Study on Mechanical Properties of Surrounding Rock and Combined Stress of Composite Lining in the Diversion Tunnel

To determine the mechanical properties of rock mass in Nansha Branch, three in-situ tests (on-site pressure plate, borehole TV and acoustic wave, deformation methods) were carried out. Based on characteristics mass, finite element numerical method is used to study combined stress composite lining diversion tunnel. The results demonstrate that modulus values are similar by comparing them plate method. It shows accuracy reliability obtained In addition, wave velocity fitted obtain a power function relationship. pelitic siltstones was estimated. After Branch tunnel filled with water, maximum principal pipe piece 1.953 Mpa tensile stress, located at outside waist both sides piece. reinforced concrete 5.407 Mpa, top bottom inside. stresses have exceeded standard strength vulnerable cracking. Special attention should be paid above parts regard long-term operation.