Study Of Optimization Design On Supporting Structure Of Deep Excavation Engineering In Rich Water Half Diagenetic Sandstone

In the design and construction of deep foundation pit excavation in areas which have high water level,local variations of hydrogeological conditions due to dewater and excavate,deformation of the supporting structure and the changes of the surrounding environment are interrelated.This article systemat ically sorted and analyzed the monitoring information for the deep foundation pit works of Lanzhou rail transit line wulipu station.By using finite element software to simulate the dewatering and excavation process of foundation pit,in-depth study on deformation characteristics of deep foundation pit at the station in tertiary rich water semi-diagenetic sandstone strata area.The influence factors of the deformation of deep foundation pit with row piles structure are discussed,through the comparison and analysis,the influence degree of each factor on the deformation is obtained,which provides guidance for the optimal design of the supporting structure and the dewatering conditions.The main work and research results were as follows:(1)Combined with the analysis of real-time monitoring data in various conditions of the horizontal displacement of the pile,the settlement of the ground surface around the pit,the axial force of the steel support,the displacement of the top of the pile and the buildings and pipelines.Revealing the deformation characteristics of deep foundation pit of Wulipu station in tertiary rich water semi-diagenetic sandstone special strata,the deformation rule of deep foundation pit(25m depth),that with the supporting system consists of drilling bitten pile and steel supports,under the process of dewatering excavation is obtained.In this paper summarizes the whole set of foundation pit dewatering measures,including water seal,dewatering,drainage,water plugging and seepage prevention.The dewatering results show that the selection of supporting structure and groundwater treatment measures are feasible.(2)To establish the numerical model of dewatering simulation to the excavation of foundation pit,it is concluded that changes in displacement field and seepage field,horizontal displacement of pile,surface settlements and uplift,and analyze the rule of deformation changes with the development of construction steps.The results of simulation and measurement show that the results are similar,it can reflect the deformation law of foundation pit and surrounding soil during the excavation of foundation pit,which can help to predict the deformation in the process of construction and guide the follow-up construction.(3)Through the numerical simulation,the design of supporting structure is analyzed and optimized.Analyze the supporting structure design parameters(row pile diameter,buried depth,steel support position,pre axial force and stiffness)and dewatering conditions(precipitation depth,soil elastic modulus and permeability coefficient)in the process of foundation pit excavation pile horizontal displacement of pit and the distribution characteristics of surface subsidence and deformation rule.Research results have certain reference value to design of the deep foundation pit supporting structure and dewatering in the tertiary rich water semi-diagenetic sandstone special stratigraphic area.