Research On The Influence Of Voids Behind Tunnel Lining On The Safaty Of Tunnel Structure And Preventive Measures

The development of China's tunnel engineering is fastest in the world,the number of tunnel engineering built or under building is increasing.With the growth of service time in the tunnel and a varity of influence factors,there are a large number of tunnels to be overhauled because of serious diseases and many tunnels are still in service with diseases,such as lining cracking,breakage,spalling,Water Leakage and mud pumping.These diseases affect the sevice life of linging seriously and traffic safety.In the formation of many tunnel diseases induced by many factors,the voids behind the lining is one of the main causes of diseases of tunnel structure.To ensure the safety of tunnel structure and used for a long time,it is necessary to study on linging sress?deformation and safety with voids behind the linging systematicly and put forward effective treatment measures timely.This paper starts from the formation mechanism of voids behind the lining,analysising the characteristics of the voids behind the lining(diversity,ambiguity and development).Then regarding the formation mechanism of voids behind the lining and damage to the lining structure as the main research content,focusing on the following several aspects: 1?voids formation during the period of construction;2?formation of voids induced by design factor;3?formed during the tunnel operation;4?forms and types of the tunnel diseases after the formation of voids.Analysing the stress?deformation and safety of lining structure because of voids behind the tunnel in detail,using finite element analisis software ANSYS to eastablish voids fininte analysis model,considering the following situations:1?deferent positions(vault?arch waist and inverted arch);2?different rock classification and different thickness of lining;3?different size of voids;4?single void and group voids.The voids behind the tunnel change the stress state of lining structure,change the distribution pattern of surrounding rock pressure and make the lining structure move towards unfavorable direction.With the increase of service time,lining cracking?water leakage and bias will occur.So,taking the corresponding effective preventive measures is very necessary.Therefore,this paper puts forward the preventive measures with voids existing behind primary support and secondary lining,establishes the risk classification system for the voids diseases,and puts forward different treatment measures for different voids.Therefore,this paper provides reference value for the prevention and treatment of voids behind tunnel lining.