In-Situ Stress State and Stability of the Northern Tianshan Tunnel Project
YU Lei
ZHANG Qingjian
LI Yugui
SHAO Yidi
Abstract：With the development of water conservancy and hydropower projects in western regions,research on the characteristics and distribution patterns of in-situ stress fields is crucial for evaluating the stability of surrounding rock in tunnel engineering.Based on the three-borehole hydraulic fracturing method,three-dimensional in-situ stress measurements were conducted at key locations of the northern Tianshan water diversion tunnel's entrance section,yielding excellent results.Numerical simulations were used to analyze the three-dimensional stress state of the tunnel entrance.The results showed that the maximum principal stress values at the measurement points ranged from 8.20 to 9.40 MPa,intermediate principal stress values ranged from 7.00 to 8.90 MPa,and minimum principal stress values ranged from 5.60 to 6.00 MPa.The numerical simulation results indicated that the simulated maximum principal stress values at stations 1+700 and 1+885(approximately 8.00 MPa)had an error of 2.5%～17.5%compared to the measured values(8.20～9.40 MPa),indicating that the simulation results were reliable.The maximum principal stress varied with fault distribution characteristics,showing significant changes with depth near faults.Stress values decreased in shallow fault zones but exhibited stress concentration at certain depths,particularly due to the significant influence of Fault F72 on the principal stress distribution.The tunnel entrance section fell within a medium-to-low stress zone,and the tunnel segment from station 0+000 to 3+150 exhibited good excavation conditions with little risk of rockburst.Comprehensive analysis of rock physical and mechanical properties and in-situ stress distribution revealed that the tunnel segment from station 3+150 to 5+100 was prone to large deformation,which was unfavorable for surrounding rock stability.This study serves as a typical case and paradigm for revealing the stress state at critical locations in deep,long tunnels and provides guidance for future research on three-dimensional in-situ stress states and stability in hydropower tunnel projects.
Keywords：Northern Tianshantunnel engineeringhydraulic fracturing techniquein-situ stress staterockburstengineering stability
Publication Date：2025-09-20
Online Publishing Date：2025-10-10(First online date of this platform, not the publication date of the document)
Pages：6( 79-83,96 )