Study On Deformation And Destruction Characteristic Caused By Foundation Excavation Based On Strain Softening Model

The instability and destruction of foundation pit were affected by many factors, the main reason from two aspects:one is the condition of foundation pit soil, including soil bearing capacity, mechanical properties; another one is how to choose and apply supporting structure after the excavation of foundation pit. Therefore, it is significant to choose the appropriate supporting structure and supporting form according to different soil condition.Based on the strain softening model, soil softening rate was analyzed in this thesis. The influence on the foundation pit deformation process, failure mode, also were researched. According to different failure forms and destruction features, we put forward the reasonable supporting advices. Then we analyze the influences of embedded depth of cantilever supporting structure on foundation pit. Came to the following conclusion:(1) Softening rate of the soil has an important influence on the damage scope and destruction form of foundation pit. If soil softening slower, the range of destruction of foundation pit is relatively small, the slip line is closer to a straight line, the soil above slip line will be more integrated. If soil softening faster, the range of destruction of foundation pit is bigger, the slip line is more pliable, soil above the slip line crushed more serious. According to the damage characteristics, two damage forms were defined as the "fragmentary collapse" and "integral sliding". If soil softening slower, more attention should be paid on the basal part of the supporting structure, which located on the corner of the pit bottom, because it is easily to be sheared failure by the sliding soil. If soil softening faster, we should improve the stability of the whole supporting system, to prevent the unstability of the supporting structure and the foundation pit.(2) Adequate embedded depth was important prerequisite of the stability of foundation pit. But in weak stratum, supporting structure embedded more deeply will tend to increase the depth of destruction region, to a certain extent, because the deep stratum is disturbed by the retaining structure. It is more obvious when is higher. When apply supporting structure, it is better to avoid that the strength of supporting structure is surplus. Then the destruction region will be reduced, when the foundation pit collapse.