Numerical Analysis Of Support Engineering In Foundation Pit Of XiaoCunQiao Subway Station

With the continuous development of the modernization, more and more underground structures and high-rises are appeared. The scale and the depth of deep foundation excavation are increasing. The conditions around foundation pit are more and more complex. The existing foundation design theory and normal construction technology cannot meet the smooth construction requirements and the protection of the environment. Therefore, the numerical simulation technology of foundation has important significance of theoretical and practical engineering.In this paper, large general-purpose finite element program ANSYS software is as a platform, and the XiaoCunQiao station which is one of Beijing subway stations is as the foundation pit project. On the basis of considering soil-structure interaction, a 2-D plane FEM model is established. In the model, soil body use PLANE42 element and anchor rod use LINK1 element. The soil adopts D-P constitutive model. The contact pair element is used for describing the relationship between the pile and soil. The"element birth and death"method is adopted to simulate the stepping excavation of the foundation pit and supporting applied. Compare the calculated displacement values with field results to get the corresponding conclusions. Meanwhile, change the supporting condition and simulate again. Then, compare the characteristics of the foundation pit between different supporting conditions to get the corresponding conclusions.Based on the calculated results of the finite element analysis, some conclusions are obtained as follows: For the project, the apophasis of the pit bottom increases along with the stepping excavation. It reaches the maximum value in the middle of the pit and decreases with the shorter distance from the wall. The sedimentation values of earth surface around the pit increases gradually along with the stepping excavation and decreases with the longer distance from the pit. The maximum horizontal displacement value of the pile appears in the top at the beginning of excavation and gradually appears in the waist with the stepping excavation and supporting applied. The displacement of both ends is smaller. The equivalent stress value of the soil is minimal at the bottom of the pit and earth surface, the maximum value appeared at the bottom of pile and the corner of the pit in the soil. The stiffness of pile and pre-stress anchor is much bigger than the soil, so the extent around them appears stress concentration phenomenon. Compared with the actual monitoring data, it is consistent with the reality.Change the actual engineering support method to interior support and compare the calculated results with bolting support. All sorts of deformation, stress, etc have almost the same change trend, but the effect is better than bolting support method.Through the above research, it shows that different types of support produce different effects on deformation of foundation pit engineering. Meanwhile, ANSYS finite element analysis software can be used as a tool in foundation pit engineering field. It can simulate foundation pit engineering of different complex conditions and provides some theoretical basis and guidance to the actual construction design. It also has practical significance to ensure the safety of the practical construction.