Study On Horizontal Displacement Pushover Analysis And Stability Evaluation Of Restraint Pile In Deep Foundation Pit

Retaining pile has become the main form of support occupies an important position in the foundation pit support with the continuous development of foundation pit engineering.Retaining pile as part of the foundation pit support system,mainly to ensures the safety of surrounding buildings and underground pipeline,the stability of the slope,and resists the displacement of the soil caused by the unloading of the foundation pit in the process of foundation pit excavation and the use of the foundation pit.In order to ensure the safety of the foundation pit and maintain the stability of the foundation pit,retaining pile needs to have enough bearing capacity to play its important role in the foundation pit,so the retaining pile needs to be designed according to the foundation pit requirements.The design elements of the retaining pile include pile diameter,pile length,reinforcement,embedded depth,etc.Retaining pile forms a lateral stiffness sufficient to resist the displacement of the foundation soil to meet the needs of the foundation through the combination of many design elements.As an important supporting structure for maintaining the safety of the foundation pit,the reinforcement of the retaining pile is much larger than that of the pile which is subjected to the vertical load.The design of the retaining pile should be based on the actual conditions of the foundation pit,with sufficient capacity at the same time,to avoid the waste of experience and budget overrun caused by design.Therefore,it is necessary to analyze the displacement and stability of the retaining pile to optimize the design parameters of the retaining pile.In this paper,a foundation pit in Shanghai supported by retaining pile is been taken as an example,the foundation pit retaining pile is been seen as a flexible foundation beam,while the internal support and the base pit under the soil is been seen as a flexible bearing.In this paper,the horizontal displacement of the retaining pile under the load is calculated by separating the retaining pile pile into the units using the finite element method.The elasto-plastic state of the retaining pile is analyzed by the step-by-step loading based on the Pushover analysis,which provides the basis for the design and displacement monitoring of the retaining pile.The main contents of this paper are as follows:1.This paper details the displacement analysis of retaining pile and the development of pushover analysis methguod at home and abroad,and summarizes the contributions of many scholars in this research direction and the inadequacies of existing methods.At the same time,it emphasizes the importance of support in foundation pit engineering,and points out the necessity of displacement analysis.2.The retaining pile is discretized as the unit.According to the characteristics of external force of retaining pile under the pressure of each soil layer,the displacement of the retaining pile element node is calculated through the finite element method,Of the displacement state,and the displacement state of the retaining pile is obtained.This method overcomes the shortcomings of the traditional retaining pile displacement calculation method.3.In this paper,Pushover analysis is carried out for retaining pile.The horizontal displacement of the retaining pile is calculated by the stepwise loading of the lateral pressure,and the position of the retaining pile in the plastic stage and the ultimate displacement value of the retaining pile are analyzed.4.The concept of safety factor of retaining pile under Pushover analysis is put forward,The stability of the retaining pile and safety load is calculated based on this concept.At the same time,the influence of pile diameter and embedding depth on its horizontal displacement is discussed,which can provide reference for retaining pile design and monitoring.5.The model of retaining pile is established by MIDAS-GTS / NX finite element software,and the elastic-plastic evolution process of retaining pile under excavation and additional load is analyzed and its plastic zone position is determined.