Finite Difference Mathod Analysis For The Deformention Of The Deep Foundation Pit In Soft Ground

Shoring deep foundation pit is an engineering intimately related to soil, especially to the typical soft soil district represented by Shang Hai. Aside from its time effect, the spatial effect of soil is also prominent. Agreement has been reached by rock and soil engineering circle that the displacement of retaining wall would be efficaciously controlled if we take full advantage of the spatial effect of soil and demarcate the exposed space of foundation pit reasonably. Accordingly, the cost of engineering will greatly reduce. In today's world, to use spatial effect appropriately has become increasingly important to surrounding enviroment in deep foundation pit. Nevertheless, many issues remain in the process of digging foundation pit, which are concerned with the rules of deformation of retaining wall of deep foundation pit, displacement of surrounding stratum, deformation of civic pipelines in the neighborhood and the relations among them.This thesis adopts the method of limited difference which has presented its obvious advantage in solving great deformation of rock and soil engineering, applies the powerful analysis software in rock and soil engineering, namely Flac3D, establishes practical model of three-dimension analysis. In this model, in consideration of elastic-plastic mechanics of soil, I use the Mohr-Coulomb elastic-plastic model to deal with it; apply zone element to retaining wall to model the deformation, and stress of it effectively; adopt interface element to model the contact influence between stake and soil; consider the fluid-mechanical interaction effect of water and model the precipitation process. Meanwhile, in this article, I also introduce how to ascertain the specific materials and parameters in this model and make efforts to use common parameters and simple but practical method in engineering designing.In the following part, this article applies this model to a specific example to analyze the rules and characteristics of the deformation of retaining wall, the settlement of the earth's surface, the displacement of stratum and surrounding pipelines. In regard to the deformation of retaining wall, I mainly model the following factors: the depth of digging, the size of foundation pit, the stacking and unpacking of construction, groundwater and emphasize the influence of digging depth and the size of foundation pit to the deformation of retaining wall. Concerning settlement of earth's surface and displacement of surrounding pipelines, I focus on modeling the following factors: digging depth, distance from foundation pit, depth of the pipelines being buried, size of foundation pit and influences of neighboring building.Analyzed data indicates that taking full advantage of the spatial effect of soil could reduce cost effectively, thus exhibiting prominent economic benefits. It also presents the necessity of adopting three-dimension analysis and points out the rules and characteristics of deformation of retaining wall, displacement of earth's surface and civic pipelines in the condition of soft soil, which sheds light on the inspection, measurement and protection of surrounding buildings and civic pipelines in the future.