Study On Displacement Of Soil Around Foundation Pit Under Lateral Unloading

With the rapid development of social productive forces and economic, to discuss about high-rise buildings and develop of underground space becomes a spot of city building. The excavation design foundation pit is transformed from strength control to deformation control. For control deformation and protect the environment and make safe economic, it is necessary needs further research and exploration the soil deformation around foundation pit.By laboratory experiment and numerical simulation, relation between soil pressure and displacement under lateral unloading on foundation pit is studied, useful results on engineering is obtained.(1) This paper briefly discussed the deformation characteristics of soil when excavation and the factors of deformation characteristics. Theoretically analyzed the stress path, deformation control standards of the soil when pit excavation and three-dimensional effect of excavation.(2) On the basis of ordinary triaxial and true triaxial shearing experiment, the relation curves of stress-strain are described, the stress-strain character is analyzed under isotropic consolidation: At stress path of constant vertical loading and reduction confining pressure, curves are strain hardened and hyperbolic. Vertical size is comperssed and radial size is expanded. At this stress path and same confining pressure, in connection with failure principal stress difference, true triaxial test value is higher than ordinary triaxial test value, ordinary triaxial drained shear test is higher than the undrained shear test, the value of failure vertical strain is twice of radial. In normal , the vertical failure vertical strain value and radial strain value is equal.Formula of vertical and radial deformation modulus is derived under draining and lateral unloading.(3) At last, simulated a foundation project using the finite element software PLAXIS. We studied the force of supporting structure and horizontal displacement of the soil around the pit and got some conclusions about the horizontal displacement of the soil around the pit.