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Zhengzhou, China

Bai W.-F.,CAS Zhengzhou Research Institute | He W.,Zhengzhou Metro Co. | Zhang Y.,Dalian University of Technology
Sichuan Daxue Xuebao (Gongcheng Kexue Ban)/Journal of Sichuan University (Engineering Science Edition) | Year: 2013

Scaled boundary finite element method (SBFEM) was applied to solve the boundary value problems of the electrostatic field in coaxial-cable, i.e., ring-type domain. To avoid the singularity in eigenvalue method, Schur decomposition was employed to update the original method. With scaled boundary coordinate transformation, the governing Laplace equation was semi-discretized to set of a second-order ordinary differential equations (ODEs) by the weighted residual approach. Introducing auxiliary variables, the rank of ODEs was reduced to one, and the general solution of electric potential was obtained by Schur decomposition. Integral constants were determined by the boundary conditions. Numerical examples, including coaxial-cable with various types of cross-section, were calculated and the result showed that singularity is terminated by the proposed approach in respect to Schur decomposition. Wide adaptability, excellent results and less amount of computation consumption are reached beyond other methods. Source

Ye G.,Tongji University | Zhang Q.,Tongji University | Zhang Z.,Tongji University | Chang H.,Zhengzhou Metro Co.
Soils and Foundations | Year: 2015

A new soft ground improvement method is proposed combined with soil-cement columns and prefabricated vertical drains (PVDs) to increase the bearing capacity and to accelerate the consolidation process of soft soil. A series of centrifugal modeling tests is conducted on an embankment on a composite foundation, combined with soil-cement columns and PVDs. The effects of column spacing and column length on the behavior of the composite foundation are considered. For comparison, two centrifugal modeling tests are conducted on the embankment, one involving only soil-cement columns and the other involving only PVDs. The embankment loads are applied in four stages using a hydraulic jack mounted on top of a strongbox. Scaled-down model columns and a kind of wool strings are used to simulate the prototype soil-cement columns and PVDs, respectively. The load sharing ratio, defined as the proportion of external loads carried by the columns, is used to evaluate the load transfer between the columns and the surrounding soil. The test results indicate that the load sharing ratio increases with an increase in column length and a decrease in column spacing. The ground settlement and the lateral displacement decrease with an increase in column length and a decrease in column spacing. Finally, the use of the combined method to mitigate differential settlements at a bridge approach is discussed. © 2015 Japanese Geotechnical Society. Source

He W.,Dalian University of Technology | He W.,Zhengzhou Metro Co. | Chen J.-Y.,Dalian University of Technology
Zhendong yu Chongji/Journal of Vibration and Shock | Year: 2012

Due to the disturbance of ground adjacent building to the site, the seismic response of underground structure in the site will be influenced. The non-linear interaction finite element models were set up, which are composed of buildings, soil and underground structures. A hysteretic nonlinear soil constitutive model was used in the analysis. In the interaction finite element models were taken into account, the contact surface characteristics between the structure and soil and the impact of foundation's infinite domain. The models were analyzed numerically in time domain. The results show that the displacement response and force response of underground station structure are significantly amplified due to the existence of ground adjacent building. Additionally, a comparative study on influencial factors which affect the seismic response of underground structures was carried out. Here, the influencial factors include natural periods of adjacent building and relative distances between ground buildings and underground structures. Some useful conclusions were obtained through analysis, which are beneficial to engineering designs. Source

Li X.,Beijing Jiaotong University | Duan C.,Zhengzhou Metro Co.
Applied Mechanics and Materials | Year: 2012

It is of great significance to estimate the range of saturated ground around leakage pipelines when tunneling near the pipelines. The range of saturated ground can be determined from the distributions of the water content and pore-water pressure in ground around the leakage pipelines. The leakage pipeline being modeled as an injection well, a series of unsteady seepage numerical analysis is performed to understand the effects of the internal water pressure of pipelines on the range of saturated ground surrounding the pipelines, and computation results show the exponential relationship between them. In the unsteady seepage analysis, the hydraulic conductivity function and the volumetric water content function must be determined beforehand to get reasonable results of the range of saturated ground. © (2012) Trans Tech Publications, Switzerland. Source

He W.,Dalian University of Technology | He W.,Zhengzhou Metro Co. | Chen J.-Y.,Dalian University of Technology
Zhendong yu Chongji/Journal of Vibration and Shock | Year: 2011

Because of exploitation of urban underground space recently, a lot of large-scale subway stations were built. So, a new issue appeared for engineering design. The procedures for artificial simulation of multi-point seismic waves based on the code response spectrum were presented here. The generated seismic waves were spatially correlated to the ground motion, and had the double non-stationary properties of strength and frequency. The three-dimensional numerical models of a subway station were established under three different site conditions, and the infinite domain of soil was simulated with an infinite element. On this basis, the seismic responses of the subway station under non-uniform ground motion were analyzed compared with those under uniform seismic excitation. The results showed that horizontally relative displacements between top and bottom at different axial sections of the subway station have a great phase difference in soft sites because of non-uniform seismic action, and the effect on the dynamic stress of the side wall is great; the influence of the non-uniform feature on the dynamic response of the station is insignificant in medium hard sites and hard sites; a suggestion is given that the spatially multi-support earthquake excitations must be considered in the seismic analysis of a large-scale subway station in soft sites. Source

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