The Application Of Critical Slip Field Theory In The Stability Analysis And Support Design Of Deep Foundation Pit

After more than 20 years of continuous development and improvement,the Critical Slip Field theory has increasingly become a mature and efficient stability calculation method in slope engineering.Based on the review and summary of the research and application status of Critical Slip Field,this paper analyzes the previous research gaps in the theoretical direction,focusing on the calculation method of Critical Slip Field in foundation pit engineering,further improving and perfecting the theory,and expanding its application range.Based on the original theory of programming and optimization,relying on the actual engineering case,this paper initially establishes the numerical analysis method of Critical Slip Field of foundation pit,puts forward the joint calculation method of active and passive sliding field of multi support pile wall foundation pit and equivalent beam method,and analyzes and discusses the influencing factors of the joint method,which is summarized as follows:Considering the influence of various factors such as support on the stability of foundation pit,the strip calculation format of M-P method is improved,and the Critical Slip Field numerical method of foundation pit based on strict method is preliminarily proposed.Based on relevant engineering examples,the variation of the overall stability of foundation pit under the influence of excavation depth and support is studied,and the check calculation results are compared with arc sliding strip method.The calculation and analysis show that in the absence of horizontal support,the initial test value of safety factor should be small,and the dangerous sliding surface and direction field of foundation pit without considering the support are steeper than those with considering the support,which is easy to lead to relatively small sliding area in the entrance section;Compared with the circular sliding surface assumed by the foundation pit code,the method proposed in this paper can search out a more reasonable cr itical sliding surface of any shape,and the checking value of the safety factor can be high reliability.Based on the original Critical Slip Field of foundation pit,the simulation program was modified and optimized,and the Active and Passive Critical Slip Field of the soil before and after the pile wall and the soil pressure of pile body were simulated and calculated,proved the rationality and effectiveness of the application of the Critical Slip Field theory in pile-wall foundation pits;at the same time,the active and passive fields of the foundation pit are applied to the equivalent beam method,and a joint design method which can consider the friction between piles and soil and heterogeneous soil is proposed and compared with the original equivalent beam method,and some influencing factors of the joint design method are analyzed.A large number of calculations show that the joint design method is more reasonable than the original equivalent beam method in the parameter design of the foundation pit supporting structure,has higher credibility and accuracy,can effectively improve the safety of the foundation pit project,and can be close to the project actual;at the same time,the effects of frictio n angle in soil and friction angle between pile and soil on the calculation results of joint design method were analyzed more comprehensively,which provided a reference for foundation pit support design under different engineering geological conditions.