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31 October 2023, Volume 37 Issue 5 Previous Issue    Next Issue

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Case Study of the Effect of Vacuum Preloading Combined with Surcharging Method for the Improvement of a Railroad Subgrade over Soft Soils GONG Yi, WANG Liangmin 2023, 37 (5):  703-706.  Abstract ( 380 )   Save The vacuum preloading-combined surcharging method is an effective way to consolidate soft soils by using both vacuum preloading and the surcharging preloading methods. Based on the Darcy’s law, the seepage rate of the pore fluids in the porous media is proportional to the hydraulic gradient, so that the soil consolidation can be accelerated by increasing the head pressure or decreasing the drainage path. This paper presents a case history of the ground improvement of a railroad subgrade over soil soils. By monitoring the surface settlement and performing the laboratory testing on the mechanical properties of the subsurface soils, the effect of the ground improvement by using the vacuum preloading combined with surcharging method can be evaluated. It is concluded that the vacuum preloading method can reduce the pore water pressure of porous media and form a hydraulic gradient to accelerate the flow of pore fluid.  The surcharging can improve the shear strength of soft soils by dissipating pore pressure under the surcharging load. Under combination actions of two methods, the positive and negative excessive net pore water pressure will significantly improve the effect of soft improvement.  Related Articles | Metrics

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Application of Blasting Compaction in a Highway Embankment Over Soft Soils by Reclamation ZHANG Wenlong, ZHENG Wenfu 2023, 37 (5):  707-711.  Abstract ( 246 )   Save In the soft soil treatment, the blasting replacement of the soft soils has the characteristics of convenient in construction, low cost, short construction duration and significant soft soil improvement effects. This paper takes the blasting soil replacement method instead of the original sand drain and pipe pile method for the soft soil improvement for a road reclamation project in Ningde City. Based on the construction characteristics of the project, the physical and mechanical properties of the mucky soils and the original construction difficulties, this paper presents a new ground improvement method of using blasting replacement of the mucky soils and its design parameters. The potential hazards induced by the blasting and the safety measures are also discussed in the paper. Monitoring results show that the embankment stability is satisfactory, the monthly post construction settlement is less than 6mm. The application of the blasting replacement method in the soft soil improvement is feasible. Related Articles | Metrics

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Tunneling Rate of EPBS in Hard-Soft Heterogeneous Ground LIANG Chen, HUANG Yiqin, SHEN Ziyu 2023, 37 (5):  712-714.  Abstract ( 202 )   Save This paper presents a case history of construction of the segment between Huanghe Road Station and Huaihe West Station of Qingdao Metro No. 6 Line. A finite element analysis model of the cutting blade in the upper soft and lower hard strata is established by using the three-dimensional dynamic numerical model. The relationships among the load on the cutting blade at the soil-rock interface, the penetration depth and the speed of the cutting head are analyzed. The possible reasons for the slow tunneling rate of the shield in hard-soft heterogeneous ground are explained. The results show that: (1) the greater the penetration depth, the greater the steep load increase at the soil-rock interface; (2) the faster the cutting head rotates, the load increase at the soil-rock interface remains essentially unchanged, but the load growth rate increases (3) In order to reduce the adverse effect of the mutation load at the soil-rock interface on the stability of the blade ring, it is necessary to reduce the penetration depth and the rotating speed of the cutting head, so the tunneling speed of the shield in hard-soft heterogeneous ground is much slower than that of the single formation. Related Articles | Metrics

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Application of the Composite Gravity Dam in a Deep Excavation Support of a Wastewater Treatment Plant in Soft Soils LU Shanjia 2023, 37 (5):  715-719.  Abstract ( 210 )   Save With the ever increasing of urban population, the speed of modernization and renewal, and the continuous improvement of residents’ living standards, upgrading of various wastewater treatment plants has become the development trend of the urban wastewater treatment projects. This paper presents a case history of a comprehensive deep excavation for a wastewater treatment plant in Shanghai. The gravity supporting structure formed by soil-cement mixing with HP pile insertions is numerically simulated by using the commercial finite element analysis software PLAXIS. The HS-Small soil constitutive model is implemented in the analysis of the deformation and stability of the supporting structure and the analytical results are compared with the construction monitoring data. The results show that :(1) for some special elements of the waste treatment structures, the footprint size is large and the required excavation depth is about 5m~7m. The conventional plate enclosure + internal support system not only increases the cost but also has the construction difficulty of the main structure, while the compound gravity dam can resolve the above problems; (2) The composite gravity dam supporting system has good feasibility and engineering application effect in the range of 6.95m local depth of shallow foundation pit, which can be used as a supplementary form of cantilever retaining in the future deep excavation support. (2) The HS model used to simulate deep excavation in soft soil area has good convergence and is close to the monitored data; (3) The field monitoring results show that the H-section steel and steel pipe in the composite gravity dam can provide large lateral stiffness, resist most of the earth pressure, and control the slope of the dam body to a certain extent. (4) Composite gravity dam can solve most of the problems in practical engineering, and the pit depth is suggested to be between 5 and 7 m. Related Articles | Metrics

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Stability of Deep Excavation of a Comprehensive Utility Culvert ZHENG Zhongliang, YU Tingfu, LIU Yang, ZHANG Zehao 2023, 37 (5):  720-722.  Abstract ( 273 )   Save This paper presents the finite element analysis results of a deep excavation stability for a comprehensive utility culvert by using commercial software MIDAS GTS NX. The horizontal displacement of the soldier pile induced by the excavation, the settlement of the surrounding ground, and the axial force of the inner support were evaluated. The results show that the maximum horizontal displacement of the soldier pile is 8.56mm, which is at the base position; the surrounding surface settlement has an obvious “groove type”, and the maximum surface settlement is 17mm, which is at the position 12m away from the edge of the excavated area. The supporting axial force is greater than the inner supporting axial force of the first layer of concrete strut, which meets the requirements of the design value; the simulated data is in good agreement with the measured data. The deep excavation has good stability, which can provide guidance for subsequent construction. Related Articles | Metrics

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Case History of a Design Example of a Deep Excavation Supporting Beam in Wuhan ZHANG Wei 2023, 37 (5):  723-726.  Abstract ( 191 )   Save When a 10 m-deep foundation site in thick soft silty peaty soils in Wuhan was excavated to the second internal cross supporting layer, an excavator was overturned and seriously damaged the concrete supporting beam. To mitigate this accident, the excavated area was backfilled so that the horizontal displacement and the internal force in the supporting beans were effectively controlled. But the support beam was seriously damaged, the balance of the support system was destroyed. The remediation work was performed on the support beams and nodes were reinforced in a timely manner. The following excavation was performed safely. This paper introduces the project overview, accident cause and remediation plan and site monitoring program. Deep excavation construction accidents are relatively common, according to different conditions of the effective remediation program selected is also valuable engineering experience. Related Articles | Metrics

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Application of Permeable Foundation in Engineering GUO Shengjuan, TANG Wei 2023, 37 (5):  727-729.  Abstract ( 182 )   Save In practical engineering, the common methods of the ground improvement include replacement, grouting reinforcement, surcharging and preloading, composite foundation and micro pile reinforcement. The main consideration of these traditional foundation treatment methods is to improve the foundation bearing capacity and control the foundation settlement, and other factors are rarely considered. However, for some special projects, not only the above factors but also the influence of ground improvement on the flow direction of the groundwater should be considered. Combined with an engineering example, this paper introduces a ground improvement method which can not only meet the requirements of the foundation bearing capacity and settlement control, but also does not affect the flow direction of the groundwater flow. It is called the permeable foundation here. With the development of the economy and the society, people have higher and higher requirements for groundwater environment. It is believed that similar problems will become more and more prominent. Related Articles | Metrics

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Application of Soil-Cement Mixing Wall with Uniform Thickness Inserted with Hot Rolled Steel Beams Supporting in Deep Excavations in Urban Area of Wuhan CHU Wei, JIANG Qigang, GAO Xieliang, DAI Ye 2023, 37 (5):  730-735.  Abstract ( 211 )   Save The practice of promoting the concept of green environmental protection is the goal of all walks of life. As a temporary project, the deep excavation engineering has considerable amount of waste of resources, especially in the urban center, the large use of concrete pile + concrete support beam, the occupation of the underground space and other leftover problems are complex, so it is more necessary to forge ahead in the direction of green environmental protection and conservation. The supporting structure of the uniform thickness soil-cement mixing wall with the insertion of hot-rolled steel beams has the advantages of the fast construction progress, the recyclable hot-rolled steel beams after the completion, cost saving and minimal leftover in the later stage, and no occupation of the underground space. It is a typical example of practicing the concept of green environmental protection and conservation; Like the traditional concrete pile, the supporting structure can be combined with the support and the ground anchor to form a variety of combined support structures, which can also be adopted according to local conditions in complex urban centers, and has certain popularization significance. Related Articles | Metrics

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Application of Suspension Slurry Method in the Mechanical Borehole Cleaning in Pile Installation WANG Ling, Xu Jianbao, JIANG Di 2023, 37 (5):  736-740.  Abstract ( 193 )   Save The subsurface conditions in Qianhai area of Shenzhen are special. Because of the reclamation of land in the previous years, the upper part is mostly formed by large-size riprap replacement of the silty soft soils, the rock-filling layer is deep, and the lower part is the Quaternary marine-terrestrial sedimentary layer, which makes the borehole forming of the cast-in-place concrete pile difficult. In order to resolve the construction problem of the rotary excavation of the cast-in-place concrete pile in this special rock and soil strata, a project case history in this area is introduced to analyze the geological conditions and compare the construction method. This paper introduces the preparation of high-quality slurry and the mechanical borehole cleaning method of the suspension slurry method. The major points of the operation through the improvement and optimization of the construction are provided. Key construction procedures, the problems and treatment methods that might be encountered during the construction are also discussed in the paper. These methods are of high practical value, which can effectively ensure the safety, quality, progress and construction efficiency of the pile, and have little impact on the surrounding environment. Related Articles | Metrics

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Treatment and Prevention of the Sand Burst in a Deep Excavation in a Stratum with Artesian Water Head GU Haoran 2023, 37 (5):  741-745.  Abstract ( 379 )   Save The artesian water head condition is an important feature of the deep excavation projects in this area, which is close to the sea and close to the river. In the process of construction, it is a common and extremely difficult problem mitigating the water and sand burst hazards. This paper presents a case a deep excavation project in Qingdao. In the process of the excavation support design, the local experience of setting a seepage stop curtain between and behind the soldier piles was adopted to minimize the problems of separate row of water stop curtain which is difficult to adopt effective remedial measures in the later stage. At the same time, combined with the concept and measures of the sand burst control before the water plugging, the quicksand is controlled by embedding the drainpipe, filling the flexible materials such as quilts and thermal blankets, and tamping in the rigid materials. The double liquid slurry is poured through the reverse pressure of the drainpipe to achieve the purpose of water plugging. It has successfully resolved the problems in the region, and also provided the valuable experience for reference for the mitigation of similar engineering hazards. Related Articles | Metrics

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Design and Construction of a High Retaining Wall in Complicated Geological Conditions GENG Xuefeng, XU Xing 2023, 37 (5):  746-752.  Abstract ( 175 )   Save This paper presents a case history of the design and construction aspects of a high retaining structure in Guangming District, Shenzhen. The slope stability problems before and after the mitigations are discussed with engineering analog, theoretical approach and numerical analysis approaches. The slope stability mitigation recommendations are proposed and the construction monitoring program and criteria are also presented. The results indicate that, the optimum retaining structure is selected from the various feasible retaining walls. After the design and construction, the monitoring data indicate that the slelected wall type is safe and stable. The completed structure is also stable. Related Articles | Metrics

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Integral Bottom-up Construction Technology of Underground Space of Protective Historic Buildings in Soft Soil Area HUANG Kaiyong, WANG Qiangqiang, LIANG Zhirong, WEI Xiang 2023, 37 (5):  753-758.  Abstract ( 209 )   Save Key technology of partial covered excavation and integral bottom-up construction of underground space under protective historic buildings is introduced based on a case history in Shanghai. After the pre-reinforced historic buildings were transferred to transition positions, the retaining and supporting structures of the excavation were interspersedly constructed with the vertical supporting systems and the B0 slabs of the permanent positions. After that, the historic buildings were transferred to the pre-constructed permanent positions before  underpinning. So that the entire excavation was constructed by the integral bottom-up method while regions under the historic buildings were partial covered excavated. By using the innovative excavation technology, the safety of the historic buildings was achieved while the underground space was integral developed. Furthermore, the construction period was shortened and the construction cost was saved as well. The historic buildings elevated mildly after subsiding slightly during excavation according to monitoring data. The technical scheme and field data may provide reference for similar projects in future. Related Articles | Metrics

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The Investigation and Grouting Treatment for a Mined-out Area of Clay Mineral in Zhangqiu District of Jinan TIAN Dongjun 2023, 37 (5):  759-763.  Abstract ( 488 )   Save A proposed project site is at the typical mined-out area of the clay mineral in Zhangqiu District of Jinan. Within the project limits, there are two clay mining sites that had a production period between 1999 and 2014. The mine layer called Layer B was the top of the Permian Shihezi Formation. So, it is critical to identify the distribution range and scale of the mined-out area and to treat it appropriately before the construction. Based on a geological study of the mining area, the geophysical prospecting by using magnetotelluric sounding and exploratory drilling to verify the depth section of the goaf distribution and delineate the plane range for treatment were successfully implemented. A 60-meter survey line was located on both the east and west sides for the magnetotelluric sounding. Then three (3) boreholes were drilled for the verification. According to the Technical Code, the grouting system, in which the treatment area of mined-out area, the amount of work and the injection pressure were determined. The technical workflow and the experience of this project have some applicability in the treatment of the mined-out area extracted from the clay minerals and from the small mines. Related Articles | Metrics

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Comparative Analysis of Different Well Shutdown Schemes in the Process of Point Well Dewatering QIAO Chengjie, YANG Wenqiang, CHEN Junwei 2023, 37 (5):  764-768.  Abstract ( 158 )   Save In the view of the shutting down the operation of some point wells will not affect the dewatering effect and reduce the construction cost after a period of dewatering operation in many of the deep excavation projects, this paper presents a case history of a dewatering project in Zhengzhou. Throughout the simplification of the surrounding environment, soil layer data and dewatering design parameters, the phreatic incomplete well was modelled to check and to analyze different well conditions. The adjusted single well water yield, hydraulic gradients, and the water level drawdown at any point in the excavated area can meet the requirements of design and construction. It is feasible to dynamically adjust the number of dewatering point wells. The proposed method is simple and reliable, the calculation content is less, and the reduction of the number of point wells significantly reduces the operation cost of precipitation, which has a certain reference significance for practical engineering. Related Articles | Metrics

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Numerical Analysis of the Influence of an Underlying TBM Water Tunnel on an Existing Highway Tunnel WANG Wei 2023, 37 (5):  769-772.  Abstract ( 183 )   Save With the increasing of hydropower infrastructure projects in China and the gradual transferring the construction projects to mountainous areas, the mechanized construction has become the mainstream direction. The TBM tunneling technology has become one of the important methods of diversion tunnel construction. Often water diversion tunnel project is at the relatively remote area, mostly without sensitivity surrounding the building structures, and emphatically introduced in this paper under the water diversion tunnel engineering in an existing highway tunnel, the removal of soil and rock will induce the process of TBM construction original stress release, causing additional stress in the existing highway tunnel. The analysis under different working conditions is very important to the impact of the highway tunnel structure. In this paper, the commercial software, Midas GTS, is used to simulate the disturbance of the TBM construction to the strata, and a 3D model of the TBM tunneling through the existing highway tunnel is established. TBM construction parameters are carefully simulated, and the influence of various working conditions on the stress increment and deformation of the existing highway tunnel are analyzed. Through analytical results show that under the oblique in TBM tunnel construction, the above the highway tunnel will result in the surface of the large differential settlement, at the same time the uneven lateral highway tunnel lining structure, oblique position near the existing highway tunnel structure under the lateral appeared different degree of tensile stress and deformation, the deformation and meet the requirements to ensure the normal operation of the existing road tunnel. Related Articles | Metrics

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Analysis of Safety Assessment of Existing Subway Tunnels of a Nearby Deep Excavation GUO Shen, LAI Yinnan 2023, 37 (5):  773-777.  Abstract ( 157 )   Save This paper presents a case history of a deep excavation near an existing regional subway tunnel. The entire excavation and supporting process are three dimensionally simulated throughout a numerical model by using the commercial software Midas GTS NX. The influence of excavation on the ground subsidence, vertical and horizontal deformation of the supporting structure and on the deformation of lining structure of the existing tunnel are analyzed. The results show that the maximum settlement of the surrounding surface caused by the excavation is 8.20 mm, the maximum horizontal deformation of the enclosure structure is 10.86 mm, and the maximum vertical deformation is 3.28 mm, all within the specification limits. The maximum horizontal deformation of the existing lining structure is 3.88 mm, and the maximum vertical settlement is 2.28 mm. All deformations meet the limit requirements for safe operation of the interval tunnel.  Related Articles | Metrics

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Stress-Strain Analysis of a Deep Excavation Support Structure Connected to an Existing Adjacent Underground Structure#br# LEI Heng, WANG Hao, LIU Donghai, ZHAO Yongsheng 2023, 37 (5):  778-781.  Abstract ( 146 )   Save In this paper, the numerical methods are used to study the stressstrain relations of deep excavation support system in confined spaces in urban area. The main feature of the excavation support system studied in this paper is that it forms an entire body with the surrounding buildings to resist the deformation induced by the excavation. The main conclusions are as follows: the underground garage reduces the volume of the upper soil behind the supporting soldier piles and increases the lower soil load, resulting in a wavy shape of the supporting piles as an entire body after the excavation is completed. The deep excavation has a small impact on the underground garage, the weak position of which is the column. The impact of the underground garage on its lower soil during excavation was approximately 0.15 times its height. The above results provide a new feasible solution for the excavation support under the narrow space in the city, and have certain guiding significance for the deep excavation projects. Related Articles | Metrics

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Study on the Influence of Three-Dimensional Pore Microscopic Properties on the Permeability of Coral Sands CUI Xiang, YAO Jinsong, YANG Jihong, ZHU Changqi 2023, 37 (5):  782-786.  Abstract ( 196 )   Save The pore is the space in porous medium where gas and liquid can exchange materials. The porous properties are mainly controlled by the morphology of the constituent particles, which determines the permeability of the medium. Due to the special formation mechanism, the coral sand has irregular particle shape and special pore properties. In this paper, the coral sand and terrestrial quartz sand are established as the control group, and the difference mechanism of their pore properties is studied from the microscopic point of view. The essential factors of the permeability difference are compared between the two sand samples. The results show that the pore properties of the coral sand can be described comprehensively by using pore radius, pore shape factor, throat radius, throat length, coordination number and pore to throat ratio. The permeability of the coral sand is affected by the properties of porosity and the particle surface. Among which, the pore connectivity and the pore throat size have the greatest influence on the permeability, followed by the pore shape. The surface properties of particles also influence the permeability, but this effect is more obvious in the range of fine particle size. Related Articles | Metrics

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Equivalent Stiffness Replacement Method of PRC Supporting Pipe Pile in a Deep Excavation in Xuzhou SHEN Rongfeng 2023, 37 (5):  787-791.  Abstract ( 211 )   Save The equal stiffness substitution method is often used in PRC pipe pile supporting structure analysis, but for large spaced supporting piles, the existing substitution method will lead to the calculated width of the soil resistance inconsistent with the actual conditions. It is of practical significance to find an equal stiffness substitution method for the calculation of the large spaced supporting pipe pile. This paper presents a case history of a deep excavation project in Xuzhou, Jiangsu Province. Combined with the calculation method of the soil reaction width, the stiffness of supporting pipe pile is replaced by the rectangular square pile. To highlight the advantages of this method, the case without anchor is analyzed first, and compared with the existing equal stiffness substitution method. Then, this method is applied to calculate the PRC construction method pile and prestressed anchor support condition. The comparative analysis results show that for the large spaced soldier piles, the existing equal stiffness substitution method reduces the calculated width of the soil reaction force, and its predicted deformation is too large. The equal stiffness substitution for the rectangular square piles can avoid this problem. The stiffness substitution method of the PRC pipe pile is studied in order to provide a reference for similar deep excavation problems. Related Articles | Metrics

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Mechanism and Influencing Factors of Pressure Dispersed Ground Anchor and the Retaining Wall Reinforcement LIN Lijian 2023, 37 (5):  792-796.  Abstract ( 185 )   Save In this paper, the mechanism and influence factors of combined reinforcement of pressure dispersed ground anchor and retaining wall are analyzed by the numerical simulation on a practical example. The results show that the pressure dispersed ground anchor can strengthen the soil slope by applying the prestress of the ground anchor to the soil between the retaining wall and the anchor plate. As the height of the retaining wall decreases and the number of the ground anchor increases, the soil pressure decreases and the stability of reinforcement effect increases. When the anchor bolt is set in the middle of the retaining wall, the reinforcement effect is the best. Related Articles | Metrics

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Study on Formation Mechanism of Paired Loess Landslides CHEN Yuanyong 2023, 37 (5):  797-801.  Abstract ( 193 )   Save In the geological mapping process of Luoquan section of Yinbai expressway, it is found that the landslides in Ranjiagou are distributed in pairs, and each landslide has very similar deformation and failure characteristics. Based on the field geological survey data, combined with the basic theoretical knowledge of the engineering geology and the geomorphology, the formation mechanism of paired loess landslides is studied. The basic conditions for the formation of landslides in Ranjiagou are complex topography, special stratum structure and geological structure. The main inducing factor of landslides is rainfall. The formation of the paired distribution landslide is that the water erodes the concave bank of the Ranjiagou first, causing the side slope to lose its support and lead to the traction sliding. The huge sliding mass flows into the gully and blocks it. The water in the gully gathers to form a barrier lake of a certain scale. After the lake water gathers to a certain extent, the water changes the channel and erodes the opposite bank slope, and then causes instability sliding of the opposite bank slope, thus forming the current paired distribution landslide. The formation process of the paired landslides can be divided into six stages, which are the erosion stage of the water on the concave bank, the unstable sliding stage of the concave bank slope, the erosion stage of the water on the convex bank, the unstable sliding stage of the convex bank slope, the water erosion stage of the landslide front and the formation stage of landslide secondary sliding surface. Related Articles | Metrics

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Design Method of Multi-Columns Composite Foundation PENG Liangquan, 2023, 37 (5):  802-806.  Abstract ( 198 )   Save In view of the problems existing in the design of multi-columns composite foundation, such as the large subject of the estimation results due to the empirical value to the bearing capacity correction coefficient of soils and columns, as well as the large difference between the estimated and the measured settlement values when the composite compression modulus is used in the improvement area for the composite foundation. By using the column-soil deformation conformity method, the real column-soil stress ratio and bearing capacity correction coefficient are obtained theoretically, which avoids the defect of determining the bearing capacity correction coefficient subjectively and makes the settlement and bearing capacity estimation of the composite foundation more accurate and scientific. In the view of the problems that the composite foundation cannot be formed and the building foundation and the natural ground are separated due to the qualitative design of the composite foundation cushion layer, a quantitative design method of the cushion layer is proposed according to the formation conditions of the composite foundation, which avoids the defects of qualitative design. Related Articles | Metrics

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Field Tests and Analysis of In-Situ Deep Horizontal Displacement in Intertidal Soft Soils Strengthened by Blasting Replacement Method YAN Juefu, YU Han, PAN Chaohao, QIN Wei, ZHANG Liujun, CHEN Fenjian, QIU Youqiang 2023, 37 (5):  807-810.  Abstract ( 209 )   Save Blasting replacement method is a soft soil improvement method with high efficiency, low construction cost and satisfactory treatment effect. Its main construction methods can be divided into side explosion and end explosion according to the position of explosives buried. The most effective evaluation of the blasting replacement application is the measurement of the depth of the riprap rock that are brought into the soft soil by the explosion. In order to detect the intertidal zone and depth of the riprap into the soil, in this paper, based on some blasting replacement projects in the Ningde City, the deep horizontal displacement monitoring was performed for a long time. The results of the side and end the horizontal displacement of blasting replacement projects are also compared with the settlement of the above highway embankemnts. It provides reference for similar projects. Related Articles | Metrics

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Application of Comprehensive Methods in Underground Pipeline Detection in a Port Area of Caofeidian LIU Hewen, Wang Rongli, CHEN Yuntao, YUAN Fanglong, 2023, 37 (5):  811-815.  Abstract ( 128 )   Save With the indepth development and utilization of urban lands, the accurate locating of underground pipelines has become a primary problem to be resolved; Firstly, this paper summarizes the principles, applicable conditions and specific operation methods of various pipeline detection methods. On this basis, various methods such as the direct method, the electromagnetic induction, the ground penetrating radar methods and the excavation verification are comprehensively applied to detection of underground pipelines in a port area of Caofeidian. Methods of effectively identifying the type, quantity, buried depth and other information of underground pipelines, the existing problems in the detection process are analyzed, and reasonable suggestions and relevant quantitative indexes are proposed. A number of underground pipeline detection methods are summarized, which can provide reference for similar projects. Related Articles | Metrics

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Study on the Fitting SWCC of a Granite Residual Soil CHENG Yuyang, WANG Mengqi, SHI Zonggang 2023, 37 (5):  816-820.  Abstract ( 195 )   Save The Soil Water Characteristic Curve (SWCC) is an important hydraulic parameter of soils, which can reflect the properties of soil samples such as the permeability and the shear strength. To facilitate the determination of the SWCC curve of a granite residual soil sample and to explore a more convenient as well as faster model and the method to fit the SWCC curve of granite residual soil, firstly, the data points corresponding to the suction and moisture content in the process of dehumidification and hygroscopicity of granite residual soil are measured by using an indoor plate pressure instrument. The Gardner model was used for the dehumidification process and the hygroscopic process. The results of lsqcurvefit and nlinfit functions in the MATLAB software are similar, and the sum of the squared residuals is less than 0.0001. The results show that both lsqcurvefit and nlinfit functions are good for the fitting SWCC curves of granite residual soils, and either one can be used in future studies. Related Articles | Metrics

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Evaluation of Ground Improvement Using Vane Shear Test ZHANG Lifeng, HAN Wenyong, HAO Jiafu, ZHI Liyuan, LIU Peng, YUAN Pengju 2023, 37 (5):  821-824.  Abstract ( 177 )   Save With the development of engineering technology and the extensive distribution of new constructions, new buildings have to be constructed on soft soil where various ground improvement methos are developed. This paper presents a case history of ground improvement using vacuum preloading method. The improvement effect was measured by the vane shear test and laboratory tests before and after the ground improvement. The following results are obtained: the soft soil before the treatment has poor mechanical properties, poor stability, low strength, fluid plasticity, high compressibility, and large thickness, and is not suitable for a bearing layer; After the ground improvement, the undrained shear strength value of soil increased by 262.5% compared with that before the treatment; and the remolded undrained shear strength value increased by 225.3%. After the ground improvement, various mechanical performance indexes of the soil mass are improved, and the soil is significantly improved, the treated soil is suitable for the building foundation construction. Related Articles | Metrics

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Atterberg Limits Tests Data Processing by Origin Based Least Square and Analytical Methods ZHANG Xuefeng, LI Zhong, CHEN Cheng, XU Zifei, 2023, 37 (5):  825-829.  Abstract ( 259 )   Save In view of the shortcomings of the data processing of the combined Atterberg Limits test results, the least square method and the analytical method based on the Origin commercial software are proposed to process the test data. The silty clay samples in Kaifeng are used for the data verification. The results show that the two methods can quickly draw graphs and automatically extract the 17 mm liquid limit, the 10 mm liquid limit and the plastic limit. For the Origin least square method, the derived Adj.R-Square value of 0.9785 can quickly determine whether the test data is acceptable. It is not necessary to calculate the difference between the corresponding two water contents at the cone penetrating depth of 2 mm, which has the advantages in batch processing of test data. Compared with the mathematical analytic method, Excel and AutoCAD software, the Origin analytic method is simpler and faster, with clear process, which is easy to be popularized and applied in the commercial laboratory tests. Related Articles | Metrics

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Cone Factor Determinations in Penetration Test GUO Jianxiang, WEI Xiaobin 2023, 37 (5):  830-834.  Abstract ( 190 )   Save As a reliable method to determine the liquid limit of finegrained soils, the falling cone test is widely used in soil laboratory testing. At the same time, the undrained shear strength of the soil can be determined from the cone factor K. By studying the theoretical and experimental values of K, combined with concepts of quasi-static and dynamic infiltration, the mechanism of the cone entering into the soil sample is analyzed in this paper. By using the analytical method, the expression of the dynamic undrained shear strength is proposed, and the cone surface roughness, the shear strain rate and the soil heave are considered, so the theoretical expression of the cone factor K can be obtained. Throughout the comparison, it is found that the cone factor K of a 30° cone has a large dispersion. Finally, based on the theoretical analysis results, it is suggested that the 60° cone is more suitable for determining the liquid limit than the 30° cone. Related Articles | Metrics

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Experimental Study on Shear Strength of a Root-Soil Composite of a Modified Expansive Soil WANG Tao, HU Bo, LIU Jun, CHEN Pinzhang 2023, 37 (5):  835-840.  Abstract ( 186 )   Save To explore the effect of compaction and vegetation root content on the shear strength of the modified expansive soil, The root-soil composite samples of the modified expansive soil were prepared, and the direct shear tests were performed. The test results showed that the shear strength behavior of the remolded root-soil composite samples conform to the Coulomb equation. The shear strength of composite samples increases with the increase of the degree of compaction as well as the root content. With the increase of the degree of compaction, the cohesion and the internal friction angle increase, but the increase of the cohesion is greater than that of the internal friction angle. There is a positive correlation between the root content and the cohesion, c, while the internal friction angle, φ, has little relation with the root content; the m value of reshaped soil samples with roots is between 1.31 and 2.31, and the bermudagrass root-soil composite is at the low positive. It is more effective to improve the strength of the soil under the lower stress than the higher stress. The bermudagrass root system has a better effect on the shallow reinforcement of the slope; the plant root system has a good reinforcement effect on the modified expansive soil which significantly enhances the shear strength of the base material. Compared with the remolded soil, the binding force between the root and the soil of the undisturbed soil is larger, and the root system has a more obvious strengthening effect on the strength of the root-soil composite. Related Articles | Metrics