-heat Transfer Model
    ZHENG Chuan, PAN Biaokai, MO Hongyan
    2021, 35 (3):  338-342. 
    Abstract ( 404 )   Save
    In this paper, a one-dimensional seepage-heat transfer model test-bed is built to study the influence of seepage velocity and direction on the heat transfer characteristics of buried pipes. Based on the theory of heat transfer in porous media and groundwater flow, a simplified three-dimensional numerical model was established through the simulation software COMSOL Multiphysics, and the calculated value was compared with the measured value to verify. The research shows that the effect of groundwater flow on the original medium-sand temperature field is as follows: at lower seepage velocity, the effect of seepage can be ignored, and at higher seepage velocity, seepage enhances heat transfer. And the higher the seepage velocity, the stronger the heat transfer effect. The influence of the seepage direction on the temperature field of the middle sand is the heat transfer range.  When the seepage direction is opposite to the heat transfer direction, the heat transfer range is small, which can be used as a reference basis for the arrangement of buried pipes. After simulation verification, the result error is small, and the established physical model is relatively reliable.

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    Finite Element Analysis of Stability of Unsaturated Double Layer Soil Slope under Heavy Rainfall
    LI Xike
    2021, 35 (3):  343-346. 
    Abstract ( 289 )   Save
    In this paper, the two-dimensional finite element model of unsaturated double-layer soil slope is established based on the seepage theory and the strength theory of unsaturated soil. The distribution of pore water pressure field and the slop stability coefficient under the condition of heavy rainfalls are analyzed. The results show that the distribution of pore water pressure field of unsaturated soil slope is related to the duration of rainfall. In the early stage of rainfall, the pore water pressure at the toe of the slope increases. With the rainfall time increase, the positive pore water pressure on surface gradually expands and penetrates, and the range of negative pore water pressure gradually reduces. The stability coefficient of the unsaturated soil double-layer soil slope decreases linearly with the increase of rainfall time.
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    Stability Analysis of Highway Weathered Rock Slope Based on FLAC3D
    SU Yang, Qin Xiaoyu, LIU Zhikui, DAI Xinghai
    2021, 35 (3):  347-351. 
    Abstract ( 369 )   Save
    The stability of a granite slope is analyzed by the FLAC3D numerical simulation software. The target slope was selected from the slope group on the east side of the great outer ring road in Fenghuang Community, Guangming New District, Shenzhen. Based on the Mohr Coulomb yield criterion, it is assumed that the cohesion and internal friction angle are reduced by different reduction factors, and the actual structure is simulated by adjusting the three-dimensional mesh element. A representative cross-section 8-8IJK as analyzed with the resultant safety factor of 1.21, which was less than the required factor of safety. Therefore, it is necessary to recommend a reasonable slope control plan, which could provide a useful reference for engineering technicians to prevent and control slope instability.
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    Slope Stability and Construction Risk Analyses of a High Cut Slope
    SUN Tonghe
    2021, 35 (3):  352-355. 
    Abstract ( 365 )   Save
    In order to study the impact of excavation and grading construction process on the slope stability of a high cut slope, and to assess the risks caused by improper construction to the slope stability, finite element analysis were performed using PHASE2 software. This paper presents the actual cut slope stability numerical simulation results. The construction loadings and their distributions on the stability were investigated and excessive slope cut on the construction risk was also evaluated. The main conclusions of this paper are as follows: the exposure of the specific rock-soil interface in the slope will form a shear zone and reduce the stability of the slope; if the excavation softens the slope of the crude oil slope, it will help to increase the stability of the slope.

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    Stability Analysis of High Embankment with Special Soil Using Limit Equilibrium Method
    XIA Yi, FANG Zhengfeng
    2021, 35 (3):  356-358. 
    Abstract ( 373 )   Save
    Through the limit equilibrium method to study the influence of different factors such as embankment backfill material, embankment height, slope angle and other factors on the stability of the special soil embankment. The results of this study show that the embankment height has a significant impact on the stability. The lower slope angle, the better the stability of the expansive soil embankment. The slope ratio of 1∶1.5 to 1∶1.75 is more adequate as the embankment slope angle. The influence of natural ground slope on the embankment slope stability is small; increasing the internal friction angle of the embankment material can correspondingly improve the stability safety factor of the embankment, but when the strength of the natural ground exceeds the strength of the backfill material of embankment, increasing the internal friction angle of the natural ground soil is not effective to improve the stability safety factor of the embankment.
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    State of the Art Review of Improved Soil
    XIAO Xiang, HU Dongdong, HE Xiaoli, LIU Zhikui
    2021, 35 (3):  359-364. 
    Abstract ( 445 )   Save
    To study the physical and engineering properties of the improved soil under different chemical additives and dry-wet cycles conditions, this paper summarizes the state-of-the-art research of improved soils. Soil sample with different amounts of cement, lime and fly ash are reviewed and the impact of these additives on the physical and mechanical properties of improved soils are investigated. At the same time, the physical and mechanical properties red mud with various amounts of additives are also investigated.
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    State of the Art Review of Freezing in Support of Excavation Engineering
    BI Shuqi, GAN Binlin,
    2021, 35 (3):  365-370. 
    Abstract ( 480 )   Save
    The recent deep excavation projects present the characteristics of deeper depth, larger area and more complicated geological conditions with an increasing utilization of underground space and the construction of major projects. Owing to the characteristics of temporary support, groundwater stops and groundwater cut-off, wide application range and minimal pollution, the artificial freezing method has received an increasing in the excavation supporting projects. The application status of the artificial freezing method in foundation pit engineering were summarized in this paper, and the research of freezing parameters, temperature field, frost heaving force and deformation characteristics were also discussed comprehensively in this paper. Problems existed in the application of artificial freezing method in deep excavation projects were investigated. It is concluded that the limitations of the analytical theory and model, the intense heat exchange in the excavated area, the ambiguity of interface mechanism and influence range, and the imperfection of relevant standards are the main reasons that might impede the application of the artificial freezing method in excavation supporting projects. This paper presents that the future development trends are the in-depth study of the design theories, the establishment of the standard system and the information management during the entire construction process.

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    AN Artificial Intelligent Based Method of Determining the Bearing Capacity of Foundation Soils
    LUO Jinhua, JIANG Jie
    2021, 35 (3):  371-374. 
    Abstract ( 367 )   Save
    Most of the existing bearing capacity calculation methods of foundation soils are empirical formulas in the design specifications or manuals. Each of them has its own applicable range and it has regional in characteristics. It is therefore necessary to select different empirical formulas to reliably determine the foundation bearing capacity values according to different insitu test methods and considering local experience. In order to determine the characteristic value of the bearing capacity of foundation soils more efficiently, this paper presents an artificial intelligencebased method for determining the bearing capacity value based on the BP neural network. Throughout the characteristic values of the bearing capacity of foundation soils obtained by using different test methods in the project, a training set and a test set are established. Test results show that the bearing capacity of the foundation soil determination method based on BP neural network established in this paper has advantages of high efficiency and reliability, and it can quickly and effectively give the characteristic value of bearing capacity value based on test data.
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    Numerical Study of the Influence of Deep Excavation and Rainfall on the Adjacent Railway Subgrade
    YAN Bochong, WANG Xiaolong
    2021, 35 (3):  375-379. 
    Abstract ( 408 )   Save
    With an accelerated development of infrastructure construction in Yangtze River Delta, there are more and more engineering projects constructed near the existing railway lines. The related construction processes such as deep excavation and backfill might induce the excessive deformation of the adjacent railway subgrades. This might finally affect the safety operation of these railway lines. Based on the reconstruction project of the Qingyang Port Channel Section of the BeijingShanghai Railway, this paper presents the numerical analysis to evaluate the impact of deep excavation and rainfall on the adjacent railway subgrade. Studies have shown that after the deep excavation, the soil surrounding the excavated area and the railway subgrade will deform to a certain extent. The lateral deformation of the excavation supporting structure demonstrate a pattern of larger at upper portion and smaller at lower portion, which is similar to the deflection in a cantilever beam. The maximum displacement occurs at the bottom of the railroad embankment. When an unfavorable condition, such as rain, is encountered, the strength of the surficial soil of at the excavated area and the roadbed will be weakened. When the strength reduction coefficient is in the range of 0.5~0.6, the overall displacement of the railway roadbed will increase sharply. In actual projects, it is necessary to strictly control the deep excavation area in stages, improving the railroad track monitoring in the process, and strictly implement the rail inspection system during and after the precipitation to ensure the safety of railway operations.
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    Discussions on the Finite Element Analysis of Slope Stability using Strength Reduction Method
    LIU Yan, NIE Lei, LIU Zhipeng, LIU Kai, PENG Kunjie, CHEN Fengguang
    2021, 35 (3):  380-384. 
    Abstract ( 422 )   Save
    The strength reduction method in the finite element analysis is widely used in slope stability analysis. However, the analytical accuracy of the strength reduction method is controversial due to the various limitations. In this paper, the strength reduction method is used to calculate the factor of safety of a slope, and the results are compared with the results from the conventional limit equilibrium method. The influencing factors of the numerical analysis accuracy of the strength reduction method are investigated, and the application of the strength reduction method is verified throughout an example. The results indicate that, the element type has the largest influence on the accuracy of factor of safety to slope, while the number of elements and the search method of reduction coefficient have little influence on the accuracy of factor of safety of the slope. The factor of safety obtained by the strength reduction method is close to that of calculated by the limit equilibrium method, and the analytical error is very small. Further, it is very clear that the slope is circular sliding along the toe of the slope.
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    Discrete Element Analysis of Sinkhole Collapsing Process in Shallow Karst in Wuhan
    QU Ruofeng, PENG Shenggang, YANG Yuting
    2021, 35 (3):  385-389. 
    Abstract ( 347 )   Save
    Sinkhole collapse hazards induced by karst geology have caused huge losses to Wuhan economic and social activities. Based on a combination model of sandy soil and clayey soil in overburden soil over karstic rocks, the risk hazards of the karst geological structures are divided into I, II, III and IV four categories. Many numerical analyses have been performed using the software PFC2D to investigate collapsing process of overburden soil in karst geological structures. The results indicate that the sinkhole collapsing mechanism of the all sandy soil in Class I karst geological structure belongs to sand leakage mode. The sinkhole is funnelshaped, which has a large opening at top and a small bottom. The sinkhole bottom has a loose disturbed zone deposited. The sinkhole collapsing mechanism of overburden soil consisting of upper clayey soil and lower sandy soil in Class I karst geological structure belongs to the compound failure mode of sand leakage and clayey soil bending and cracking. The upper part of sinkhole opening is a well-shaped and the lower part is a funnel shaped with loose disturbed zone at the bottom. The sinkhole collapsing mechanism of overburden soils consisting of upper sandy soil and lower clayey soil in Class II karst geological structures belongs to the failure of the lower clayey soil mode. The sinkhole collapsing mechanism of classes III and Ⅳ karst geological structures belongs to the proof collapsing in an overburden soil void mode.
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    Slope Reinforcement and Vegetation Methods under Complex Conditions
    LI Yucai
    2021, 35 (3):  390-392. 
    Abstract ( 430 )   Save
    Mining, road construction and other human activities might damage the mountain structure and the adjacent ecological environment. If these damages are not mitigated and repaired in time, it is likely to cause instability and other damages to the mountain slopes and geological structures. At the same time, the construction conditions of mountain slopes are more complex and difficult, so it is necessary to study the reinforcement and protection methods of mountain slopes under various conditions. Based on the slope reinforcement and vegetation project of the fire passage in Danan Mountain Forest Park, the mountain slope reinforcement and vegetation methods under complex conditions such as loose soils, narrow roads, steep terrain, high rock content, and large number of slopes are summarized in this paper. The slopes are divided into four different types in accordance with the slope angles. Combining the characteristics of different types of slopes, the targeted reinforcement and vegetation methods are proposed, and the control points in the construction process are analyzed.
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    State of the Art Review of Testing Methods of Bound Water Content in Clay
    MO Yankun, LIU Guanshi, MOU Zhi, ZHAO Qingsong
    2021, 35 (3):  393-399. 
    Abstract ( 652 )   Save
    In this paper, the concept and characteristics of bound water in clayey soils are described. Representative methods of measuring the bound water content in clayey soils are introduced in detail. These methods are volumetric flask method; isothermal adsorption method; thermal analysis method; qualitative analysis method; nuclear magnetic resonance (NMR) method and theoretical formula method. Both advantages, disadvantages, characteristics and influencing factors of these methods are also discussed. It is found that the comparison of the bound water content obtained by different measurement methods is generally as follows: theoretical formula method<isothermal adsorption method≈thermal analysis method<volumetric flask method. A large number of test results prove that the results obtained by the comprehensive measurement methods using the isothermal adsorption method and the thermal analysis method are more accurate. Finally, the factors influencing the bound water content in clayey soils are summarized. It can be predicted that all methods have some limitations, and the rapid and accurate measurement of the bound water content in clayey soils is the future development direction.

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    Accuracy of the Automatic Settlement Observation with a Long Hydrostatic Level System
    YU Bing
    2021, 35 (3):  400-403. 
    Abstract ( 406 )   Save
    In this paper, the principles and installation precautions of the automatic settlement observation system with a long hydrostatic level are described in detail, and an adjustment method for data post-processing is proposed. The accuracy of every observation index in two sets of automatic observation systems with a long routine with large elevation differences, excessive turning points and measuring points is estimated in the paper. The adjustment method could be verified by comparing the staged automation results with the manual survey results. After the adjustment, the results are more consistent with the manual survey results. This method effectively improves the reliability of settlement automatic observation results.

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    Analysis of Vertical Displacement Measurement Errors in Static Axial Pile Load and Plate Load Tests#br#
    CHEN Daosong, CUI Wei, JIANG Guangzhan, HUANG Liangfa
    2021, 35 (3):  404-408. 
    Abstract ( 408 )   Save
    This paper presents the vertical displacement measurement errors from static axial pile loading tests and plate load tests on soils. The results indicate that, the possible sources of the vertical displacement measurement errors are errors from the measurement equipment, improper equipment installation and disturbance from the adjacent environment. These factors lead to various errors in the vertical displacement measurement, and the errors appear to be inaccurate and unreasonable to the justify the test results. The factors causing the vertical displacement measurement errors are analyzed in detail, and the method of displacement correction is also provided to judge the conclusion from the corrected data. Suggestions for minimizing or eliminating various errors in the static load test on piles and on soils are also provided in the paper.

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    Application of DMT in Soft Marine Soils in Hangzhou Area
    CHEN Ziliang
    2021, 35 (3):  409-412. 
    Abstract ( 360 )   Save
    The soft marine soils in Hangzhou area is a typical structural soil and the engineering test results might be offset by the samples disturbances in the sampling and test preparation process. The dilatometer has an excellent performance in the insitu testing of soft soils. This paper presents comparative studies between the laboratory test and insitu dilatometer test results on soft marine soils in Hangzhou area. The results indicate that: (1) the uniformity of soil has an obvious influence on the index parameters of soft marine soil; (2) the curve changes of soil index and lateral expansion modulus are similar. In the characterization of the soil stratigraphy change in soft marine soils, the soil index and lateral expansion modulus curve can be integrated to improve the accuracy; (3) in soft marine soils, the coefficient of horizontal subgrade modulus obtained by the flat dilatometer test is too large, so the difference in soil types should be considered and used carefully.
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    Influence of Freeze-Thaw Cycles on the Mechanical Properties of Compacted Soils under Open Atmosphere Conditions
    WANG Xiaochun
    2021, 35 (3):  413-416. 
    Abstract ( 455 )   Save
    To study the effect of freeze-thaw cycles on the mechanical properties of compacted soils under open atmosphere conditions, the levee backfill soil samples filling soil taken from the Songhua River levee project were investigated. The laboratory freeze-thaw tests and triaxial compression tests were conducted on specimens with different initial states under open atmosphere conditions. Results show that the water supply during the freezing process can accelerate the development of stable state in the failure strength and the elastic modulus of soil samples. Further, the reduction rates in the failure strength and elastic modulus reach 85% and 92% after 7 F-T cycles, respectively. The degradation effect of freeze-thaw cycles on the mechanical property of the backfill soil can be reduced by enhancing the dry density or by moderately raising the moisture content of soil.
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    Stability Monitoring of a High Slope of Chashan Highway and Yangxi Avenue Interchange
    XIONG Yi
    2021, 35 (3):  417-420. 
    Abstract ( 294 )   Save
    In order to ensure the construction safety of a high slope of Chashan Highway and Yangxi Avenue Interchange Project in Gaoming District of Foshan City, this paper establishes a comprehensive monitoring system for the high cut slope on the left side between Station K9+065 and Station K9+216. Throughout the monitoring results, the magnitude, pattern and trend of the cut slope can be systematically understood. The monitoring results show that: 1) the daily change of individual monitoring points might exceed the alarm value, but the entire monitoring data were relatively normal on the whole; 2) The slope was in a stable state, and no obvious cracks and deformation were observed on the surface of the monitored slope.
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