Analysis And Research On The Dynamic Response Of Tunnel Secondary Lining Layer With Crack Defection

As the concrete structure layer in the outermost tunnel engineering,tunnel secondary lining layer and intial support constitute a composite lining.And it plays a crucial supporting for the stability of surrouding rock around tunner structure as well as has the function of decoration and waterproofing.Tunnel as the underground buliding structure,most of its projects have different degrees of damage due to influence of complex geological and poor construction conditions,unreasonable design and various dynamic factors in operation.However,the craking destruction of tunnel secondary lining is especially prominent among these many types of damage.Tunnel structure with crack is easy to gain stress concentration,so it has become the key and urgent problem to ensure the dynamic stability of secondary lining structure of this tunnel under earthquake,especially in the strong earthquake.With the help of the dynamic nonlinearity program ABAQUS,this thesis conducts systematic study on numerical model,dynamic response rules and influence factors of tunnel lining structure with crack.According to the analysis,it concludes the shock absorption measures for this kind of tunnel structure.Here are some achievements as following:A brief analysis on the characteristics of tunnel secondary lining crack defection and its implementation in the numerical simulation.This paper expounds a lot on the characteristics of tunnel second lining crack defection in the operating.It concludes characteristics about the general distribution and fracture morphologyof tunnel second lining crack defection.Besides,this thesis introduces the basic principles of the extended finite element method for numerical simulation of crack and the main points inits implementation of the finite element program.Study on the valid earthquake input in aseismic analysis for underground engineering based on infinite element artificial boundary.The accurate earthquake input is the essential part for the research on seismic dynamic response of underground engineering.With the infinate domain characteristics of underground engineering,if the input methods of underground structure are same as the methods of surface buildings,there will be the problem that the reflection of earthquake wave could cause disturbance.Therefore,this dissertation employs the infinite element artificial boundary and a reasonable earthquake input method — — equivalent earthquake load which based on wave field separation.Taking the radiation damping of the seismic interval and effect on seismic reflection and scattering,this method derives the equivalent earthquake load formula in different boundary surfaces for seismic waves vertically incident from the bottom of computational domain.And according to this formula,the author designs some related programs and verifies the validity of this method with some numerical examples.Analysis on seismic response of tunnel secondary lining based on crack defection under earthqauke.Based on the characteristic analysis of tunnel secondary lining,this paper makes the numerical calculation about different crack forms and distributions of tunnel secondary lining and figures out the worst crack forms and distributions of crack defection in tunnel secondary lining under earthquake.Taking the tunnel secondary lining structure with crack defect in the most disadvantageous state as the research object,the response characteristics of stress,displacement and damage of tunnel secondary lining are analyzed and compared with that of non-destructive lining.The stress maily concentrates around the crack of tunnel secondary lining,and the crack defection will increase the stress levels and damage degrees of tunnel secondary lining.If the size of cracks is smaller,seismic waves will reflect and scatter in cracks,which will consume energy of some earthquake waves.But if the size is larger,the existence of cracks in tunnel lining will increase the seismic disadvantage of tunnel lining structure.And if the earthquake is stronger,this cracks will also raise the disadvatage.This paper also studies the differences on seismic response of tunnel secondary lining about crack size,surrounding rock grade,tunnel depth and lining thickness.Finally,this thesis has a brief introduction on Seismic Damage Mechanism of tunnel secondary lining with cracks and concludes two measures on seismic absorption and resistance for this kind of tunnel lining structure.One is to reatrain the development of crack size.And the other is to reduce the effect of earthquake on tunnel lining structure.All of these analyses provide a certain reference value for the construction and reinforcement of actual tunnel engineering in the future.