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24 February 2023, Volume 37 Issue 1 Previous Issue    Next Issue

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Key Construction Methods for the Zhouzhou Railway Station Exit Underpass Crossing the Beijing-Guangzhou and Shanghai-Kunming Freight Lines ZHANG Zhihao 2023, 37 (1):  1-5.  Abstract ( 774 )   Save This paper presents a case history of constructing an underpass tunnel of Zhuzhou New Railway Station that crossing several active railway lines with high safety hazards. The open cut and cover method was selected from the comparison of different tunnel construction methods and from the site-specific conditions. Type D temporary beams were used to support the existing railway alignments and the temporary supporting structures were monitored. The sloped open excavation was protected by steel rakers on the concrete blocks to ensure the construction safety and quality. The construction methods used in the open cut and cover tunnel project is also summarized in the paper which can provide a reference for the similar construction projects in the future. Related Articles | Metrics

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Study on Effect of a Deep Excavation Construction on the Adjacent Tunnel YU Guozhao, LIU Houcheng, GUO Qijun, 2023, 37 (1):  6-9.  Abstract ( 290 )   Save In this paper, a deep foundation excavation project adjacent to the subway tunnel is taken as an example, and the three-dimensional model of the deep excavation near the existing tunnel is established by the numerical simulation software to study the influence of deep excavation construction on the adjacent tunnel. Throughout the comparative analysis, the need of considering the operative subway load is further clarified, and the deformation relationships in the excavation and the existing subway tunnel are evaluated in the paper. The results show that the deformation of the existing tunnel induced by the deep excavation construction in subway operative period is significantly greater than that in non-operative period; With the increase of the horizontal distance between the excavated area and the tunnel, the deformation of the deep excavation supporting structure and the tunnel gradually decreases, and the influence is smaller and smaller; When the tunnel is in the middle portion of the diaphragm wall, that is, the maximum horizontal displacement of the diaphragm wall, the influence of the diaphragm wall and the tunnel is the most significant. Related Articles | Metrics

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Application of the Steel Tube Soil Nail Supported Deep Excavations in High Fills ZHOU Xinglong, ZHOU Lihong 2023, 37 (1):  10-13.  Abstract ( 462 )   Save As a large technical challenge, the deep excavation in high fill soils usually is usually sensitive to the adjacent environmental impact due to their heterogeneous nature of the backfill soils and poor engineering properties. The excavation supporting structure in these areas are usually have the characteristics of high investment cost and long construction schedule. The steel tube soil nail wall is installed by driving (or predrilling and placing) the perforated steel tube with barbs into the borehole and the grouting the tubes. The major difference between the steel tube soil nails and conventional soil nails is that the steel tube soil nails utilizing the perforated steel tubes comparing the regular reinforcement bars, and it is more suitable applying in the loose soil strata. This paper presents a combination of steel tube soil nail wall plus sloped open cut. The construction experience indicates that this type of soil nail wall is applicable to the loose fill soils with low groundwater table. Related Articles | Metrics

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Design of a Double Row Soldier Pile with Ground Anchor Supporting a Deep Excavation Near a Subway YAO Guopeng, WU Chao 2023, 37 (1):  14-17.  Abstract ( 267 )   Save The deep excavation engineering is a systematic engineering. The design and construction of the excavation support are not only related to the hydrogeology engineering, but also related to the surrounding environment of the excavation, the requirements of deformation limits, the importance level, and other factors. At the current stage, with the rapid development of the urban underground space and high-raised building construction, there are more and more deep excavation projects adjacent to these already densely located buildings. Many researchers and engineering practitioners have completed much research on the control of the deformation in the support structures, the surrounding strata displacement and the adjacent building deformation. Valuable experience has been accumulated throughout these projects. In this paper, a deep excavation project near the subway is presented. The engineering geology and surrounding environment of the project are evaluated, and the double row soldier pile wall with ground anchor as well as internal strut support are selected as the excavation supporting structure. The construction monitoring data proved the effectiveness of this type of supporting structure. Which can be used in supporting of the deep excavations with deformation sensitive adjacent structures. Related Articles | Metrics

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Deformation of Deep Excavation in Complicated Subsurface Conditions YAO Chong 2023, 37 (1):  18-22.  Abstract ( 217 )   Save This paper presents the evaluation of the construction monitoring data of a deep excavation in the complicated soil and rock conditions. The deformation of the supporting structures, ground subsidence and the axial force data are statistically analyzed. The results indicate that these data are closely correlated, and they are the results from the subsurface conditions, excavation sequence and construction plan. Smaller deformation and axial force are observed in soil strata with better geotechnical properties. When the excavation reached the design elevations, the internal strut support and concrete floor covering the excavation should be placed as soon as possible to avoid the excessive exposure of the excavated ground in the ambient environment. Related Articles | Metrics

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Application of Multi-Process Excavation Method in the Construction of a Transverse Drainage Tunnel Near a Highway Tunnel with Active Traffic LEI Wanxiong, Li Qugang, LIU Yongxiang, YANG Hongwu, LIU Zhongwan 2023, 37 (1):  23-26.  Abstract ( 415 )   Save Constructing a drainage tunnel next to the highway tunnel with active traffic to “collect” the groundwater can effectively minimize the groundwater inrush in the operating tunnel. To expedite the drainage tunnel construction, part of the active highway tunnel could be utilized as the construction access as well as the multi-process drainage tunnel excavation faces. The blasting excavation is a commonly used tunnel construction method in the high strength rock mass where the machine excavation is not efficient. However, the excessive vibration induced by the blasting excavation might adversely affect the safe operation of the existing highway tunnel. In tis paper, a new segmental blasting method is proposed to resolve the low efficiency, high vibration and potential safety hazards in the conventional blasting excavation method.  Related Articles | Metrics

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Measurement and Analysis of a Tunnel In-Situ Geo-Stress Using the Single Borehole Hydraulic Fracturing Method WAN Xiaole, YANG Jianbiao 2023, 37 (1):  27-30.  Abstract ( 223 )   Save The hydraulic fracturing in-situ geo-stress measurement is to obtain the characteristic value of geo-stress and time curve through the rock mass deformation caused by the induced hydraulic pressure. This method has the advantages of simple test process and large testing depth and has been widely used domestically and oversea. In this project, throughout the application of the single borehole hydraulic fracturing to measure the in-situ geo-stress in the tunnel engineering of the important node of the weather natural pipeline, the mechanical parameters such as the magnitude of the in-situ geo-stress and the direction of the principal stress in the tunnel site are obtained, and the rockburst and deformation of the surrounding rock mass are predicted, which provides an important basis for the design of the safe construction scheme of the tunnel. According to the lithology of the tunnel, it is mainly moderately weathered bedrock, which belongs to hard rock. At the present survey stage, it is predicted that there will be no large deformation of the surrounding rock during the construction period. For the local possible weak rock stratum or interlayer, rock fracture zone, etc., the rock is weak, and there may be a small amount of plastic deformation of soft rock. Related Articles | Metrics

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Stability Analysis of an Expressway Slope Using Midas GTS HAO Yu 2023, 37 (1):  31-35.  Abstract ( 510 )   Save To study the variation characteristics of the high cut slope stability after the excavation of an expressway, this paper presents the strength reduction method (SRM) in the numerical analysis using Midas GTS finite element software. The factor of safety for the global stability, deformation and potential sliding plane are determined under the unsupported and heavy precipitation conditions. The appropriate support remediation measures were provided based on the analytical results. Two different remediation methods are studied in the paper: one method was providing more ground anchors grids only and the other approach was the combination of increasing the number of ground anchors and widen the platform on the slope. The results indicate that, only widening the platform on the slope has limited slope stability increase. The combination of ground anchor grid and the widening of the platform can effectively improve the global stability of the cut slope, control the deformation and manage the construction risks. Related Articles | Metrics

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Analysis of Deformation Intrusion limit of Tunnel Primary Lining and Reinforcement Design Validation LIU Baotong 2023, 37 (1):  36-39.  Abstract ( 234 )   Save The intrusion deformation in the tunnel induced by the poor geological conditions and other reasons after the installation of the primary lining was observed and the thickness of the secondary lining did not meet the original design requirements. The evaluation of the construction monitoring data of the intrusion deformation during the primary lining stage indicated that the deformation in the lining system had stabilized. To minimize the disturbance in the primary lining system caused by the removal of the steel supporting system, the design change approach was implemented by reducing the thickness of the secondary lining and strengthening of the steel reinforcement bars in the secondary lining system. The new design approach in the secondary lining system was validated by using MIDAS-GTS NX finite element numerical analysis software. It is concluded that the factor of safety in the strengthening segment met the design requirements. The construction monitoring indicate that the new approach was safe, and no cracking was observed. Related Articles | Metrics

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Geotechnical Investigation of a Special Wharf Supporting for the 2×5 000 T New Dry Clinker Cement Production Line in Sulawesi Utara of Indonesia XIA Yuyun, LIU Min, SHAO Bingchang, WANG Ran, HUANG QianFeng, LIU Yunchang, ZHOU Xiaosong 2023, 37 (1):  40-45.  Abstract ( 222 )   Save The special wharf supporting for the 2×5 000 T new dry clinker cement production line is in the nearshore area of Sulawesi Utara of Indonesia. The complicated subsurface soil conditions consist of soft soil, saturated sand and soft rock. The physical and mechanical properties of saturated sand are analyzed and evaluated by test boring, in-situ testing and laboratory tests. And the liquefaction potential of the saturated sand layer is therefore determined. The engineering results provide a reference for the study of the complex foundation soil characteristics and the selection of foundation system in overseas water transportation projects. As a large-scale overseas project, this project promotes the export of Chinese technical standards, which is of great significance in the construction of the Belt and Road Initiatives. Related Articles | Metrics

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Effect of a Deep Excavation and Construction on the Existing Railway Structures WANG Ling 2023, 37 (1):  46-50.  Abstract ( 229 )   Save A three-dimensional numerical model of the station including the station structure, entrances and exits, the ventilation pavilion and the ventilation tunnel was established. The influence of the deep excavation and construction of the three new towers on the displacement of the existing station structure are analyzed. The following conclusions are obtained: the excavation stage has the most obvious influence on the existing railway structure and is the critical stage for protecting the existing structures; the stability of the existing structure can be effectively protected by steel pipe piles, steel mesh and angle steel braces; under the same conditions, among the factors affecting the excavation, the location of the structure is higher than the scale of the structure. Related Articles | Metrics

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Application of the Staggered Soldier Pile Layout in Supporting a Deep Excavations of an Underground Parking Garage YAO Xiaobo, TIAN Tian, HU Jin 2023, 37 (1):  51-54.  Abstract ( 210 )   Save The soldier pile lagging with concrete internal strut is a common supporting structure in the deep excavation. Most of the soldier pile supporting structures have a straight-line layout due to their simplicity and the construction convenience, however, the stiffness of the straight-line layout has difficulties meeting the requirements of supporting large excavations. This paper presents a case history of a large sized deep excavation supporting design for an underground parking garage in Wuhan. the horizontal deflection at the pile head during the progress of the excavation of both the staggered and straightline soldier pile layouts are numerically analyzed and evaluated. The design parameters and optimized layout for the staggered soldier pile supporting structure are proposed based on the site-specific subsurface conditions. The comparison of the construction monitoring and numerical simulation results indicates that, the maximum lateral deflection in the staggered soldier pile supporting is 3.8 mm and is located at the middle of the exposed supporting structure. The lateral deflections in the staggered soldier pile wall meet the design requirements. Related Articles | Metrics

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Application Effect of Pile Tip Grouting Method for Bored Pile in Sand Layer HU Xiaoming, LIU Yanfeng, YUAN Wei, 2023, 37 (1):  55-58.  Abstract ( 221 )   Save The pile tip grouting is a common method to improve the bearing capacity of bored piles. To study the application effect of pile tip grouting method for the bored pile in sand layers, the installation and test of the test pile were performed in a municipal bridge pile installation project. The pile tip grouting adopts the open grouting method, the maximum grouting pressure in the process of the grouting is 3 MPa, and the total grouting is 2.4 cubic meters. The static loading test of using the selfbalanced method was conducted before and after the trial pile tip grouting to measure the displacement under each load increment and the pile strain at different elevations in the test process. The pile side friction in different range of pile length and pile tip resistance were derived. The test results reveal that, the bearing capacity of the trial pile TP1 increases 31%, pile shaft bearing capacity increases 28%, pile tip bearing capacity increases 46%. The pile tip grouting method can effectively improve the bearing capacity and deformation capacity of bored piles. Related Articles | Metrics

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Research Progress on Image Processing of Expansive Soil Cracks YAN Xiaoling, WANG Weiwei, LIU Jiesheng 2023, 37 (1):  59-63.  Abstract ( 248 )   Save The research on the fracture characteristics of the expansive soil is the foundation of the fracture research. Qualitative and quantitative description of the development of fissures can further understand the properties of expansive soil. The development and present situation of micro measurement methods of expansive soil are discussed, and the commonly used micro measurement methods are summarized. The conclusions are as follows: (1) Although there are many quantitative analyses, it is mainly qualitative analysis, quantitative index and system need to be improved and the relationship between microstructure and mechanics needs to be improved. (2) The influencing factors of the formation of the cracks in expansive soil are introduced. (3) The direct observation method, the indirect observation method and the statistical analysis method about the fracture microstructure of the expansive soil are summarized. Related Articles | Metrics

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Numerical Analysis of Active Earth Pressure Conversion Based on Deformation WANG Xudong 2023, 37 (1):  64-67.  Abstract ( 192 )   Save The estimation of the lateral soil pressure on the side of foundation excavation is the key to the deep excavation support design and has drawn a wide attention by academia and partitioners in the field. Although the Rankine and Coulomb soil pressure theories, which are characterized by the limit state and the linear distribution of soil pressure, are simple and practical, they are not consistent with the actual distribution of deep excavation mechanical properties. In this paper, considering the deformation of the soil and the deformation of the soil and the supporting structure, using the numerical methods, under the condition of different excavation depth and different top horizontal displacement in the excavation supporting structures, the distribution characteristics of lateral soil pressure, its development trend and transformation characteristics are extensively studied in this paper. The relationship between the lateral soil pressure transformation and the plastic yield is summarized. At last, the formula of the residual sliding force and the coefficient of the residual sliding force are proposed. Related Articles | Metrics

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Mechanical Performance of Double-Row Pile Supporting Structure Using on Pile-Soil Interface Elements LIU Chengjun, WANG Yizhao, CHEN Junsheng, ZHANG Siyuan, GUO Kangshi, CHEN Shihong, GUO Zijian, ZHANG Ronghui 2023, 37 (1):  68-73.  Abstract ( 341 )   Save The double-row pile system has been extensively used in the excavation support due to its advantages such as large lateral resistance stiffness, strong site applicability and convenience. This paper considers the interaction between piles and soil in the form of contact element to study the displacement and internal force of the double-row pile using MIDAS GTS NX. Combined with the field monitoring information, this paper verifies the safety and reliability of the double-row pile supporting structure, which provides reference for related projects. The result shows that by establishing the pile-soil contact surface, the deformation of the double row piles can be simulated more practically. About 3.5 times of the pile diameter is a reasonable pile row spacing, which can make full use of the mechanical properties and space effect of double row piles. About 2 times of the distance between piles in the front row is a reasonable distance between piles in the back row, which can save the project cost in the case of ensuring safety. Making a comparison between the numerical calculation consequences and the monitoring information, this paper verifies the necessity of establishing the pile-soil contact surface elements in the numerical simulation of the double row piles and the rationality of the support scheme of double row piles. Related Articles | Metrics

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Back Analysis of Bearing Capacity and Settlement Coefficients of Soil Among Timber Piles LIAO Jingwang, LIU Chuanshun, LIU Yong 2023, 37 (1):  74-77.  Abstract ( 291 )   Save The timber pile is widely used in the soft soil improvement of small projects because of its low cost, easy material source and convenient construction. The design of composite foundation of timber pile can be estimated according to the composite foundation of cement-material columns. However, the existing design code of pile foundation lacks the values of the coefficient β of the bearing capacity of soil among timber piles and the empirical coefficient of settlement φs, which are important parameters of the composite foundation design and directly affect the safety and cost of the project. In this paper, PLAXIS software is used to simulate the estimating of Chinese fir timber pile composite foundation, and two empirical coefficients can be obtained from the back analysis, which can be used for a reference in the practical engineering application. Related Articles | Metrics

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Analysis of Submarine Protective Device for the Production System Impacted by the Ship Anchor Drops AN Weizheng, FAN Xiaoliang, WANG Dong, LIU Guoheng, SHEN Xiaopeng, ZHENG Jingbin, LUAN Lubao 2023, 37 (1):  78-82.  Abstract ( 301 )   Save The normal operation of the submarine production system will be adversely affected by the emergency anchor drops. Approaches of model tests and numerical simulations are used in this paper to analyze the influence of anchor drops on protective devices for the submarine production system. At the first, a dynamic model test of anchoring impact is designed based on the practical engineering, to conduct the corresponding tests at different heights of dropping anchors. Time domain responses of the protective device are analyzed: the protective device is impacted followed by a second impact. Secondly, the dynamic interaction model of the anchor drop-protective system-submarine soil is established using the commonly used finite element software i.e. ABAQUS to conduct related numerical simulations. The practicability of the finite element model is verified through results of the model tests.  Related Articles | Metrics

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End Bearing and Side Resistances of the Static Pressed Steel Sheet Pile Using on CEL Method GAO Zhenyu, LI Yuhang, YANG Xueqiang, WANG Kun 2023, 37 (1):  83-87.  Abstract ( 307 )   Save To study the variation of the pile driving resistance of static pressed steel sheet pile in layered soils, a layered soil model of the static pressed steel sheet pile is established by using the ABAQUS finite element software. The variation characteristics of the pile driving resistance with the pile penetration depth in the process of the pile driving are discussed in this paper. At the same time, comparative studies are performed with different constitutive models (such as extended Drucker Prager model and Mohr Coulomb model) in sand layer in combination with an engineering case history. The results show that the resistance of the steel sheet pile increases gradually with the penetration depth of 3 meters, and then tends to be stable. The research results can provide a reference for the engineering practice of similar static pressed steel sheet piles.  Related Articles | Metrics

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Risk Identification and Prevention Measures of a New Deep Excavation Next to the Existing Railway Tunnel QIU Yongyuan 2023, 37 (1):  88-91.  Abstract ( 208 )   Save To study the deformation characteristics of adjacent railway tunnels induced by the foundation excavation of new projects nearby, and to identify these risks to existing railway tunnels during the deep excavation, effective control measures are proposed. This paper presents a deep excavation of the real estate project in Longyan area. The effect of the excavation on the adjacent railway tunnel was numerically simulated by using the MIDAS-GTS three-dimensional finite element calculation software. Risks associated with operating adjacent railway tunnels and corresponding control measures are evaluated with the foundation excavation process. The analysis results show that with the increase of the excavation depth, the deformation of the railway tunnel is also larger. The deformation of the railway tunnel and railway facility should be monitored during the deep excavation. The risk factors should consider the site-specific conditions, such as, survey data, design parameters, construction methods, construction equipment and machinery, construction personnel, etc. Related Articles | Metrics

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Discussion on the Use of Danish Formula to Determine the Pile Driving Criteria XIN Jian 2023, 37 (1):  92-93.  Abstract ( 967 )   Save The driving criteria is an important parameter for the prestressed pipe pile installations. The common practice adopted in the construction was mainly with the emphasis on the pile tip elevation and aided by the penetration blow counts. Due to the excessive emphasis on the pile tip elevation control and the length of the pile, pile installation hazards such as broken piles and pile head damage occur frequently, which causing unnecessary extra cost to the construction. There is no clear statement in the relevant specifications for the determination of the hammer blow counts. This paper presents a case history of pile installation in a railway project using blow counts methods that are widely used in Europe and US. The Danish formula is used to establish the corresponding relationship among the ultimate bearing capacity, the penetration depth and the hammer blow counts. The penetrations is not greater than the anticipated value and the hammer blows counts required for last 25cm penetration is not less than the anticipated value as the main pile driving criteria. Related Articles | Metrics

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Stability Analysis of Ditch-Type Waste Soil Landfill Site in Mountainous Area XIE Changbing, HUANG Qiuxiang, GUO Haofeng, SHEN Jipeng 2023, 37 (1):  94-98.  Abstract ( 360 )   Save The waste soil landfill sites are numerous and widely distributed. Affected by various adverse geological hazards during the operation period, the stability of theses landfill stie vary significantly and some of them might be critical. Among various waste soil sites that with slope stability concerns, the mountain ditch type of landfill site is the most prominent. However, few studies are reported. This paper presents the stability analysis of the Mao’an waste soil landfill site. Based on the site topography survey and subsurface geotechnical investigation results, the three-dimensional numerical models were established with FLAC3D software. The surcharge conditions induced by the debris flow as the results of the strong rainfall are analyzed. The response characteristics of the debris flow in the field area are obtained through the stress and strain variation relation in the numerical simulation results. The results show that the rainfall infiltration and debris flow overflow loading lead to the increase of the surface tensile stress, which leads to a local tensile plastic yield. The potential failure form in the field is the shallow surface sliding due to the tensile failure of trailing edge. The research results can provide a reference for the remediation of the failed landfill site and protection of landfill sites of the same type. Related Articles | Metrics

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Seismic Response of the Underground Powerhouse of SK Hydropower Station in Pakistan LI Yi, ZHANG Hongshan 2023, 37 (1):  99-103.  Abstract ( 236 )   Save There is a complex geological structure and well-developed seismic activity in at the underground powerhouse of SK Hydropower Station site in Pakistan, so it is urgent to study the seismic response of the underground structure. The three-dimensional numerical model was established by using the finite element software ABAQUS. The acceleration, velocity and stress response characteristics of the underground powerhouse were analyzed by using the dynamic time-history analysis method, and its seismic stability was also studied. The results show that: (1) There is an obvious seismic amplification effect on the free face of the underground powerhouse. The worse the quality of surrounding rock, the more obvious the amplification effect. (2) During the earthquake, the stress state of the underground powerhouse is mainly affected by the original stress field formed after excavation. (3) The underground powerhouse is basically in a stable state under the earthquake with an exceedance probability of 50% in 100 years; the stability of underground powerhouse may not meet the requirement under the earthquake with an exceedance probability of 3.3% in 100 years. The study results can provide a reference for the actual engineering and similar engineering. Related Articles | Metrics

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Mechanism of Wujiagou Landslide in Xiangxi River in Three Gorges Reservoir Area WANG Shuai, ZHENG Hongwei, LIANG Guanting 2023, 37 (1):  104-108.  Abstract ( 395 )   Save The Wujiagou landslide in the Three Gorges reservoir area was originally a loosely colluvium bank slope in a stable state. However, after the transformation of human engineering activities, the bank slope slipped during heavy rain and reservoir water drawdowns. The geological characteristics and sliding depth are identified by means of survey, field monitoring, and limit equilibrium analysis approaches. The impact of the three environmental variables of the terrain, the rainstorm, and the reservoir water on the factor of safety of the landslide is quantitatively analyzed by the theoretical analysis. The formation mechanism of the landslide was discussed. The main sliding surface of the Wujiagou landslide is the contact zone between the silty claystone spoil and the bedrock layer. It becomes the slip plane under the long-term softening effect of reservoir water drawdowns. Engineering activities such as surcharging at the top of the slope and unloading at the toe of the slope have resulted in a “steep up and gentle down” topography of the bank slope. The activity provided space for the formation and development of the landslide. The torrential rain happened now when the reservoir water level dropped to the most unfavorable water level, and finally induced a landslide. The research results provide a reference for the subsequent construction of the reservoir area. Related Articles | Metrics

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Seepage Characteristics and Stability Analysis of a Waste Soil Slope Under Rainfall Conditions XU Chengbin 2023, 37 (1):  109-113.  Abstract ( 590 )   Save The rainfall affects the slope stability and is an important inducement of the landslide geological hazards. This paper presents evaluation results of the slope of a project spoil site. The seepage characteristics of the slope under continuous rainfall and rainfall with different intensities are studied using the Geo Studio software SEEP/W module. The limit equilibrium method is used to analyze the slope stability under different rainfall duration through SLOPE/W module. The results show that the pore water pressure in the shallow layer of the slope changes greatly at the beginning of the rainfall, and then quickly tends to be stable. Under the same rainfall duration, the influence of the heavy rain, the rainstorm and the heavy rain on the pore water pressure of the slope gradually weakens. After 7 days of continuous rainfall, the infiltration depths corresponding to the different rainfall intensities are 12.1m, 6.9m and 1.6m respectively. Under the condition of the heavy rain, with the increase of rainfall time, the slope safety factor shows a decreasing trend, from 1.903 in natural state to 1.765, and the safety factor decreases by 8%, but it is still greater than 1.20 specified in the specification under the condition of heavy rain. Therefore, the factor of safety of the waste soil slope meets the code requirements. The research content of this paper will provide a reference for the stability evaluation of the similar slope under the rainfall conditions in the future. Related Articles | Metrics

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Stress Relaxation Effect in a Soft Rock Tunnel with High Geo-Stress CHEN Feifei, WU Jianli 2023, 37 (1):  114-117.  Abstract ( 274 )   Save The construction of the deeply embedded tunnel in the soft rock with high in situ geo-stress and its long-term stability evaluation are still the worldwide technical and theoretical challenges. This type of tunnel construction hazard prevention has become the focus of the excavation construction engineering. After the tunnel lining installation, on the one hand, it would be able to carry the creep deformation caused by the low strength of the surrounding rock mass, on the other hand, it also could take the relaxation load caused by the continuous reduction of the self-supporting capacity of the surrounding rock mass with time. Therefore, it is a key developing direction for the design and construction of the tunnel in the soft rock mass with high in-situ geo-stress to reduce the deformation and looseness range of the surrounding rock mass and reduce the load acting on the lining system as much as possible by selecting the reasonable construction methods and support parameters. In this paper, a highway tunnel in the soft rock mass is presented as an example to study its relaxation mechanism through the in-situ geo-stress tests and numerical simulation, which provides a useful exploration for the design and construction selection of tunnels in the soft rock with high geo-stress. Related Articles | Metrics

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Research Progress on Settlement Factors and Estimation Methods of Composite Foundations Formed by Soil-Cement Mixed Columns WEI Quanyu, SHI Jun, FENG Zheyuan, LI Hongya, HUA Ruiping 2023, 37 (1):  118-123.  Abstract ( 349 )   Save The soil-cement mixed column method has the advantages of high utilization rate of the in-situ soil, less environmental impact of in the mixing installation and lower construction cost. This method is widely used in the ground improvement projects. There are many factors affecting the settlement of the soil-cement mixed column composite foundations. The research on the load transfer mechanism and the settlement estimation method is not well-developed, and there is no matured and widely accepted design methodology available. The effective column length and the optimal column-soil modulus ratio are the key factors to control the settlement of the composite foundation, while the selection of the column spacing and the replacement ratio needs to systematically consider the engineering safety and the construction cost. In addition, the load transfer mechanism of the column is validated, and the major settlement estimation methods of the composite foundation are compared in this paper. Related Articles | Metrics

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Dynamic Characteristics of Coarse Grained Backfill of High Railway Base Under the Traffic Load PENG Huiyuan 2023, 37 (1):  124-127.  Abstract ( 212 )   Save In this paper, the dynamic characteristics of the coarse-grained backfills of high-speed railway subgrade under the influence of traffic load are studied by the GDS dynamic and static triaxial apparatus. The results show that: when the cyclic stress is large, the greater the frequency of loading is, the greater the volume strain of coarse-grained subgrade backfill will be. The subgrade backfill will have higher degree of compaction. However, when the cyclic stress is equal to the confining pressure, the effect of the loading frequency on the cumulative volume strain of the coarse-grained subgrade backfill is limited; When the applied cyclic stress is large, the increase of load frequency leads to the increase of the resilient modulus of subgrade backfill, and the axial cumulative deformation of the coarse-grained backfill increases significantly; When the cyclic stress is close to the confining pressure, the load frequency has little effect on the axial cumulative deformation of the coarse-grained packing. According to the research results, the corresponding control measures for subgrade filling construction are proposed, which can provide reference for similar projects. Related Articles | Metrics

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Data Mining Analysis of Oxide and Strength Characteristics of Contaminated Red Clay Using CART Method LI Kunyao, WANG Xueqing, WANG Yongwei 2023, 37 (1):  128-133.  Abstract ( 177 )   Save As a regional special soil, the red clay has the characteristics of well-developed cracks and poor mechanical properties. The instability of the compositions in the red clay can be aggravated by the heavy metal (such as Cr3+) contaminations. To investigate the strength characteristics of Cr3+ polluted red clay samples, the relationships among the content of oxides (Al2O3, TiO2, K2O, etc.), mechanical properties and the content of Cr3+ in contaminated red clay were analyzed through the X-Ray Fluorescence (XRF), the direct shear and the consolidation tests. The variation of mechanical properties with the Cr3+ concentration is predicted based on the classification and regression tree (CART) method, and the effect of oxides on the strength of red clay was analyzed by data mining approach. The experimental results show that the shear strength and internal friction angle of the red clay decrease with the increasing of Cr3+ concentration, while the cohesion increases. The CART modeling shows that the oxides in the soil can affect the strength characteristics of the red clay. Related Articles | Metrics

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Experimental Study on Mechanical and Permeability Characteristics of Soil Rock Mixture with Different Mixing Ratios GENG Chuanhao, ZHENG Xing, YANG Wenchao, WEI Weiqiong, 2023, 37 (1):  134-137.  Abstract ( 340 )   Save The compaction, mechanical and permeability tests are conducted after the fine-grained soil and crushed stone are mixed with different mixing ratios. With the increase of the gravel content, the maximum dry density of soil rock mixture increases and the optimal moisture content decreases. After the compaction, with the increase of rock content, the shear strength, the compression modulus, and the permeability of soil rock mixture increases. The reason for the above engineering characteristics of mixture is that with the increase of gravel content in the soil, gravel particles in the soil gradually form a skeleton, and fine-grained soil is filled in the skeleton. The formed soil structure contacts and occludes with each other during the shearing process, which enhances the shear strength and reduces the compressibility. At the same time, more voids are formed in the soil, the permeability increases. Related Articles | Metrics

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Application of Slope Monitoring in the Emergency Remediation of a High Slope Hazard in Western Hubei SUN Futian, WANG Bin, ZHU Jiebing, HE Yuwei, CHEN Weitao 2023, 37 (1):  138-141.  Abstract ( 249 )   Save The geological conditions of a high cutting slope located in Xianfeng interchange of En-Qian Expressway are very poor. During the construction period and the trial operation period, the slope platform collapse with various scale, retaining structure cracking and median separation zone deviation are observed which makes the remediation difficult and with potential high risk. Throughout the safety monitoring of the slope in the early stage of the remediation, the emergency remediation period and the operation period, the monitoring data are provided for the expressway operation safety and construction real-time feedback, which ensures the smooth construction treatment of the slope hazards and provides the basis for the remediation effect evaluation. Related Articles | Metrics

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Application of Flat Dilatometer Tests in Deep Soft Soils of Wenzhou Suburban Railway Projects TU Qizhu 2023, 37 (1):  142-146.  Abstract ( 450 )   Save The flat dilatometer test is an advanced in-situ test method, which can obtain a variety of important geotechnical parameters. This paper presents the application of flat dilatometer tests in deep soft soil layers in Whenzhou Suburban Railway Project to provide design and construction support of the underground engineering. The results indicate that: the horizontal consolidation coefficient obtained from the flat dilatometer test is about 0.74 times that of from the pore pressure dissipation test, and the undrained shear strength obtained from the flat dilatometer test is about 1.04 times that of the field vane shear test, and the static lateral earth pressure coefficient and the subgrade horizontal coefficient obtained from the flat dilatometer test are close to that obtained from laboratory test and the empirical value recommended in the design code. Therefore, the flat dilatometer test can provide accurate geotechnical parameters for the design and construction of underground engineering. The results of flat dilatometer test show that the soft soil layer in the Wenzhou Suburban Railway Project has the characteristics of weak consolidation and permeability, low undrained shear strength, large coefficient of static lateral earth pressure and small coefficient of horizontal subgrade bed. During underground engineering construction, the safety risk is high of underground engineering construction. Related Articles | Metrics

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Measured Response of a Deep Excavation in Soft Soils#br# TIAN Dexin 2023, 37 (1):  147-151.  Abstract ( 289 )   Save The foundation excavation of Dongtinghu Road Station of the Suzhou Rail Transit is located on Qianjin East Road, which is one of the main transportation lines of Kunshan City. A thick layer of peaty cohesive soil is deposited at the proposed excavation project site. The monitoring of the response of the supporting structure and the adjacent ground subsidence due to the excavation are of great importance to the safety of the excavation as well as the adjacent utilities. A construction monitoring program was developed based on the site geological, hydrological conditions and the surrounding environment constrains. The following conclusions are obtained: 1) The shape of the horizontal displacement of the retaining structure induced by the foundation excavation is similar to a “shuttle” shape. The maximum horizontal displacement value gradually increases with the excavation depth, and the position of the maximum horizontal displacement gradually shifts to the lower portion; 2) The top of the retaining structure gradually produces an upward vertical displacement (the wall rises), and at the same time produces a roughly outward and symmetrical horizontal displacement; 3) The displacement characteristics of the enclosure wall body and the top of the wall further cause the release of the axial force of the upper support on the enclosure wall and the increase of the axial force of the lower support; 4) The cross-sectional curve of the ground subsidence induced by the excavation is in the shape of a “double bowl”, and the response of the underground utilities within the scope of the "double bowl" should be paid attention to during the construction. Related Articles | Metrics

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Static Jacked Piles in Transparent Model Soils under Different Jacking Rates SONG Wenjun, LENG Xianlun, HE Xiang, CHEN Jian, WANG Chuan, 2023, 37 (1):  152-156.  Abstract ( 226 )   Save In the process of pile jacking, the rate of jacking governs the degree of the soil disturbance adjacent to the pile. But few published studies considering the effect of jacking rate on the deformation of soil adjacent to the pile. By using a transparent soil material and the Particle Image Velocimetry (PIV) method, a series of visual model tests were conducted to analyze the displacement field and its evolution process of the soil around piles at different pile jacking rates. The results indicate that the soil displacement patterns demonstrate a dynamic process of the downward extrusion to lateral extrusion and to upward extrusion at different pile jacking rates. The reason for the variation of disturbance range at the initial and later stages of pile-jacking is that the high stress zone is produced ahead of the time under the tip of high-speed pile-jacking, and the disturbance range of the high-speed pile-jacking is slightly larger than that of low-speed pile-jacking. The general motion trend of the soil around the pile is upward, and the greater the velocity of pile jacking and the closer the distance to the pile, the greater the vertical displacement of the soil. The research results can provide a technical support for a reasonable design of the pile jacking rate and assurance of the construction quality and safety. Related Articles | Metrics

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Piping Potential and Strata Disturbance Evaluation in the Deep Excavation Using Cone Penetration Test LU Yunlong, DAI Zhengbin, TANG Guoyi, 2023, 37 (1):  157-160.  Abstract ( 265 )   Save The safety hazards induced by the artesian groundwater beneath the soil strata is one of the factors that posting safety hazards in the deep excavations. The case history of a piping accident occurred in a deep excavation project in Jiangbei New District in Nanjing City is presented in this paper. The vertical and horizontal limits of the piping disturbed zone were evaluated through the Cone Penetration Test (CPT). The CPT test result comparisons before and after the accident can have the following conclusions: the mechanical properties of the ④2a silty fine sand lens with silty soil around the piping points are close to that of worst soil area outside the excavated area. The CPT results are consistent with the failed conditions; It is feasible to use the CPT test to analyze the stratigraphic disturbance zone after the piping; which provides some reference for the remediation of the excavation piping hazards induced by the artesian groundwater below the excavation zone. Related Articles | Metrics