Evaluation Of Safety Factor Of Tunnel Surrounding Rock Based On Deformation Control

In recent years,with the improvement of economic level,the construction of the transportation network has also been greatly developed.Tunnel is a key part of transportation.For many years,its engineering design has mainly relied on experience and semi-empirical methods such as engineering rock mass classification and engineering analogy.It has been in the stage of qualitative evaluation for a long time,and it is urgent to develop in the direction of quantitative evaluation.Therefore,this paper proposed a method for quantitative evaluation of tunnel surrounding rock stability based on deformation control,and analyzed and used this method.The main research work and results are as follows.First,it introduced the basic theory of the strength reduction method and the FLAC^{3 D} software using the finite difference method,and demonstrates the characteristics of both.On the basis of predecessors,this paper combined these two methods to propose a quantitative evaluation method for the stability of tunnel surrounding rock based on deformation control.Secondly,through a numerical example,the mechanism and specific realization method of this method were further explained,and some characteristics of this method were shown.This method takes the ultimate strain around the tunnel as the limit state in the strength reduction method,and reduces the elastic modulus in the same proportion when the c andφvalues of the rock and soil are reduced.Based on this improved strength reduction method,using FLAC^3D and the FISH language tool in it,self-editing program codes to realize this method.Comparing this method with the safety factors of the calculation examples obtained by other three common criteria,it was found that the method in this paper is conservative compared with the results obtained by these three criteria,but it is closer to the real situation.It is relatively simple to use,and is especially suitable for situations where deformation is the control condition.Then,taking the surrounding rock of theⅡandⅢgrade tunnels after the initial support as the research object,selected the appropriate influencing factors and designed the orthogonal test.The test was divided into two groups according to the grade of surrounding rock.Using the method in this paper,each group performed 32times value simulation calculations to obtain the test results.The results were visually analyzed and multi-factor analysis of variance,qualitatively and quantitatively analyzed under the conditions of using the method in this paper,the significance of the influence of each factor on the safety factor was analyzed.After that,using regression analysis methods,the quantitative relationship between the safety factor and each factor was established,and the results were tested for significance,and the conclusion that the regression model is good and the regression effect is very significant was obtained.Later,the ultimate strain was used as an experimental factor to further discuss,and it was found that its influence on the safety factor is very significant,and regression analysis was also carried out here.After that,after removing the insignificant factors,a linear regression analysis was performed on the results of the orthogonal test.Here,the same regression analysis was performed for the case of considering the ultimate strain.The regression results are relatively good,and the quantitative relationship between the safety factors and the various factors under different conditions were established.Finally,taking three engineering examples as the research object,the safety factors of their surrounding rocks were obtained using the method in this paper,and the calculation results were predicted using the regression equations of the safety factors and various factors obtained previously under different conditions.According to the calculation results of the three examples and related analysis,it can be considered that the method in this paper is more suitable for deep buried II and III grade tunnels,and the safety factor obtained is basically reasonable;the regression equation has a acceptable and valueble predictive ability for the safety factor.