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30 June 2022, Volume 36 Issue 3 Previous Issue    Next Issue

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Dewatering Optimization Analysis of a Deep Excavation Above an Existing Shielded Tunnel ZHOU Zhenhua 2022, 36 (3):  295-300.  Abstract ( 460 )   Save The effect of point-well layout, starting time and operation duration on the dewatering results are evaluated in this paper and the dewatering plan of a deep excavation project over a shielded tunnel in Xiamen was also optimized. A three-dimensional seepage numerical model was established by using PLAXIS 3D commercial software to study the potential factors that affecting the dewatering results. The results show that: the spacing of well points is 15 m is an appropriate distance; In Model No. 1, the single well-point did not obtain a high yield of water volume due to the interaction of well point surrounding it when they were operating at the same time. In Model No. 2, the dewatering results was not ideal due the well pints for the next construction section did not operate. When a zoned dewatering plan is desired, the dewatering well point for the next stage should be operated in approximate 30 days ahead of the desired excavation date. The final field practice showed that the dewatering planed used was reliable and the excavated area was safe and stable. Related Articles | Metrics

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Stability Analysis of a Deep Excavation Near Municipal Road Live Traffic Loads SHEN Yutao, ZHANG Lu 2022, 36 (3):  301-303.  Abstract ( 310 )   Save This paper presents the stability analysis of a deep excavation project near the live municipal traffic load condition. The excavation sequences were numerically simulated with three-dimensional finite element software, PLAXIS 3D. In the numerical model, the stress and the displacement of the diaphragm wall were used as major indices for the evaluation of deep excavation under the municipal traffic loads. The results show that the maximum horizontal displacement of the diaphragm wall under municipal road traffic load occurs in the middle of diaphragm wall near the municipal road side, the maximum horizontal displacement of the diaphragm wall under the municipal road traffic load is significantly larger than that of under no traffic load condition; the maximum bending moment of the diaphragm wall near the municipal road side under the municipal road traffic load is higher than that of without the municipal road traffic load The maximum value under through load also increases significantly.  Related Articles | Metrics

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Study on improvement of Cutter Head-Mud Blocking to EPB Shield Tunneling Machine#br# WANG Wen, PAN Xueying, ZHAO Yanping, YAN Mengqiu, LU Di, CHEN Konglei 2022, 36 (3):  304-307.  Abstract ( 573 )   Save The mud cake blocking at the cutter head will slow down the construction progress of the shielded excavation and event result in serious accidents such as excavation failure and other geohazards. In order to study the effect of hydro-chemical-mechanical coupling on the flow plasticity and the strength of shielded cutter slurry, CaCl2 solutions with different concentrations, such as, 0 mol·L-1, 0.5 mol·L-1, 1.0 mol·L-1, were used to saturate the shield cutter mud cake samples. The mud cake samples after the saturation were tested for Atterberg Limits and modified direct shear tests. The test results show that the increase of the solution concentration can effectively reduce both the plastic and the liquid limits of soil samples; reduce the soil cohesion. However, the increase the solution concentration, the internal friction angle and the overall shear strength are increased. These changes might be the results of the thin water film incorporated at a high concentration; the soil sample’s water retention capacity becomes weak resulting in a decreased plastic limit. With the increase of the solution concentration inhibit soil electric double layer thickness, so that the soil particle agglomeration, the repulsion between the particles decreases, biting force among soil particles increases, thus weakening the cohesion, the internal friction angle increases. Related Articles | Metrics

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Application of Rolled Steel Reinforced Concrete Column in the Cut and Cover Construction of a Metro Station CAI Leichuan, TIAN Qingbiao, TANG Zhitong, ZHANG Dongdong 2022, 36 (3):  308-312.  Abstract ( 409 )   Save Metro station using cut and cover construction method often uses rolled steel reinforced concrete as the permanent and/or temporary supporting columns, but there are disadvantages such as complicated connection joints and difficult for the installation. In this paper, a single-story auxiliary structure constructed by the cut and cover excavation in a station of Tianjin Metro Line 6 is presented with a new type of rolled steel reinforced concrete composite column. The new structure is composed of concrete encased angle steel column. Some studs are welded on the outside of the angle and plate steel and the plate columns to improve the shear resistance, and some reinforced bars are placed in the concrete column. The longitudinal steel reinforcement bars of the beam at the beam-column joint pass through the angle steel gap of the concrete column, and the steel bars cut by the Angle steel are welded on the Angle steel and the fix plate, and the reinforcing longitudinal bars are provided. Rolled steel columns are also used as temporary columns to support the roof in the construction stage. After the foundation is excavated to the bottom, the composite column concrete is poured to form permanent columns. The connection method of the column joints optimizes the connection between the envelope structure and the connection joints. The field practice has proved that this method is convenient for the construction and reliable in quality control. Related Articles | Metrics

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Application of High Vacuum Preloading Method in Soft Soil Improvement of a Harbor Project WANG Ruifang, ZHU Jia 2022, 36 (3):  313-316.  Abstract ( 362 )   Save A thick, soft clay soil is deposited under a harbor project area. Due to its low permeability, low shear strength and heterogeneous distribution, no engineering structures could be constructed directly on this soil layer. Several ground improvement methods were proposed based on subsurface condition of the harbor and the purpose as the steel storage yard and the high vacuum preloading method was selected. The ground improvement design, post construction settlement estimation, informational construction aspects for the harbor construction are introduced in detail in this paper.   Related Articles | Metrics

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Deep Excavation Techniques in Silty Fine Sand Soil for a Raft Foundation at Hillside in Jinan City JIANG Wenfu, MENG Yan, SUN Wenlai, ZHANG Mingshan, 2022, 36 (3):  317-322.  Abstract ( 411 )   Save This deep excavation for a raft foundation is located at the northwest side of Yaoshan Mountain in Jinan City. The excavation included many components, which possesses the characteristics of large scale, deep dewatering depth, and short construction duration, etc. During the support of excavation and dewatering period, several construction difficulties were encountered and were resolved successfully. These challenges included excavation difficulties in the several soil strata, such as, silty fine sandy layers, the thick-bedded miscellaneous soil and the hard rock at the bottom of some cast-in-situ concrete piles; the conflict between the constructed raft foundation and dewatering well points, etc. For the first time, the concept of perched groundwater in depressed soil layer is proposed in this study. This paper summarizes potential factors that might results in groundwater leakage in the waterproof cut-off wall formed by jet grout method. And the solutions to the groundwater leakage are suggested. It is very beneficial for making use of the exploration data from the dewatering well points. The ground anchors with casing pipe were used with satisfactory results. The rotary drilling and the long all-flight bored technics were used flexibility in the soldier pile construction. During the construction of the raft foundation, a new dewatering device for the submersible pump left-in-place was invented, which can solve the contradiction between the dewatering devices for the foundation pit and the completed raft foundation. By utilizing this new method, the raft foundation and other structure were installed satisfactory.  Related Articles | Metrics

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Analysis of Geotechnical Engineering Investigation of Hainan Weathered and Eroded Landform WU Fuliang 2022, 36 (3):  323-326.  Abstract ( 386 )   Save Combined with an engineering survey example under a weathered and eroded landform in Qionghai City, Hainan Province, the geotechnical engineering conditions of the site were identified by using a variety of investigation methods. There are different types of bedrocks with different degrees of weathering at the site. The sandstones and granites formed in the early period and the basalts formed in the Early Pleistocene of the Quaternary are filled with cohesive soil and sandy soil of marine and terrestrial deposits, forming a complex spatial distribution. Uneven hardness within the rock mass, large difference in shear strength, weak interlayer and other characteristics of the bedrock and soil layers. According to the investigation results, the complexity and uniformity of the proposed foundation under such geotechnical conditions are evaluated, and the influence of the characteristics of the large undulations of the bedrock surface, the soft interlayer between the bedrock and the hard interlayer of volcanic rock on the construction of the project is analyzed. For the individual building structures with different dimensions in the residential complex, potential geotechnical engineering problems, and the treatment measures and suggestions are presented in the paper. Related Articles | Metrics

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Cut and Fill Design Analysis of Airport in the Potential Landslide Zone ZHAO Liang, PENG Jun 2022, 36 (3):  327-330.  Abstract ( 225 )   Save Landslide, as a most frequently encountered geohazard, is critical to the accurate analysis of slope stability and to the geohazard prevention and mitigations. The conventional two-dimensional analysis methods could usually not to reflect the on-site stability status due to the actual topographical boundary constraints. This paper presents a refined three-dimensional numerical finite difference geological model by considering the actual topographic conditions, soil strata distribution, soil rock mass shear strength parameters as well as the construction sequence. The numerical model also considers the change of sliding direction and the side resistance surrounding the sliding body. The stability of the proposed soil/rock mass under different loading conditions and different improvement methods are evaluated and the optimized improvement method is therefore selected.  Related Articles | Metrics

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Geological and Geophysical Investigation Analyses of Dalailong Railway Subgrade Materials CHEN Hao, LIU Bingwen, SONG Shuguang, ZHOU Zonghe, ZHANG Rutao 2022, 36 (3):  331-334.  Abstract ( 280 )   Save The geological and geophysical investigations were performed to analyze the geological condition and bearing capacity aspects of Dailailong railway subgrade materials. Based on the electrical differences between the normal and the abnormal geological bodies, The Controlled Source Audio Magnetic Telluric (CSAMT) was used to identify unfavorable geological conditions of Dailailong railway subgrade material by analyzing the apparent resistivity cross-section diagram, three-dimensional diagram, shear deformation area diagram and curve diagram, and two-dimensional inversion diagram. Secondly, by using of Evd Edynamic modulus detection method, the subgrade bearing capacity of Dalailong railway subgrade was detected by analyzing the settlement value and dynamic deformation modulus of the measurement points. The results show that the subgrade slope of Dalailong railway contains sliding bodies and uncompacted sliding surfaces, and the bearing capacity of the subgrade is unevenly distributed, which requires further filling and compaction. Related Articles | Metrics

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Analysis on Stability of a Cut Slope of Gravel Cohesive Soils LING Xiaomei, XU Baotian 2022, 36 (3):  335-339.  Abstract ( 372 )   Save Field investigations and studies indicate that the stability of a cutting slope along Qing-Chang Line, Yizheng City, is mainly controlled by the thick silty clay layer including a large amount of gravel. The maximum height of the cutting slope would reach 20 m. The gravel content in the clay varies greatly, the strength of the soils is strongly affected by the gravels. Combined with the site topography and landslide investigation, it is found that the sliding surfaces were through the layer of silty clay, so the strength parameters along the sliding surface were inversely evaluated, the soil strength parameter values with the change of gravel content were obtained. According to the strength parameters of the soil under different conditions, the stability coefficients of slopes under different slope ratio were analyzed. It is recommended that the slope ratio should be 3H:1V or 2H:1V, if the slope is cut in the cohesive soil layer.  Related Articles | Metrics

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Stability Analysis and Mitigation Measures of Mugong Landslide in Yaojiaping Water Conservancy Project in Hubei Province NIAN Fuxi 2022, 36 (3):  340-343.  Abstract ( 427 )   Save This paper presents the slope stability analysis of Mugong landslide on the left bank of the reservoir area of Yaojiaping water control project in Hubei Province. The limit equilibrium method was used in the analysis of the reservoir under different rapid drawdown conditions after pooling. The results show that the potential landslide body is in the stable state in general. The proposed water pooling would not trigger the landslides at locations with elevation above 800.0m. In the direction of potential secondary landslide (M1) on the east side, the surficial soil layer is marginally stable under the condition that the elevation of 723.0m ~ 746.5m with a rapid drawdown from the normal pool level of 745.0m to the dead water level of 710.0m. For the surficial soil layer within this zone, it is recommended that the anti-slide caisson could be used as the mitigation method. For the potential secondary landslide of in the direction of Aimenlow (M3), the slopes within the zone between elevation 806.0m and 875.0m are basically stable. As this area in in the non-affected area of the project, the water storage of the project has no impact. The real-time slope deformation monitoring tools should be adopted. The potential sliding bodies below the elevation of 700.0m are below the dead water level, so it is considered that instability is not likely. Related Articles | Metrics

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Optimization of Double-Row Piles for the Deep Excavation Supporting Structure JIANG Guangzhan, LUO Junmin, JIANG Kai 2022, 36 (3):  344-349.  Abstract ( 330 )   Save This paper presents the optimization results of double-row piles as the deep excavation supporting structures for a case history in Nanning, Guangxi. A three-dimension numerical model of the supporting structure of double-row piles to analyze the deformation characteristics under various conditions was established by commercial finite difference software FLAC3D. The results indicated that the increasing the row spacing can effectively reduce the excavation induced risk and the horizontal displacement of the piles. The horizontal displacement in the double row soldier pile is gradually increasing with the decrease of the pile length and the diameter of the rare-row piles but the deflection value is within the allowed range. Therefore, the length and the diameter of the rare-row piles can be appropriately reduced if the safety of the excavation can be ensured. Related Articles | Metrics

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Effect of Shallow Embedded Large Diameter Shielded Tunnel Underpass Large Buildings QIU Shouhui 2022, 36 (3):  350-354.  Abstract ( 179 )   Save In order to study the influence of shallow-buried and excessive-large diameter shielded tunnel excavation in the saturated sand layer underneath of a large footprint building, a numerical finite element model was established by using commercial software MIDAS GTS. The settlement and deformation of above building without protective measures were numerically evaluated. From the numerical results, the proposed protective measures included tunnel excavation control as the primary measured and aided by the secondary grouting. The deformations of the building with and without protective measures were compared with the monitoring data. The results show that: 1. Without protective measures, the maximum settlement at the crest of the tunnel was about 18.2mm, and the maximum differential settlement of the adjacent columns of the inner frame was 6.45mm. After the completion of the tunnel, the maximum settlement of the soil mass above the tunnel was 28.2mm, and the settlement of the inner frame column has exceeded the warning value. (2) The maximum differential settlement of pillar foundation was about 2mm by the numerical prediction after the primary excavation control and supplementary grouting reinforcement measures applied in the tunnel. (3) Based on the analysis of onsite monitoring data, the monitored differential settlement of the maximum pillar foundation was about 0.8mm after the twocell tunnel passing through. The predicted data from the numerical simulation and the monitored data were consistent and the of control indices for the construction safety control met the requirements. Related Articles | Metrics

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Stability Analysis of a Municipal Roadway Landslide in Colluvial Soils ZHOU Kun, WANG Bo, YAN Junfeng 2022, 36 (3):  355-359.  Abstract ( 212 )   Save This paper presents a case history of Baoshan landslide in the colluvial soils throughout the data collection and field mapping. The deformation and development of the Baoshan landslide are investigated, and the conditions and mechanism of the landslide are studied. On this basis, the residual thrust method was used to evaluate the stability of the landslide. The global slide of the potential area will cause serious hazards to the roadway at the toe of the slope and the residential development under construction, so it is necessary to analyze and study the potential factors that might contribute to the stability of the landslide. Related Articles | Metrics

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High Slope and Its Comprehensive Treatment Plan TANG Jing, WANG Xiaoxu 2022, 36 (3):  360-364.  Abstract ( 290 )   Save The high slope of a highway in Hubei Province was deformed and damaged at the cut area. For construction safety and minimizing the community impact, highway slope hazards within this section are in an urgent need of mitigation. The slope deformation data were collected, the geological and hydrological conditions ate the potential sliding body were investigated and the stability was evaluated. The landslide mitigation measures were also designed and implemented. The results show that high slope deformation hazards are still in the development stage. The slope is in an unstable state under the heavy precipitation, continuous rainfall and under the seismic conditions. As comprehensive mitigation measures, the steel pipe pile as antisliding pile, railway track steel segment as the retaining wall toe protection, seal off cracks at surface and promoting drainage were applied. Related Articles | Metrics

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Design Practice of Deep Excavation in Soft Soil Above Subway Lines LI Huihui, WANF Ying, CEN Yangrun, LIU Hengxin 2022, 36 (3):  365-369.  Abstract ( 214 )   Save There are more and more deep excavation projects directly above or very close to the existing or planned subway tunnels. The design and construction aspects of deep excavation support have always a challenge in the industry. This paper presents a case history of deep excavation in soft soils directly above the planned subway line in Hangzhou urban area. The engineering characteristics, deep excavation support design selection and monitoring results are introduced in detail in the paper. Technical difficulties in the design of subway tunnel underneath the existing excavated foundation, including deformation control of supporting structures, soil strengthening at the bottom of excavation, reservation of the shielded tunnel crossing pass and reduction of the influence of various construction stages are also summarized. The monitoring results show that the selection of deep excavation support system is reasonable and its impact to the surrounding environment is minimal. After the basement floor was completed, the shielded tunnel crossing is favorable to the control of deep excavation deformation. Related Articles | Metrics

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Research on Application of Circular Grouting Anti-slide Pile in Unconsolidated Formation Landslide WANG Zhangyun, YANG Qinfu 2022, 36 (3):  370-374.  Abstract ( 267 )   Save In order to solve the problems of poor performance of anti-slide caisson in the mitigation of potential landslide in the unconsolidated overburden soils, a post grouted circular anti-slide caisson structure is proposed to improve the performance of the traditional circular anti-slide caisson structure. The caisson structure is mainly composed of steel casing, grouting pipe, circular anti-slide caisson longitudinal reinforcement and circular stirrup. The post grouted caisson is a caisson-soil compound structure. The sliding force is carried by the anti-slide caisson and the adjacent grouted soils, which has the advantages of minimizing the borehole collapsing, improving anti-slide performance and stabilizing the geomaterial among caissons. The design approach of the post grouted circular anti-sliding caisson is also proposed in the paper. The engineering application shows that the post grouted circular anti-slide caisson can effectively reduce the lateral earth pressures of the caisson, lower the location of the maximum lateral earth pressures and improve the stiffness of overburden soils.  Related Articles | Metrics

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Factors Contributing to a Highway Landslide in Hubei LEI Qiguo, CHENG Wei 2022, 36 (3):  375-378.  Abstract ( 312 )   Save Tensional cracks were observed at the top, toe of slopes as well as the retaining walls of a newly constructed highway embankment in Hubei Province after a prolonged heavy precipitation. The length of this embankment is approximately 160 meters with a slope one the left-hand side and retaining wall at the right-hand side. The maximum backfill height of the embankment is 8 meters. The maximum overburden soil thickness is 8 meters on the well-developed karstic rock pinnacles. The limestone with thin layers of shale bedrock is severely folded with bedding planes that is anticline to the direction of slope at right hand side. The day-lighted bedrock bedding plane has a small angle to the direction of the embankment slope at left hand side. The observed geohazards induced significant difficulties so that many change of design and construction occurred. Based on the geological conditions, soil and rock stratigraphy, hydrological conditions, embankment backfill characteristics and deformation monitoring results, it is concluded that the defects observed is a translational movement and the target embankment is at the instable condition.  Related Articles | Metrics

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Application of Construction Technology of Percussive Bored Concrete Piles for Highway Bridges in Mountainous Area LAI Dayong, MO Qingwen, WU Shitao 2022, 36 (3):  379-382.  Abstract ( 473 )   Save This paper presents a case history of the highway bridge project in Enshi, Hubei Province. The bridge foundation type selected the percussive bored and cast-in-place concrete piles based on the characteristics of the rugged and complicated geological conditions in mountainous areas. Due to the complexity of the geological conditions at the project site, different percussive installation methods with small, medium and large strokes drilling should be utilized in the construction in accordance with various subsurface conditions. At the same time, the drilling waste should be discharged immediately to maintain the required density and viscosity of the drilling slurry. The bored pile shaft quality inspection was also performed by the ultrasonic method on the shafts that meeting the curing age. The test results show that: the integrities of bored pile shaft structures were sound with a Class I grade. The results also suggested that the application of the percussive installation method can effectively ensure the quality of the bored pile foundation for highway bridges in the mountain area.  Related Articles | Metrics

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Cracks in Composite Lining of a Highway Tunnel and Mitigation Measures LIAN Qiang, FENG Kai 2022, 36 (3):  383-386.  Abstract ( 278 )   Save To solve the service life reduction and operation safety risks induced by structural cracks in the composite lining of a highway tunnel, this paper presents the typical geological section of Yangling Tunnel in Yixing as a case history and evaluates the influence mechanism of the geological conditions of surrounding rock mass, construction methods and the concrete material on the structural cracks in the secondary lining. The results indicate that, (1) the premature form work removal resulted in insufficient early strength of the secondary lining of the concrete, which led to hidden cracks in its interior under the action of dead weight stress and the surrounding rock compressive stress; (2) the stress concentration at the end of the crack induced by the temperature gradient stress induced by the under-curing of concrete led to the growth and the coalescence of the hidden cracks inside. In the view of the cracks with different opening degrees, the corresponding grouting reinforcement treatment measures are proposed to improve the strength and the integrity of the lining structure and effectively ensuring the safety of the surrounding rock mass and the maintenance structure during the operation of the tunnel. Related Articles | Metrics

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Site Classification Method at a Building Site Near Mountain with Significant Elevation Difference XU Youna, WANG Wenzhe 2022, 36 (3):  387-390.  Abstract ( 258 )   Save Borehole shear wave velocity measurement and thickness of overburden soil estimation for buildings in plain regions are based on the relative depth to the surface elevation. For the site preparation of construction projects in mountainous area, the foundations for a lot of buildings would experience cut or fill conditions. Therefore, the seismic site class might be changed, site seismic performance would be therefore different, so that the site seismic class might also be different at the project site. In this paper, based on datum at each building after the site preparation, and the proposed ground surface elevations adjacent to the proposed buildings, the average overburden soil thickness is re-estimated so that that the site seismic class at each building could be estimated. This paper provides a new method for the site seismic classification for building sites with significant elevation differences in the mountainous areas. Related Articles | Metrics

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Prediction Model of Ground Subsidence Induced by Sand Intrusion WU Yin, ZHANG Xiangxiang, ZHANG Xiang 2022, 36 (3):  391-394.  Abstract ( 243 )   Save Under the hydraulic action, the saturated sand intrusion might occur and then induce the ground subsidence to form a funnel-shaped depression zone. This paper proposes a prediction model of sandy soil subsidence range, and the expressions of the settlement radius and depth at the center of the subsidence are presented. This formula can directly predict the range and volume of subsidence. The potential influencing factors involved in the expression are evaluated through the model tests from the fine grain content, hydraulic gradient, and diameter of the sand intrusion zone. The results show that the subsidence zone formed after the intrusion is approximately funnel-shaped, and the average of the relative errors between predicted values and measured values of subsidence radius and depression center depth are 5.6% and 7.4%, respectively. The proposed model can predict settlement range accurately. According to the predictive model, the influence of the soil fine grain content, hydraulic gradient, and the diameter of the sand intrusion zone on the ground subsidence induced by sand is consistent with the laboratory test results.  Related Articles | Metrics

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Analysis of Reliability of Using Soil Nail as the Deep Excavation Supporting Structure YANG Yizhou 2022, 36 (3):  395-399.  Abstract ( 217 )   Save The traditional fixed-value method of designing the soil nail support system for a deep excavation project has challenges such as failure of the excavated area. Therefore, the reliability analysis of various failure modes such as, translational, overturning and pulling failures in the excavation support design of a project were performed by using the checkpoint method and Monte Carlo method. The results indicated that there are some errors in the reliability indices of the supporting structure failure categories predicted by the checkpoint method and the Monte Carlo method. Based on the theoretical and practical project experience, this paper recommends that the checkpoint method should be used. The reliability approach can provide the specific location of the supporting structure that requires improvement. Related Articles | Metrics

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Numerical Simulation of Cone Penetration Tests in Hydrate Bearing Sand KONG Zhuangzhuang, SHEN Zhicong, CHEN Qiang, LI Yanlong, SUN Jianye, ZHAO Zhichao, WANG Dong 2022, 36 (3):  400-405.  Abstract ( 289 )   Save The main hydrate storage layer in the South China Sea is fine sand reservoir. To obtain the mechanical properties of the hydrate reservoirs rapidly and accurately is critical to the development and utilization of the nature gas hydrate. A modified Mohr-Coulomb model was introduced to describe the stiffness, strength and deformation characteristics of hydrate sand by using the commercial finite element software ABAQUS. The constitutive mode response was calibrated by the isotropic compression tests in conventional sand samples and the plastic parameters were determined by the drained triaxial test on the hydrate bearing sand samples. A large deformation finite element method in the form of Arbitrary Lagrange-Eulerian was used to simulate the cone penetration tests in the hydrate sand layers. The numerical model allowed the different flow velocity between the soil and the mesh to avoid the element distortion around the cone tip. An empirical equation for the cone tip resistance varied with different saturation was obtained. Related Articles | Metrics

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Influence of Water Content on Submerged Erosion of Gravel-Sand Foundation A Case Study of Li River Terrace in Guilin NI Zhe, LIU Zhikui, LI Shanmei, DONG Binghong, XI Danni, TAN Mingcan 2022, 36 (3):  406-409.  Abstract ( 312 )   Save The basic characteristics of the gravel-sand binary structure such as Guilin was evaluated by sampling at the first terrace of Lijiang River and the collected samples were divided into nine different grain size groups throughout the sieving analyses. By using the in-house developed erosion deformation test device, the samples with the same gradation were prepared with the compaction in lifts. Under the condition of the same degree of compaction, the influence of different moisture contents on the seepage erosion failure of in the gravel-sand binary structure was evaluated by controlling the moisture content of sand samples. The test results show that the moisture content has a great influence on the erosion speed, and when the fine sand and the gravelly sand are at the optimal moisture content, the erosion speed is relatively low. At the same time, the test results show that the influence of the moisture content on the stability gradient of the erosion velocity is not obvious. Related Articles | Metrics

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Frost Heaving Pattern and Prevention of Power Transmission Projects in Western Inner Mongolia DU Lanna, ZHANG Wei, QU Hongjie, WUDABALA 2022, 36 (3):  410-413.  Abstract ( 283 )   Save The seasonal frost heaving hazards of the electrical power transmission and transformation projects in western Inner Mongolia are evaluated. This paper analyzes factors that might potentially cause and influence the seasonal soil frost heave are presented. Based on the regional topography, hydrometeorology, stratum lithology, groundwater level and other aspects, along with the field survey sampling results and the regional engineering original data, the regional frost heaving grade trend distribution map was developed. At the same time, according to the literature research and the characteristics of frozen soil in the western Inner Mongolia, several measures to prevent frost are proposed. This paper provides some significance to the study of the electrical power construction, site selection and alignment selection of electrical power facilities in the region of seasonal frost heaving soils in western part of Inner Mongolia. Related Articles | Metrics

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Stability of Landslide Due to Effective Weight Loss in Three GorgesReservoir Under the Rapid Pool Level Rise DENG Yonghuang, LIU Qing, HUANG Xiaohu 2022, 36 (3):  414-416.  Abstract ( 261 )   Save Since the impoundment of the Three Gorges Reservoir, many landslides and other geological hazards have occurred in the reservoir area. Based on the analysis of the relationship between the GPS monitoring data and the reservoir pool water level, the Sunjiazhuang landslide in the three Gorges Reservoir area was selected to evaluate the stability. It is concluded that the sliding belonged to the buoyancy weight loss landslide type. The SEEP/W and SLOPE/W modules in geo-studio software were used and the seepage field under different pool water level rising rate conditions was evaluated. The variation of the stability coefficients was analyzed in detail. The results show that in the process of reservoir water rising, the sliding resistance section at the leading edge of the landslide body is continuously submerged, the anti-sliding force decreases, and the stability coefficient decreases. The smaller the rising rate of reservoir pool water, the smaller the stability coefficient. Related Articles | Metrics

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Common Technical Problems and Countermeasures of Geotechnical Engineering Investigation in Hilly Soft Rock Area of Northeast hunan TANG Daqian, GE Yanming 2022, 36 (3):  417-419.  Abstract ( 232 )   Save With special geotechnical properties, the soft bedrocks such as, muddy and silty sandstone and slate, are widely deposited in the regions of low hill and rolling hill of east Hunan Province. In this paper, several key technical points in the geotechnical investigations are analyzed and discussed. For the broken and strongly weathered layer, the double casing coring along with the vegetable jell as the drilling method should be adopted to improve the drilling quality; when the strongly weathered bedrock is thick, and it can be divided into several sub layers so that the detailed variation of the geotechnical characteristics in the rock mass can be captured. Mudstone lenses are frequently encountered in the soft bedrock and its influence on the stability of the day-lighted rock slopes should be fully investigated. Drainage ditches and French drains should be provided in order to reduce the groundwater level and minimize the cost for the buoyancy construction. Related Articles | Metrics

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Influence of Deep Excavation on the Deformation of Adjacent Pipelines at Various Embedment Depths YE Kejiong 2022, 36 (3):  420-423.  Abstract ( 268 )   Save This paper presents a case history of influence of deep excavation on the adjacent utilities with embedment depths. The cut-and-cover method was used in the Zaozhuang Station of Zhengzhou Transit Project No. 8 Line and the effect of deep excavation on the adjacent pipelines with various embedment depths. The results showed that the deep excavation of the subway station has influence on the deformation of pipeline, and the pipeline with deeper embedment depth is less affected. With the increasing of excavation time, the influence on pipeline will gradually decrease. Related Articles | Metrics

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Review of Developments in Sampling Device and Process the Investigation in Contaminated Soils MENG Junsheng, LI Xiaoling, SUN Shouyi, JIANG Lirong, LIU Yue 2022, 36 (3):  424-426.  Abstract ( 290 )   Save Sampling devices and process are the key factors in the environmental investigation of contaminated soils. This paper compares the aspects of the contaminated soil investigation with the traditional geotechnical sampling and testing procedures. The soil and water sampling devices that are commonly used in different contaminated sites and various soil stratigraphy are reviewed and commented. The key technical procedures in the investigation are also introduced in detail in the paper. The future development of contaminated soil sampling device and drilling process are reviewed. It is concluded that the current soil and water sampling devices should be appropriately modified to meet the requirements of the contaminated soil investigations. Related Articles | Metrics

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Analysis of Combined Utility Gallery of a Shield Tunnel Near a Deep Excavation XIONG Shudan, YANG Lanqiang, XU Da, XIONG Chuyan 2022, 36 (3):  427-431.  Abstract ( 233 )   Save During constant unloading inside a deep excavation, the vertical and horizontal displacements at the adjacent combined utility gallery will occur. When the deformation of the combined utility gallery is excessive, it might cause the leakage at the deformation joints of the gallery and cracks within the utility gallery structure, thus, affect the normal operation of the utility gallery. This paper presents threedimensional finite element analysis results by using commercial software MIDAS GTS NX. The influence of large deep excavation on the deformation of the adjacent combined utility gallery in soft soil area is evaluated. The results of 3D FEM analysis and field monitoring were compared. The results show that the supporting option of bored pile plus a concrete strut (hanging from the bottom) has a good effect on the deformation control of the deep excavation in soft soils. Related Articles | Metrics

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Deformation Characteristics of Deep Excavation Supporting Structures in the Seasonal Frozen Region SUN Yizhe, HUANG Yuhui, ZHAO Xiaolei, LIU Jingjing, WANG Wei, CHEN Junjun 2022, 36 (3):  432-436.  Abstract ( 358 )   Save With the development of economy and the increasing number of highrise buildings, the dimensions of deep excavation projects become larger and larger, and the foundation construction duration becomes longer and longer. Especially, excavated areas in the deep excavation in seasonal frozen soil areas will inevitably encounter the geohazards induced by the cold weather. In order to study the deformation characteristics of supporting structures in the deep excavation in seasonal freezing areas under the effect of freezing and thawing cycles, numerical analyses are performed for the support system of a deep excavation project in Changchun. It is found that the freezing effect will reduce the ground subsident at the top of the excavation; increase the bottom heave at the excavated area and increase the horizontal displacement of the supporting structure and the axial force of the reinforced concrete internal support. After the thawing effect, the ground subsidence, the bottom heave at the excavated area, the horizontal displacement of the supporting structure and the axial force of the reinforced concrete internal support are all greater than those before the freezing. By comparing with the construction monitored data, it is found that the general trend of simulated values and monitored values are consistent, and the effect of freezethaw cycle has produced unrecoverable deformation in the deep excavation supporting structures. Related Articles | Metrics

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Experimental Study of the Effect of Particle Shape on the Permeability in Calcareous Sand HUO Yulong, WANG Xueqing, Jiang Kaifan, WANG Yikun, WU Yongjie, 2022, 36 (3):  437-441.  Abstract ( 320 )   Save The shape of the calcareous sand is often irregular, porous and it is fragile due to its unique biological origin. The influence of the particle shape on the permeability is a question worth of further evaluation. Therefore, this paper selected the calcareous sand and shelly sand of the same grain size distribution and the shape parameters of the two samples through PartAn3D particle morphology measurement were determined. The void ratio was used as the control parameter to perform conventional permeability tests and to compare and analyze the impact of particle shape on the permeability, which initially explained the difference in the permeability caused by the particle shape. The test results show that the length-to-thickness ratio, Pval, and the concavity degree of the calcareous sand sample are smaller than those of the shelly sand sample, while the roundness, sphericity and the circularity are larger than those of shelly sand samples. With the same relative density, the permeability of calcareous sand sample is greater than that of the shelly sand sample. In the medium relative dense samples, the hydraulic conductivity values of the calcareous sand sample and the shelly sand are close to a small difference. In dense samples, the difference in the hydraulic conductivity of the calcareous sand sample and the shelly sand sample decreases with the increase of the relative density. In terms of the influence of the void ratio on the permeability of two different types of samples, when the void ratio is less than 1.45, the hydraulic conductivity increases slowly with the increase of the void ratio; when the void ratio is greater than 1.45, the hydraulic conductivity increases significantly with the increase of the void ratio. Under the same void ratio conditions, the hydraulic conductivity of the calcareous sand sample is greater than that of shelly sand sample, and the difference increases with the increase of void ratio. The reason why the hydraulic conductivity of the calcareous sand sample is greater than that of shelly sand sample under the same void ratio might be explained by the difference in the head loss when the water flows through the sand column per unit length. This difference might be caused by the different particle shape.  Related Articles | Metrics

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Evaluation of Performance of the Lime Improved Iron Tailing Sand Highway Subgrade DING Feng 2022, 36 (3):  442-445.  Abstract ( 296 )   Save Iron-tailing sand, as an industrial waste, would take a significant amount of land for the disposal, along with the local environmental pollution at the disposal site. Therefore, if the iron tailing sand could be used as highway subgrade fill material, it would reduce the disposal area if the strength of the iron tailing sand could be improved the lime to meet the strength and compaction requirements of the subgrade fill material for the expressway construction. The maximum dry density and the other basic physical and mechanical indices of the modified iron tailing sand were tested. Throughout the comparative study, it was found that the strength of the modified iron tailing sand was much stronger than that of the natural tailing sand. The seven-day unconfined compressive strength of the modified specimen after 5 and 10 dry and wet cycles was tested, and compared with the natural tailing sand samples, it was found that the strength of the iron tailing sand would change to different degrees with the increase cycles. When the lime soil ratio reaches 12%, the strength curve maintains a stable trend after several cycles, which indicating that the sample durability also meets the requirements of the subgrade material for the highway construction. Related Articles | Metrics

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Experimental Study on Slaking of Red Clay by the Cluster Analysis MA Jiangmin, LIU Baochen, ZHANG Binghui, XIONG Junhao 2022, 36 (3):  445-451.  Abstract ( 389 )   Save The red clay is widely distributed in Guilin City and its adjacent areas. With the influence of human activities, geological structure and climate, geological hazards related to the red clay slaking occur from time to time. The geohazards might cause significant life and property loss in this area. Considering the slaking of the red clay under the action of water, the laboratory red clay slaking test in solutions with pH values of 2, 7, and 12, respectively, were performed. Combined with the cluster analysis, the test used the time of sample disintegration and the residual volume rate as reference indicators. The systematic cluster analysis in SPSS divided the samples that disintegrate in acidic and neutral solutions into four different categories. Under both acidic and neutral solutions, the disintegration occurred often accompanied by the escape of gas bubbles. Slaking phenomenon is very similar, and the pH value is almost unchanged; the samples that disintegrated in the alkaline solution were divided into two categories, and the sample is completely disintegrated, and its pH value decrease. Throughout the cluster analysis results combined with the experimental observations and the data to summarize the slaking characteristics of various samples under different environments and provided a theoretical basis for the prevention and the control of geological hazards caused by the red clay slaking in the engineering practice. Related Articles | Metrics

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Rapid Determination Method of Soil-Water Characteristic Curve for the Compacted Yan’an Loess WEI Xiaoqi, CHEN Pan 2022, 36 (3):  446-450.  Abstract ( 290 )   Save The soil-water characteristic curve (SWCC) is a curve that describing the relationship between the soil moisture content and the matrix suction, and it is an important constitutive relationship in the unsaturated soil mechanics. The traditional testing method of gradually the applying suction and obtaining the moisture content in equilibrium is usually both time and labor consuming. Based on the recently developed new method of using nuclear magnetic resonance (NMR) technique, this paper presents a method of rapid determining the SWCC of compacted loess and the results are compared with the measured data. The results show that the soil-water properties of compacted Yan’an loess are greatly affected by the initial moisture content and dry density. Both methods have different influence mechanisms. The rapid determination method has a better predictive result for the soil-water characteristic relationship curve of the compacted loess with higher dry density, while the predictive result of soil-water characteristic relationship for the lower dry density soil samples is slightly worse. The main reason is that the higher the compaction density, the closer the measured porous distribution is to the unimodal distribution, and the more accurate prediction results. For the prediction of soil-water characteristic curve with obvious bimodal porous size distribution, the rapid method needs to be further investigated. Related Articles | Metrics

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Influence of Relative Density on the Strength and Deformation Properties of Coral Sand Samples HUANG Xiaofang, MENG Qingshan, JIANG Xue, 2022, 36 (3):  451-454.  Abstract ( 291 )   Save Focused on the special physical properties, a series of triaxial consolidated undrained shear test of different relative density of coral sand samples were performed to analyze the influence of the different relative density on the stress-strain relationship. Throughout the analysis of test results, it is concluded that the density has a significant influence on the stress-strain relationship of the coral sand. With the relative density increase, the peak deviator stress of the sample gradually increases; the secant modulus, E1, increases with the increase of the confining pressure and the relative density , E1 has a good linear relationship with the change of the confining pressure; as the density increases, the strength indices, c and φ values, both increase with the increase of the density, and the density has a greater impact on the cohesion of the coral sand sample and has little effect on the angle of internal friction.  Related Articles | Metrics

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Application of Transient Surface Wave Method for Unit Weight Estimation of Earthwork Backfills ZHANG Shutao, FU Hui, LUO Xiaobin 2022, 36 (3):  462-465.  Abstract ( 236 )   Save The unit weight of earthwork backfills is the key index to evaluate the backfill quality. It is both time and labor consuming to estimate the unit weight by the traditional method, and the test results are significantly affected by the operation factors. In this paper, a large-scale earthwork backfills test results of Ezhou Huahu airport project are presented. The wave velocity of the multi-channel transient surface wave of the compacted backfill material and the dry density results obtained by the traditional irrigation method are compared and evaluated. It is found that there is a good linear relationship between both methods. Therefore, a new method and its calculation formula for estimating the unit weight of the backfill material by the transient surface wave velocity are proposed. Meanwhile, based on the results of many fields screening tests, the applicable boundary conditions for the new method are also recommended. The results of this paper provide an experimental basis for the application of transient surface wave method in the accurate determination of the earthwork quality. Related Articles | Metrics

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Application of Laser Particle Size Analyzer in the Grain Size Distribution Test for Geotechnical Purposes MA Jie 2022, 36 (3):  466-470.  Abstract ( 300 )   Save In this paper, the application of laser particle size analyzer in the geotechnical grain size distribution analysis was evaluated by the repeatability tests and parallel comparative tests. The grain size distribution tests of 88 sets of quaternary marine and continental interactive sedimentary soil samples from Bohai region and Shanghai region were performed by using the traditional method and the laser particle size analyzer methods, respectively. The principle of the data interception is proposed, and the applicable range of grain size is determined in the application of laser particle size analyzer. The test results show that: 1. The average absolute value of the percentage difference of each group obtained by the two methods is less than 8%. the average absolute value of the maximum grade in the entire samples was 5.88%, which was 0.075~0.005 mm; The lowest average value was 0.19%, which was 0.50~0.25 mm grading group. 2. The comparative study shows that the deviation of the results obtained by the two methods is within the acceptable range. The laser particle sizer method has good repeatability, wide grain size measurement range and high accuracy. The laser particle sizer method can be used replacing the traditional method in the geotechnical grain size distribution analysis. 3. The grain size distribution test of laser particle size analyzer determined by the laser particle size analyzer model and test method. Winner 2009 laser particle size analyzer could be measured range: in wet method, it was 0.00001~2 mm, in dry method, it was 0.00001~2 mm, and the traditional method in theory has no minimum measured particle size. Related Articles | Metrics

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Liquefaction Determination Method using CPT Tip Resistance LIN Biming 2022, 36 (3):  471-474.  Abstract ( 213 )   Save This paper presents a new method of liquefaction determination method based on the tip resistance of Cone Penetration Test (CPT) approach in the Shanghai Municipal Code. The linear regression analyses were performed between the clayey content, ρcand the tip resistance, ps, from a large amount of CPT test data from the coastal area of Dafeng area, Jiangsu Providence. So that the tip resistance reference value corresponding to the seismic intensity is established, and then the method for determining the liquefaction of CPT in the coastal Dafeng area is obtained. By comparing and verifying the crimination results with the SPT method, the applicability of this method in the coastal Dafeng area is explained, and it provides scientific and effective liquefaction prediction for future major projects in this area, which has very important reference significance. Related Articles | Metrics

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Estimation of Undrained Shear Strength of Soft Clay Variation Characteristics for the Haitai River Crossing Tunnel by Cone Penetration Tests TAN Benxing, ZHANG Guochao, YU Song 2022, 36 (3):  475-480.  Abstract ( 264 )   Save The random field theory is one of the most effective tools to study the spatial variability of soil properties. Cone penetration tests with tip resistance and shaft friction measurement for Haitai River Crossing Tunnel project are presented in this paper to study the spatial variation of site soft cohesive soils. The tip resistance and shaft friction of 26 CPT locations are analyzed, and the entire project investigation zone was divided into six areas to study the “point characteristics” of strength parameters. The linearly detrended function was used to obtain the stationary fluctuant component, in order to study the spatial variability of strength parameters, the vertical fluctuation scale is calculated throughout three common correlation functions. The results show that the volume of CPT sampling size and its strength parameters are sensitive to the variation of soil mechanical properties, so it is suitable for evaluating the soil spatial variability, and the variation coefficient can be used to divide soil mechanical properties. In the same soil layer, there is a good linear fitting relationship between the tip resistance and the shaft friction. Compared with the other two correlation functions, Markov function has the highest fitting accuracy and is the best fitting model. The variation range of the tip resistance in the vertical fluctuation scale is 0.60 ~ 0.90 m, as well as shaft friction. However, in general, the vertical correlation distance of the cone tip resistance is slightly larger than that of the shaft friction. Related Articles | Metrics

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Testing of Pile Dynamic Parameters Using Large Shaking Table XU Lei, ZHOU Yuming, CAI Kejian 2022, 36 (3):  481-485.  Abstract ( 283 )   Save This paper presents extensive and accurate dynamic parameters testing results on model piles by using a large shake table device. The model tests were performed on model pile foundations with exposed and buried pile caps under vertical, lateral and torsional loads by using forced vibration method. The testing results indicated that the compressive, shear and torsional stiffness, damping ratio in various directions and total mass in vibration of single pile with a buried pile cap are obviously higher than that with exposed pile cap. The test data also showed that the soil surrounding the model pile is also involved in the vibration and the mass would affect the foundation stiffness, but the soil mass could be neglected in the dynamic parameter analysis. The role of soil surrounding the pile is also important to the mass and elastic damping system in the seismic vibration reduction by using shaking table. Related Articles | Metrics

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Practical Application of In-Situ Pumping Test to Determine Coefficient of Permeability of an Aquifer MA Sai, WANG Kang, FU Zhibin 2022, 36 (3):  486-490.  Abstract ( 548 )   Save The coefficient of permeability is predominantly determined by the pumping test. There are many analytical methods to interpret the test results for the coefficient of permeability. In general, the test conditions of the in-situ measurement method are more consistent with the actual subsurface condition than that of the laboratory test condition, because laboratory test method cannot simulate the on-site soil layers accurately. It is necessary to determine the site coefficient of permeability by in-situ measurement for a specific soil layer in an actual project in Beijing. Throughout the dewatering wells around the site, a non-pressure complete well point was used for the pumping test, an average coefficient of permeability of the soil layer in the zone by the groundwater variation in the stage of the deep excavation and foundation construction was measured by the in-situ pumping test. The results show that: (1) after a long period of discharge of groundwater, the groundwater level changes significantly; (2) the actual coefficient of permeability k value of the first aquifer layer measured within the dewatering depth ranges from 40 to 50m/d, which is lower than the empirical value recommended in the survey report. (3) The analysis shows that the cobble stratum filled with medium to coarse sand has a significant influence on the coefficient of permeability, and the long-term drainage is the main reason for the decrease of coefficient of permeability. (4) Comparing with the groundwater inflow to the excavated area, the difference of groundwater inflow of different coefficient of permeability is large, which directly affects the construction cost. Related Articles | Metrics

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Full Spectrum of Soil-Water Characteristics Curve of Guangzhou Granitic Residual Soils XU Yanglin 2022, 36 (3):  491-496.  Abstract ( 310 )   Save Soil-Water Characteristic Curve (SWCC) is a fundamental concept for the studying of the mechanical properties and hydraulic characteristics of unsaturated soils. In this paper, a granitic residual soil in Guangzhou area was used in the laboratory study. The soil-water characteristics and infiltration characteristics of unsaturated residual soils at low saturation (high suction) were investigated by using the salt solution vapor balance method and the filter paper method to obtain the SWCC of residual soils at the full suction stage. The results show that the moisture content of the SWCC curve decreases sharply with the increase suction in the early stage and then decreases slowly in the later stage. In addition, the existing SWCC models were compared with the experimental data to characterize the soil-water characteristics of the residual granite soils in Guangzhou, and the Fredlund-Xing model was found to be suitable for describing the soil-water characteristics of these unsaturated soils. Finally, the soil-water characteristics obtained from the Fredlund-Xing model are combined with the Mualem infiltration model to propose a suitable model for predicting the infiltration coefficient of unsaturated granitic residual soils in Guangzhou. The research results of this project provide an important basis for the further research on the mechanical and hydraulic properties of unsaturated granitic residual soils in Guangzhou. Related Articles | Metrics

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Experimental Study on Anchorage Mechanical Characteristics of Wind Turbine Foundation Ring GONG Jianwu, PETER George, WEN Bingyan 2022, 36 (3):  497-500.  Abstract ( 233 )   Save The improvement of wind turbine foundation bearing capacity plays an important role in ensuring the safe operation of wind turbines and wind power efficiency. The pull-out test of the anchoring effect between the foundation steel ring and concrete was carried out to study the mechanical properties and failure characteristics of the foundation steel ring anchorage under different combinations of end plates and transverse ribs. The test results show that for the stress state of the concrete of the wind turbine foundation, the transverse rib structure is better than the end plate structure. The end plate and transverse rib structure are set in the wind turbine foundation at the same time, which can give full play to the protective effect of the end plate structure and significantly improve the ultimate bearing capacity of the wind turbine foundation. The research results can provide a reference for the design and construction of relevant wind turbine foundation project. Related Articles | Metrics