Behavior Of Bridge Piles Subject To Excavation-Induced Soil Movement

With the rapid development of urban construction,deep foundation pit excavation on nearby buildings influence had got more and more attentions.This thesis studies the subject on the basis of summarizing the existing research results,combining with an instance of a sluice foundation pit excavation,using mature geotechnical finite element software PLAXIS to analysis of the influence of sluice foundation pit excavation of adjacent bridge pile foundation.Usually,the adoption of the plane assumption simplified models and improved calculation speed,but it ignored the significant 3D effect of deep foundation pit excavation engineering,and the soil idealized resulting in an inaccurate calculation result.Three-dimensional simulations is necessary.In order to further research the influence of excavation on adjacent pile foundation, following works have been done in the paper and obtain the corresponding results.1、Considering the actual soil distribution, the geotechnical finite element numerical analisis software Plaxis 8.2 is used to simulate the process of excavation; and the effects of many factors on the behaviors of adjacent pile are investigated, including net distance between excavation and pile, stiffness of pile, stiffness of diaphragm wall, vertical load, constraint conditions of pile head. The behaviors of lateral displacements and bending moments of pile are studied in detail.2、Firstly, the concept of stress path is reviewed. Proposing the three-dimensional stress path considering the rotation of princupal thress axis by combining excavation and dewater.Then the analysis of the stress path during excavation and dewatering is carried out by numerical method. It is shown that different stress path of soil mass unit developed toward to the different way.Last, the typical stress paths of both inner and outer parts of foundation pit during excavation and dewatering are obtained.3、Based on the two-dimensional model, finite element numerical analisis software Plaxis 3D is used to simulate the process of excavation, and the behaviors of adjacent pile are investigated, the simulation has captured lateral soil movement on the both sides of the pile. Compared with2D and 3D results, verifying the large spacing of pile foundation plane equivalent is reasonable. Summarizes matters that should pay attention to in the plane equivalent simplified. Finally this paper puts forward the corresponding reinforcement measures.After reinforce, we achieves good effect.4、Compared with the measured data, the results of numerical analysis is larger than the measured data, it indicates the numerical simulation is effective for the practical engineering and provides a reference for the actual pit construction and design.Through the above analysis shows that numerical analysis can better simulate the excavation process, the influence of soil movement induced by the deep foundation pit excavation on adjacent pile can’t be ignored. During the construction, it is necessary to strictly control each step of the excavation depth and monitor the displacement of bridge pile foundation.