Mechanical Behavior Analysis Of Cement Soil Reinforcement In Passive Zone Of Deep Foundation Pit In Soft Soil Under Vehicle Load

With the speeding up of urbanization in our country, deep foundation pit excavation engineering in urban downtown has been very common. The design of deep foundation fit has been gradually towards to overall pit deformation control, which is not only to fit the basic requirements for the deep foundation, but to ensure the safety of adjacent buildings and infrastructure. Engineering Practice has proved that passive zone reinforcement is a common method to improve the physical properties of soft soil foundation soil. In China, the current deep foundation design rarely consider the impact of vehicle load, and intensive impact on traffic safety can not be ignored pit, so the design is unsafe. If considering the soft soil foundation reinforcement passive zone, while considering the effect of vehicle load, it may makes pit design more reasonable.In this paper, using ABAQUS finite element software to establish a two-dimensional vehicle loads in deep excavation passive zone reinforced finite element numerical simulation models. In selecting an appropriate model of vehicle load, the analysis of different widths reinforcement, reinforcement depth and add solid elastic modulus of the pit area reinforcement effect of passive influence, made a reasonable reinforcement design, provide a reference for future projects. In this paper, some researches has been studied as follows:(1) It describes the reinforcing mechanism of reinforced cement-soil passive area, soil mechanics propertiesand explores the mechanism of reinforcement in passive zove. Analysis of soft soil foundation soil characteristics of passive earth pressure area, comparisoning of reinforcement deformation excavation by finite element method.(2) Analysis of the type of vehicle load model, based on the role of the object, select the appropriate vehicle load model, established excavation pit model under consideration vehicle load.(3) Select the appropriate soil constitutive model, using ABAQUS establish a two-dimensional pit numerical simulation model, taking into account vehicle load down from plus solid strength, reinforcement depth, width, etc. reinforcement, analyze the results, summarized in the passive zone after reinforcement changes in laws, determine deep excavation passive zone reinforcement reasonable design, provide a reference for future designs.Main conclusions of this study are as follows:(1) The negative impact of pit top vehicle load for the global stability of foundation pit can not ignore. The considering of foundation pit supporting design for the hole top vehicle load is insufficient, which lead design result unsafe. Using cement-soil reinforcement method on passive zone of soft soil foundation pit can effectively control the global stability of foundation pit and prevent in the process of the excavation effect on existing buildings around.(2) If consider both vehicle load effect and passive area soil reinforcement, priority should be given to increase the reinforcement depth, which can get more economic and efficient reinforcement scheme. The current strength of foundation pit supporting design seldom focus on supporting structure itself. When using passive area reinforcement, Supporting structure should be designed for the upper strength is low, while the lower intensity is high.(3) In foundation pit design, consider uniaxial static load and additional dynamic load as Vehicle load is safe, which also conforms to the actual situation; while for uniformly distributed load, the design will be the economy. We suggest that choose the reasonable form of vehicle load should according to the engineering actual situation, in this way can both economic and safe.