Safety Assessment Of Existing Tunnel Structures In Urumqi City Based On Threshold Interval Method

Tunnel affected by environment,design,construction and operation,the influence of different degree of disease,these diseases light to reduce the function of normal use in the tunnel,reduce the service life of the normal operation of tunnel,or threatening the safety of people,vehicles,road,so the city’s existing tunnel structure safety inspection and evaluation is very important.The comprehensive evaluation of tunnel structure safety usually adopts the methods of weighted comprehensive evaluation and fuzzy comprehensive evaluation,which will weaken the influence of some diseases to a certain extent and cause the safety evaluation to be not very accurate.There are problems such as too large division of evaluation grades,lack of evaluation attribute indexes,too small and crossover.In this paper,disease detection and comprehensive safety evaluation are carried out based on the existing tunnel inspection projects in Urumqi city.Based on the deficiencies of the existing comprehensive evaluation methods,an optimization method is proposed and verified.The main work and achievements of this paper are as follows:(1)Starting with testing methods and testing equipment,the advantages and disadvantages of nondestructive testing methods are compared and analyzed,and equipment selection and testing scheme are made based on the characteristics of existing tunnels in Urumqi city.(2)A comprehensive health diagnosis was made for the existing tunnels in Urumqi,and the statistical data of cavities,cracks,water leakage and other diseases in 12 single tunnels were obtained.The tunnel structure was evaluated for safety,and the causes of the diseases and the general law of development were analyzed.(3)With the help of MIDAS GTS software,the finite element analysis method was adopted to establish the mechanical model of lining cavity disease under three different working conditions according to the "most unfavorable principle".The safety factor of lining structure is calculated by using the internal force value after operation of the model,and the influence of cavity disease on tunnel structure safety is analyzed.(4)In view of the drawbacks and deficiencies of the existing safety assessment methods for tunnel lining structures,this paper introduces the concept of "tunnel lining structure safety threshold",and puts forward a tunnel safety assessment method with threshold interval divided into four levels and taking the median value.The feasibility of this method is verified by engineering cases.