Study On The Supporting Performances In Foundation Pit Of Multi Arch Cement Soil Mixing Walls Reinforced By Section Steels

With the development of urbanization,the development and utilization of underground space has been greatly improved.In order to ensure t he safety and economy of foundation pit engineering,the foundation pit supporting structure has higher and stricter requirements.At the same time,due to the complex diversity of rock and soil,there is a big hidden danger in the complicated foundation pit engineering.So the problem of foundation pit has become a hot and difficult point of the foundation pit engineering.In this paper,a new type of support structure named multi arch cement soil mixing walls reinforced by section steels was proposed based on the mixing performance of propping mechanics in foundation pit wall of straight type steel reinforced cement soil and combined with the multi arch retaining structure advantages.The main research contents and conclusions are as follows:(1)According to the design,construction and monitoring of foundation pit engineering,the straight type steel reinforced cement soil mixing wall mechanical properties of foundation pit were analyzed by using the finite element software PLAXIS.The results showed that the wall supporting structure can achieve good sealing effect,retaining the straight type steel soil cement soil deformation effectively and the lateral control of foundation pit and the top,and had certain reference significance for other foundation pit engineering design;(2)Summarized the research status of multi arch retaining structure,and expounded the calculation method of earth pressure calculation theory and design of foundation pit.Based on the soil mechanics and structural mechanics theory,the calculation model of multi arch cement soil mixing walls reinforced by section steels was proposed.When the multi arch combined supporting structure was simplified to two hinge arch,the stress state of an arbitrary cross section was deduced from the horizontal and vertical direction;(3)Three dimensional model was established by ABAQUS finite element software for multi arch cement soil mixing walls reinforced by section steels in foundation pit engineering,considering the interaction between the wall and the soil,the wall and the steel.Using the method of layered excavation,the displacement and stress of the supporting structure had a detailed analysis.The results showed the multi arch cement soil mixing walls reinforced by section steels can effectively control the pit and the top of the lateral deformation,and could be used in practical engineering;(4)By changing the span of arch,arch,arch height,thickness of arch foot pile diameter,steel flange thickness and web thickness of steel,the supporting performance of multi arch cement soil mixing walls reinforced by section steels was analyzed.The results showed that on the basis of the strength of the supporting structure,the larger arch span,the smaller arch thickness,the smaller arch height and the smaller diameter of the arch foot pile should be chosen as far as possible;steel could be removed and reused at the end of the project,so increasing the steel flange thickness and web thickness could improve the strength of multi arch cement soil mixing walls reinforced by section steels,which reduce the project cost.