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Chen J.-J.,Shanghai JiaoTong University | Zhang L.,University of Arizona | Zhang J.-F.,Shanghai JiaoTong University | Zhu Y.-F.,Shanghai Tunnel Engineering Co. | Wang J.-H.,Shanghai JiaoTong University
Journal of Geotechnical and Geoenvironmental Engineering | Year: 2013

The installation of soil-cement columns causes excess pore-water pressures and movements of surrounding ground, which affect adjacent underground structures. In Shanghai, a triple-shaft deep soil mixing (DSM) method has been proposed and is widely used to minimize the installation effects. However, when this DSM method was used to install soil-cement columns close to a Metro tunnel, unacceptable soil displacement was caused, even at the very beginning. Therefore, it was decided to conduct field tests to investigate the effect of major factors affecting DSM installations and then modify the construction parameters so that the soil displacement caused by DSM construction would not exceed the allowable limit. The field tests consisted of two phases: Phase I tests of single DSM column installations close to the Metro tunnel to modify the construction parameters, and Phase II tests of continuous multiple DSM column installations far from the Metro tunnel to validate the modified construction parameters. Detailed pore-water pressure and soil displacement measurements were conducted during the field tests. Based on the field tests, the traditional DSM method was modified by using a higher water/cement ratio, lower mixing speed, and no injection during withdrawal, and adopting a new installation sequence for continuous construction that started from the farthest row and moved closer to the tunnel. Using the modified construction parameters, the triple-shaft DSM method was successfully applied to the large-scale soil improvement of an underground highway excavation project close to the Metro tunnels. This paper describes the background, the field tests, the modified DSM method, and its successful application. © 2013 American Society of Civil Engineers.

In this paper, a computation formula is deduced that can be used to judge the safety status of a hazardous buried pipeline when a super-large diameter shield is crossing under it. The relationship between the pipeline's stress status and the ground deformation above the pipeline is established. Using the measured ground settlement data, the equation for a deflection curve of the buried pipeline is fitted. The stress status of the pipeline is then deduced from the curvature functions, which can be established using a differential calculation for the deflection curve. Finally, the pipeline safety factor is determined by comparing the actual stress to the allowable stress, and this factor can be used as a reference parameter for shield construction. Using an example of large-diameter shield construction from Shanghai, and based on measured data from rings 950 to 1040, the safety factor for pipelines is calculated. The results show that the safety factor varied from 5-15, resulting in a reduction of the pipeline safety. Controlling the shield construction parameters could ensure the pipeline's safety. ©, 2014, Editorial Office of "Modern Tunnelling Technology". All right reserved.

Gu C.,Shanghai Tunnel Engineering Co.
Modern Tunnelling Technology | Year: 2014

Due to the special environment of underground tunnel, various factors may cause different degrees of damages to lining whether in tunnel under construction or that during operation. And relevant reinforcement is an effective way to avoid further deformation of damaged tunnel. Taking the tunnel constructions in multiple cities in China as aexamples, this paper analyzed some reasons and types of tunnel damage, introduced the key technical measures on waterproofing and structural reinforcement, and presented a new installation equipment for steel ring support and its technological process, thus providing reference for similar projects. ©, 2015, Editorial Office of "Modern Tunnelling Technology". All right reserved.

Hu T.,Shanghai Tunnel Engineering Co.
Modern Tunnelling Technology | Year: 2014

The cross-river tunnel in West Changjiang Road, as a super-large diameter shield tunnel, has its flue sheet with a structure of large-span and thin-wall, so it is difficult for the cast-in-situ construction to control the linear appearance, safety and concrete construction, etc. This paper describes the technology measures such as segmental flow construction, gantry type formwork, positioning truss, concrete pouring and construction safety. As a result, the construction quality of cast-in-situ flue sheet is good. ©, 2015, Editorial Office of "Modern Tunnelling Technology". All right reserved.

Ge W.,Shanghai Tunnel Engineering Co.
Modern Tunnelling Technology | Year: 2014

According to the geological survey, the running tunnel from Binjiang station to Fuchun station of Huangzhou Metro line 1, which passes through the Qiantangjiang River, is constructed under complex geological conditions (methane, confined water and sandy cobble stratum), there are some risks for the application of horizontal freezing method for construction of connecting passage in the river bottom. In order to reduce the risk as far as possible, and to ensure safety construction of connecting passage under the river, a series of technical measures are adopted, such as methane release by drilling, intensive ventilation, strengthened frozen curtain in confined water strata, improving of sealing technique for orifice of freezing pipe and modifying of freezing pipe structure in sandy cobble stratum. As a result, it goes smoothly during the construction of connecting passage. ©, 2015, Editorial Office of "Modern Tunnelling Technology". All right reserved.

Wei L.,Shanghai Tunnel Engineering Co.
Modern Tunnelling Technology | Year: 2014

The mining method with soil reinforcement is now mainly adopted in the construction of cross passages of shield tunnels, which is characterized by high risk and complex working conditions. In this paper, based on the adoption of a specially developed rectangular pipe-jacking machine with a planetary cutterhead, full-face cutting tests are carried out on concrete samples of different strength grades. Research on cutting-tool selection and layout, as well as the machinability of pipe-jacking with a planetary cutterhead, are undertaken, providing a technical reference for future cross-passage construction in shield tunnels adopting pipe-jacking to cut concrete composite segments, thereby refraining from exposing the reinforced soil mass due to segment removal, and greatly reducing the construction risk. ©, 2014, Editorial Office of "Modern Tunnelling Technology". All right reserved.

Zhang L.,Shanghai Tunnel Engineering Co.
Modern Tunnelling Technology | Year: 2014

Based on a shield tunnel of the Zhengzhou metro that passes under an electric power tunnel, a numerical simulation analysis was carried out by ABAQUS software and the settlement laws of the ground surface and the electric power tunnel were researched, as well as shield tunnel construction in sandy strata. The results show that: the maximum ground surface settlement that occurred at the middle of the two tunnels is about 12mm, while the maximum ground settlement of the electric power tunnel, occurring at the intersection of the two tunnels, is about 15mm, all of which are within an allowable range. Thus, it is concluded that the settlements are both controlled by targeted construction measures, which ensure the security of electric power tunnel. ©, 2014, Editorial Office of "Modern Tunnelling Technology". All right reserved.

Wen S.-L.,Shanghai Tunnel Engineering Co.
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2010

Critical construction techniques used in the deep excavation for West-East Transport System (WETS) are presented. Protecting the Shanghai Metro line 2 traverse by WETS in complex geological condition is of great concern. The construction scheme is established according to the principle of ″time-space effect″ and ″stiffness of tunnel″. Deep soil mixing method is used to construct retaining walls which divide the excavation area into several little pits. Excavation sequence of the pits are jumping and single pit is excavated by staged method. The monitoring results show that the proposed series of techniques is effective and the uplift of the tunnel is controlled within a safe range.

Tian J.,Shanghai Tunnel Engineering Co.
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2010

Optimized construction and control techniques are studied to reduce the deformation of running tunnels caused by deep soil mixing. The construction techniques are improved by changing the grout composition, construction order and schedule. Optimized control parameters are obtained by in-situ tests on construction of single and group piles. In engineering practice of the background project, the heave of the tunnel is smaller than that of traditional method, which guarantees the safety of the tunnel and can be referenced for similar projects in the future.

In strengthening a tunnel structure, the mortar-filled fibre tube composite lining (FMTCL) is a new structure with the advantages of high strength, convenient operation, efficient installation, small occupied space, and especially suitable for reinforcing the structure of urban subway. In the current study, a series of experiments were conducted on standard/reinforced segment joints to investigate the flexural behaviors of segment joints strengthened with FMTCL under negative moment. The load-deflection curves of the standard and reinforced opening segment joints were then obtained. The load-angle and load-stiffness curves and the failure patterns of the standard and reinforced segment joints were furthermore analyzed. It shows that the negative flexural bearing capacity of segment joint reinforced with FMTCL, corresponding to the mid-span deflection of 10mm, is 221% higher than that of unreinforced segment joint. The ultimate bearing capacity of reinforced segment joint is 101% larger than that of unreinforced segment joint. The average rotation stiffness of reinforced segment joints increases about 4.3 times than the unreinforced one. Therefore, FMTCL may efficiently enhance the flexural bearing capacity and rotation stiffness of segment joints in the negative moment area; FMTCL is a new technique in reinforcing the structure of shield tunnel in the future. ©, 2015, Editorial Office of China Civil Engineering Journal. All right reserved.

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