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28 December 2019, Volume 33 Issue 6 Previous Issue    Next Issue

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Loose Sand Improvement for a Central Asia’s Natural Gas Facility Expansion Project WEI Wei 2019, 33 (6):  627-629.  Abstract ( 614 )   Save This paper presents soil improvement method of loose fine sand soil in the deep desert area of an arid Central Asia country for the natural gas facility expansion project. The proposed site required a very deep treatment depth. In addition to dynamic compaction and other conventional local available soil improvement methods for the arid fine sandy soils, the water submerging method was introduced in this project. The results of the water submerging method treatment at the proposed site was examined by the late loading tests, standard penetration tests and heavy dynamic cone penetration tests. The test results of all three methods showed that the soil improvement method as acceptable and it is concluded that the water submerging method was successful in treating the arid fine sandy soils. Related Articles | Metrics

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Stability Evaluation and Mitigation Design of Transmission Towers on Slopes WANG Chen, YE Chenggeng, , LIU Wei, XU Haiyuan, LIU Ruhai 2019, 33 (6):  630-633.  Abstract ( 646 )   Save Failure of transmission towers that constructed on slopes due to the excessive movement of slopes are frequently encountered. This paper presents a case history of stability remediation of a transmission tower on a slope with an objective of the enhancing the importance of the stability evaluation of the slope before the transmission tower construction. Based on the geological and geographical conditions at the project site, the failure modes of the slope are established, and the stability of the slope was evaluated with the commercial software Slope/W. The slope was then stabilized, and drainage measures were installed. Related Articles | Metrics

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Evaluation and Stability Analysis of Ground Improvement of Thick Collapsible Loess Fill Embankment for an Airport LI Haipeng, ZHU Hengyuan 2019, 33 (6):  634-638.  Abstract ( 581 )   Save The collapsibility of loess soil fill materials was evaluated based on the sitespecific engineering geology and hydrogeological characteristics of an airport project. The effect of dynamic compaction on the collapsible loess fills was evaluated throughout the laboratory soil tests, field standard penetration test and insitu direct shear test. The results from the insitu direct shear tests were used to evaluate the stability safety of the slope of a high fill embankment. The following conclusions can be summarized: (1) The optimum number of blows of dynamic compaction was 6 and the accumulated settlement was about 40cm through trial test zone; (2) The density if the loess was apparently improved after the dynamic compaction. The blow counts of standard penetration test increased almost linearly along the depth. (3) The loess soil layer in the field is characterized by the low liquid limit loesslike silt, slightly wet, dense, low compressibility. (4) After the ground improvement by dynamic compaction, the collapsibility of loess in the field was eliminated. (5) After the dynamic compaction, the internal friction angle of loess samples become less variable with a significantly variable cohesion values from the insitu direct shear test result. The insitu tested shear strength values could be used for the slope stability evaluation of the high fill embankment. It is concluded that stability of the loess fill embankment met the design requirement. Related Articles | Metrics

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De-watering Design Considering the Post Construction Settlement WU Lujun, DAI Ye 2019, 33 (6):  639-641.  Abstract ( 366 )   Save Ground subsidence might be occurred after the dewater operation around the deep excavation site. The ground movement might adversely affect the adjacent building foundations, pavements and underground utilities. It is therefore, during the dewater design stage, the effect of the adjacent environment should be appropriately evaluated. Related Articles | Metrics

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Analysis of Leakage Defect Patterns at Structural Construction Joints of a Subway Station ZHANG Zheng, WU Ke, ZHAO Jiahui, ZHANG Qianjin, CUI Shuaishuai 2019, 33 (6):  642-646.  Abstract ( 395 )   Save Most of the subway stations are located near the groundwater zone, and the longterm water erosion will easily result in leakage hazards at the construction joints of the main structure of the subway stations, which will adversely affect the service life and safety of the subway station structures. This paper presents a case history of construction joints treatment for the groundwater leakage in the construction of Shangzhi Street Station of the first phase of Harbin Rail Transit Line No. 2. Based on field construction data, this paper discusses the leakage patterns observed in the construction joints. The groundwater leaking problem was then numerical analyzed throughout a threedimensional finite element by using Midas GTS NX software. The patterns of seepage hazards induced by construction joints of metro station structure was extensively investigated. And the groundwater leakage at the metro station structures was then able to be mitigated due to a better understanding of the process of seepage occurrence, development and hazard at construction joints of underground reinforced concrete structures. Related Articles | Metrics

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Stability Analysis of a Syncline Bedded Rock Slope near a Gas Station DENG Diping, YANG Cheng 2019, 33 (6):  647-649.  Abstract ( 363 )   Save A syncline bedded rock slope is near a gas station on the northwest side of Fengwu Community, which is on the InnerCity Loop Road, Dazhou City. This paper presents the stability evaluation of the rock slope. The results indicated that, the bedding plane and the fissured surface are unstable structural surfaces. The stability of the excavated slope will be a concern due to the potential slip within the structured weak suface, especially, under the heavy rains. The paper also provides slope stability mitigation measures. Related Articles | Metrics

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Optimization Study on Widening Excavation of an Existing Tunnel in Weak Rock Mass ZHONG Yuanqing 2019, 33 (6):  650-654.  Abstract ( 381 )   Save The existing Housi Tunnel had two tunnel tubes in the weak rock mass, and it was decided to widen this tunnel into four tubes. The proposed CRD method had the disadvantages of complex excavation procedures, a relative high risk of temporary supporting system removal and longer construction schedule. The benching tunneling method was proposed to replace the CRD excavation method. The proposed benching tunneling procedure was simulated through numerical analysis and was verified through the construction monitoring. The results indicated that, the benching tunneling method is feasible for the excavation of large cross section tunnel and optimized excavation procedure used in the construction was successful. Related Articles | Metrics

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Rapid Response of Groundwater Gushing at an Irrigation Tunnel at Right Shoulder of a Gravity Dam ZHANG Jiatuo, LAI Lin 2019, 33 (6):  655-659.  Abstract ( 394 )   Save This paper presents a case history of rapid treatment of groundwater gushing in an irrigation tunneling excavation at the right shoulder of a doubleway gravity dam in Southwest China. The treatment measures included diverting groundwater through concentrated boreholes drilled in a very short period and drilling inclined borehole for the cement slurry grout. After the shortterm treatment, the longterm treatment measure was to grout the rock mass after the installation of the reinforced concrete liner. The grouting curtain in the longterm treatment was over lapsed with the slurry wall above the tunnel so that the irrigation tunnel was surrounded by the grouted curtain. This treatment can provide a short response time and rapid treatment of the groundwater 〖JP2〗gushing hazards. This method can also provide experience for the rapid groundwater diverting, grouting procedure and rapid tunnel liner installations. The testing on the grouted area indicated that the treatment method was successful. Related Articles | Metrics

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Evaluation of the Niushuoshan Landslide in Nanjing WANG Wei, XU Baotian 2019, 33 (6):  660-664.  Abstract ( 628 )   Save The soil and rock strata of Niushuoshan landslide in Nanjing city, are mainly comprised of volcanic tuff of Jurassic Dawangshan Formation (J3d). Field investigation results showed that the landslide had historically undergone a large deformation, which is called an ancient landslide. The investigation results indicated that the highly weathered stratum leads to the formation of relatively impermeable kaolin aquitard layer, and the reduced mechanical properties result in the slope instability concerns. Cracks are well developed in moderately weathered strata, which are beneficial to the surface runoff seepage and to the formation of confined aquitard under the highly weathered stratum. The transient flow was evaluated by the finite element method, when the rainfall intensity reaches 10~20 mm/d and durations are between 4 and 6 days, the slope may reach its stability limit state. The excess pore pressure in the highly weathered strata is not easily to dissipate, which leads to a long period of continuous deformation of the slope and the stability could not be recovered in a short time. Related Articles | Metrics

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Numerical Analysis of Stress and Deformation Characteristics of L-Shaped and Soil Filled Retaining Walls LIU Xuehui 2019, 33 (6):  665-667.  Abstract ( 450 )   Save The stress and deformation characteristics of a model LShaped, soil filled model retaining wall as well as a conventional LShaped retaining wall was numerically studied by using a commercial finite difference software FLAC3D. The lateral earth pressures acting on both wall types and the lateral deflection of both walls are investigated in this paper. The results indicate that, LShaped and soil filled wall can effectively control the lateral deflections. It is also concluded from the numerical analysis that the stress concentration is occurred at the connection point between the bottom slab and vertical box. Related Articles | Metrics

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Impact Analysis of Deep Foundation Excavations on Superstructure of Neighboring Buildings XU Jianning 2019, 33 (6):  668-673.  Abstract ( 481 )   Save To have a better understanding on impact of deep foundation excavation on the internal force and the gravity secondorder effect of the superstructure of adjacent buildings, the author developed an overall “pitsoilbuilding” numerical model with geotechnical finite element software PLAXIS88 to study the change rules of the total settlement, differential settlement and angles the of multistory framed buildings on the shallow strip foundation, the box foundation and the pile foundation respectively at different distances from the foundation excavations. Then, the rules of impact on the internal force and the gravity secondorder effect resulted from base displacement of the neighboring buildings caused by the foundation excavation was further studied through SAP2000 finite element method. The results show that the foundation excavation impacts the neighboring buildings on the box foundation heavier than it impacts those on the shallow strip and the pile foundations. This case study indicates that the impact of foundation excavation is generally and relatively small on multistory frames of the neighboring buildings. Specifically, the variations of the internal force of the multistory frame structures of the buildings on strip, pile or box foundation caused by the foundation excavation are all within 11%. When a building has more stories the gravity secondorder effect（PΔ）increases and 〖JP2〗the building of 12 stories has the largest PΔ effect (7.5%). Further, the impact is under control, for the bearing capacity of the building components can meet the requirement for a nearby foundation excavation according to calculation. However, with the increase of the number of stories, the PΔ effect of adjacent structures and the change trend of internal forces will increase. Therefore, for highrise or superhighrise buildings, special calculation and research are needed to determine the change of overall bearing capacity and effectively control the deformation of foundation pit according to the change of bearing capacity. Related Articles | Metrics

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Simplified Method for Estimation Internal Force of Reinforced Concrete Frame with Prestressed Ground Anchors WANG Chunguang, ZHU Shouzeng, , LIU Yukun, PANG Banghui, HUI Yanglei 2019, 33 (6):  674-678.  Abstract ( 684 )   Save Reinforced concrete frame with prestressed ground anchors has many advantages and therefore, it is widely used as the supporting structures in the engineering excavations. However, the design analysis of this system requires complicated hand calculations and is not efficient for the design engineers. This paper presents an improved hand calculation method for estimating of the internal force in the ground anchored reinforced concrete frame. The joint forces in the longitudinal and transverse beams are arbitrarily distributed; then based on the analytical solution for the finite beam on Winkler foundation and the superposition principles, the distribution of the internal force and the ground reaction of the beam on elastic foundation under the action of multiple concentrated forces is obtained. Finally, in the paper, the deformation characteristics of the ground anchored reinforced concrete frame system is evaluated and the simplified the internal force estimation method is summarized. Related Articles | Metrics

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The Location Optimal Study of Slope Reinforced by Prestressed Ground Anchors HOU Wencui 2019, 33 (6):  679-682.  Abstract ( 443 )   Save The stability of a non-homogeneous three-tier slope in rolling hill loess region in northwest Shaanxi was numerically evaluated through finite element software PLAXIS using strength reduction method. The analytical results indicated the slope stability mitigations are required. The single layer prestressed ground anchor caisson system was selected for the slope stabilization work. Under various loading combinations, the factor of safety, limits of plastic soil zone, the maximum bending moment deflections in the caisson were evaluated and the effect of anchoring location on the slope stability was also investigated. The results indicated that, when the caisson is located at the top of middle tier slope, the most appropriate position applying the ground anchor was 0.4 meters below the top of caisson. Related Articles | Metrics

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Study of Dynamic Characteristics of Mushroom Shaped Short Pile in Rubber-Sand Mixture Composite Cushion YAO Yuwen, LIU Fangcheng, BU Guobin, MA Qianfeng 2019, 33 (6):  683-689.  Abstract ( 418 )   Save The rubber-sand-mixture soil is usually lack of the required vertical modulus, a short mushroom-shaped pile is then proposed to reinforce it so as to reduce the vertical deformation dramatically under the condition that it has certain isolation performance. The cyclic shear simulation of the mushroom shaped short pilerubber sand mixture (MP-RSM) composite isolation device is carried out by Marc that is a type of finite element software. The effects of different pile crown deviation angle θand pile belly diameter d on the dynamic performance of the composite device and the effect of reinforcement on the vertical deformation of RSM are compared and analyzed. The results show that: 1) when the strain is small, the dynamic shear modulus of MP-RSM composite cushion gradually increases and tends to be flat with the increase of the pile crown deflection angle, while when the strain is large, the influence of the pile crown deflection angle is small; with the increase of the diameter of pile belly, the dynamic shear modulus of composite cushion increases slightly, but the change is not obvious; 2) when the diameter of pile belly is the same, the dynamic shear modulus of MP-RSM composite cushion increases with the increase of the pile crown the damping ratio of composite cushion increases gradually and tends to be gentle under the shear strain; the influence of the diameter of pile web on the damping ratio of composite cushion is not obvious; 3) The composite cushion has variable horizontal stiffness and good hysteretic energy dissipation characteristics, and can effectively reduce the vertical deformation of rubber sand, which can be used as isolation cushion. Related Articles | Metrics

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Shear Strength Characteristics of Fill Soil Grouted Through Steel Pipes WU Hao, , ZHANG Keneng, , QIN Libin, ZHANG Yunyi, , QIU Dian, ZHU Kaofei, , JIN Fuxi, 2019, 33 (6):  690-692.  Abstract ( 695 )   Save The shear strength characteristics of fill soil grouted through steel pipes and conventional permeable grouting methods are studied throughout laboratory and field direct shear tests. This paper presents the comparative studies of grouted soils from a building site in Zhuzhou City, Hunan Province. The laboratory studies were concentrated on the grouting reinforcement through steel pipes and the cement slurry in the soil on the shear strength. The test results indicated that the grouting reinforcement can enhance the shear strength of improved soil to 1.29 times of the original soils. The shear strength of soil improved with permeable grouting was proportional to the cement content. When the cement ratio is at 6%, the shear strength of improved soil could be twice of the original soils. The field insitu tests indicated that the grouting improved soil could have a shear strength nine times of the original soils. It is therefore concluded that, in addition to the grouted column formed through the grout operation and the soil shear strength improvement, the cementation of cement slurry between the boulders, gravels and other material could also contribute the shear strength increase. Related Articles | Metrics

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The Unconfined Compressive Atrength and Failure Characteristics of Zhuanglang Compacted Collapsible Loess Soils LU Zhaosong, ZHAO Guanghong, WAN Qiwei, ZHU Qilin, CHEN Long 2019, 33 (6):  693-696.  Abstract ( 947 )   Save The collapsible loess of Level II~IV soils is widely distributed along the PingliangMianyan highway alignment. It is necessary to study the strength and failure characteristics for selecting better design parameters for the highway construction. In this paper, physical properties, mineral composition and compact characteristics of collapsible loess were extensively tested. Based on the unconfined compressive strength and failure characteristics tested under different degree of compactions and initial water contents, the conclusions could be made as follows: (1) The unconfined compressive strength and capacity of holding moisture are enhanced with increasing the degree of compaction; (2) The unconfined compressive strength achieved maximum value when the water contents were much higher than the optimum moisture content, however, the water content should not exceed 3% of the optimum moisture content; (3) The shear failure of soil samples was more and more obvious with the increasing degree of compactions, and conical failure mode was observed when the degree of compaction reached 100%. Brittle failure characteristics was less and less obvious with the increasing initial water contents, and lateral dilation behavior was presented when the water content reached 19%. Related Articles | Metrics

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Testing of AtRest Lateral Earth Pressure Coefficient of Coral Sands ZHANG Poyu, , ZHU Changqi, WANG Rui, , WANGBU Xueyan, 2019, 33 (6):  697-700.  Abstract ( 570 )   Save The at-rest lateral earth pressure coefficient is an important soil parameter that indicating the relationship between the vertical and lateral stresses in the soil mass and poses an important role throughout every aspect of geotechnical engineering. The coral sand is a unique geotechnical material with a relatively low individual grain strength and welldeveloped angularity, therefore, the engineering properties of the coral sands are significantly different from those of quartz sand of land origins. This paper presents the laboratory at-rest lateral earth coefficient test results of coral sand samples under various relative density and moisture contents throughout the Anteus high-pressure consolidation test devices. The results indicated that: 1) the tested at-rest lateral earth pressure coefficients are between 0.20 and 0.29 and these values are smaller than those of from quartz sand samples. 2) The at-rest lateral earth pressure coefficient of coral sand samples increases with the moisture content, but the increment is not significant. 3) The effect of density of samples on the magnitude of lateral earth pressure is not significant. Related Articles | Metrics

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Study on Corrosivity of Underground Soil to Concrete Structure in Zhanjiang LIU Xiaoyan, JIANG Xiaojing, CHEN Mingzhu, FENG Zhiguo 2019, 33 (6):  701-703.  Abstract ( 456 )   Save The pH value of a special subsurface soil in Zhanjiang is laboratory tested to be less than 3.5. In accordance with the current Code for Geotechnical Engineering Investigation, it is concluded that this soil is strongly corrosive to underground concrete structures. The further investigation indicates that the corrosion mechanism for this type of soil is microbial induced. When the permeability of soil layer is poor and the anaerobic sulfate reduces bacteria propagate, so that the sulfate in the pore water I the soil is reduced to sulfur or sulfide. When the permeability of the soil layer is improved, most sulfur and sulfide are not oxidized to sulfuric acid. After many years of experiment and research, it is concluded that this special subsurface soil in this area can be classified as weak corrosive soil to the underground concrete structures. In other words, if the selection of underground construction materials and the foundation construction procedures are appropriate, measures used for the weak corrosive soils can result in a significant construction cost saving. Related Articles | Metrics

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Effective Hydrostatic Pressure of Slurry and Its Role in Stabilizing the Slurry Wall Excavation ZHENG Wandong, , SHEN Hong, JIN Lian, GUO Yunhua, CHEN Yandong 2019, 33 (6):  704-708.  Abstract ( 821 )   Save The quality of the mud cake is critical to the quality of the slurry wall construction for the seepage control. In current engineering practice, the preparation of slurry in the construction is mainly relied on the empirical method. In order to have a better understanding of the formation of mud cake in the slurry wall construction, parameters that resulting the formation of mud cake and the trench wall stability are related. The results indicated that when strength of the mud cake reaches 0.125 MPa and the trench excavation rate is less than 0.5 m/h, the stability of the cobble layer can be maintained during the excavation. Related Articles | Metrics

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Development and Preliminary Application of an Improved Testing Device for Consolidation and Permeability of Gassy Soils REN Wenqi, WANG Yong, SUN Jizhu 2019, 33 (6):  709-712.  Abstract ( 325 )   Save A gassy marine soils usually demonstrate poor engineering properties. The conventional consolidation test device was improved so that it can conduct the consolidation and permeability of gassy marine soils. The improved device can separate the pore water and gas during the testing. The air and water tightness inside the ring and the friction between the piston and the ring are also effectively improved. This paper also presents the results on the gassy soil testing using the improved device. The results are gas content in the soil, preconsolidation pressure, compressibility and coefficient of permeability. The tested parameters are consistent with the soft soil performance and the reliability of the improved device is also verified. Related Articles | Metrics

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Field Tests and Numerical Analysis of Anti-Buoyancy Anchors QIU Zhihua, , DAI Zihang, XU Xiang, ZHAO Wuyang, CHEN Baolin,  2019, 33 (6):  713-716.  Abstract ( 530 )   Save With the development of urban construction, the utilization of underground spaces becomes more and more popular, and the buoyance concerns of underground buildings and structures becomes increasing urgent. Especially in areas with high groundwater level, the impact of antifloating stability on the structural safety is also increasingly prominent. In this paper, the mechanism and failure modes of antifloating anchors are evaluated. The mechanical and deformation characteristics of antifloating anchors are discussed by field tests and the threedimensional finite element model throughout commercial software ABAQUS. The mechanism of the antifloating anchor is revealed, and practical conclusions are also provided in the paper. Related Articles | Metrics

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Application of The Borehole Magnetic Survey Method in the Deeply Buried Pipelines Detection LV Ming 2019, 33 (6):  717-719.  Abstract ( 468 )   Save This paper introduces the basic principles of the borehole magnetic survey method. The borehole magnetic survey method was used to detect metal pipelines, stormwater and sewer pipelines that containing ferromagnetic materials and nonmetallic pipelines with holes through which strong ferromagnetic bars can be inserted and have achieved good results. Through the analysis and the study of detection results, it is proved that the borehole magnetic survey method is feasible for the detection of deeply buried pipelines containing ferromagnetic materials, and the detection accuracy is related to the plane position of the measured hole, but not related to the buried depth of the pipelines. The detection errors of this method can meet the engineering needs and relevant specification requirements, and the detection results can provide scientific basis for engineering design and construction. This paper summarizes the procedures of the borehole magnetic detection pipelines, the main sources of errors, the technical measures to reduce errors and the advantages and disadvantages of the detection methods. It also provides references for improving the detection efficiency of deeply buried pipelines containing ferromagnetic materials and reducing errors. Related Articles | Metrics

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Geological Hazard Idendification Technology Based on High Definition Remote Sensing Image in Power Transmission Line Installation DAI Xuming, LANG Jianwei, LIU Wei, ZENG Weixiong 2019, 33 (6):  720-725.  Abstract ( 471 )   Save The application of remote sensing in the investigation and evaluation of geological hazards can save significant labor and other costs. This paper presents the remote sensing results for the power transmission towers along Pengshen Line and Jiteng Line. The geological hazard identification, evaluation and rick analysis works are based on the high definition remote sensing images. The following conclusions can be made from the results: 1) Three geological hazard zones can be divided within the power line alignments: high hazardous zone, medium hazardous zone and low hazardous zone. Of a total of 146 towers in Pengshen Line, 62 towers are in the high hazardous zone, 22 towers are in the medium hazardous zone and 66 towers are located in the low hazardous zone. Of a total of 92 towers in Jiteng Line, 62 towers are within the high hazardous zone and 30 towers in the low hazardous zone. 2) Three risk zones are identified in all work zones: high risk, medium risk and low risk. The remote sensing identified 20 high risk zones with landslide hazards and 9 slope stability locations; 4 medium landslide zone and 2 low risk landslide zones are also identified. These results from the remote sensing are consistent with the actual ground reconnaissance. Related Articles | Metrics