Study On Working Behaviors Of Soil Nailing Wall And Pile-anchor Combined Supporting Structure In Filling Foundation Pit

In recent years,with the rebuilding of the old city and the expansion of the new city,land resources have become increasingly scarce.Therefore,there are more and more foundation pit projects for excavation and support in the fill area.Soil-nailed wall and pile-anchor combined support structures are gradually being used in filled foundation pits.Compared with soil-nailed wall support,the safety of the combined support structure has been significantly improved.Compared with pile-anchor support structures,the safety of the combined support structure has been significantly improved.The cost has been reduced,so its application in deep foundation pit support projects has become more and more extensive.However,there are some problems in the application process.The main reason is that the theory lags behind the practice.The synergistic mechanism of the soil nail wall and the pile anchor in the filled foundation pit is not clear.It is very necessary to understand the synergistic mechanism.Based on the Jinan Lishan Yongxiangli Project,this paper first conducts a theoretical analysis of the combined support design of soil nailing wall and pile anchor in the filled foundation pit,and establishes three different numerical analyses using finite element analysis software and corresponding design models.Model,analyze the action mechanism of the soil-nail wall and pile-anchor combined supporting structure,introduce the over-consolidation ratio OCR,analyze the influence of the under-consolidation characteristics of the fill on the working behavior of the foundation pit supporting structure,and study the influence on the combined supporting structure Factors of work traits.The main work and content are as follows:(1)Based on the under-consolidated characteristics of the fill,the static earth pressure calculation method suitable for under-consolidated formations such as fills is analyzed.The analysis shows that the static earth pressure of the under-consolidated formations such as fills is greater than the static soil of the normally consolidated formations.pressure.(2)Relying on the foundation pit support project of Yongxiangli Garden in Lishan,Jinan,the corresponding numerical analysis model is established: one is to simplify the soil in the upper soil nail wall support range to overload and establish an overload model;the other is to build the upper soil nail wall Transform into a self-stabilizing slope and establish a grading model;third,consider the synergy mechanism of the soil-nailed wall supporting structure and the pile-anchor supporting structure,and establish an overall model;the results show that the overall model is due to the upper soil-nailed wall Play a role,the horizontal displacement of the pile body and the vertical displacement of the ground surface are minimal,thereby improving the safety of foundation pit excavation.(3)The finite element software was used to establish a three-dimensional overall model,and the influence of different values of the over-consolidation ratio OCR on the performance of the foundation pit support structure was analyzed.The analysis shows that as the over-consolidation ratio OCR increases,that is,the degree of under-consolidation of the soil decreases,the maximum horizontal displacement of the pile and the maximum surface settlement outside the pit gradually decrease.The comparative analysis shows that when When the OCR value of the overconsolidation ratio is 0.6,the numerical simulation results are in good agreement with the field measured data.(4)The single factor analysis method is used to analyze the influencing factors of the joint support structure’s working behavior,and the influence of the change of each support parameter on the deformation and force of the foundation pit is quantitatively analyzed.