Environmental Impact Analysis Of The Pile-anchor Foundation Pit In Kunming

Deep foundation pit engineering is often located in complex environment now. Too large deformation of foundation pit engineering will damage adjacent buildings, subway tunnel, road and pipeline. Considering that the pile-anchor supporting structure is widely used in foundation pit engineering, researching the environmental impact of it has guiding significance on design and construction of engineering. In this paper, the condition of on-site construction and actual monitoring data of a pile-anchor foundation pit engineering in Kunming were sorted and analyzed. Based on the project, a three-dimensional finite element model is established by Midas/GTS finite element software. The model considered the interaction of soil, pile-anchor supporting structure and the surroundings. The construction process is simulated according to the construction plan. Consistency of numerical analysis results and actual monitoring data proves that, the modified Mohr Coulomb model parameters and the pile-soil contact parameters are selected reasonably. And the analysis method is reliable.In addition, the influence of different factors on the deformation of pile-anchor foundation pit and adjacent structures are explored. This involve considerations such as stiffness and depth of retaining structure, pre-tension of anchor, position and load of surroundings. The adjacent structures are building with pile foundation, building with shallow foundation and subway tunnel. Main conclusions of the study are as follows:(1) When the nearby surroundings are pile foundation building, Lateral envelope curve substantially shaped belly. Maximum lateral displacement range at 0.23% 0.29% of foundation pit depth (H), and it occurs at the 0.6-0.8 of H. Ground settlement curve distributes as a groove. The largest settlement located at 0.26-H behind the retaining pile. The largest settlement range at 0.05%-0.14% of H, and the largest effected region of surface subsidence is about 3.7H. The maximum for building deformation located at the side close to the excavation line.(2) When a building of shallow foundation close to the pile-anchor foundation pit, deformation of both are larger than when there is a pile foundation building. Maximum lateral displacement generally occurs at the top of pile, it can reach 0.53% of H with the impact of building load. The largest settlement located at the corner of building close to the excavation line. It will be danger when the building close to the pit foundation.(3) Without considering the dynamic load of subway, the deformation of foundation pit and nearby subway tunnel are researched. The main influence factors are excavation depth, distance between subway and pit, buried depth of subway. Lateral envelope curve shaped belly. Maximum lateral displacement generally located at the 0-0.6H.Surface subsidence curve is double fluted, the nearer one situated at 0.33H away from the retaining piles, and the other at 1.32H. The largest effected region of ground settlement is 3.6H.The upper part of the tunnel with a large deformation, the lower portion is less deformed.