An uncoupling analysis method is traditionally used to evaluate the dewatering-induced deformation of the soil base in China, which is firstly conducted to obtain the seepage field of the soil base. Accordingly, the settlement of the soil base is calculated using the one-dimensional layer-wise summation method. In this paper, a FE method was employed to analyze the coupling behavior of seepage and deformation of the soil base induced by dewatering. The analysis results showed that the coupling analysis and traditional method yielded similar distributions of water head in the soil base. However, the deformation of the soil base obtained using the coupling analysis was significantly smaller than the one obtained using the traditional method. The distributions of the settlement with the different methods were various from each other. It can be concluded that the difference in the deformation of the soil base is mainly due to the effect of seepage force and the coupling of horizontal and vertical deformation, which could not be considered in the traditional method. The influence of the curtain depth in the pit was discussed with a series of numerical simulations.

抄録全体を表示

Two-dimensional model tests of shallow tunnels and the corresponding numerical analyses were carried out to investigate the interaction between the tunnel excavation and the adjacent foundation. The existing building loads are applied on the ground considering pile foundation. Here, the interaction effects are investigated varying the lateral distance between the tunnel and the foundation. The model tests were conducted using a newly developed device to simulate circular tunnel excavation. Non-linear finite element analyses corresponding to the model tests are also conducted using FEMtij-2D software where the subloading tij model is used as a constitutive model of soil. Surface settlement and shear strain of the ground, and earth pressure around tunnel are investigated. It is found that tunneling influences on the existing foundation when super structure exists within a certain distance from the tunnel.

抄録全体を表示

Recently, opportunities to construct earth retaining structures nearby other structures or other earth retaining structures have increased due to a variety of construction projects. In these cases, it is considered that the earth pressure on the earth retaining structures greatly changes because of the complicated interaction between the soil and the structures. With regard to the adjacent earth retaining structures, some studies on the set spacing between buildings and the deformation mode of these structures under a static condition have been conducted. However, the mechanism of the dynamic earth pressure on the adjacent earth retaining structures has never been analyzed. In this research, shaking table tests and finite element analyses are carried out to clarify the influence of the set spacing and the deformation mode of adjacent earth retaining structures upon the mechanism of the dynamic earth pressure. The adjacent earth retaining structures in this study are modeled as two walls. As a result, the influence of the set spacing and the deformation mode of adjacent earth retaining structures on the mechanism of the dynamic earth pressure is clarified.

抄録全体を表示

This paper presents a study on excavation-induced deformation characteristics of ground and adjacent building using three-dimensional (3D) decoupled simulations. A decoupled analytical technique is proposed to enhance the consideration of both the 3D nonlinear soil behavior and the inelastic structure responses. The excavation effects and the adjacent structure’s responses are decoupled and simulated by two separate programs: PLAXIS 3D for excavation and SAP 2000 for structure. Two models are bridged by a simple iteration scheme. A well-documented excavation case history and low-rise framed building are used for demonstration. The obtained results exhibit that the decoupled analytical method is feasible to incorporate properly the 3D nonlinear soil behavior and the inelastic structure responses. It also seems practical to use since the numerical outcomes often converge within several iterations. The analytical results show that the lateral and vertical movements of the structure are significantly different from those of the greenfield ground. In addition, more in-depth inelastic structure responses can be investigated such as where the plastic hinge may occur in the structure. This is a significant advancement as it provides additional insights on assessing the building’s potential damage and serviceability.

抄録全体を表示

Buttress walls are a common construction method in Taiwan for protection of adjacent buildings during excavation but their mechanism in restraining movements was not fully understood. This study performs three-dimensional finite element analyses of two excavation cases with buttress walls to establish the numerical analysis model. Then a series of parametric study were performed by varying the length of buttress walls. Results show that the main restraining effect for rectangular shape buttress walls comes from the frictional resistance between the buttress walls and adjacent soil while the buttress walls were demolished along with the removal of soil. The efficiency of reducing wall deflection will increase with length of rectangular shape buttress wall. If the rectangular shape buttress wall length was less than 2.0 m, the buttress wall was unable to restrain the wall deflection. The restraining effect for T-shape buttress walls comes from the frictional resistance between the buttress walls and adjacent soil and bearing resistance from the flange. Increase of the web length has a slightly better effect in reducing the wall deflection than that of the flange length for T-shape buttress wall.

抄録全体を表示

Estimating damage potential on buildings induced by excavations is required because more and more foundation pits are excavated near existing building. Thus, displacement control becomes a critical indicator of excavation design. Unfortunately, there is nearly no simplified method that can estimate the influence of excavation on existing building supported by deep foundations and can be easy to be used. Small strain behavior of soil should also be considered when establishing method to estimate influence of excavation on adjacent building for the strain of the soil is very small under displacement control design. In order to fit the requirement for simplified method to estimate the influence of excavations on existing buildings supported by pile foundations, a two-stage method is proposed herein to estimate the responses of piles adjacent to excavations. Firstly, the empirical method based on small strain behavior of soil proposed by Mu and Huang(2013) is employed to calculate three-dimensional free-field soil displacement induced by excavation. Then, an elastic theory method is proposed to calculate the vertical and horizontal pile responses in layered soil. The method is verified through comparison with results from FEM.

抄録全体を表示