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30 April 2023, Volume 37 Issue 2 Previous Issue    Next Issue

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Vegetation Restoration Method of Weathered Migmatitic Granite Slopes in Lincang Area YU Yang, QI Ziyuan, YANG Xin, YAN Song, 2023, 37 (2):  161-165.  Abstract ( 303 )   Save The weathered migmatitic granite slopes are widely distributed in Lincang area. It is difficult to restore vegetations after the slope excavation for the expressway construction. The resultant erosion hazards consequences are serious. The field investigation and analysis of the vegetation restoration and erosion control of dozens of slopes of Mo-Lin Highway are presented in this paper. The vegetation restoration and erosion control conditions of two typical slopes with one high slope and the other medium-low slope are investigated, evaluated and the results are introduced in the paper. The main internal and external factors affecting the slope erosion of the migmatitic granite slope are summarized in accordance with the field investigation results. For the different types of migmatitic granite slopes and different locations on the slopes, reasonable vegetation restoration methods are proposed, which can effectively minimize the slope erosion hazard. The effectiveness of the vegetation restoration method is verified by an engineering slope case istory. Related Articles | Metrics

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Seismic Response Analysis of the Supporting Structure for a Subway Station Deep Excavation ZHAO Tengyun, NIU Ruipeng, WANG Xiaopeng 2023, 37 (2):  166-169.  Abstract ( 277 )   Save This paper presents a case study of the effect of surfaced traffic loads on the dynamic response of a subway train station supporting structures. The results show that: in addition to the design static load, the prestressed steel struts designed in accordance with the current code can still taking the vibration load and maintain the stability of the deep excavation. When considering the traffic load on the surrounding surface, it is necessary to design the deep excavation support structure in strictly accordance with the existing specifications. During the installation of the prestressed steel support, special attention should be paid to the influence of the supporting structure, assembling method, prestressing method and prestressing time on the supporting effect. Related Articles | Metrics

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Comprehensive Investigations of a Complex Subsurface Conditions with Karstic Sinkholes LI Yongxin, ZHANG Tanggui, DENG Guanmin, QU Xingwen 2023, 37 (2):  170-172.  Abstract ( 386 )   Save The geotechnical engineering in Karstic sinkholes area typically involves aspects of hydrogeology, engineering geology and environmental geology. A single conventional investigation method is difficult to solve these complex problems accurately and reliably. Based on the data collection, the means of geological mapping, geophysical exploration, drilling and other field as well as laboratory geotechnical tests are comprehensively applied to explore the evolutional characteristics, formation mechanism and development trend of sinkholes, and reveal the engineering hydrogeological conditions for construction giant elevators in the karstic sinkhole area. The results show that the development of sinkhole is closely related to lithology, tectonic structure, and groundwater conditions. The development of a sinkhole is relatively matured and in a stable period. The safety of the hazardous rock and slope stability can be minimized and mitigated. The comprehensive investigation provides a reliable technical support for a smooth progress of the project and can provide reference for similar projects in karstic sinkhole area and other karst areas. Related Articles | Metrics

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The Excavation and Support of a Rock Slope and Its Stability Analysis WANG Fei, SHI Xubo, FENG Shikai 2023, 37 (2):  173-177.  Abstract ( 727 )   Save With the continuous development of urban areas, there are more and more rock slope excavation and support problems, and the research on the stability of the slope excavation process becomes more and more important. This study intends to establish a Midas-GTS-NX three-dimensional numerical analysis model for a rock slope of a subway station in the mountainous area and analyze the stress distribution within the slope and the settlement of the road surface at the crest of the slope during the different stages of rock slope excavation. The study results show that the stability factor of safety of the slope is 1.10 in the initial state of the slope, and it is in a marginal stable state. The excavation of the slope causes a large stress concentration phenomenon at the bottom of the excavation area, but the shear stress value less than the shear strength value of the sandstone rock structure, the foundation excavation project will not have shear failure; due to the reinforcement of the soil at the top of the slope, the displacement and deformation value of the crest of the slope during the excavation process is small, which will affect the road surface. The rock slope structure will not be damaged; for the horizontal displacement value, tangential displacement value and settlement value of the upper retaining wall of the slope at different slope excavation stages, the simulation results are all less than the on-site monitored values, but the trend of the simulation results is the same as the on-site monitored data. The same, and the displacement values of the retaining wall during the slope excavation are all within the stable range. These study results can provide references for the similar type of projects. Related Articles | Metrics

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Deformation Control Methods of a Deep Excavation Near a Large Diameter Pipeline  WANG Ganggang 2023, 37 (2):  178-181.  Abstract ( 214 )   Save With the rapid development of China's urbanization process, the development and utilization of urban underground space has entered the fast lane. The surrounding environment of deep excavation engineering is more and more complex, and there are more and more deep excavation projects near the large diameter municipal pipelines. As an important urban infrastructure, the protection requirements of these large-diameter municipal pipelines are much higher than other conventional utilities. How to control the influence of deep excavation on the adjacent large diameter pipeline has become a key challenge faced by many deep excavation projects. This paper presents a deep excavation project of Chenming Culture Square in Xinzhuang Business District of Shanghai. Several targeted control measures are compared with the numerical simulation results. Related Articles | Metrics

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Deformation Characteristics of Parallel Shielded Tunnels Passing Through Existing Bottom Reinforced Concrete Frame-Masonry Structure Building ZHANG Jiantao 2023, 37 (2):  182-187.  Abstract ( 320 )   Save A bottom reinforced concrete frame and masonry mixed structure in Changchun is next to a proposed parallel shielded tunnel excavation. Its deformation characteristics during the tunnel excavation is studied with the combination of construction monitoring and the numerical analyses methods. The stiffness of this mixed reinforced concrete frame and masonry structure has the characteristics of “upper flexible and bottom rigid” and the impact of the total and differential settlement on the performance of this structure are investigated throughout the analysis of these independent footings. In the construction process of the subway section excavation, the settlement of this structure is greatly affected by the construction of the upper portion of the shielded tunnel, but less affected by the construction of lower portion of the shielded tunnel. In the construction process of the parallel shielded tunnel that crossing the mixed structure building, the construction sequence of the first constructing the lower portion of the shielded tunnel and then constructing the upper portion of the shielded tunnel can effectively control the settlement and differential settlement of the above building and reduce the impact on the existing building structure. Related Articles | Metrics

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Side Frictions of the Large Diameter Piles in the Coral Reef Strata ZHANG Rong, YU Song, ZHANG Guochao, LIU Jianping 2023, 37 (2):  188-192.  Abstract ( 231 )   Save Large diameter piles have the advantages of high axial capacity and small settlement and are increasingly used in large bridge projects across the river and sea. The coral reef limestone formed by bio-deposition has weak cementation and high porosity characteristics, when the pile foundation of the bridge rock-socketed in this stratum, the side friction has its own characteristics and the traditional method of estimating the pile side friction resistance and axial capacity is not applicable. Combined with a bridge project in Maldives, the characteristics of the side friction resistance and axial capacity of the large diameter bridge pile foundation in the coral reef strata are studied by means of laboratory model test and field self-balancing load test. The test results are compared with the code suggested values. The results show that the coral reef stratum has large side friction resistance and axial capacity, and the large diameter pile foundation can be used as a common foundation form. The side friction of the reef limestone piles has experienced four stages: contact compaction, elastic shear, shear failure and friction shear. The strength of the reef limestone has a large structure, and the drilling process has a great disturbance to the reef limestone stratum, which makes the mechanical properties of the reef limestone significantly reduced. Related Articles | Metrics

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Investigation of a Railway Embankment Settlement XUE Shuangbing 2023, 37 (2):  193-196.  Abstract ( 275 )   Save The settlement of a railway embankment between Station DK56+043 and +150 is presented in this paper. The railway embankments are monitored, and the data are analyzed by applying the subsurface soil and groundwater conditions so that the factors that triggered in the settlement are evaluated. The deformation of the embankment and the subgrade soils are correlated with the total settlement at the embankment so that the embankment settlement control measures are proposed. The following conclusions are obtained: the compactive deformation due to the self-weight the embankment and the subgrade fills are observed. Most of the settlements are due to the compaction deformation of the less compacted soil layers; there is a small portion of the settlement is due to the consolidation settlement. Based on the settlement rate of the monitored data and the groundwater level variations; the consolidation settlement is due to the lowering the groundwater level. Related Articles | Metrics

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Analysis of Safety Impact of New Railway Subgrade Passes Through an Existing Highway Bridge XIN Jian 2023, 37 (2):  197-200.  Abstract ( 290 )   Save The new railway subgrade passes through the existing highway bridge in the form of embankment. Aiming at the safety impact of the subgrade on the bridge, this paper presents a case history of a new railway project under passing the highway bridge and effect of the railway embankment on the bridge safety is evaluated. The three-dimensional numerical analysis model is established by using the finite element software Midas GTS. The three types of embankments, namely, slope at both sides, U-shaped structure, U-shaped structure and sheet pile, are compared and analyzed. The results show that the risk control effect and the economy of the U-shaped structure scheme are better. The maximum value of the additional horizontal deformation in the bridge direction is 2.863mm, the maximum value of the additional vertical settlement is 1.189mm, and the maximum value of the additional horizontal deformation in the direction of the bridge is 0.076mm, which meets the requirements of the relevant design codes for the deformation and displacement limits of the existing bridge piers. In addition, the combination of the continuous deformation monitoring during the railway construction and the operation can ensure the operation safety of the existing highway bridges. Related Articles | Metrics

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Application of the Combined Supporting and Anchoring System for a Deep Excavation in Soft Soils CAO Qiang, MEI Qinghai, JIANG Qigang, PENG Peng 2023, 37 (2):  201-205.  Abstract ( 295 )   Save Deep excavation engineering is a temporary supporting structure for the excavation of underground construction. It has the characteristics of the short service life, and the supporting structure will be out of service when the underground construction is completed. Therefore, the improvement of the cost effectiveness of the excavation supporting is becoming an imperative requirement of the entire construction industry. With a high construction cost, the strong soldier pile with a strong stiffness of the supporting structure is a major design trend of the urban deep excavation projects due to the restrictive requirements of the adjacent urban environments. In the deep excavation in thick and soft cohesive soil, the deformation and global stability could be adjusted the solider pile length, diameter and the number of steel reinforcement bars. The combined support and anchor system is a support system in which the support and the ground anchor are used simultaneously on a supporting system. Adding the ground anchor to the soldier pile supporting system can improve the stress and deformation of the support soldier piles, which can effectively reduce the overall construction cost of the support structure while meeting the safety requirements. Related Articles | Metrics

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Discussions of the Advanced Treatment of the Deformed Tunnel Sections Excavated by TBM  ZHANG Hui, ZHAO Jian, YANG Fan 2023, 37 (2):  206-208.  Abstract ( 228 )   Save To minimize the construction safety hazards induced by the TBM (Tunnel Boring Machine) excavation in the unfavorable geological conditions, the application of the safety monitoring and the early warning technology of TBM construction in a hydraulic tunnel is studied in this paper. In view of the specific difficulties of the project, this paper adopts the monitoring scheme of steel plate meter to effectively perform the engineering safety early warning; The monitoring results indicated that the rare and the bottom of the shielded support did not meet the stability requirements of the tunnel cavities, and pretreatment techniques such as reinforcement of the surrounding rock mass were used to reduce the number of TBM jams and minimize hazards such as buried machines, which ensure the stability of the excavated spacing and the safety of crew and equipment. Related Articles | Metrics

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Settlement Analysis of Anchor Jacked Pile Reinforcing of the Existing Building Foundations SONG Xiaoguang 2023, 37 (2):  209-212.  Abstract ( 542 )   Save The settlement induced by the anchor jacked pile reinforcing the existing building foundations is divided into immediate settlement and settlement after construction. The immediate settlement is induced by the lateral deformation and the strength reduction of the surrounding soft soils. Results of the finite element analysis show that the foundation heave or settlement change caused by the lateral soil squeezing is related to the upper load and the properties of foundation soil within 15m below the ground, the worse the soil property, the larger the settlement, that is, the major factor of the settlement in most of the reinforcing projects. At the same time, the project case history shows that, there is a hard soil layer under the foundation, which may be heaved due to soil squeezing around the pile. The worse the soil property is, the larger the influence range of immediate settlement is, the lower the strength of soil mass and the force bearing area are, thus increasing the settlement. According to the measured settlement data of typical buildings, the building the immediate settlement consists of 80% of the total settlement. Combined with the characteristics of the anchor jacked pile construction, the post construction settlement cannot be ignored. Based on immediate settlement characteristics, the “suspended loadingcontrollock up loading” procedure is proposed to minimize the settlements of buildings. Related Articles | Metrics

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Stability Analysis and Emergency Remediation of a Cut Slope Near an Active Expressway XIONG Qihuan, YANG Zhao, MAO Yongqiang, YU Jin, CHEN Shihao 2023, 37 (2):  213-216.  Abstract ( 247 )   Save The instability of the cut slopes is a common geological hazard of the expressway under operation. Back pressure at the toe of the slope can quickly restrain the deformation of the potential landslide and ultimately improve the stability of the cut slope. However, the phenomenon that the horizontal deformation of the slope near the back pressure area does not converge in a short period of time often occurs, and reason that causing the sustained deformation is still unclear. Therefore, this paper presents the case history of a cut slope instability of an expressway at Station K46. The s of the slope instability and slope deformation induced by emergency remediations are evaluated. The results of the field survey and the theoretical analysis show that plugging of the seep holes leads to a poor drainage of groundwater, which is an important contribution factor to the slope instability. The traffic load on the top of the slope increases the driving force of the landslide, which leads to creep deformation of this cut slope. Related Articles | Metrics

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Design and Study of a Very Deep Excavation Support Above a Subway Tunnel XU Chengbin 2023, 37 (2):  217-222.  Abstract ( 283 )   Save With the rapid development of the urban subway, more and more deep excavation for new projects needs to be installed in the safety protection zone of the active subway. The active Metro No 4 Line under passing the proposed OCT Wuhan Plot P (2018) 158 project. The distance between the supporting structure and the regional subway tunnel structure is only 11m, and the distance from the bottom of the deep excavation to the top of the subway tunnel varies from 2.6 to 8.2m. The surrounding environment of the deep excavation is extremely complicated, and the deformation control requirements for the excavation support structure are very restrictive, which poses great challenges to the design and construction. On the other hand, the soil fills up to 15 meters in height within the proposed excavated area needs to be unloaded. The control and remediation of the heaving deformation of the tunnel structure under unloading conditions is also an important part of this project. According to the characteristics of this project, the design of the deep excavation is based on the principles of safety, reliability, economic rationality, constructability, and construction schedule. For the first time in Wuhan area, the scheme of “upper unloading + soldier pile +a layer of reinforced concrete waler beam” is proposed and adopted in the deep excavation support design of the metro protection area. At the same time, to control the tunnel heaving deformation induced by the upper unloading of the regional subway tunnel, it is proposed to use perforated pipe grouting to reinforce the poor soil layer above the tunnel. The strength of the surrounding rock mass is effectively improved, and the heaving deformation of the subway tunnel during unloading is reduced. The monitoring data during the entire dep excavation construction process shows that all the monitoring data are within the allowable range and meet the requirements of the subway impact assessment, which can be used for the reference by similar projects. Related Articles | Metrics

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Stability Analysis and Reinforcement Measures of a High Rock Slope LIU Yunhao 2023, 37 (2):  223-226.  Abstract ( 294 )   Save Based on geological conditions of a high rock slope, the potential failure mode of the slope is evaluated, which belongs to the sliding failure along the structural plane. Then, the stability analysis model is established, and the rigid M-P method is utilized to analyze the stability of the high rock slope. Furthermore, the high rock slope was reinforced by using ground anchors. The stability was also assessed after the reinforcement. The analytical results show that, after the excavation, the high rock slope was unstable under the three working conditions, namely, natural state, heavy rain, and earthquake conditions. Moreover, the potential failure characteristics was analyzed, the stability of different potential sliding body was evaluated, and the most dangerous sliding body was determined. After the reinforcement, the high rock slope met the safety requirements of the relevant specifications. The construction recommendations are proposed when the slope was excavated and reinforced, which can provide the construction reference for similar the high rock slope. Related Articles | Metrics

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Analysis of the Geotechnical Characteristics of Bioclastic Layer in Marine Geomorphology LI Chaowei 2023, 37 (2):  227-230.  Abstract ( 266 )   Save Throughout the geotechnical engineering investigation of a marine secondary terraces site in Haikou City, Hainan Province, this paper evaluates the geotechnical engineering characteristics of bioclastic layer by various comprehensive means and proposes the selection of the basic criteria under this geological condition, to provide reference for geotechnical engineering investigation of similar marine geomorphologic strata. Related Articles | Metrics

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Compressive Modulus Prediction Using Generalized Regression Neural Network OUYANG Lei, DENG Xiping, HE Lijun, LIU Jiayin, CHEN Peng 2023, 37 (2):  231-235.  Abstract ( 162 )   Save The compression deformation is an important factor that affecting the magnitude of the settlement. If its value is too large, it will induce the major geological hazards. The compression modulus is an important index. Predicting the magnitude of the compression modulus is of great significance for preventing geological hazards. Throughout basic principles of the generalized regression neural network, with the conventional soil property indicators as the input vector and the compressive modulus (ES1-2) as the output vector, the maximum and minimum relative errors of the network output results are 10.73% and 0%, respectively. The mean square error is 0.6831, which is in good agreement with the true value, so the model can be used to predict the compressive modulus. Comparing the mean square error under different smoothing factor values, the mean square error at 0.9 is smaller than other values, so the smoothing factor value should be selected correctly during the parameter setting process. To prove the performance of the prediction model throughout the generalized regression neural network, compared with other algorithms based on the mean square error, the mean square error of the generalized regression neural network prediction model is less than that of other algorithms, indicating that the prediction model throughout the generalized regression neural network has superior performance based on prediction models constructed by other algorithms. Related Articles | Metrics

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Formulations for Predicting Compression Modulus in Soil Mechanics FAN Qinglai, WU Yue, MA Siqi, LIU Zhihao 2023, 37 (2):  236-240.  Abstract ( 508 )   Save The compression modulus is an important concept in the soil mechanics, which is often used to evaluate the compressibility of the soil and estimate the final settlement of foundation soil. At present, there are different types of definition or formulations of the compression modulus in different versions of textbooks or design codes domestic and abroad, which is easily to induce the ambiguity in the academic and in the engineering practice. This paper firstly analyzes the various definitions of the compression modulus, and then discusses the different derivation processes of two expressive formulas, throughout a set of one-dimensional compression test data in the existing textbooks. The results show that the two formulas are consistent in general, but different strain measures are utilized. When the applied compressive pressure is not very high, there is little difference between the results from the two formulas. Only when the applied pressive pressure is very high, there is a significant difference between them. From undergraduate education point of view, it is suggested that the engineering strain should be used in the derivation of formulas for the estimating of the compression modulus in the soil mechanics. Related Articles | Metrics

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Numerical Simulation of the Ultimate Bearing Capacity of Geomaterials for High-Rise Buildings ZHANG Huineng 2023, 37 (2):  241-244.  Abstract ( 214 )   Save To solve the problem of the large difference between the simulation results and the actual value when the traditional numerical simulation method is used to simulate the limit value of the bearing capacity of the geomaterials for the high-rise buildings, which causes the low numerical simulation accuracy, a numerical study of the limit value of the bearing capacity of the geomaterial for the high-rise building is presented in this paper. A new numerical simulation method is proposed by establishing the bearing capacity model of the geomaterial for the high-rise building, setting constraint conditions and evaluating the ground stress, and simulating the numerical change of bearing capacity under different base conditions. Experiments have demonstrated that the new numerical simulation method can obtain results closer to actual values in practical applications, and the simulation accuracy can be significantly improved, which can provide a more accurate numerical reference basis for the construction of high-rise buildings. Related Articles | Metrics

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Study on the Stability of Soft Foundation Based on Straw Drainage Horizontal Reinforcement  CHEN Xiaojun, WANG Shan, CHEN Xianyong, GAO Wenchuan, YIN Li 2023, 37 (2):  245-248.  Abstract ( 148 )   Save To study the stability of the soft soil with the reinforced straws, this paper uses the numerical simulation method to study the reinforced soft soils. The influence of reinforcements is investigated by analyzing the soil with and without the reinforcement, the reinforcement layers and the reinforcement spacing within the soft soils. The simulation results show that reinforced can change the failure mode of the soft soils from the overall shear failure to the punching failure. The number of reinforcement layers and the reinforcement spacing have less effect on the sliding failure of the reinforced soft soils. Reinforced straw can effectively improve the bearing capacity of the soft soils, which will improve with the increasing o the reinforcement layers. And the smaller the bar spacing, the better the reinforcement effect. Related Articles | Metrics

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Numerical Simulation of the Optimization of the Precast Arch Slope Protection Structure ZHOU Pingting 2023, 37 (2):  249-252.  Abstract ( 240 )   Save The excessive weight of precast blocks will seriously affect the efficiency of the workers moving them by hands, which will affect efficiency of the construction of slope protection structure. To study the influence of reducing the weight of precast blocks on the structure, four types of precast arch skeleton slope protection structure models are established by using the ABAQUS finite element software. Namely, V1 is the original type (the arch skeleton is composed of precast blocks A, B, C and D); V2 is the improved type (removing the upper stop of precast block C on the basis of the V1 type), V3-1 is another improved type (trenched and reducing the size of precast blocks A, B and C on the basis of the V2 type, and cutting off and reducing the size of precast block D), V3-2 is the improved type (trenched and reducing the size of precast blocks A, B, C and D on the basis of V2 type), The stress and displacement of key points of each version of the prefabricated arch skeleton slope protection structure model are compared and analyzed. The results show that: V3-1 type is the lightest structure; The stress in the V3-2 structure is the largest, and the rest are V3-1, V1 and V2 in turn; In each type, the stress of precast block C is the largest, followed by precast blocks A and D, and B is the smallest; V1 type has the strongest resistance to the deformation, and V2, V3-2 and v3-1 types decrease in turn. Related Articles | Metrics

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A Review on Evaluation of Different Types of Soil Landslides Triggered by Rainfall GUO Hanyu, LI Cong, ZHANG Zihao, WANG Jiajun 2023, 37 (2):  253-259.  Abstract ( 435 )   Save For different soil types, there are obvious differences in the formation mechanism, deformation and failure characteristics and development conditions of the rainfall-triggered landslide. At present, the classifications on the rainfall-induced landslides have not been systematically distinguished based on the types of landslide soil. It is of great significance to perform the research on the rainfall-induced landslides in different type of soils. In this paper, the landslide mechanism, failure mode and early warning criterion of different type of soil slopes under the rainfall are summarized in detail. These soils include the unsaturated soil, loess, gravelly soil, expansive soil, and other special soils. The current main landslide problems in these soils are discussed, and the future research needs are proposed. It is concluded that the characteristics of different types of soil landslides under rainfall conditions, the process of rainfall-induced deformation and failure of special soil landslides and the early warning criteria of rainfall-induced different soil landslides need to be further studied. The research finds are of a reference value to the research and minimize the rainfall-triggered landslides. Related Articles | Metrics

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Study on the Effect of the Unloading and Loading in the Deep Excavation on Underlying Shielded Tunnel JIA Minghui, LIANG Yankun, HU Yu 2023, 37 (2):  260-265.  Abstract ( 188 )   Save To study the influence of the unloading loading process of the deep excavation on the underlying shielded tunnel, the Midas GTS NX is used to establish a three-dimensional numerical analysis model of the shielded tunnel and the deep excavation in a subway construction project near Beijing. The numerical simulation is performed based on the specific engineering geological characteristics, geotechnical parameters, excavation support type etc. The analytical results indicate that, the distribution patterns of the displacement and stress of the shielded tunnel by the ratio k of the distance from the bottom of the excavation to the centerline of the tunnel and the diameter of the tunnel during the unloading-loading construction process of the excavation are analyzed. The results show that: the excavation unloading loading construction has little effect on the stress of the underlying shielded tunnel, but it has great effect on the deformation of the top of the underlying shielded tunnel and changing the distance between the bottom of the excavation. The horizontal axis of the underlying shielded tunnel can effectively slow down the deformation of the shielded tunnel during the construction. The k is in the range of 4.0-4.5 has little effect on the displacement of the tunnel. Related Articles | Metrics

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Evaluation of Sandstone Characteristics of Early Silurian Fentou Formation in Wuhan QUAN Feng, ZHENG Siwei, ZHU Fanji, DENG Qingjun 2023, 37 (2):  266-269.  Abstract ( 747 )   Save The Silurian Fentou Formation is widely distributed in Wuhan, and formation consists of mainly argillaceous siltstone, siltstone, and silty mudstone in the area. Based on the microscopic thin section mineral composition identification, rock sample description and uniaxial compressive strength tests, the mineral composition and the engineering properties of quartz fine sandstone and quartz sandstone with bedrock in the Wuhan area of the Fentou Formation are comprehensively studied. The results showed high quartz and feldspar contents in the bedrock mineral composition and high saturated uniaxial compressive strength in the engineering properties. These characteristics are obviously different from the mudstone of the Fentou Formation. However, they are similar in appearance, which is the reason for easily misclassification of the bedrock. It should be determined as the fine sandstone rather than the mudstone. The exposure of the quartz fine sandstone and the quartz sandstone with rock debris has enriched the bed rock types and stratigraphic relationships of the Fentou Formation in Wuhan. Based on the types and the characteristics of fossils in the lower layers of the Fentou Formation, the geological age of the Fentou Formation in Wuhan should be Early Silurian. Related Articles | Metrics

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Analysis of Basal Heave Stability for Excavation in Soft Clay WANG Li 2023, 37 (2):  270-274.  Abstract ( 304 )   Save The analysis of the basal heave stability for the excavation is the core of deep excavation engineering design in the soft clay, which not only relates to the stability of the excavation and the safety of the surrounding environment, but also affects the construction cost of the excavation project. In this paper, the analytical methods, and applicable conditions of the basal heave stability for the excavation are combed. Combined with the engineering examples, based on the circular slip failure mode in the limit equilibrium method, the influence of the embedment ratio of the supporting structure, the position of the lowest support, the reinforcement in the excavation and the size of the excavation on the basal heave stability of the excavation are analyzed. The results show that increasing the embedment ratio of the supporting structure, reducing the distance between the lowest support and the excavation, and increasing the soil reinforcement at the excavation can effectively increase the basal heave stability of the excavation; For the narrow excavation with small width, the space constraint effect should be considered. If the traditional circular slip mode is too conservative, it will cause a large construction cost waste. Related Articles | Metrics

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State of the Art Review of the Shear Strength of Unsaturated Soils JIA Lingci, LIU Zhen, LI Kaiqiang, GUO Yinzheng 2023, 37 (2):  275-278.  Abstract ( 304 )   Save The shear strength of soils is an important theoretical basis for the design and analysis of geo-structures in the engineering practice. For the unsaturated soil, because its microstructure is more complex than that of the saturated soil, the shear strength is more difficult to determine. To determine the shear strength of the unsaturated soil, many scholars have studied the microstructure, the expression form and the measurement of unsaturated soils. Among them, the soil-water characteristic curve is of the great significance, and the soil will have obvious influence on the soil-water characteristic curve after the dry and wet cycle, which is an important basis for studying the shear strength of unsaturated soil. To deepen the understanding of the shear strength of the unsaturated soil, the current progress of the shear strength research of the unsaturated soil was described by the reviewing many literatures, and the shear strength formula in recent years was summarized, and the direction for future research was suggested. Related Articles | Metrics

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A Characterization Study on Coral Sands Interface Shear Practice Breakage YAO Qi, YU Jianmin, ZHENG Hongjian, WEI Houzhen, CHEN Pan, LI Huan 2023, 37 (2):  279-283.  Abstract ( 250 )   Save The interaction between the coral sand and structures widely exists in the island-reef engineering practices. Due to the low structural strength and fragility of coral sands, it is prone to the particle breakage under the external loads, resulting in more complicated mechanical properties of the interface. Through the ring shear tests of the coral sand-steel plate interface and the comparison with the quartz sand, the particle breakage evolution, and the particle shape change rule of the coral sand interface after the shear are revealed. The results show that, under the same conditions, the content of small particles produced by the coral sand is significantly higher than that of the quartz sand, and there is a critical vertical pressure of 300 kPa and 200 kPa for the coral sand with 0.5-1 and 1-2mm particle sizes, respectively. When the vertical pressure is higher than the critical pressure, the impact of the vertical pressure on the PSD curve is significantly reduced. The crushing rates of the coral sand and the quartz sand increase with the increase of the vertical pressure. The trends demonstrate an exponential function relationship and linear relationship with the vertical pressure respectively. After shearing, the particle shape develops from the irregular to rounded, and when the vertical pressure is large, the particle shape of the coral sand and the quartz sand is relatively close to each other, and both tend to be rounded. Related Articles | Metrics

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Determining Characteristic Value of Bearing Capacity of Shallow Sand Foundation LI Jian 2023, 37 (2):  284-287.  Abstract ( 478 )   Save In geotechnical engineering investigation of a shallow sand foundation site, to determine characteristic value of the bearing capacity, a variety of in-situ tests were used including the standard penetration test, the heavy-duty dynamic penetration test, the portable cone sounding test and the shallow plate loading test. Throughout these in-situ tests results, the corresponding characteristic value of bearing capacity were obtained. The analysis reveals that, at site without sufficient engineering experience, the determination of the bearing capacity by a single in-situ test result has fundamental flaws. There are differences in bearing capacity results by different in-situ tests and explore possible explanations for the differences. The shallow plate loading test is of high reliability and has been applied widely in the determination of the bearing capacity value. The comprehensive analysis and discussion on the characteristic value of bearing capacity could improve the safety and economics for the foundation design. Related Articles | Metrics

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The Deformation and Stability Evaluation of High-Fill Slopes in High Cutting Area SONG Dingfeng, XU Junjun, HU Jun, ZHANG Zhenping, FU Xiaodong 2023, 37 (2):  288-294.  Abstract ( 478 )   Save With the increase of urbanization construction in mountainous areas in China, the problems of stability of high-filled slopes, foundation settlement and deformation induced by the hill cutting project are becoming more and more prominent. In this paper, the study on the deformation and stability assessment of the high-filled slope are performed comprehensively using the mechanical property test, finite element simulation, limit equilibrium analysis, and automatic construction monitoring in the Hejia Poverty-Alleviation Industrial Park in Yunxi County, Shiyan City, Hubei Province. The evaluation results show that the maximum settlement at the site during the time-step filling process appears in the surface area. The settlement pattern shows the maximum settlement is at the center and gradually decreasing with the increases with the backfill depth and horizontal distance, with a more obvious spatial influence range. The factor of safety is 2.531 after the backfill. The high-filled slope is in a safer state. However, considering the influence of the subsequent rainfall and the construction load, engineering measures should be applied consequently. The slope deformation was observed occurring mainly within 10 m below the ground surface by combining the long-term monitoring data of settlement and the inclination measurement. The results can provide technical and practical experience for the risk assessment, the geohazard prevention and the control of high-filled slopes in the hill cutting project. Related Articles | Metrics

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Measurement Method and Experimental Study of Karst Rock Cavity Volume XU Guanyu, CHEN Junsheng, WU Bingxin 2023, 37 (2):  295-299.  Abstract ( 460 )   Save In the treatment of the urban karstic rock cavities, grouting is often used to fill and to reinforce the karstic rock cavities. However, it is difficult to obtain the volume information of the cave and the grouting quantity is difficult to control. Therefore, the key to fill the rock cavities is to obtain the volume information of the karstic rock cavities. Based on the experimental principle of the ideal gas state equation, a method of the volume measurement for a closed dry cave is proposed by using the method of the gas injection pressure excitation. That is, the volume of the cave is estimated by measuring the change of the air pressure and the temperature before and after the gas exchange between the model of cave and auxiliary measuring device. The simplified test principle is verified by the CFD software FLUENT. The experimental equipment is designed for the indoor test. The test results verify the feasibility of the simplified principle and the operability of the test device. This method is simple in both principle and application and has the application potential of the cavity connectivity judgment, size estimation and the cave volume estimation. Related Articles | Metrics

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Experimental Study and Analysis of the Physical Properties of Poyang Lake Soft Soils CHEN Youhua, LIU Ziyi, LIU Mingming, LEI Zuxiang 2023, 37 (2):  300-304.  Abstract ( 188 )   Save In recent years, with the rapid development of economy and engineering technology, the number of highway transportation projects such as bridges on the soft soils has increased dramatically. The requirements for the soft soil treatment have also become more restrictive. In view of the particularity of the lacustrine soft soils and the demands from engineering projects, a series of geotechnical investigations were conducted on the lacustrine soft soils through the on-site soil testing, including density, moisture content, specific gravity, Atterberg Limits and permeability tests. The experimental results show that the Poyang Lake soft soil is a typical lacustrine soft soil. There exists a deep silty soil in this area, which has the characteristics of the large water content, low strength and poor permeability. The study results will be used for the future treatment of the Poyang Lake soft soils and for the value of the engineering parameters. Finally, the correlations among the physical properties of the silty soil in the Poyang Lake area are analyzed.  Related Articles | Metrics

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Analysis on Self-Balanced Method for the Bi-Directional Loading Test on Cast-In-Placed Bored Piles ZHANG Zhaobin, HAN Wenyong, ZHANG Kaiwei, LI Fulai, GUO Honglin, GU Liqiang 2023, 37 (2):  305-310.  Abstract ( 331 )   Save The deformation-loading characteristics of the cast-in-place reinforced concrete piles are evaluated throughout the bi-directional loading tests and the loading results are compared with the conventional top-town loading test results. When the test pile reaches the limiting state, the tested end bearing resistance results from the bi-directional loading test is usually greater than that of from the conventional pile loading tests and the side friction values are similar in both testing methods. In the bi-directional loading tests, the side friction values are different in the upper portion and the lower portion of the testing device. Usually, the tested mobilized side friction in the upper portion is less than the limiting value tested in the conventional top-down loading tests and the mobilized value in the lower portion from the bi-directional loading test is greater than that of from the conventional loading test. An improved equivalent top-down loading-settlement curve conversion method is proposed by comparing the pile top settlement in the conventional loading test and the deflection in the upper shaft in the bi0directional loading test. It is found that the proposed method is more accurate than the code suggested method. Although the converted equivalent top-down settlement-loading curve predicts larger pile settlement than that of the conventional loading test, the deflection-loading curves from both test methods have similar trend and it is demonstrated that the bi-directional loading test can provide an effective loading test results for the pile design.  Related Articles | Metrics

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Laboratory Model Test Study of Side Friction Reduction Material for Concrete-Soil Interface RAO Weisheng, WANG Xinlong, MA Chao 2023, 37 (2):  311-314.  Abstract ( 148 )   Save By wrapping the side friction reduction material outside the caisson, the side friction resistance of the caisson during sinking installation can be reduced. In order to study the side friction reduction effect of the different side friction reduction materials, namely, silica gel, rubber, polytetrafluoroethylene, iron sheet, were selected for the laboratory model test. With the contact material type as a single variable, the relative side friction between different friction reduction materials and the adjacent soil is obtained. The test results show that the side friction between PTFE, rubber and soil is similar, and the friction reduction effect is satisfactory, which has the engineering application value. The relevant research conclusions can provide basis for the selection of sinking aids for the caisson installation. Related Articles | Metrics

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Experimental Study on Unconfined Compressive Strength of Water Glass Modified Recycled Aggregates WEI Meng, FANG Jiyuan, ZHAO Lijun, SONG Ke 2023, 37 (2):  315-317.  Abstract ( 196 )   Save The recycled aggregates are generated from the old pavement structure removal throughout the sieving and selection process. To study the effect of water glass on the improvement results of the recycled aggregates, the results of the unconfined compressive strength of the improved aggregates with various water glass contents was selected as the index. The water glass additives are the weight of the aggregate of 0.04%, 0.06%, 0.08%, 0.1% and 0.12% with the curing ages of 7 days and 28 days, respectively. The test results indicate that, the strength of the recycled aggregate can be improved by the addition of the water glass. The stress-strain relationship meets the strain soften curve; the optimum water glass content is 0.08%.   Related Articles | Metrics

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Standard Penetration Tests in Yulin Aeolian Sands ZENG Erxian, LI Yiyang, ZHAO Qingsong, ZENG Shiwen, FENG Heng, ZHANG Chengcheng, 2023, 37 (2):  318-321.  Abstract ( 378 )   Save The standard penetration test is one of the most used in-situ testing methods for sandy soils. To understand the details of the soil stratigraphy and the soil bearing capacity of Maowusu Sandy Land in Yulin, the standard penetration test was performed for the study. The results show that within the depth of 5m below the ground surface, the change of the blow count after correction is small, which indicates that the aeolian sand layer is relatively uniform and the aeolian sand is relatively uniform; The data obtained from the empirical relationship between the SPT blow count and the soil bearing capacity proposed by the Third Survey and Design Institute of the former Ministry of Railways is more reasonable, but it is smaller than the field static plate load test results; The compactness of the aeolian sand directly determined by the SPT blow counts is slightly higher than that of determined by the relative density estimated by the Meyerhof formula; The internal friction angle estimated by the Peck formula is consistent with the results of the direct shear tests. Related Articles | Metrics

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Comparative Experimental Study on the Dynamic Properties of Undisturbed and Remodeled Cohesive Soils in Hefei LI Penggang, HU Jinhu, REN Shuai 2023, 37 (2):  322-325.  Abstract ( 257 )   Save To study the influence of soil disturbance on the soil dynamic characteristics, undisturbed and remolded cohesive soil samples from various depth at the Baohe District of Hefei were collected for the laboratory study by using the GCTS STX-100 two-way vibration triaxial testing system. Based on the dynamic triaxial test results, the following conclusions are obtained: (1) Under the same confining pressure, the difference of the dynamic characteristic parameters (maximum dynamic stress τdmax, maximum dynamic shear modulus Gdmax) of the undisturbed and remodeled cohesive soil samples vary with the increase of sampling depth. It gradually increased; under the low confining pressure (50kPa), the τdmax and Gdmaxof the undisturbed samples and the remodeled samples had little difference, and the relationship curves tended to overlap. With the increase of the confining pressure, the relationship curve is rapidly separated, the τdmax and Gdmax of the undisturbed samples are larger than those of the remolded samples, and the increase range gradually increases with the increase of the confining pressure. When the confining pressure reaches 300kPa, the deviation range can reach more than 30%; (2) The damping ratio λd of the undisturbed samples and the remolded samples decreases with the increase of the confining pressure under the same dynamic strain; λdmax is between 0.2-0.3; (3) The dynamic strength and the dynamic shear modulus of the soil decrease due to the disturbance of the soil. Related Articles | Metrics

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Application of Low Strain Wave Reflection Method in Length Estimation for the Cast-in-Place Piles KONG Deyong 2023, 37 (2):  326-329.  Abstract ( 556 )   Save The low strain acoustic detection method is a relatively matured method in the pile integrity determination, but it has not been widely used in the pile length estimations. This paper presents a case history of an application of the acoustic method in the pile length estimations. The estimated length is compared with the pile length recorded in the pile installations, as well as the length from the pile coring. Related Articles | Metrics

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Effect of the High Temperature Cooling Process on the Porosity of Sandstone  DENG Kunyao 2023, 37 (2):  330-334.  Abstract ( 219 )   Save To study the influence of different liquid nitrogen and water cooling temperatures on the physical properties of the white sandstone, the low-field nuclear magnetic resonance imaging (MRI) method was used to measure the T2 spectrum of the white sandstone. The water and liquid nitrogen were used to cool the rock mass at different temperature stages (200℃~600℃). The influence of temperature, water-cooling and liquid nitrogen-cooling on the physical properties of the white sandstone is analyzed from the microscopic point of view, namely the change of rock pores. The test results show that: the 500℃ can be used as a critical value of different cooling methods on the changes in the intrinsic properties of the rock mass, above 500℃, the internal porosity of the rock mass changes significantly. The results show that the change of rock mass after the liquid nitrogen cooling is greater than the effect of the water cooling. Related Articles | Metrics