Numerical Simulation Of Force Measurement And Construction Excavation Of The NJ Diversion Tunnel In Pakistan

Pakistan NJ project is known as Pakistan's "Three Gorges Project",The diversion tunnel through the high depth,soft and hard rock sandwich,large convergence deformation of the lot,its Geological conditions are more complex,in the diversion of tunnel excavation construction process,the surrounding rock instability happend many times,once affected the progress of the project,based on the joint training of Nanchang Institute of Technology and China Gezhouba Dam Group International Engineering Co.,Ltd.,the authors participated in the field work of the in-situ stress of the surrounding rock of the diversion tunnel section of the project,and the variation of the surrounding rock in the stress concentration area of the diversion tunnel during the excavation process is studied.This paper collects and studies the data of engineering geological investigation,and the in-situ stress in the diversion tunnel site was measured,the method of combining theoretical analysis with numerical simulation is studied,it can provide scientific basis for the design and construction of the diversion tunnel.The main contents of this paper are as follows:1)The present situation of stress measurement at home and abroad and the analysis status of diversion tunnel are systematically summarized and reviewed;2)The survey and analysis of the engineering general situation and engineering geological background data of the project area are carried out;3)The hollow inclusion strain gauge is used to measure the in-situ stress of the diversion tunnel in the NJ engineering by using the stress relief method,the stress magnitude and direction of the measured points are obtained,the general law of crustal stress distribution in this area is obtained,the preliminary prediction of the surrounding rock properties of the diversion tunnel is carried out;4)Establishment of 3D numerical simulation model for excavation of diversion tunnel under high buried depth,by contrasting the initial lining and the two lining which are simulated in the excavation process,the two stress field,displacement field,plastic zone,lining structure and bolt axial force of the top,bottom,left and right side walls of the monitoring section are monitored,the variation characteristics of surrounding rock properties of water diversion tunnel before and after excavation and initial lining and two lining are analyzed and compared,according to the numerical simulation results of construction excavation,the corresponding engineering measures should be taken in excavation construction.The research results of this paper have a certain guiding value for the construction of NJ project diversion tunnel.