STUDY OF CONTACT STATE BEHIND TUNNEL LINING IN PROCESS OF RAILWAY OPERATION AND ITS ANALYSIS

There are three types of contact states between the primary linings and the secondary linings for the railway tunnels.Those are tight contact state,loose contact state and voids.Both the loose contact state and the voids behind the linings can be regarded as poor contact,which are deemed as typical tunnel quality defects.The research results show that the poor contact states have great influence on tunnel structure safety.General law of contact states behind railway tunnel linings in China is obtained according to the lining nondestructive test data of more than 100 railway tunnels.The research results show that:(1) Poor contact states behind linings are more incidental and serious in single shell lining than in the composite lining under the same conditions.(2) The occurrence proportion and severity of poor contact conditions behind linings have a close relationship with the surrounding rock classification;and they are more disadvantageous in the poorer surrounding rock.(3) The occurrence proportion and severity of poor contact states behind linings are affected by the positions of the poor contact states around the tunnel cross-section.The negative effects of the contact states decrease from the tunnel crowns to tunnel feet.(4) The appearance of the voids is affected by tunnel design principle,construction quality control,operational maintenance efficiency,etc.The prompt contact grouting between the primary lining and surrounding ground is the key to control this undesired phenomenon.The results obtained in this study can provide useful reference for studying the contact states between the primary linings and the secondary linings.It will also be helpful to study the development of the defects in the tunnel structure system.