Study On Surrounding Rock Pressure Characteristics And Support Optimization Of Deep Buried Soft Rock Tunnel

In recent years,C hina’s transportation construction is increasingly developed,and the length of highway and railway construction has reached a new milestone.The excavation length and section size of tunnel construction are developing towards the direction of super long and super large.At the same time,the soft surrounding rock stratum and the phenomenon of large buried depth or complex stress are often encountered in tunnel construction.After excavation,the surrounding rock stress is too large,the initial support deformation is serious,which affects the construction progress.The determination of surrounding rock pressure in the field of tunnel engineering is the premise of tunnel design.Therefore,it is of great significance for the safe construct ion and operation of tunnel engineering to explore the distribution characteristics of surrounding rock pressure and deformation of surrounding rock under the condition of deep buried soft surrounding rock.Based on a soft rock highway tunnel project in Northwest China,this paper studies the surrounding rock pressure and support system of deep buried soft rock tunnel by using comprehensive research methods such as theoretical analysis,field monitoring and numerical simulation,and obtains the following results:(1)From the point of view of tunnel surrounding rock pressure,this paper introduces the formation,classification,main influencing factors of surrounding rock pressure and the applicability of calculation method of surrounding rock pressure of deep buried tunnel;analyzes the initial stress state of surrounding rock and summarizes the mechanism of initial support: the main performance is to improve the surrounding rock stress conditions,support the surrounding rock,common bearing and dense surrounding rock and surrounding rock integration of these three main aspects.(2)Based on the project example,the field monitoring is carried out,the monitoring results are sorted out,and the surrounding rock pressure and support stress characteristics are summarized and analyzed,including the variation law,distribution characteristics and range distribution of surrounding rock pressure,and the stress characteristics and distribution rules of the initial support steel arch frame and shotcrete are analyzed.(3)The ABAQUS software is used to establish a three-dimensional numerical model,and the numerical simulation is carried out based on examples.Under the condition of three steps and seven steps construction method,37 working conditions such as different lining thickness,elastic modulus,bolt length,surrounding rock strength and tunnel buried depth are established to analyze the distribution characteristics of surrounding rock stress and deformation of deep buried soft rock tunnel,so as to provide a reference for reasonable support parameters.