Sresearch On The Influence Of Loag-bearing Performance And Structural Safety Of Cracked Lining In Qingdao Underpass Tunnel

With the continuous increase in the service life of subway tunnels,various types of diseases appear in the tunnel structure.Among them,the tunnel structure lining cracks are the most significant.This paper takes the tunnel engineering under the special ground conditions of the Qingdao subway as the background.Study the influence of tunnel cracks on the lining from two aspects of load-bearing performance and safety performance Based on the three-dimensional numerical model,this paper focus on the study of structural bearing mechanical characteristics under different lining cracking conditions and the effect of lining cracking on structural safety.The main contents of the research are as follows:(1)The investigation work was carried out on the typical tunnel section of Qingdao Metro Line 3 where cracks occur frequently.It mainly investigated and analyzed the lining crack distribution law and crack geometric characteristics in this section,and combined the distribution law and the geometric characteristics of cracks to carry out special detection of important parameters such as crack strength,length,width,and depth.Integrating on-site inspection content and mathematical statistical analysis methods to evaluate the internal law of crack distribution and the degree of dispersion of geometric properties,laying a sufficient reference basis for subsequent numerical simulation calculations.(2)Using ABAQUS finite element calculation software,design 13 sets of working conditions,compare and analyze the surrounding rock-lining contact stress and tensile damage process of the lining structure based on different parts and different geometric characteristics of Qingdao special stratum conditions,and analyze the results of numerical calculations.The lining crack evolution law and the effect of cracks on the bearing characteristics of the structure under the instability state.(3)From the force characteristics of the lining structure,the law of deformation,and the law of internal force distribution of the lining structure,it is revealed that the changes of cracks at different locations,cracks of different depths,cracks of different lengths,and cracks of different widths on the safety of linings.Based on the internal force distribution law of the lining section,the safety factor of the lining structure is calculated,and the analysis of the law of influence on the safety of the tunnel section is completed.(4)Combining tunnel crack detection methods,tunnel crack classification and grading standards and other lining crack research methods,and comprehensively considering the geometric state indicators of subway tunnel lining cracks,establish a universal and improved safety evaluation structural model based on fuzzy neural network,complete the qualitative and quantitative classification and quantification of multiple indicators of tunnel lining cracks,and evaluate and analyze the safety level of Qingdao subway tunnel cracks.