Research On The Creep Size Effect And Long-term Settlement Law Of Surrounding Rock In Soft Soil Subway Tunnel

With the comprehensive advancement of the national development strategy of the Guangdong-Hong Kong-Macao Greater Bay Area,the rapid development of urban and inter-city rail transit projects in the Bay Area has resulted in a series of major engineering and technical problems.Deep silty soft soil layers are widely distributed in the Pearl River Delta region,and the soft soil have significant nonlinear creep characteristics.Under the long-term action of the vibration load of subway trains,the soft soil foundation of the interval tunnels will cause excessive post-construction settlement,or even uneven settlement,which will seriously affect Subway trains operate safely.Therefore,it is of great theoretical and engineering significance to study the creep characteristics of soft soil and its size effect in the Pearl River Delta region to analyze and discuss the long-term operation and settlement of subway train tunnels.In this paper,the typical soft clay in the Pearl River Delta region is taken as the research object,and the nonlinear creep characteristics and size effect of soft clay are deeply analyzed through the combination of laboratory test,theoretical analysis and numerical simulation.Taking a certain section tunnel of a subway in the Pearl River Delta region as the research object,the long-term settlement law of the subway section tunnel in the soft soil layer under different reinforcement conditions is analyzed and discussed.Besides,taking a certain section tunnel of a subway in the Pearl River Delta region as the research object,the long-term settlement law of the subway section tunnel in the soft soil layer under different reinforcement conditions is analyzed and discussed.The main research contents and results of this paper are as follows:(1)This paper summarizes the current research status of soft soil creep characteristics and long-term operation settlement law of subway train tunnels and related research results,and discusses the problems and deficiencies in the current research on soft soil creep characteristics and tunnel operation settlement prediction.(2)Through the indoor undrained triaxial creep test of saturated soft clay,the nonlinear creep characteristics of two samples of soft clay with different sizes are analyzed.The results show that the nonlinear creep of soft clay in the Pearl River Delta region has obvious size effect characteristics.(3)Through the indoor undrained triaxial creep test of saturated soft clay,the nonlinear creep characteristics of two samples of soft clay with different sizes are analyzed.The results show that the nonlinear creep of soft clay in the Pearl River Delta region has obvious size effect characteristics.(4)Using the soft clay creep test and creep model research results,based on the ABQUAS nonlinear finite element analysis platform,a three-dimensional finite element analysis model of the subway section tunnel was established,and the vibration load of the subway train was simplified with reference to the current code,and the longterm settlement of the subway section tunnel was studied.By analyzing and predicting the long-term post-construction settlement during subway operation,some research conclusions with theoretical significance and engineering reference value are obtained.