Table of Content

31 October 2024, Volume 38 Issue 5 Previous Issue    Next Issue

For Selected:

Download Citations EndNote Reference Manager ProCite BibTeX RefWorks

Toggle Thumbnails

Select

Three-Dimensional Analysis of Interaction Between Adjacent Deep Excavations LI Jin 2024, 38 (5):  739-745.  Abstract ( 238 )   Save In the construction of urban underground projects, especially in the central urban area, the adjacent foundation excavation projects are often encountered due to the restriction of land and construction schedule. Compared with the independent foundation deep excavation projects, the interaction of adjacent foundation excavations has an impact on the deformation of the supporting structures and the deformation of the surrounding soils. These factors will make the stress, deformation of the supporting structure and the impact of the surrounding environment more complex. The interaction between the foundation excavations cannot be ignored. This paper presents the foundation excavation of a storage tank and local treatment station in Jiujiang City, Jiangxi Province as the case history. This paper uses the numerical simulation method to study the influence of different excavation methods of the adjacent deep excavation and compares the difference and change pattern of the synchronous excavation and step-by-step excavation of the adjacent excavation from the perspectives of the soil deformation, internal force and deformation of the supporting structure, and the influence of the surrounding environment. It provides a reference for the relevant projects. The results show that: 1) the synchronous excavation has more disadvantageous in terms of the surface settlement between the adjacent excavations. The surface settlement can be reduced by about 18% if the step-by-step excavation is adopted; 2) Under different excavation methods, the maximum horizontal displacement of the supporting structure is similar, and the overall bending moment of the soldier pile is not different; 3) From the settlement of the existing pipelines, the step-by-step excavation is more unfavorable. The maximum settlement occurs after the excavation of a single deep excavation. If the synchronous excavation method is adopted, the pipeline settlement can be reduced by about 28.6%. 4) For the settlement of buildings, in the case of the synchronous excavation, the maximum settlement occurs near the storage tank. Under the step-by-step excavation, the maximum settlement occurs near the local treatment station. Related Articles | Metrics

Select

Application of Various Geophysical Methods in Karst Investigation of a Municipal Road ZHANG Heng, MENG Baohua 2024, 38 (5):  746-749.  Abstract ( 183 )   Save With the development of science and technology, a variety of geophysical methods are increasingly used in the karst explorations. The commonly used test methods of geophysical exploration include high-density electrical method, transient surface wave method, electromagnetic wave CT detection and geological radar, etc. In view of the complexity of the karst terrain investigations, a single geophysical method is difficult to fully meet the exploration requirements. To overcome the limitations of a single method, the comprehensive application of multiple geophysical methods can effectively resolve this problem. Combined with the complementary verification of the traditional drilling, it has become a reliable option for the current karst investigation methods. Related Articles | Metrics

Select

Effect and Influencing Factors of “Soldier Pile-Slurry Wall Integration” Supporting Structure LI Hongwei, YANG Guangyu, XIE Liang 2024, 38 (5):  750-754.  Abstract ( 175 )   Save This paper presents a case history of a deep excavation project in Wuhan. The cooperative mechanism of the soldier pile- slurry wall integrated supporting structure is evaluated and the influence of the change of the section size of the force transfer plate on the soldier pile-slurry wall integrated supporting structure is discussed. The results show that the soldier pile-slurry wall combined supporting structure has significant synergistic effect, which can effectively reduce the displacement and the internal force acting on the underground structures. The change of the section size of the force transfer plate has little impact on the underground structure. On the premise of meeting the effective force transfer and the required construction spacing, the section size of the force transfer plate can be appropriately reduced to save the construction materials and costs. Related Articles | Metrics

Select

Comprehensive Site Investigation and Treatment Methods for Abandoned of Small Coal Mine Cavities WANG Liuwen, WANG Tongbiao, CHEN Jinhong, PAN Xianwei, LI Hai 2024, 38 (5):  755-759.  Abstract ( 208 )   Save Small coal mines are mostly uncertified mining. There is no mining planning, no mining maps for these mined galleries. They have the characteristics of small mining depth, complex distribution of mined areas, and extremely difficult to locate all these abandoned galleries. Locating these empty mined area distributions and their influence area have significant importance of the project. This paper presents a case history of the comprehensive geotechnical investigation and mitigation program at the abandoned mining area for a main area for a power plant. The testing program after the ground improvement show that the effect of the control measures used in the investigation and mitigation are satisfactory, and the comprehensive investigation methods used are appropriate for the exploration of the abandoned galleries of small coal mines, which can provide a strong basis for the control design and can provide a useful reference for similar projects in the future. Related Articles | Metrics

Select

Deformation and Failure Mechanism of a Mechanically Stabilized Earth Retaining Wall SHI Jianfeng, TANG Hui, ZHANG Ruisong, DONG Chenfan, SUN Kai 2024, 38 (5):  760-764.  Abstract ( 160 )   Save To study the deformation and the failure mechanism of a mechanically stabilized earth (MSE) retaining wall, the effect of the increase of moisture content on the deformation and the failure of the MSE wall is analyzed and studied through the testing on the undisturbed samples collected from the field. The stability of the MSE wall is validated by the numerical simulation. The results show that the shear strength of the MSE wall decreases with the increase of the moisture content. The shear strength of the saturated soil decreases significantly compared with that of the soil at the natural state; and the shear strength of the saturated soil decreases with its dry density. The numerical results show that the stability of the original design meets the requirements, but a large deformation will occur in the middle and at the upper part of the MSE wall under the rainfall infiltration condition. The mechanism of inducing the deformation and failure of the MSE wall is that the wall with a poor drainage deteriorates after the increase of the moisture content in the backfill due to the infiltration of the rainwater in the rainy season, which leads to the increase of the active earth pressure of the retaining wall and then the increase of the lateral deformation in the middle and at the upper part of the retaining wall. Related Articles | Metrics

Select

Application Landscaping Technique in the Rolling Hill Topography WU Heng 2024, 38 (5):  765-769.  Abstract ( 172 )   Save The geomorphology of Shanghai rolling hills is complex, which is divided into high hills and low hills, due to the erosion and the deposition processes by rivers, ocean, lakes and marshes. Then, how to control the differential settlement of soils in the rolling hill terrain? This paper studies the safety and technique aspects of the landscaping, which is constrained by the subsurface conditions as well as unknown hazards. This paper presents a landscaping technique for a villa project in the western suburbs of Shanghai. Through summarizing the research background of the project, the problems of landscaping hills are evaluated. On the basis of briefly describing the construction sequence of the project, the design process is demonstrated in detail. Among them, the entire process of the landscaping construction also includes the comparison and selection of analytical methods, proof load test to failure, potential hazards evaluation, the piled foundation design to minimize the potential risks as well as the post construction differential settlement evaluation. These results have an important reference value for the construction projects in soft soils. Related Articles | Metrics

Select

A Case Study of Emergency Reinforcement Design Using Steel Rakers for A Deep Excavation Support in Wuhan Soft Soils HU Ke, HAN Shuai, TAI Jun, ZHANG Jie, ZHAO Chenxi 2024, 38 (5):  770-774.  Abstract ( 274 )   Save This paper presents a case history of analyzing a sudden excessive deformation of the soldier piles of a deep excavation support project within the first terrace of Yangtze River in Wuhan. Throughout an emergency reinforcement project, the importance of implementing the design conditions during the deep excavation supporting system construction is demonstrated in the paper. When the excessive deformation occurred, it is necessary to analysis the deformation and stress characteristics in the original support system as well as the monitoring data. It is also important to find out the reasons that resulting in the support structure failure, to analyze the condition of the soldier piles after the support structure undergone the stress deformation, and to develop feasible reinforcement measures based on site conditions. These timely measures prevented further deterioration of the failure, and the full-process monitoring data analysis fully validated the rationality and the effectiveness of the emergency remediation plan. This case study fully demonstrates the necessity of the implementing of design conditions and has important significance for improving the construction management of deep excavation projects. It also provides a reference for preventing similar accidents in the future. Related Articles | Metrics

Select

Design and Construction Method of Large Span Continuous Three Arch Tunnels on Chongqing Urban Rapid Transit Line DENG Ruyong 2024, 38 (5):  775-780.  Abstract ( 150 )   Save Based on the project between Jiuquhe East Station and Chongguang stations of Chongqing Urban Rail Express Line No. 15, this paper studies the applicability of different excavation methods in the construction of a continuous three-arch tunnel by using numerical calculation methods. The results indicated that the construction of the continuous three-arch tunnel in this project using methods of side tunnel, middle tunnel, and pilot tunnel resulted in a maximum surface settlement of no more than 5.56mm. The control effect of the surface settlement during the construction of this project is the best using the pilot tunnel method, followed by the side tunnel method, and the worst using the middle tunnel method. The plastic zone of the surrounding rock during the tunnel construction in this project is mainly distributed on the outer side of the side tunnel arch wall, as well as in the middle tunnel arch shoulder and arch foot area. The anchor rods of the arch shoulder system penetrate the main plastic strain area and have a good anchoring effect. The design of the anchor rods of the arch crown system can be appropriately optimized. By comprehensively comparing the advantages and disadvantages of four excavation methods in terms of strata deformation control, material consumption, and construction difficulty, and considering the actual situation, it is recommended to use the side tunnel method for the construction of the continuous triple arch tunnel in this project. The research methods and conclusions of this paper can provide a reference and the guidance for the similar engineering design and construction. Related Articles | Metrics

Select

Application of Cement Mixed Soil Columns with PRC Pipe Pile Inclusions in a Deep Excavation Project FENG Zhongwen 2024, 38 (5):  781-784.  Abstract ( 184 )   Save The pipe pile has many advantages, such as low cost, fast construction, and less environmental pollution. In particular, the PRC pipe pile equipped with prestressed steel bars and ordinary steel bars is widely used in the deep excavation because of the high shear and flexural resistances. In response to the lateral squeezing problem during the construction of the pipe pile, combined with the deep excavation project in Zhuhai, a design program used cement mixed soil columns with PRC pipe pile inclusions in a sand layer area is introduced, the construction process, conditions of the excavation and the monitoring data have been analyzed. The results show that the pipe pile embedded in the triaxial mixed soil column can resolve the issues of the lateral squeezing in the soil caused by the construction and protect the surrounding environment and results in a safe excavation. It can also provide a valuable reference application of similar projects in the future. Related Articles | Metrics

Select

Ecological Restoration and Comprehensive Treatment of an Abandoned Quarry-A Case Study of Eastern Honghualing Quarry Longgang of District, Shenzhen LI Ming, LUO Xiaobin, HUANG Min 2024, 38 (5):  785-791.  Abstract ( 281 )   Save Currently, there are many abandoned quarries having geological and environment hazards in Shenzhen. The case history of the Eastern Honghualing Quarry of Longgang District, Shenzhen is presented in this paper as an example for the detailed global and local stability analysis on the slope throughout the field investigations. The current slope failure modes, vegetation distribution and the soil erosion of the quarry are investigated. Comprehensive remediation measures such as slope clearing, SNS active protection net + ground anchor, reinforced concrete grid beams + ground anchor and drainage ditches are proposed for the quarry slopes. The ecological and environment restoration program include the stacking ecological bags within the grid beams, planting of climbing vines and shrubs in the planting channels and spraying and mixing plants to restore the vegetation. The analysis of the construction process and the monitoring results after the construction shows that the slope deformation has tended to be stable, and the quarry has been environmentally restored. The remediation program is feasible and provides a reference for the restoration and comprehensive treatment of the ecological and environmental issues of the similar abandoned quarries.  Related Articles | Metrics

Select

Foundation Deformation of a Nuclear Island on Soft Rock AI Hongtao 2024, 38 (5):  792-796.  Abstract ( 161 )   Save A typical soft rock foundation deformation case of nuclear island in China is analyzed in this paper. Two-dimensional as well as three-dimensional finite element models of the nuclear island foundation are established. The uncertainty of the distribution of strongly weathered rock mass within moderately weathered rock mass beneath the nuclear island foundation and the uncertainty of key geotechnical parameters were considered in the numerical models. The influence of the layered rock mass distribution on deformation parameters is also considered. The foundation deformation of the nuclear island was estimated and analyzed comprehensively. The total and differential settlement of the soft rock foundation for the nuclear power plant are obtained, and the estimation and analysis methods are compared in the paper. The analysis results show that the maximum total and differential settlements of the nuclear island foundation meet the design and specification requirements. The distribution of the strongly weathered rock under the nuclear island foundation has less influence on the maximum settlement of the foundation. The proposed estimation and analysis methods for the soft rock underneath the nuclear island foundation can be used for the subsequent settlement estimation and analysis of similar projects. Related Articles | Metrics

Select

Methods and Practices of Oil Pipeline Crossing the Deep Excavation Area HE Lihong, LIU Yanlin 2024, 38 (5):  797-799.  Abstract ( 177 )   Save This paper discusses the protect methods of the safe crossing of a military oil pipeline under crossing a deep excavation of a comprehensive utility culvert in Wuhan. A pile foundation plus the hot rolled steel beam system is used as the vertical support member of the culvert, which optimizes the component size combined with the supporting structure. The coordination between the supporting process and the excavation progress to ensure the safe operation of the oil pipeline during the utility culvert construction is also performed. This method can provide a reference for the safe construction of other important pipelines across the deep excavation. This paper introduces the technical details in each stage, such as the support structure design, the reinforcement process, and the culvert backfill. It is concluded that the use of the hot rolled steel supporting beam replacement system and cast-in-place soldier pile can effectively enhance the capability of the culvert foundation to resist the deformation during the deep excavation. Related Articles | Metrics

Select

Continuous Karst Cavity Treatment and Surrounding Rock Stability Analysis of Bangshan Tunnel in Xiamen-Chengdu Expressway ZENG Xiangjin 2024, 38 (5):  800-804.  Abstract ( 130 )   Save This paper presents a case history of Bangshan Tunnel of the Xiarong highway capacity expansion project. The engineering geological conditions and the hydrological characteristics in the tunnel site area are investigated and evaluated. The numerical simulation methods are used to analyze the impact of the hidden continuous karst cavities on the stability of the tunnel surrounding rock mass. The locations, developments and the fill material of the karst rock cavities are evaluated. The following results are obtained: 1) When bead shaped karst rock cavities develop at the top of the tunnel, the deformation of the tunnel surrounding rock mass is large, but the impact on the deformation of the arch crown and the arch waist surrounding rock is different. At the same time, under the influence of the excavation disturbance stress, the surrounding rock mass and the support stress near the karst cavities significantly increase. The stress concentration occurs at the arch crown and the arch waist. 2) Research and practice have shown that the proposed karst rock cavity mitigation plan is reasonable and feasible, which ensures the safe and smooth construction through the karst section of the tunnel. The relevant results can provide a good guidance and reference for the design and construction of tunnels in the karst areas. Related Articles | Metrics

Select

Analysis and Failure Mechanism of an MSE Wall YANG Yunlin 2024, 38 (5):  805-810.  Abstract ( 135 )   Save This paper presents a case history of the mechanically stabilized earth (MSE) retaining wall hazard remediation project in a primary school in Longyan, Fujian Province. Based on the understanding of the general subsurface conditions of the project, the failure characteristics of the MSE wall are obtained through the on-site geological survey. Combined with the original design data, the failure triggering factors of the hazards are identified. The main factors include the rise of groundwater level in the wall due to the rainfall, the increase of hydrostatic pressure, and the fracture of the connectors that connecting the ecological bags. Based on the deformation characteristics and triggering factors, a physical and mechanical model of the MSE wall is established. The finite element simulation is performed with Phase2 software. The failure characteristics are in general consistent with those observed in the field, and the failure mechanism of the MSE wall in this project was obtained. Finally, the mitigation plan by using the soil nailing wall plus shotcrete panel plus drainage are proposed for various defect conditions. The remediation result is satisfactory after the implementation of the mitigation plan, which provides a good reference for the treatment of MSE wall with similar hazards. Related Articles | Metrics

Select

Stability Analysis of Terraced Farm Field Considering Spatial Variability CHEN Jiajun, WU Kai, RONG Kejin, CHEN Zhiyuan, LI Bingyi 2024, 38 (5):  811-815.  Abstract ( 178 )   Save The rainfall infiltration will affect the soil stability, which may eventually lead to terraced farm field landslides and the crop yield reduction. Therefore, it is of high social and economic benefits to study the stability of the terraced farm field slopes under the rainfall infiltration. In this study, based on the random field theory, the finite element limit analysis combined with the strength reduction method is used to analyze the reliability of the terraced farm field stability under the rainfall by evaluating the terraced farm field factor of safety, the failure probability, and the destabilization risk. The results show that the traditional qualitative analysis does use a unique factor of safety to evaluate the stability of slopes, but the same factor of safety may correspond to multiple slip surface forms and landslide volumes, which is easy to overestimate the safety reserve of these slopes. Based on the random field theory, the slope stability is evaluated comprehensively by combining the slope factor of safety, the failure probability and the failure risk, which can more reasonably assess the risk of terraced farm field slope instability. Related Articles | Metrics

Select

Impact of Shielded Tunnel Excavation on the Ground Subsidence ZHANG Zhen, DONG Yabo, LUO Mingfu, LIU Yantao, WANG Binbin 2024, 38 (5):  816-820.  Abstract ( 177 )   Save The shield tunnel construction will cause a certain disturbance to the surrounding environment. The surrounding soil and rock mass deformation and ground subsidence exceeding certain limits will threaten the main structure of the tunnel and even affect the safety of the surrounding environment. Therefore, the ground subsidence is one of the necessary items to be measured in the shielded tunnel excavation, and the prediction of the ground subsidence is also the focus of the project. In the study of the ground subsidence caused during the shielded tunnel excavation, the Peck’s formula is a more widely used model. However, the Peck’s formula has some limitations and errors can occur in engineering applications. Therefore, based on the construction monitoring data of the shielded tunnel of Xiong’an Metro Line No. 1, the Peck formula is combined with the linear regression equation. The two correction coefficients, the settlement trough width coefficient K and the stratigraphic loss rate η, are introduced to the Peck formula. The Peck equation is modified so that it is more applicable to the geological conditions of the Xiongan area. Related Articles | Metrics

Select

Slope Stability Remediation Using Anti-Slide Caissons ZHOU Hanqi 2024, 38 (5):  821-824.  Abstract ( 154 )   Save The strength reduction method is used to establish a three-dimensional finite element model of the slope stability improvement by using anti-slip caisson. The bending moment, the shear force and the factor of safety of caissons under different design parameters are evaluated by changing the caisson location, the length and the spacing. Throughout the study of the force and the displacement of the caisson shaft under various circumstances, it is concluded that when the caisson length is short, it is in the middle and lower part of the slope, and when the caisson length is long, it is most beneficial to the stability of the slope to be set in the middle area. When the caisson is at both ends of the slope, the caisson length has little effect on the factor of safety. Finally, for a large number of mitigation plan, the optimal design of the slope stability support is determined, which can provide a good reference value for similar projects in the area. Related Articles | Metrics

Select

Characteristics of Slate in Muzhailing Tunnel GAO Qinyun 2024, 38 (5):  825-827.  Abstract ( 259 )   Save To evaluate the large deformation of the Permian age slate interbedded with carbonaceous slate in Muzhailing Tunnel, the bedrock, rock mass characteristics and engineering mechanical properties of the slate interbedded with the carbonaceous slate are analyzed and studied in detail by means of tunnel face sketch, grinding plate identification, X-ray diffraction, electrical microscope scanning, point load strength index test and large shear tests. The internal cause of the large deformation is also investigated. Meanwhile, the analysis and the understanding of the squeezing bedrock are performed. The conclusions are as follows: (1) the slate and the carbonaceous slate are composed of variable residual debris, peat and sericite, and the mineral particles form a “laminar flow structure” under the strong directional stress, with the remarkable anisotropy; (2) the integrity of the rock mass is poor and the shear strength is low; the main type of the deformation and the fracture are bending and plastic flow; (3) it is a high geostressweak expansion composite in the soft rock mass, which is a typical squeezing bedrock mass. Related Articles | Metrics

Select

Development and Treatment of Karst Rock Cavities in Qinduankou in Wuhan WANG Hui 2024, 38 (5):  828-831.  Abstract ( 215 )   Save To identify the karst rock cavity development at Xiaoqiao in Qinduankou, the statistical as well as the analytical studies are conducted at Pier 0 and Pier 1, respectively. The results showed that the karst formation at Xiaoqiao, Qinduankou is at the north side of the proposed bridge, which belongs to the L2 bridge zone. The soluble bedrock is the Permian Qixia Formation (P1q) limestone; The probability of encountering karst rock cavities in boreholes is 36.8%, among which 4 boreholes have developed 3-6 karst cavities in a string shaped development, accounting for the 57% of the entire coring length. The maximum linear karst rate is 44.12%, and the karst is therefore strongly developed. The of karst pinnacles are concentrated in the right side the area. The thickness of the karst development zone is 15 meters; Compared with the previously discovered karst development zone under bridge conditions, the overburden soil thickness in this area is greater, and the embedment depth of the bottom plate of the karst cavity below the bedrock surface is mostly 9.80-14.7m; ② The quasi embedded karst geological structure is a new geological structure, and the non-soluble bedrock is the carbonaceous shale of the Lower Permian Qixia Formation (P1q). According to the engineering characteristics and geological conditions of the proposed pile foundation, the karst cave was treated by compaction grout. During the construction, the combination of exploration grouting is used to maximize the economic effect of the geotechnical drilling. Related Articles | Metrics

Select

Soil Deformation of a Deep Excavation Between a Railway and Buildings LI Jinchi, SHI Hejie 2024, 38 (5):  832-835.  Abstract ( 159 )   Save This paper presents a case history of investigating the deformation of the surrounding soil and the supporting structures caused by the deep excavation in complex urban environments in Wuhan. The deep excavation is simulated by using the commercial finite element software PLAXIS2D. The excavation supporting structures as well as the loads imposed by adjacent railway trains and existing buildings, are reasonably simplified. The deformation of the soil mass and supporting structures within the excavation area are analyzed. The results indicate that, during the excavation process, the maximum deformation of in supporting structures adjacent to the railway side is greater than that on the side of existing buildings. The maximum vertical displacement of the soil occurs at the center of the excavation, while the maximum horizontal displacement takes place at the slope of the railway subgrade close to the excavation side. Both the deformation of the supporting structures and the soil deformation meet the relevant regulatory requirements. Related Articles | Metrics

Select

The Interaction between the Pile Foundation and the Adjacent Subway Tunnel Construction QIU Yanbin, 2024, 38 (5):  836-840.  Abstract ( 145 )   Save The installation of piles in subway protection areas has the characteristics of concealed construction, and the significant disturbance to the underground space. Therefore, the interaction between the pile foundation and adjacent subway tunnels is significant and complex. Understanding this interaction is of great significance to the safety of subways and adjacent buildings. A pile installation project near a subway tunnel in Shenzhen case history is presented in this project. A threedimensional numerical model is established using finite element analysis software to analyze the effects of the pile installation, building loading on the tunnel, and tunnel construction on the pile performance of this project. Results indicate that if the tunnel structure is constructed first, the impact of pile installation and building loading on the tunnel is mainly due to the vertical deformation of the tunnel rock mass and the soil caused by the additional stress; If the piles the building are constructed first, the subsequent tunnel construction stress unloading and possible groundwater level drop will cause the vertical deformation of the pile and the building. The vertical deformation mainly occurs during the groundwater drop stage; After the analysis, the impact of the pile and the adjacent subway tunnel construction on each other is within the allowable range of different stake holder and design specifications. However, the real-time monitoring during the construction has a great importance to the safety during the construction and operation. Related Articles | Metrics

Select

Experimental Study on Deformation Characteristics of Soft Clay Under Cyclic Loading CHEN Zehui, ZHANG Yan, BAI Xiao 2024, 38 (5):  841-844.  Abstract ( 122 )   Save The accumulated axial strain behavior of the saturated clay under the cyclic loading in partially drained conditions is analyzed. Among that, the effects of the cyclic stress ratio, and number of cycles are investigated. The test results show that the accumulated axial strain increases rapidly at the initial stage of the test, and then reaches a stable value with the increase of number of cycles under different cyclic stress ratios. Based on that, an empirical model to predict the accumulated axial strain of the saturated soft clay (Model 3) considering the effects of the cyclic stress ratio and the number of cycles is proposed, and the evaluation results of the three empirical models for the accumulated axial strain are compared and analyzed. The results show that Model 3 has a good prediction capability for the accumulated axial strain. Related Articles | Metrics

Select

Geotechnical Test Data Conversions Between Chinese Standards and US Standards TANG Zhenghong 2024, 38 (5):  845-848.  Abstract ( 214 )   Save In a foreign geotechnical investigation project, the geochemical test results are required to be provided in accordance with both the Chinese national standards (GB/T 50123-2019) and United States standards (ASTM). The major differences in these standards are in three aspects, namely, grain size distribution, liquid limit, and soil classifications. The sieve analysis and the liquid limit tests are performed on the same soil sample according to the Chinese national standard and US standards, respectively. The results show that: (1) Under the sieve analyses on the same soil sample, the difference between both standards is within 5% and can be used interchangeably without significantly affecting the engineering results. (2) For the liquid limit results, a linear regression analysis is performed between the results using both standards. And a linear relationship exists. (3) After the relevant conversion of the grain size distribution analysis and the liquid limit between the Chinese national standards and the US standards, the soil classification name conversion can be converted accordingly. Related Articles | Metrics

Select

Laboratory Testing of Degradation of Straw Wick Drains CHEN Tao, DENG Mingshun, SU Yinqiang, YANG Qian, CHEN Guang, ZHANG Liqiang 2024, 38 (5):  849-853.  Abstract ( 205 )   Save In soil improvement with vacuum preloading projects, plastic prefabricated vertical drains (PVD or wick drains) are inserted into the foundation soils to provide vertical drainage channels. After construction, a large number of plastic wick drains are left in the soils, resulting in not just white pollution but also potential groundwater contamination. In this paper, three different types of biodegradable wick drains made of straws are laboratory tested. The feasibility of the straw wick drains to be applied in the practical engineering projects is verified. The results showed that the straw wick drains are degraded by bacteria in soils, the water discharge capacity and tensile strength decreases with the increase of time. The degradation rate is 40% after 240 days. The water flux and tensile strength of degradable wick drains are lower than those of the plastic wick drains, but they all meet the project requirements. It can be used instead of the plastic wick drains in the vacuum preloading soil improvement projects, which can not only solve the environmental pollution problem, but also expand a new way of comprehensive utilization of straw resources. Related Articles | Metrics

Select

Experimental Study of the Silty Peaty Soil Improvement with Electroosmosis with Staggered Energization Mode YANG Kaixiang, WANG Ningwei, LI Wei, LUO Yuechun, XIA Bintong 2024, 38 (5):  854-858.  Abstract ( 131 )   Save The traditional electroosmotic energization mode generally inputs the electrical current into the upper part of the anode and the cathode. One of the problems is that the lower part of the electrode is seriously corroded, and the strength of the soft soil is not uniformly improved. To solve this issue, a staggered current mode is proposed, and the effectiveness of this mode is verified throughout experiments. In this paper, two silt peaty soil electroosmosis samples are prepared; one is prepared by using the traditional energization mode and the other is using the staggered energization mode. The test results show that: (1) under the same water discharge conditions, the energy consumption of the staggered energization mode is reduced by about 23% compared with the traditional energized mode; (2) Compared with the traditional current mode, the cumulative water discharge in the staggered current mode is increased by about 60%; (3) Using the staggered energization mode, the shear strength of the soft soil after the improvement is increased by about 80% compared with the traditional energization mode. The improvement result in soil mass is more uniform. This test proves that the staggered energization mode has a better improvement effect and lower energy consumption, which can provide a good reference for the future research and practical projects. Related Articles | Metrics

Select

Study on the Seismic Trap Characteristics of Structural Soft Clay Soils Under Dynamic Loading ZHU Yi, SHANG Yingjie, YANG Aiwu 2024, 38 (5):  859-864.  Abstract ( 128 )   Save The seismic properties of the soft clay under the dynamic loading are closely related to its structural properties, and the study of the seismic properties of the structural soft clay is of great significance for the prevention of seismic hazards in soft soil areas. Since it is difficult to obtain the soft clay with the same material composition but different structural properties in nature, four artificial structural soft clay samples with the same moisture content and similar material composition but different structural strength are prepared in this paper through comparison tests. The results show that for soft clay soils of the same structural strength, the larger the amplitude of the cyclic dynamic load and the smaller the enclosing pressure, the larger the seismic subsidence; the resistance of structural soft clay soils to cyclic dynamic loads shows a non-linear relationship with the structural strength of the soil. In addition, an analytical model is constructed to estimate the seismic subsidence of soft clay soils considering the influence of the structural strength. The results can provide scientific basis for the relevant engineering projects. Related Articles | Metrics

Select

Application of Magnetic Logging Method in Estimating the Length of Reinforcement Cage of Cast-in-Place Concrete Piles LIU Junjiang, YUAN Jinxing, ZHANG Ye, WANG Yuexiang 2024, 38 (5):  865-867.  Abstract ( 194 )   Save The magnetic logging is a common method for measuring the length of steel reinforcement cage of the cast-in-place piles. The detection principle is to analyze the magnetic anomaly curve around the pile based on the distribution characteristics of the magnetic field around the pile to estimate the length of the entire steel reinforcement cage. The detection curve of the steel reinforcement cage with a good integrity is uniform and stable, and there will be reflected signals when passing through the pile bottom. Therefore, the detection method can provide an important basis for the identification of the abnormality of the steel reinforcement cage at the suspected pile length or pile end. By introducing the basic working principle of the magnetic logging method and measuring the integrity of the underground steel reinforcement cage, and combining with a new construction project in Suzhou, the magnetic anomaly curve of the steel reinforcement cage of the cast-in pile was analyzed. The test results confirmed the feasibility and accuracy of using the magnetic logging method in measuring the length of the steel reinforcement cage of the cast-in place pile, as well as its feasibility in the field of engineering testing and quality assurance. Related Articles | Metrics

Select

Application of High-Density Electrical Method in Water-Bearing Characteristics of Karst Overburden Soils in Jiufeng, Wuhan HUO Yulong, ZHANG Cong, 2024, 38 (5):  868-872.  Abstract ( 104 )   Save The overburden layer above the karst rock is often used as the bearing layer of buildings, and its moisture content characteristics have both the theoretical and the practical significance. In this paper, the relationship curve between the elevation and the water content is divided into four different types: gradual decline curve, steep decline-stable curve, steep decline-slow rise curve and stable-steep decline-stable curve. Each of these curves can be superimposed with the inclusion of the overburden with the extreme water content to form a composite curve. The peak value and the valley value of the curve have engineering significance, or can reflect the prominent hard layer in the overburden, or can represent the soft underlying layer buried deeply in the overburden. The study area is in a limestone belt, and the karst geological structure type is the Type IV. The porous medium in the overburden is less affected by the seasonal precipitation and more affected by the fissure water in the deep strata. Highdensity resistivity method can be used to analyze the characteristics of the water content in overburden soils. The water content decreases with the increase of the resistivity, and the resistivity value increases with the increase of depth. The abnormal areas with a high resistivity and a low resistivity can be characterized as abnormal areas with the water content in the engineering practice. Related Articles | Metrics

Select

Deformation and Control Methods for the Adjacent Subway Induced by Deep Excavations in Deep Sand Layers DAI Zhonghai, WU Lei, 2024, 38 (5):  873-877.  Abstract ( 135 )   Save In the area of deep sand layer, the deep excavation must be performed at a safe distance from the active subway tunnel structure to ensure the operation safety of the subway. The deformation of the tunnel structure must be strictly controlled. The design, construction and monitoring aspects of the deep excavation have extremely high requirements. Focused on the specific engineering examples, the deformation patterns of the subway tunnel structure at different distances from the deep excavation are studied by using the methods of on-site monitoring and numerical analysis. The results show that the supporting structure with the secant pile wall combined with the concrete internal support meet the deformation control requirements. Moreover, the closer the subway tunnel is to the deep excavation, the greater the horizontal and vertical displacements. Among them, the measured maximum vertical displacement of the subway tunnel roof is 5.65mm, and the maximum horizontal displacement is 4.60 mm. In the design of the deep excavation, the stiffness of the supporting structure should be strengthened locally according to different distances, or the soil improvement on the side of the subway tunnel structure should be performed. Related Articles | Metrics

Select

Effect of Delayed Compaction on the Engineering Characteristics of Cement Improved Soils NIE Wei, YANG Fei, SONG Changjun, LIU Wenjie 2024, 38 (5):  878-882.  Abstract ( 151 )   Save To investigate the effect of the delayed compaction on the engineering properties of the improved soil, this study focuses on the subgrade soil from an expressway in Hunan Province. Various samples with different cement contents and delayed compaction time were prepared, and multiple series of compaction tests and the unconfined compressive strength (UCS) tests were conducted to assess the influence of the delayed compaction on key engineering characteristics. Subsequently, a regression model was developed to quantify the degree of influence. The findings indicate that the maximum dry density (MDD) of the cement-modified soil decreases with the increasing cement contents and the delayed compaction time. The delayed compaction has an adverse effect on the UCS for the cementimproved soil; therefore, it is crucial to ensure a proper connection between the mixing and the compaction processes. As the duration of the delayed compaction increases, the stiffness of the cement-modified soil decreases while its toughness increases. Regression models for the MDD and the UCS considering both the delayed compaction and the cement contents were established, demonstrating a close agreement between measured values and predicted values. It is important to reasonably consider the impact of the delayed compaction when dealing with the subgrade filling for cement-improved soils. Related Articles | Metrics

Select

Early Warning Method for the Instability of Expansive Soil Canal by Slope Deformation Monitoring GAN Xudong, LIU Jun, HU Bo, JIANG Shiming, ZHANG Xiaoyu, ZHANG Zhenshan 2024, 38 (5):  883-888.  Abstract ( 152 )   Save The stability and the deformation of the expansive soil canal are closely related to each other. Several landslides occurred during more than 2 years of the expansive soil tests in a large water diversion engineering project. The inclinometer was used in the in-depth lateral deformation monitoring. Based on the analysis on the extrinsic and intrinsic connections between the stability and the deformation of an expansive soil canal, it is suggested that the deformation rate and the accumulative displacement are the main early warning indices, and the development time of the deformation, the change of environment and the response of the slope are the reference indices in distinguishing the expansive soil canal instability. Moreover, the forecast and the early warning method of the expansive soil landslide is proposed, which provides a reference for the rational evaluation of the safety state and the development trend of expansive soil canal slopes. Related Articles | Metrics