Table of Content

31 August 2023, Volume 37 Issue 4 Previous Issue    Next Issue

For Selected:

Download Citations EndNote Reference Manager ProCite BibTeX RefWorks

Toggle Thumbnails

Select

Evaluation and Analysis of Intertidal Soil Peaty Silt Soil Improvement by Blasting HU Yonggang, CHEN Wenbin, YANG Shanpian, ZHANG Ailun, QIN Wei, ZHANG Liujun, ZHANG Zhizhou 2023, 37 (4):  545.  Abstract ( 241 )   Save Blasting is one of the commonly used methods to improve the thick, soft peaty silt soils, especially for the embankment construction over the thick, soft soils in the coastal intertidal zone. The main technical aspect is to evaluate the improvement depth in the thick and soft cohesive soils. This paper presents a case of an engineering project using the blasting compaction of peaty silty soils in coastal Fujian Province. The effect of the blasting compaction and stone filling for the embankment over thick and soft soils is evaluated by the combination applications of ground penetrating radar and long-term settlement observation methods. Through comparative analysis, it is concluded that the change of bottom depth of rock filling layer examined by the ground penetrating radar is also reflected in the cumulative settlement report of the long-term settlement observation, indicating that the ground penetrating radar detection and settlement observation results confirm each other, which can better meet the purpose of evaluating the improvement effect of the blasting improvement method. Related Articles | Metrics

Select

Study on Engineering Geological Hazards and Mitigation Measures of Artificial Landscaping WANG Chuan, ZHANG Jihong 2023, 37 (4):  549-552.  Abstract ( 196 )   Save Under the guidance of a new development concept, the artificial landscaping engineering projects are widely used in the urban construction, and the correspondent engineering hazards are also significantly increasing. In this paper, the engineering geological hazards in an artificial landscaping project is analyzed, and it is considered that differential settlement of the soils and the deformation of filled body in the construction are the direct engineering geological hazards encountered. The correspondent slope instability and excessive deformation at the surface and within the fills as well as the deformations in structures near the fills are the direct concerns. To minimize these potential hazards, the dynamic compaction method was utilized by using the compaction energy of 1000kN.m for two passes with a grid pattern. The footprint compaction that using the compaction energy of 500 kN.m. The artificial landscaping filling material, construction equipment, construction technique and construction monitoring measures are discussed in the paper. The results are satisfactory. Related Articles | Metrics

Select

Analysis of the Collapse During the Tunnel Excavation in Saturated Completely Weathered Granite Soils YANG Zhao, SHI Zhangru, LUO Huiwu 2023, 37 (4):  553-557.  Abstract ( 482 )   Save The causes of tunnel collapse are complicated. In order to study the causes of a collapse in the tunnel excavation in saturated completely weathered granite soils, this article analyzes the loss of fine particles from the tunnel excavated area. Combined with the triaxial test and the permeability test results, this paper analyzes the structural damage of the completely weathered granite and factors that causing the tunnel collapse. The results are shown as follows. Firstly, as the tunnel is excavated, seepage causes the gradual loss of fine particles at the excavated surface and changes the composition of the completely weathered granite soil structure, so that both the dry density decreases and the void ratio increase. While the coefficient of permeability increases significantly, this leads to intensified piping. The structural damage in the granite soils caused by the seepage is the physical factor of the collapse. Secondly, While the seepage causes the structural damage, the disintegration of the completely weathered granite soils gradually increases, the surrounding rock is softened by the water, the cohesion, the internal friction angle and the shear resistance, the strength decreases accordingly, further reducing the self-stability of the surrounding soil and rock mass, which is the mechanical factor for the collapse of blocks during the excavation process. The structural damage of the completely weathered granite soils caused by the seepage induces tunnel collapse. Controlling the seepage conditions of the groundwater in the stratum is the key to minimize the deterioration of the completely weathered granite mechanical properties due to the seepage and can significantly improve the stability of the tunnel. Related Articles | Metrics

Select

Case History of a Semi-Rigid Composite Ground and Its Working Mechanism XIA Lulu, ZHAO Zhiyong, ZHOU Puhong, WEI Liucheng, CHEN Wuwen, ZHOU Hui 2023, 37 (4):  558-561.  Abstract ( 245 )   Save With the continuous development and improvement of composite foundation technology, the soil improvement technology of the semirigid columns represented by the cement mixed soil column has drawn more and more attention by engineers and technicians in the engineering practice. The improvement mechanism, stressstrain characteristics, failure modes and bearing capacity characteristic value of the soil among columns after the treatment of the semirigid columns have become the focus of the study. In this paper, the reinforcement mechanisms, stressstrain characteristics and failure modes of the semirigid column composite ground are evaluated and analyzed. The working mechanisms and stressstrain characteristics of the semirigid column are demonstrated by an engineering case history. Based on the field test results, the increased ratio of foundation bearing capacity of soils among columns after the ground improvement with the semirigid columns is also evaluated in this project. This can provide valuable practical experiences and a reference point for similar projects in the future. Related Articles | Metrics

Select

Optimization Design of Supporting Structures for Two Adjacent Deep Excavations LI Jin 2023, 37 (4):  562-565.  Abstract ( 185 )   Save During the construction of urban underground space engineering, due to the contradiction between land use and construction duration, two or even more deep excavations will be constructed concurrently, resulting in the different impact on the adjacent environment. The design of deep excavation support structure will face the selection of the same pit excavation and sub pit excavation plans. Different excavation plans have an important impact on the safety, economy and surrounding environment of excavation engineering. This paper presents a case history of the deep excavation of a regulation and storage tank and local treatment station in Jiujiang City, Jiangxi Province. The stress characteristics, safety and economy of the excavation supporting structure are evaluated. The different design plans for the excavation supporting structures for the two adjacent projects are compared and the design of the construction of the same excavation and separate excavation of the other pit are selected. Related Articles | Metrics

Select

Effect of Inorganic Salts on the Sedimentation Rate of an Aluminum SlimeCase History of the Pingguo Aluminum Tailings Slurry DENG Xu, SUN Gangchen, ZHANG Xiwei, GONG Zilong, HE Jianbo,  2023, 37 (4):  566-569.  Abstract ( 198 )   Save Guangxi Pingguo aluminum tailings slurry has the characteristics of small particle size, electric charged, large specific surface area, high water content, difficult to settle, and containing Al3+ impurities. As Pingguo aluminum slime particles charged, the Van der Waals force in the mine slurry particles has a great influence on its sedimentation, and the ionization of the inorganic salt will have an impact on the thickness of the electric layer, and then affect the slurry of the sedimentation rate. In this paper, a common inorganic salt, NaCl, was selected to be added into the slurry and fully stirred. The influence of adding the NaCl on the sedimentation rate of the slurry was analyzed according to the relationship between the height and the settling time of the supernatant of the slurry. The results show that there are three stages of the slime sedimentation: the turbulence influence stage, the main settling stage and the secondary settling stage. With the increase of the NaCl concentration, the rate of the slurry gradually decreased. Related Articles | Metrics

Select

Analysis of Emergency Response to an Anchor Failure in a Deep Excavation Support Project LI Xilai, LEI Jinshan, 2023, 37 (4):  570-573.  Abstract ( 185 )   Save Combined with an engineering case history, a deep excavation support anchor failure may cause potential risks. A comprehensive analysis of the causes from the engineering in formation, anchor construction quality to design and other factors are performed. The corresponding emergency measures, including backfill of excavated area, existing anchor strengthening and lowering the groundwater level, were proposed. The final approach was to unload the excavated area. Related Articles | Metrics

Select

Comparative Analysis on Stabilization Schemes of a High Fill Embankment CHENG Gang, CHEN Mingming 2023, 37 (4):  574-578.  Abstract ( 183 )   Save A proposed airport is located in a rolling mountain and hilly area. The airport flight area is formed by cut and fill method. Different slope reinforcement schemes have a significant impact on the project investment and the original ecologic environment. According to the engineering geological conditions of the site, this paper takes the typical sections of the high fill embankment as the research object and proposes a gentle slope plan and a steep slope plan of the high slope reinforced by geosynthetics. Using GeoStudio software, the numerical simulation on the stability and deformation of different reinforcement schemes under normal working condition and rainfall working condition was carried out. The research results show that the geogrid reinforced steep slope scheme, combining with the topographical characteristics of the site, can save investment, reduce the amount of filling, and shorten the construction period under the premise of meeting requirements of civil airport project. It also lowers the impact from engineering construction on the original ecology of the site. This design idea of using favorable terrain factors to increase the slope rate provides a reference for the reinforcement design of similar high fill embankment. Related Articles | Metrics

Select

Analysis of the Application of the Secant Pile Supporting Structure in Large Deep Excavation Projects WANG Ling, XU Jianbao, JIANG Di 2023, 37 (4):  579-583.  Abstract ( 256 )   Save As a supporting structure for deep excavations, the secant pile is formed by cutting the adjacent piles, which constructs a continuous piled retaining structure with a good waterproof and seepageproof function. The internal bracing is a system that provides the support and the restraint for the strength, deformation and stability of exterior envelope. It is composed of horizontal bracing (corner bracing, opposite bracing, trusses and circular supports, etc.) or slanting bracing, column, etc. This paper presents a case history of a deep excavation support system in Shenzhen. Combined with the characteristics of this project, the application of secant pile bracing structure in the deep excavation under limited urban space is fully analyzed, in which not only ensures the safety of excavation bracing structure, but also ensures the deformation of the adjacent structures are within the allowable limits. The safety and the normal use of surrounding buildings are satisfactory. Related Articles | Metrics

Select

Stability Analysis of Finegrained Tailings Dam after using of Reinforced Drain Board TIAN Tian, HU Jin, YANG Xiaoliang 2023, 37 (4):  584-586.  Abstract ( 196 )   Save The stability of the tailings dam is closely related to the safety of people and properties of the downstream residents in the reservoir area and the surrounding environment. Based on the geological conditions of a finegrained tailings dam in Guizhou, the strength reduction method is used to identify the stability analysis of the dam under different support schemes. The results show that the potential sliding surface of the dam is transferred from the surface to the interior of the dam after reinforcing with proposed drain board. The reinforcement effect of the drain board is related to the height of the newly built filler. When the height of the newly built stacking material is 3.5 m, the safety factor of the dam increases by 6.4%; when the height of the additional silt filler is 30 m, the dam safety factor increases by 25%. The results verify the feasibility of the proposed drain board. Related Articles | Metrics

Select

Identification, Characterization and Treatment of a Large Landslide Site in Qulong Village, Quma Town, Yunyang County in the Three Gorges Reservoir Area LUO Jun, ZHANG Luming 2023, 37 (4):  587-593.  Abstract ( 418 )   Save Based on the preliminary survey results and investigation reports, the landslide volume in Qulong Village, Quma Town, Yunyang County, Chongqing is about 468 × 10 cubic meters. The size of this landslide belongs to a large landslide and this landslide is currently at the stage of creeping compression deformation, which may cause overall sliding hazard. Throughout several field detailed investigations, detailed exploration and engineering monitoring, the possibility of the existence of the largescale landslide, the basic characteristics and stability of the landslide are analyzed and studied. The results show that; (1) The landslide area has a three steps terrace topography in the rolling hill area with tectonic eroded cuttings. Its geologic formation is the same as the slope cross the river. (2) There is no previous large landslide in the study area. The landslide is only composed of four small to mediumsized independent landslides, and the maximum volume of a single landslide is about 15.7 × 104 cubic meters, and other slopes are generally stable; (3) Landslides are triggered by many factors such as, the prone sliding formation of sand mudstone, the steep and gentle terrain, large amount of surface water infiltration, etc.; (4) The sliding mitigation support and drainage measures are adopted for the No. 2 and No. 4 landslides which have direct threat objects. These measures effectively improve the stability of the landslides. The results can provide a reference for the judgement and mitigation of similar landslide hazards. Related Articles | Metrics

Select

Exploration and Stability Evaluation of Goaf Area in Tangye District in Jinan LIU Xinjuan, XIAO Yunlong 2023, 37 (4):  594-597.  Abstract ( 905 )   Save This paper presents a goaf area investigation and mitigation plan in Tangye District of Jinan City. The Tangye District has a rich deposition of iron ore resources with a high concentration in a very small area. An abandoned mine site was found in a local development district during the engineering investigation stage and was confirmed in the construction stage. The adopted data collection, local resident interview, a variety of means such as drilling, geophysical exploration for the minedout area prospecting, delineated the scope of goaf area, location and size of mine, and evaluate stability of goaf area. Suggestions are proposed to the goaf area to minimize the impact on the proposed building, avoid the goaf caused by environmental problems. These suggestions can provide means and methods protect and improve the abandoned mine environment, protect people’s lives and property, maintain the sustainable development of social economy service, social stability and ecological environment stability. Related Articles | Metrics

Select

Analysis and Stability Evaluation of the Hetaoping Landslide in Guizhou JIAO Jikai, HE You, SHEN Mingxiang 2023, 37 (4):  598-602.  Abstract ( 312 )   Save The Hetaoping landslide is located in Qunlian Village, south of Shanshu Town, Yinjiang Tujiazu Autonomous County of Guizhou Province. After the first sliding in June 2008, the deformation of the landslide suddenly increased followed by the continuous heavy rainfall in 2014 flood season，seriously threatening the lives and property safety of the residents of Hetaoping Group. Therefore, it is necessary to study the mechanism and stability of the landslide, providing a basis for the subsequent landslide prevention and control. The geomechanical mechanism and the stability of the landslide deformation and failure are studied by applying comprehensive research methods such as the field investigation, the geological analysis and the numerical simulation. The results show that the terrain conditions of the Hetaoping landslide area, such as steep slope above and gentle slopes below, as well as the thickness and strength of the covering layer, are the material conditions for the formation of the landslide. The extensive and long rainfall duration are important triggering factors for the formation of the landslide, and are also the main controlling factors for the development of the landslide deformation. The instability mechanical model of the Hetaoping landslide is pushtype landslide, which is currently in the stage of basically stableunstable creep deformation. The stability of the Hetaoping landslide is satisfactory under natural conditions, but the stability of the landslide is in an unstable state under continuous rainstorm conditions. Related Articles | Metrics

Select

Research on the Influence of PHC Pipe Pile Construction on the Pore Water Pressure and Soil Strength of Marine Soft Soil Foundation GU Cunlei, GAO Bei 2023, 37 (4):  603-607.  Abstract ( 309 )   Save The construction of PHC pipe piles in marine soft soils strongly will induced a strong buildup of the excessive pore water pressure and a strong disturbance on the strength of the soft soil, thereby negatively affecting the bearing capacity of the foundation soils. To better understand the influence of PHC installation on the soil pore water pressure and on the soil strength before and after pile installation, this paper presents a series of testing results such as, pore water pressure monitoring tests, static penetration tests and cross plate shear tests at different depths during PHC pipe pile construction in the site with marine soft soils in Zhejiang. These tests and evaluations may be beneficial to the optimizing construction schedule and ensuring construction safety. The test results show that the changes of the excess pore water pressure after PHC installation in the testing area undergoes three typical processes, namely, shortterm increase, longterm stability, and finally dissipation. The pore pressure dissipation with time relationship basically presents an inverted "U" shape. The increase of the pore pressure greatly reduces the insitu shear strength of soil, leading the soil shear strength to be changing in a "U" shape with soil depth. The shear strength of soil after the PHC pile installation in soft clays depends on the dissipation of excess pore water pressure, soil characteristics, and construction method. This research may be useful for the optimizing the construction timing of the PHC pipe piles in marine soft soils and ensuring the stability of the excavation close to the pile construction site. Related Articles | Metrics

Select

Simulation of a Deep Excavation Deformation by Using MIDAS GTS NX GUO Shen, ZHANG Long 2023, 37 (4):  608-610.  Abstract ( 625 )   Save This paper presents a case history of threedimensional finite element analysis simulation of the entire process of a deep excavation support project by using MIDAS GTS NX. The lateral deflection of the supporting structure and the settlement of the adjacent ground with the excavation depth are numerically monitored. The results The results show that the horizontal displacement of the excavation supporting structure is roughly divided into three stages: stable development, transition and rapid development with the excavation depth. The vertical settlement of the adjacent soil around the excavation increases with the excavation depth. It generally shows an increasing trend, and the surrounding soil from near to far shows the pattern of first heave and then downward settlement; under the same working condition, the vertical displacement of the surrounding soil first changes linearly and then settles with the increase of the distance from the edge of the excavation. The volume gradually stabilized. Related Articles | Metrics

Select

Minimizing Lateral Squeezing Force and Deformation at Bridge Abutment in Soft Soils Using CFG Columns WANG Wei, FENG Dang, CAO Xianzhen, XIE Chang, LI Fayang 2023, 37 (4):  611-614.  Abstract ( 159 )   Save To study the influence of CementFly AshGravel (CFG) columns in minimizing the lateral squeezing force, excessive horizontal displacement and abutment tilting of the adjacent abutment piles induced by the soft soil lateral flow sue to the embankment construction, a series of numerical studies were performed with the sitespecific conditions. The analysis results show that, due to the shielding effect of the CFG columns on the lateral flow of the soft soil, the lateral squeezing force and excessive horizontal displacement of the abutment pile gradually decrease with the increased number of the CFG column replacement rate, and the horizontal displacement curve of the abutment pile rotates counterclockwise with the displacement neutral point. The abutment tilting is caused by the resultant moment of abutment lateral earth pressure and abutment pile lateral squeezing pressure. With the increase of the CFG replacement rate, the abutment tilt is gradually relieved, but there is still residual rotation. Related Articles | Metrics

Select

Numerical Investigation of Change of Shear Strength Parameters in the Sliding Zone QIN Shuaishuai, ZHANG Zhansheng, ZHANG Xingchen, ZHANG Peng 2023, 37 (4):  615-618.  Abstract ( 146 )   Save With the rapid development of the economy, the construction of infrastructure has become more and more improved, and the artificial transformation of the original landform has been aggravated. Breaking the original balance of the slope might lead to a series of increasing slope geological hazards. This paper presents a case history of a landslide in Liuyang City. The landslide in the gravelly clay soils is focused on the analysis and study of the impact of the change of landslide soil parameters on the overall stability of the landslide based on the gradual failure of the landslide body. Based on the data collection, detailed onsite survey and laboratory testing, this paper uses ABAQUS numerical simulation software to establish a geological model, and compares the simulation results of different landslide soils from three aspects: plastic sliding area, displacement and stability. The impact of parameter changes on the landslide stability is thoroughly investigated. Related Articles | Metrics

Select

Analysis of Optimization Design of Beam on Elastic Foundation Method for Reinforced Utility Pipe Underneath the Active Roadway ZHOU Zhenhai, WANG Yong, CHEN Xiaoxiang, GONG Jianwu 2023, 37 (4):  619-623.  Abstract ( 265 )   Save In the section where the overlying load is large or the load distribution is uneven, such as crossing active highways and streets, the utility pipes used for highvoltage power cables often need to be encapsulated with reinforced concrete. The existing engineering practice is to use a standardized envelope structure layer, which cannot reflect the influence of different foundation soils and the geometric dimensions of these utility pipe envelope structure layer on the internal force of the structure. Encapsulated concrete projects that are sealed or reinforced according to the structure have great potential safety hazards. Based on analyzing the typical pipe structure, according to different soil bed coefficients, the properties of the beam over elastic foundation of the tubeencapsulated concrete are analyzed. The internal force solution based on the long beam and semilong beam is proposed, and combined with common engineering actual conditions, the proposed suggestions on the optimal design of the encapsulated structural layer of the pipes in the crossing section provide a reference for the construction of related projects. Related Articles | Metrics

Select

Coal Rock Porosity Property Extraction and Three 3D Reconstruction Using Hough Transformation ZHOU Zhou, ZHAO Leilei, LEI Xudong, PENG Ruidong, 2023, 37 (4):  624-628.  Abstract ( 153 )   Save A series of CT scan tests were performed on the standard coal rock samples before and after the unconfined compressive strength tests. The porosity in the coal rock samples is extracted from the CT scan images by using Hough transformation. The micro porosity structures in the standard coal rock samples are three dimensional reconstructed by adjusting the threshold values. Comparing with the conventional threedimensional reconstruction methods, the porosity extraction method has a wider application and has a better presentation of the internal damage in the standard coal rock sample. The reconstructed 3D structure is used in the numerical analysis in COMSOL model. The results indicate that, 1) the size and distribution of the porosity can be obtained from the Hough transformation; 2) The initial damage in the coal rock samples significantly reduces the strength of the coal rock samples 3) The stressstrain curves obtained from the elastoplastic threedimensional porosity reconstruction are similar to that of curves from the unconfined compressive test so that the accuracy of the porosity extraction method is therefore verified. Related Articles | Metrics

Select

Deformation and Cracking Factors of Shielded Tunnel Excavation Under an Existing Box Culvert FU Shunkang, PAN Darong 2023, 37 (4):  629-634.  Abstract ( 146 )   Save Due to various construction effects, the existing box culvert will have excessive deformation and cracking when a shielded tunnel boring machine (TBM) passes through. To analyze the deformation pattern of the existing box culvert and its relationship with the cracking when the TBM passes underneath, this paper presents a section of Changzhou Line 2 a case history. The finite element method was used to simulate the entire process of the shielded tunnel excavation passing through the existing box culvert with the onsite monitoring data and the cracking observation of the box culvert. The numerical analysis also considers the effects of construction parameters such as grouting amount, soil pressure and friction on the deformation and cracking. The results show that the cracks are controlled by the displacement in the excavation direction and the vertical displacement. The secondary grouting range has the greatest influence on the vertical displacement, and with the increase of the secondary grouting range, the settlement decreases by 84.3%; The friction has the greatest influence on the displacement in the excavation direction, and with the increase of friction, the displacement in the excavation direction can increase by 55%;The increase of soil pressure will decrease its vertical displacement, and then increase the displacement in the excavation direction. Related Articles | Metrics

Select

Design of Soil Slope Support for Small and Micro Erosion Gullies in Weathered Granite ZHOU Xinglong, ZHOU Lihong 2023, 37 (4):  635-639.  Abstract ( 164 )   Save The soil properties of the small and micro erosion gullies in the mountain areas in the weathered granite soils are generally softer and more special than those of the surrounding soil layers. The support design of the soil slope in these gullies should be focused on, and special strengthening should be performed if it is necessary. Throughout the engineering practice, this paper introduces several case histories that can be used for the reference in support design. First, pay attention to checking the accuracy and comprehensiveness of the basic survey data, especially the review of topography and the influence of microtopography on geological conditions. The second is to pay attention to the construction and dynamic design of the information method. According to the actual conditions on the site, timely and effectively adjust the support design plan. For the soil slope at the position of the small and micro erosion gullies, if it is necessary, concrete shotcrete, grouting, and deep drainage methods can be used. Measures such as sweep holes to strengthen support. Related Articles | Metrics

Select

Impact of Blasting Induced Vibration in Deep Excavation in Karst in Urban Environment JIAO Changzhou, CHEN Junsheng, , XU Guanyu, GUO Zijian 2023, 37 (4):  640-645.  Abstract ( 221 )   Save During the blasting and the deep excavation for foundations in welldeveloped karst areas, the vibrations by the blasting might cause the cracks of the rock cavities to expand and break, and then lead to the collapse of the karst cavities, it may also cause serious engineering safety hazards. Based on the blasting vibration monitoring, this paper studies the impact of vibrations generated by blasting excavation of the foundations in urban karst areas on the surrounding environment and the stability of karst cavities. And the attenuation pattern of the blasting vibration at the site is studied. This paper also investigates the reasonable cavity treatment plan and blasting construction plan. The results show that the stability analysis of the cavity under the blasting vibration is performed by using the chamber stability method for evaluating the flexural and shear strength of the roof respectively. Based on the vibration monitoring data of the protection object and the supporting structure, the corresponding empirical formula of the peak vibration velocity attenuation is obtained. The site coefficient K and the attenuation index α in the formula are negatively correlated with the hardness of the propagation medium. For the karst (soil) cavities around the deep karst excavation and below bottom of excavation, the corresponding karst treatment scope principles and measures are determined. Related Articles | Metrics

Select

Some Thoughts on Numerical Analysis of Vacuum Preloading LI Wenjie, CHEN Shiwen, LE Zaofa 2023, 37 (4):  646-649.  Abstract ( 224 )   Save By investigating the conventional methods used in the numerical simulation of vacuum preloading domestic and abroad and based on the basic theory of the finite element analysis method, this paper raises some problems that should be paid attention to the numerical analysis of the vacuum preloading site improvement. The results show that, when the vacuum preloading simulation is simplified by the twodimensional plane strain, the permeability coefficient of the drainage body should be adjusted according to the principle of equivalent degree of consolidation; In 3D numerical analysis, there are multiple methods for the modeling of drainage plate, and the modeling method should be selected by comprehensively considering the analytical cost and simulation depth; The finite element implementation methods of the straight row method or traditional sand cushion method are significantly different; The initial void ratio and boundary conditions should be determined according to the actual situation of the prototype; The selection of constitutive model which can consider the highly nonlinear characteristics of soft soil is very important for the accurate calculation of consolidation settlement of vacuum preloading. Related Articles | Metrics

Select

Numerical Analysis of Displacement Characteristics of Steel Sheet Pile Cofferdam under Dynamic Load QIN Yawei, JU Wanglai, LEI Yongjin, 2023, 37 (4):  650-654.  Abstract ( 274 )   Save The change of the water level during the construction of the steel sheet pile cofferdam will directly affect the safety of the cofferdam structure. At present, the research on steel sheet pile cofferdam mainly adopts the method of working condition analysis, which will ignore the influence caused by the change of external water level. This study utilizes the subsurface conditions and construction configuration of the Wuhan Xinhe Bridge Project, combined with the PSOSVM water level prediction model. The mode considers the predicted water level as the external change load of the steel sheet pile cofferdam and establishes the ABAQUS threedimensional finite element model under the dynamic load. This study proposes an analysis method that is more in line with the actual construction of steel sheet pile cofferdams. The following conclusions are observed: (1) With the increase of the excavation depth, the displacement of the bottom is larger. Because the existence of the castinplace pile limits the displacement of the bottom, the displacement curve presents two peaks, and the shape of the displacement curve in each analysis step is basically similar. (2) During the entire process of the cofferdam construction, the maximum horizontal displacement at the midpoint of the long side (28.54 mm) is significantly larger than the maximum displacement at the midpoint of the short side (13.88 mm). Therefore, the horizontal displacement at the midpoint of the long side should be monitored more heavily during construction. Related Articles | Metrics

Select

Discussions on the Bearing Capacity of Soft Lamellar Weathered and Broken Rock Mass CHEN Yijie, AN Hongyu, CHEN Bo, WAN Junlin 2023, 37 (4):  655-657.  Abstract ( 1024 )   Save The bearing capacity of rock mass is generally estimated from the uniaxial compressive strength test results of the intact rock core. However, in the practical engineering, the soft rock, the lamellar weathered rock, and the broken rock and other reasons such as sampling difficulties, weathering, disintegration and sample preparation disturbance, result in no intact rock core or no representative intact rock core for the uniaxial compressive strength tests. In this paper, the potential difficulties, and risks of estimating the bearing capacity of the rock mass in the broken rock site are analyzed. At the same time, the problems of the uniaxial compressive strength of the intact rock provided by the testing unit during the excavation stage are provided. Based on the analysis of the relationship between foundation loading, uniaxial compressive strength test results. plate loading test results, it is proposed that the bearing capacity of the rock mass for the soft rock, the lamellar weathered rock and the broken rock sites must be comprehensively evaluation based on test data and geological environment, and the suggestions of the range of bearing capacity of the rock mass are provided. Related Articles | Metrics

Select

Prevention and Mitigation Measures of High Embankment Fill Constructed by Special Soils in Guizhou LI Changkui, FANG Zhengfeng 2023, 37 (4):  658-663.  Abstract ( 239 )   Save Guizhou is located in mountainous area. With the rapid development of the highway construction in recent years, the number of high fill embankments in Guizhou has also increased significantly. Among these high fill embankments, many high fill embankments are constructed with special soils. The inherent engineering properties of these special soils, as well as the characteristics of large quantities, long construction periods, high filling heights, large, accumulated settlement during and after the construction and the need for the specialized analysis and the verification of stability have led to the complexity of high fill embankments with the special soils. Special high fill embankments often suffer from the local and total settlement, roadbed and pavement cracking, slope instability and collapses during the construction or operation period. These highway hazards might affect the construction safety and operation safety during the service period seriously. Combined with the typical geotechnical hazards of special soil high fill embankments in Guizhou Province, this paper proposes the prevention and mitigation measures from the aspects of design, construction, and maintenance points of view. The research results have an important reference significance for the prevention and mitigation of the special soil embankment hazards. Related Articles | Metrics

Select

Investigation Methods for Highway Widening in Soft Soils of Guangdong Province HE Xiangfeng, YAN Junfeng, WU Yinliang 2023, 37 (4):  664-666.  Abstract ( 185 )   Save To satisfy the requirements of the existing transportation and economic transformation needs, some parts of China are gradually upgrading and widening existing expressways. Guangdong Province is in the Pearl River Delta, the soft soil is extensive and poor in nature, so it is very important to perform the targeted investigation in the soft soils in the reconstruction and widening projects. By collecting and analyzing the practical experience data of the existing reconstruction and widening projects in Guangdong Province, this paper discusses the properties of soft soils, the main contents of soft soil engineering investigation, the related requirements of laboratory test and in situ test, etc. Before the investigation begins, it is necessary to comprehensively collect the monitoring deformation, reinforcement treatment and other data of the existing project for comprehensive analysis, to make a reasonable exploration plan and select the appropriate laboratory test and insitu test method. This paper summarizes and proposes the key points of investigation methods for the highway reconstruction and widening in soft soils in Guangdong Province, and provides guidance and reference for the investigation of highway reconstruction and widening projects in other soft soils. Related Articles | Metrics

Select

Study on the Particle Morphology of the Coral Reef Sand LI Hongli, WU Wenjuan 2023, 37 (4):  667-671.  Abstract ( 215 )   Save To explore the geometric and particle morphology of the coral reef sand, the particle morphology characteristics of three types of coral reef sand from different regions of an island in the South China Sea are thoroughly studied. Four parameters, namely, the aspect ratio, the aspect thickness ratio, the sphericity, and the convexity ratio, are selected to classify the particle shape of the coral reef sand. The analysis of the experimental results showed that the artificial crushed coral reef sand has the highest particle content in the block coral reef sand, It is the preferred aggregate type for preparing the coral reef sand concrete; The surface of the native coral reef sand particles is the most rough and angular, followed by the artificial fragmentation, and the surface of the hydraulic rounded coral reef sand is relatively flat and smooth; The larger the particle size, the rougher and more angular the surface of the coral reef sand particles, and the more obvious the performance of coral native coral reef sand; The angularity and the surface morphology characteristics of the coral reef sand particles with different particle sizes after artificial crushing are similar. Related Articles | Metrics

Select

Support Design and Monitoring Analysis of Deep Excavation in Urban Complex Environment LIU Dan, NIU Yan 2023, 37 (4):  672-676.  Abstract ( 154 )   Save Deep excavation is a necessary project for the construction of large urban buildings, and slope support is the validation of the safety and stability of foundation excavation engineering. A deep excavation project is close to the highraised buildings, surrounded by traffic arteries and rivers, which is significantly affected by external loads. The excavated slope is supported by soldier piles + prestressed ground anchors or castinplace concrete soldier piles + concrete waler support. In the process of foundation excavation, the development of deformation is monitored, focusing on the horizontal and vertical displacement of the top of the support structure, slope displacement and surface settlement. Based on the monitoring results, it is concluded that the pile anchor support structure can play a good role in minimizing the excavation deformation in this environment, effectively slow down the slope deformation rate and control various deformation factors within a controllable range. The support method can provide a reference for future foundation engineering support in similar complex environment. Related Articles | Metrics

Select

Study on the Influence of PAM on the Basic Physical Properties of FineGrained Saline Soil JIANG Xiaolong, LI Yuan 2023, 37 (4):  677-680.  Abstract ( 285 )   Save Under the background of the national “belt and road initiatives” strategic development, the infrastructure in the western region inevitably needs to be built in the inland saline area, and its special collapsibility and salt swelling make the finegrained saline soil unable to be applied to the subgrade filling of the highway engineering. As the soil structure modifier, the PAM (polyacrylamide) has significant application value in the fields of soil improvement, soil erosion control, watersaving irrigation, agricultural production, ecological environment protection and so on. Therefore, the application of watersoluble PAM in the solidification of finegrained saline soil and then in the subgrade filling of highway engineering has important economic value. This paper intends to study the evolution law of basic physical properties of finegrained saline soil under the influence of PAM from three aspects: boundary moisture content, compaction characteristics and dry shrinkage characteristics. It is found that finegrained saline soil after treatment with a certain concentration of PAM aqueous solution has an obvious effect on improving plasticity index, strengthening water holding capacity, enhancing compaction effect, and improving dry shrinkage deformation characteristics, in this regard, we conduct experiments and record data to provide reference for engineering application. Related Articles | Metrics

Select

Contribution rate Analysis of Loess Strength Influencing Factors Using Taguchi Method LI Na, LI Kai, ZHAO Xiaojie 2023, 37 (4):  681-684.  Abstract ( 156 )   Save The strength of loess soils has always been the key aspect of the loess laboratory tests. The moisture content, dry density, soil pressure and other tests are the basic testing closely related to the loess strength values. To quantify the contribution of potential influencing factors to the loess strength, Taguchi method is used to estimate the signaltonoise ratio (SNR) and analyze the variance of each influencing factor on the basis of the direct shear test. The results show that the normal pressure and the dry density are positively correlated with signaltonoise ratio, while the moisture content is negatively correlated. Through the analysis of variance, the maximum effect of the normal pressure is 77.55%, the moisture content is the second, and the lowest dry density is 7.80. Considering the interaction of influence factors, the maximum effect of the moisture content and the normal pressure on shear strength is 55.7%. On the unsaturated loess, the pressure on the soil and the moisture content of the soil are the main influencing factors of the strength of the saturated soil. In the prevention of the loess landslide, although the surcharge load at the foot of the slope and the pressure relief at the top of the slope are the effective measures to prevent the occurrence of the landslide, the drainage of the soil cannot be ignored.  Related Articles | Metrics

Select

TRD Method Construction Monitoring and Analysis of a Deep Excavation Supporting Structure ZHANG Zhen, LV Qibing, DONG Yabo, LUO Mingfu, WANG Binbin 2023, 37 (4):  685-688.  Abstract ( 309 )   Save Based on the characteristics of Trench Cutting Remixing Deep Wall (TRD) construction method, this paper presents a case history of constructing a deep excavation supporting structure in the cut and cover metro tunnel of Xiong’an New District of Beijing Daxing International Airport Express Line Section 1. The supporting structure using TRD construction method is studied. Both the monitored data of the horizontal and vertical displacement of the TRD constructed cementsoil continuous wall and the performance of the top and horizontal displacement of TRD formed wall are analyzed. The results show that the deformation of the TRD formed cementsoil continuous wall is lower than the allowable value for the supporting structure. The deformation of the wall is related to the depth of foundation excavation. With the increase of the excavation depth, the horizontal displacement of the TRD formed diaphragm wall increases at first and then gradually tends to be stable. Engineering practice proves that the TRD formed cementsoil continuous wall has a good soil retaining performance and water stopping effect. Related Articles | Metrics

Select

Experimental Study on Compressibility of a Structured Soil at Greater Depth HE Fengyu 2023, 37 (4):  689-693.  Abstract ( 151 )   Save This paper investigates the compressibility properties of the soil samples at a large embedment depth on the site from ChangTai Yangtze River bridge site by using the consolidation tests and the unconfined compression tests. The compression curve characteristics of the undisturbed samples are mainly analyzed to reveal the compressive strength and the compression deformation of the deep structured soil. The test results show that the consolidation curves of the undisturbed samples exhibited essentially inverse sigmoid shape, which involve four distinct phrases with a dramatical dropdown segments. The results also indicated that the tested soil samples are of high void ratio, high saturation, and high sensitivity. Such observations suggested that the deformation of the soil sample caused by the unloading should be properly taken into consideration for the deep structural soil in the engineering practice. In addition, the actual structural yield stress of the deep soil is less than pc calculated by the Casagrand graphical method. As such, it is suggested to combine e~lgPand Es~P curves to collaboratively determine the structural yield stress of the deep soil. Related Articles | Metrics

Select

Mechanical Properties of Shanghai Soft Clay under K0 Consolidated Conditions GAO Gang 2023, 37 (4):  694-698.  Abstract ( 213 )   Save This paper presents the triaxial consolidated undrained tests under K0 consolidation (CK0U) and isotropic consolidation (CIU) of a typical soft soil in Shanghai. The tests were performed by using the automatic triaxial apparatus. The variation of K0 under different confining pressures are analyzed. And the mechanical characteristics of soil samples under different confining pressures are studied. The results show that the K0 value has a decreasing tendency with the increasing confining pressures, the remolded specimens have a larger K0 than the natural undisturbed specimens of the soft clay. The main stress difference increases with increasing confining pressures. Compared with CIU test, the peak of the main stress difference by the CK0U test is larger. The strain at the peak point is smaller with the increase of confining pressures. The cohesive force value of the CK0U test is smaller and the friction angle value is larger. With the decrease of increment of each stage load, the K0 value is larger at the same condition of the maximum confining pressures of the soft clay, mechanical strength is higher. Related Articles | Metrics

Select

Effectiveness and Mechanism Analysis of Antiadhesion Coating in Shielded Excavation LIU Pengfei 2023, 37 (4):  699-702.  Abstract ( 302 )   Save When tunnel excavation in the cohesive soil formations, the shielded tunnel excavation drill bits are prone to be clogged. To investigate the effectiveness of the antiadhesion coatings on the drill bits, largescale direct shear tests were conducted to evaluate the changes in the adhesive strength for different soil samples with varying consistency indices. A comparison was made between the adhesive strengths at the interface of metal blocks with and without antiadhesion coatings, and the mechanism of the effectiveness of the coatings was explained. The results showed that, with an increased shear displacement, the shear stress at the interface between the clay and the metal initially sharply increased, followed by a gradual increment. When the consistency index was less than 0.6, the adhesive strength at the claymetal interface showed minor variations. In the range of 0.6 to 1.2 consistency index, the adhesive strength at the claymetal interface experienced a rapid increase with an increasing consistency index. When the consistency index exceeded 1.2, the adhesive strength at the claymetal interface remained essentially constant. The antiadhesion coatings significantly increased the contact angle on the surface of the metal blocks, reducing their hydrophilicity. As a result, the adhesive strength at the interface between the metal blocks with the antiadhesion coatings and the cohesive soil was significantly lower than that between the metal blocks without the coatings and the cohesive soil, thereby reducing the risk of shield clogging in tunneling. Related Articles | Metrics