Analysis Of Deterioration And Long-Term Safety Evaluation Of Railway Tunnel In Redbed Soft Rock

The technical condition of operation railway tunnel lining is directly related to the safety of railway traffic.The red layer soft rock in the study area has the characteristics of water expansion,softening,disintegration,disturbance,damage and deterioration,as well as the influence of the construction quality and the comprehensive environmental effect.Under the long-term service conditions,the red layer soft rock operation tunnel will inevitably appear various kinds of diseases,which will seriously reduce the safety of the lining structure and shorten the maintenance and residual life of the tunnel.Therefore,it is very important to study the structural deterioration and long-term safety evaluation of railway tunnel with red bed soft rock.In view of this,this paper comprehensively uses theoretical analysis,indoor test,numerical simulation and other research means to study the long-term safety of lining structure and the influence of residual life on the deterioration of the surrounding rock state of the tunnel,the inadequacy of tunnel lining thickness and the void behind the lining.The main work and research results are as follows:1?The physical and mechanical properties of the red layer soft rock of the Suining formation of the Jurassic syste m of Dacheng railway tunnel were tested.The test results showed that: the red layer soft rock large porosity,has strong water absorption;slake durability index is low,the durability is weak;the softening coefficient is low and the softening effect is obvious;the uniaxial compressive strength and shear is low strength,the cohesive ability is poor.The surrounding rock of the study area has the characteristics of water expansion,softening,disintegration,easy disturbance,damage and deter ioration and so on.In the long-term service conditions,it is easy to cause the destruction of the surrounding rock and the decline of its own bearing capacity.The complex and varied engineering characteristics of the surrounding rock in the study area is one of the main reasons for the deterioration of the supporting structure of the tunnel during operation.2?Taking the basic principle of tunnel mechanics as the starting point,set up the formation structure model of the lining thickness and the voids that beside the lining mechanics analysis model.The stress state and the safety factor change law of the tunnel lining structure are analyzed when the defect degree and the defect position change.Based on the principle of the bond slip of reinforced concrete,the mechanical model of surrounding rock deterioration of tunnel is established to simulate the whole process of tunnel lining structure from normal service to crack extension to structural failure under the condition of surrounding rock deterioration,and the method of evaluating the structure safety through the limit crack width is established.3?Taking the operation lining of the red bed soft rock tunnel as the research object,analyze the calculation method of the residual life influence factors of the lining structure of the red layer soft rock tunnel.Based on the residual life evaluation model of the operation tunnel lining structure established by the predecessors,the influence of the residual life of the single disease and a variety of diseases on the lining structure of the tunnel lining is respectively shown.Open the study.The results show that the deterioration of lining material has little effect on the remaining life of lining structure,and the deterioration of the surrounding rock will greatly reduce the remaining life of lining structure,and the comprehensive effect of various diseases will lead to the remaining life of the tunnel far below the design life.