| According to the existing specifications,for deep buried tunnel,the pressure of supporting structure is mainly from the soil weight in pressure arch,thus the pressure arch height is the main basis to determine the load of deep buried tunnel.However,the calculation formula of the pressure arch height in the existing specification is based on the drilling and blasting method,and formulated by the statistical analysis of the investigation data of hundreds of tunnel collapse,mainly with engineering analogical method.From the point of view of the formula,the pressure arch height of the tunnel surrounding rock only considers the influence of tunnel span and surrounding rock grade,but the existing research data shows that,tunnel excavation method,rock delamination interface,rock physical and mechanical properties also have great impact.From the existing formula,the pressure arch height is mainly affected by the surrounding rock grade and tunnel span,to study the pressure arch height of the tunnel under different excavation methods,it could not be studied separately.So this article is to study the pressure arch height with four different excavation methods,under four kinds of surrounding rock grade and four span tunnel,so there are 64 kinds of conditions totally,with the help of the finite element software MIDAS / GTS to simulate numerically.The main research contents and conclusions of this paper are as follows:First,summarize the research status,conclusions and main calculation theory of the pressure arch,and analyze the stress field change caused by the tunnel excavation;Second,introduce the finite element method,the tunnel construction method and the finite element simulation process,and model and calculate the tunnel under different working conditions with the finite element software;Third,in the finite element simulation analysis,the stress path and stress curve of tunnel excavation are confirmed,and the pressure arch height under different excavation methods are determined;Fourth,after analyzing the tunnel pressure arch height under different excavation methods,and comparing the calculation results,the following conclusions are drawn:a)the calculated height value of pressure arch were less than the specification of a given value under each construction method,which indicates that the standard value is safe,and can be furtherly optimized;b)the pressure arch height is different under different construction methods,and it is less when under full section method than with CD method;c)The worse the tunnel surrounding rock is,the larger the tunnel span is,the greater the pressure arch height difference under different excavation methods is.d)The construction method has influence on the height of the pressure arch,so the influence of the excavation method should be considered when calculating the pressure of surrounding rock of the deep tunnel.This paper’s calculation results can provide a reference for correction of the given formula of surrounding rock pressure of deep tunnel. |
