Study On Surrounding Rock Deformation Law And Construction Technology Of Huadu ? Tunnel

Huadu ? Tunnel has large span,low flatness and complex surrounding rock stress state,especially under complex geological conditions of severe weathering and fracture development of surrounding rock,the stability of the face of the palm is poor and the construction is difficult,once the excavation method is improperly chosen or the construction parameters are unreasonably designed,it is easy to induce large deformation of surrounding rock or even collapse.Therefore,it is necessary to take the construction project of Huadu ? tunnel as the background,through field investigation and monitoring measurement,combined with numerical simulation to study the variation law of surrounding rock deformation with time,excavation method and construction parameters under weak surrounding rock,discusses the deformation law of surrounding rock of large cross-section tunnel and puts forward reasonable excavation method and corresponding construction parameters.The main research of this paper is as follows:(1)On the basis of field investigation of engineering geology,monitoring equipments are arranged and monitoring measurements are carried out,the collected monitoring data is analyzed by using non-linear regression function model,the variation law of the surrounding rock deformation with time of grade ?,? and ? is obtained.Based on the optimal regression equation,the final deformation is predicted,and provides a reference for the construction opportunity of secondary lining.(2)The finite element software MIDAS is used to simulate the dynamic excavation process of three-bench seven-step method,CD method and double side drift method in soft surrounding rock.By comparing and analyzing the surrounding rock deformation,surrounding rock stress,surrounding rock plastic zone and the safety of initial support of the three methods,it is found that all three construction methods can meet the requirements of surrounding rock deformation and construction safety.It is suggested to adopt three-bench seven-step method which is economic and efficient in this geological condition.It can provide reference for similar projects in the future.(3)On the basis of three-bench seven-step excavation method,the influence of construction parameters such as step length,excavation footage,left-right staggered step distance and initial support closure distance on surrounding rock deformation is further studied by numerical method.On the premise of guaranteeing construction safety,the reasonable recommended value is given.The validity of leading small conduit and anchor bolt for controlling surrounding rock deformation is verified,by comparing the deformation of surrounding rock under different length and setting angle of anchor bolt,reasonable parameters of anchor bolt are selected to provide technical guidance for future auxiliary construction schemes under similar geological conditions.