Design Of Foundation Pit Support And Analysis Of Anti-uplift Stability

The rapid development of foundation pit engineering,widely exists in all kinds of large underground shopping malls,parking lot,high-rise buildings.Once the collapse instability accidents,it will bring great loss to people’s lives and property.Therefore research on foundation pit support design theory and research theory of stability is very important.Based on the background of a project according to the field survey and design data,the following work:(1)The current literature on foundation pit support design and anti-uplift stability analysis of foundation pit is collected and sorted out,and the current foundation pit support design,common theories of foundation pit anti-uplift stability analysis are summarized,and the advantages and disadvantages of various theories are compared and analyzed.(2)Based on the limit equilibrium principle,the stability analysis model of foundation pit is constructed for cantilever support structure.The sliding soil is divided into active zone and passive zone,and the main body is derived from the law of combined decomposition of forces and the principle of integration.The corresponding expression of anti-slip moment in the passive region and the favorable effect of the upper soil on the pit back to resist the uplift are taken into account.This paper presents a theoretical formula for the stability analysis of anti-uplift stability of two-dimensional homogeneous foundation pit.Based on the stability analysis of anti-uplift foundation pit in two-dimensional deep foundation pit,the checking formulas for anti-uplift stability of multi-stratum foundation pit and three-dimensional deep foundation pit are put forward.The stability analysis of anti-uplift of three-dimensional deep foundation pit assumes that the sliding body of foundation pit is a columnar body.When the aspect ratio of foundation pit is in a certain range,the value of anti-slip moment provided by soil on both ends of cylindrical body is large,which is difficult to ignore.(3)A concrete example is used to verify the rationality of the 2D and 3D methods proposed in this paper,and the safety factor of the stability of foundation pit against uplift with the physical and mechanical parameters of soil layer and the insertion ratio are discussed.It is concluded that the safety coefficient increases with the increase of cohesion,angle of internal friction and insertion ratio,and decreases gradually with the increase of groundwater level due to the effect of osmotic pressure.(4)Based on the software of Lizheng deep foundation pit support design combined withgeological survey data,the selection and design of foundation pit structure for two typical sections are carried out,and the reasons for the difference between the elastic soil pressure method and the elastic soil pressure method for the support design and their respective applicability are analyzed.