ABSTRACT
When constructing tunnels in soft rock areas, due to the low strength and strong expansibility of the soft rock, and being squeezed by high ground stress, large deformation of the soft rock is likely to occur if the construction measures are not appropriate, which brings great difficulties to the engineering construction. Based on the geological conditions of the tunnel, a numerical analysis model is established to analyze the stress state of the surrounding rock and the mechanism leading to large deformation and instability of the tunnel, and the range calculation formula applicable to the surrounding rock circle model of large deformation tunnel in soft rock is obtained. Large deformation of soft rock is a major cause of tunnel failure. Therefore, whether the deformation can be effectively controlled is an important factor to ensure that the tunnel can maintain normal construction and subsequent use. In view of the complex geological conditions of the soft rock tunnel, it is finally determined that the tunnel support should follow the principle of “rigid and flexible complementation, combination of long and short, timely initiative, and coordination control”, and optimize the system anchor parameters based on the thickness of unstable surrounding rock, effectively controlling the large deformation of surrounding rock.
