Study On Soil Pressure Characteristics At The Bottom Of Narrow Foundation Pits In Thick Soft Soils And Optimization Of Supporting Piles

Engineering practice and theoretical research have shown that foundation pit engineering has obvious spatial effects,especially the width,size and shape of the narrow foundation pit show great differences in the deformation and stability of foundation pit.However,the existing code only takes the single-side enclosure structure as the research object,ignoring the influence of width on the foundation pit foundation soil pressure and stability,resulting in a waste of foundation pit support design in practical engineering.This paper takes the narrow foundation pit in soft soil area as the research object,and the main research work is as follows:(1)By using the checking theory of the overall stability of the foundation pit,the stability of the foundation pit against the uplift and the stability of the foundation pit supporting structure to analyze the basement soil pressure of the narrow foundation pit,it is clear that in the checking process of the foundation pit stability,the width has a greater impact on the foundation pit basement soil pressure,and the traditional specification of the narrow foundation pit supporting design is conservative,with a larger space for optimization.(2)ABAQUS finite element simulation software was used to establish the numerical model of narrow foundation pit,and the basement soil pressure was studied under different excavation depths,different thickness of silt soil layer and different excavation widths,and the influence of the width of foundation pit and the thickness of silt layer on the horizontal displacement of supporting piles and the basement soil pressure of foundation pit and its variation rule were analyzed.(3)According to the variation law of soil pressure in the foundation pit of narrow foundation pit in soft soil layer,the increase coefficient of soil pressure in the foundation pit of narrow foundation pit is defined,which can quantify the variation range of soil pressure in the narrow foundation pit and reveal the influence of width on the foundation pit basement pressure(4)Combined with the influence of width on the stability of narrow foundation pit,the change trend of basement soil pressure of narrow foundation pit in soft soil layer and the increase coefficient of basement soil pressure of narrow foundation pit,the optimization idea of supporting pile of narrow foundation pit in soft soil layer was proposed.