Shanghai Municipal Bureau of Planning and Land Resources

Shanghai, China

Shanghai Municipal Bureau of Planning and Land Resources

Shanghai, China
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Gao G.-Y.,Tongji University | Li S.-Y.,Tongji University | Tu M.-J.,Tongji University | Zhang X.-L.,Shanghai Municipal Bureau of Planning and Land Resources
Yantu Lixue/Rock and Soil Mechanics | Year: 2015

Three-dimensional finite difference model of cross tunnels is established by FLAC3D to compute deformation and stress of soft soil under metro train cyclic loading which is modeled by artificial numerical exciting force. Modified dynamic deviatoric stress model for long-term settlement of soft soil combined with layer-wise summation method are adopted to calculate tunnel settlement and predict long-term settlement of cross tunnels. Long term settlement in three train-running cases is studied. Case 1, one train traveled through tunnel #1, case 2, one train traveled through tunnel #2, case 3, two trains traveled through tunnel #1 and tunnel #2 separately at the same time. Influences of train speed, stiffness and thickness of tunnel lining on long-term settlement of cross tunnels are studied. The results show that the settlement induced by train loading mainly distributes within 20 m from the central axis of tunnels. Sum of settlement in case 1 and case 2 is less than settlement in case 3; and tunnel settlement decreases with the increasing of train speed, stiffness and thickness of tunnel lining; while the influence of thickness of tunnel lining is more than stiffness of the lining. ©, 2015, Academia Sinica. All right reserved.


Gao G.-Y.,Tongji University | Nie C.-X.,Tongji University | Zeng L.,Tongji University | Zhang X.-L.,Shanghai Municipal Bureau of Planning and Land Resources
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2015

A procedure for calculating the long-term settlement of foundation subjected to moving train loads is proposed on the basis of the creep constitutive model. The excited force associated with the moving train is converted to dynamic stresses on the infinite half-space by using the Mindlin solution. The creep constitutive equations are derived based on the Boltzmann principle of linear superposition, and the integral formation of the equations is then deduced. The long-term settlement of foundation can be calculated by using the proposed equations and the layer-wise summation method. The procedure is verified by the simulation and measured data. The results show that the predicted long-term settlement by the proposed method is in good agreement with the test data. The proposed method simplifies the moving train load, but the effect on predicting the long-term settlement is negligible. ©, 2015, Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering. All right reserved.


Gao G.-Y.,Tongji University | Chai J.-L.,CREEC East China Survey and Design Co. | Zhang X.-L.,Shanghai Municipal Bureau of Planning and Land Resources | Jin Q.-S.,Shanghai Geotechnical Engineering and Geology Institute Co.
Yantu Lixue/Rock and Soil Mechanics | Year: 2012

Considering the existing calculation methods' shortcomings of water gushing in foundation pit. The strain dependent modified Cam-clay (SDMCC) model adopted to model the soil behavior and confined water was taken into account in the finite difference model by FLAC 3D. With the increase of the confined water head (H w), the foundation pit heave was divided into three stages: slow uniform deformation, accelerating deformation and sharp uniform deformation. A new method for determining critical water head (H wcr) of water gushing in foundation pit was presented based on numerical analysis; and the calculation result of the new method was compared with other methods.


Chen Q.-S.,Tongji University | Gao G.-Y.,Tongji University | He J.-F.,Tongji University | Zhang X.-L.,Shanghai Municipal Bureau of Planning and Land Resources
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2011

Dynamic simple shear tests on different types of sand under multidirectional earthquake loading are simulated by means of the finite element method. The reduced order bounding surface model is employed and its parameters are determined based on the results obtained from laboratory dynamic simple shear tests. 148 groups of ground motions with multi-components from far and/or near fields of moderate and/or strong earthquake events at different site conditions are used as input motions for strain controlled and stress controlled dynamic simple shear tests. Effect of multidirectional earthquake loading on seismic compression of sand for different earthquake magnitudes site-to-source distances and properties of sand is studied. The results show that the ratio of vertical strain induced by multi-components of seismic loading and that induced by one component of seismic loading are greatly associated with earthquake magnitude, site-to-source distance and properties of sand, the ratio of vertical strain increases with the increasing earthquake magnitude and relative density of sand, and decreases with the increasing site-to-source distances. Great limitation exists in the method considering the effect of multidirectional earthquake loading on seismic compression proposed by Pyke et al (1975) due to its lack of considering the effect of characteristics of seismic loading and properties of sand. Also, the ratios obtained from stress controlled and strain controlled simple shear tests are greatly different and the mean ratios from the former are larger than those from the latter.


Gao G.-Y.,Tongji University | Chen Q.-S.,Tongji University | He J.-F.,Tongji University | Zhang X.-L.,Shanghai Municipal Bureau of Planning and Land Resources
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2011

A dynamic model is developed based on the results of geological investigations as well as laboratory and field tests in Shanghai. The Biot's dynamic consolidation theory and reduced order bounding surface model are coupled to study the effect of the rise of groundwater table on the seismic ground response of soft soil undergoing 3-D seismic base excitations (which are obtained from Taft). The effect of the rise of groundwater table on the horizontal and vertical amplification factors, the ratio of vertical to horizontal peak acceleration, the characteristics of acceleration and response spectrum at ground surface as well as the maximum pore water pressure and pore water pressure ratio along the depth of soil layer are studied. The results show that the rise of groundwater table has dramatically different influences on the horizontal and vertical amplification effect as well as the characteristics of acceleration and response spectrum at ground surface. As the result of the rise of groundwater table, the amplification effect increases in horizontal direction but decreases in vertical direction. The ratio of vertical to horizontal acceleration decreases. The filtering effect on the acceleration with high frequency and the amplification effect on the acceleration with long period increase. The range of liquefiable soil near ground surface extends and hazard risk increases.


Gao G.,Tongji University | Wu Y.,Tongji University | Zhang X.,Shanghai Municipal Bureau of Planning and Land Resources | Jin Q.,Shanghai Geotechnical Engineering and Geology Institute Co. | Feng S.,Tongji University
Tumu Gongcheng Xuebao/China Civil Engineering Journal | Year: 2011

Fast Lagrangian Analysis of Continua in 3 Dimensions (FLAC3D) was employed to simulate stage-excavated and supported foundation pit. According to different locations between tunnel and excavation, two types-'closed-type' and 'shallow-embedded-type' and seven conditions can be categorized regarding the analysis of the interaction between deep excavation and the adjacent existing tunnel. Modified Cambridge model was adopted to model the soil behavior. And the interaction between soils and retaining structures was also taken into account in the numerical analysis. The result shows that the deformation of the tunnel is incompletely monotony with the distance from the excavation, and the presence of the tunnel imposes a 'reinforcement effect' on the soil mass behind the retaining wall.

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