Mechanical Response of Surrounding Rock and Supporting Structure Stress Characteristics in Deep-buried Soft Rock Tunnel:A Model Test Study
Based on the Chonggang Highway Tunnel in western Yunnan,this study conducts model tests on the me-chanical response of the surrounding rock and the stress characteristics of the supporting structure during the con-struction of a deep-buried soft rock tunnel.It analyzes the variation laws of surrounding rock pressure,anchor bolt axial strain,and steel arch axial strain at different distances from the excavation boundary during the three-bench construction of the tunnel.The results show that,as excavation progresses,the surrounding rock pressure at each measurement point exhibits a trend of"accumulation—release—stabilization".The surrounding rock pressure at the vault and shoulder is released quickly and significantly,while the pressure at the waist and foot is released slowly and slightly.As the distance from the excavation boundary increases,the surrounding rock pressure at the vault and shoulder can be divided into significant release zone,slow release zone,and relatively stable zone,with the signifi-cant release zone being about 0.55 times the tunnel diameter from the excavation boundary.Except for the shallow measurement point at the vault,all anchor bolt measurment points are under tension,with tensile strain less than the yield strain of the anchor bolt similar material,and the most unfavorable position is at the shoulder.The steel arch is mainly under compression,with the maximum compressive strain at the shoulder,but none reaches the yield strength of the steel arch similar material,and no adverse phenomena such as bending occur,indicating the safety of the supporting structure.
Deep-buried soft rock tunnelSurrounding rock mechanical responseSupporting structureStress charac-teristics
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