| During the construction of mountain tunnel,the instability of surrounding rock and support structure is the most common engineering disaster.Once the tunnel instability occurs,it will cause huge loss,especially for tunnel collapse which has been supported.At this time,the tunnel face has been advanced for a distance,and the collapse will cause serious consequences that the constructors and machinery sealed in the tunnel.This kind of collapse is more dangerous than tunnel face,therefore,the safety evaluation of initial support of surrounding rock and supported structure at the rear of the tunnel face has been a major technical problem to be solved for tunnel constructors.In this paper,under the science and technology project of the safety and disaster control theory and method of complex geological conditions special section long tunnel,the Yuejiagou tunnel of Zhangjiakou Shijiazhuang highway is chosen as the research object.Through the statistical analysis of the collapse accident occurred in Yuejiagou tunnel,three massive landslides occurred in the rear of the tunnel face which has been initially supported.Using a combination of theoretical analysis,numerical simulation technology based on the theory of structural reliability and the knowledge of risk evaluation,the safety risk level of lining structure of Yuejiagou tunnel is assessed given full considering to the surrounding rock deterioration.The main contents are as follows:(1)Based on consulting and reference to a large number of experimental data and literature research,through the quantitative research of GSI quantitative geological strength index,using Hoek-Brown criterion to predict the mechanical parameters of rock mass,the accurate prediction of mechanical parameters of Yuejiagou tunnel surrounding rock at all levels is made,which provides the necessary basic data for the subsequent tunnel modeling and analysis.(2)Due to disturbance and deterioration of tunnel rock unloading and adverse geological comprehensive effect of the surrounding rock behavior in the excavation process,the finite element model is established,and the typical section of surrounding rock deterioration before and after the lining structure load and deformation development variation are respectively studied;then,using statistical features ANSYS PDS module,the internal force of lining structure under two conditions are analyzed,and combined with the limit state equation established,the failure probability of lining structure under different conditions is obtained by using MALAB computing program.(3)In the risk assessment stage,the failure probability of the lining structure is taken as one of the evaluation indexes,and the matter-element model of the safety risk grade of the lining structure is established.At the same time,introducing the traditional risk matrix method,the risk matrix method and extension identification method are applied to Yuejiagou engineering practice to evaluate its lining structure safety level.The results are consistent,which verifies the correctness of the extension evaluation matter-element model. |
