Study On Large Deformation Law Of Surrounding Rock Of Zheduoshan Tunnel On Sichuan-Tibet Line

Large deformation of ultra-deep soft rock tunnel is a kind of geological hazard induced by human activities.It is a common engineering geological problem encountered in the process of underground engineering excavation;it is specifically manifested as surrounding rock deformation,lining fracture,steel arch distortion and support System failures,etc.,may cause engineering problems,ranging from a certain amount of social and economic losses,to disastrous consequences,threatening the safety of personnel and equipment.This paper takes the Zheduoshan ultra-deep buried tunnel on the Sichuan-Tibet line as the research object,uses on-site borehole stress and indoor simulation experiment data,and extracts the stress-deformation characteristics and deformation mechanism of the surrounding rock excavated in different tunnel areas for typical sections;analysis;The influence of different factors on the deformation of the surrounding rock of the tunnel;a number of large-deformation engineering cases in southwestern China are collected and trained into a prediction model,and the rough set theory and support vector machine are used to predict the large deformation.At the same time,it is compared with conventional prediction methods.The specific research content is as follows:(1)According to the engineering geological conditions of the Zheduoshan tunnel site on the Sichuan-Tibet line,the field stress of the tunnel site measured by the stress relief method collected on-site during the survey and design stage is analyzed.The principal stress value of the drill hole varies with the depth of the formation within the measurement depth range.The increase increases,and the consistency is good,in line with the existing law,the regional stress field is greatly affected by the structure,and the horizontal principal stress is dominant.(2)Refer to the completed inversion results of the in-situ stress in the Zheduoshan deep-buried tunnel on the Sichuan-Tibet line,select the characteristic section to simulate the excavation of the tunnel by the bench method,and analyze the deformation,stress,and plastic zone changes in typical parts of the surrounding rock.Surface extrusion deformation characteristics,combined with engineering geological conditions to simulate and analyze the mechanical mechanism of tunnel large deformation.(3)Establish a three-dimensional geological model of the river valley bank slope area,and then compare and analyze the in-situ stress distribution of the valley section under the action of self-weight stress and tectonic stress;on this basis,analyze the deformation and stress distribution characteristics of the tunnel excavation in the valley section.The results show that although the buried depth of the river valley slope area is small,the ground stress is high,which is prone to large deformation disasters.(4)Considering several factors of different excavation footage,different surrounding rock grades,buried depth conditions,lateral pressure coefficient and groundwater,analyze its influence on surrounding rock deformation.From the simulation results,it can be seen that the deformation of surrounding rock is easily affected by many factors.It is recommended that the excavation footage of the deep-buried tunnel in Zheduo Mountain is 1m in order to form a closed support as soon as possible.(5)Based on rough set theory and support vector machine prediction method,collect the buried depth,geological structure and other factors of the large deformation tunnel project in Southwest China,train hundreds of deformation cases to form a prediction model,and then use this model to compare the Zheduoshan tunnel Deformation is predicted and compared with the results of conventional predictions(geological comprehensive analysis method,stress intensity ratio method).The comparison results show that the prediction results of rough set theory and support vector machine are better.