Research On Prediction And Failure Criterion Of Large Deformation Of Surrounding Rock In Long Highway Tunnel

Landslide is due to poor formation,groundwater,rain erosion,improper construction and many other factors led to the top of the tunnel suddenly collapsed phenomenon.Tunnel construction,the landslide will lead directly to the duration of the delay,equipment damage,resulting in serious economic losses,and even cause heavy casualties.In this paper,Yuejiagou tunnel of Zhangjiakou to Shijiazhuang highway is chosen as the research object,for its special landslide characteristics,can be used to analyze the large deformation of the discrete element software 3DEC three-dimensional numerical simulation.The deformation and failure characteristics of the surrounding rock and the supporting structure of the Yuejiagou tunnel are obtained by simulating the process of weakening the parameters of the surrounding rock during the forward advancement of the paw,and the corresponding destabilization criterion is put forward for the collapse of the surrounding rock.The main contents are as follows:(1)The results show that the geologic prediction can only predict the depth of the front of the pile by comparing the actual surrounding rock with the results of the geological prediction of the tunnel face by the RK74 + 010,RK75 + 320 and RK75 + 880 landslide sections in the Yuejiagou tunnel.The surrounding rock of the tunnel is not predicted,and the surrounding rock of the tunnel can not be predicted.Due to the hidden nature of the tunnel during the construction process,the operation space is narrow and the geological conditions are uncertain,,And in the face of the excavation before the excavation,the construction staff is difficult to find,and the excavation of the existence of hidden crushing layer of the surrounding rock to take the appropriate support measures,so as the advance of the chin,broken rock Progressive deterioration of damage,the final collapse of the surrounding rock collapse.(2)Aiming at the characteristics of the surrounding rock in the three landslides,the discrete element software 3DEC is used for numerical simulation.By analyzing the deformation and failure characteristics of the surrounding rock and the supporting structure,it is concluded that the deformation and failure of the surrounding rock show three obvious stages with the weakening of the parameters,namely,the initial deformation stage of theinitial rock and the internal joint The supporting structure has a certain margin of strength.In the early stage of the deterioration of the surrounding rock,the supporting structure can meet the strength requirement,but with the continuous weakening of the parameters of the surrounding rock,The support structure will still be insufficient to support the deformation of the upper part of the surrounding rock damage.(3)In order to predict the failure damage of the tunnel,the stress criterion of the modified stress intensity ratio method is put forward,that is,the ratio of the principal stress and the rock mass strength of the tunnel cross section is predicted.The integrity coefficient method and Hoek-Brown The empirical strength criterion is used to estimate the strength of the rock mass,which is more in line with the actual situation of the project.For different types of surrounding rock,different stress intensity ratio indexes are given.When the measured value exceeds the corresponding index during tunnel excavation,the trend of instability of surrounding rock can be determined.(4)The method of parameter weakening is used to simulate in 3DEC,so as to find out the surrounding rock parameters in the critical state of tunnel rock,and the surrounding displacement of the tunnel under the surrounding rock condition is taken as the limit state of the surrounding rock deformation.It is calculated that when the parameters of the surrounding rock are weakened by 65%,the stability of the surrounding rock is abruptly changed,and the joint fissure is introduced.Based on the deformation state of surrounding rock at this time,the deformation control standard of tunnel surrounding rock is classified by using the three-level management mechanism which is commonly used in the current engineering community.The deformation control standard of tunnel surrounding rock under different surrounding rock grades and different burial depths is established.