Numerical Simulation And Analysis Of Intersection Part Between Inclined Shaft And Main Tunnel In Long Mountain Tunnel

During the construction of long mountain tunnels, the intersection part of inclined shaft and main tunnel has large free surface and complex force structure, so it has special requirements in determining excavation methods, reinforcing soil and rock mass at the intersection part, and in construction monitoring and measurement. The stress analysis, construction sequence, supporting measures and blasting control are still in the stage of experience accumulation. Therefore, combining with engineering practice to conduct research and analysis on mechanics of the intersection part of long tunnel has certain practical significance. When the excavation of the intersection part is finished, the excavation of main tunnel on both sides will once again lead to stress release and redistribution of the rock mass and supporting structure in the intersection part between inclined shaft and main tunnel, causing changes in mechanical behavior of the rock mass and supporting structure. In cases of different intersection angles, the effects will also be different.However, current study at home and abroad about mechanical behavior of the intersection part between inclined shaft and main tunnel of long tunnel under construction is less. Therefore, carrying out study on the excavation, initial support stress and deformation at the intersection part between inclined shaft and main tunnel of long tunnel, analyzing the different influences on stress and deformation between the intersection part and the ordinary part of main tunnel in cases of different intersection angles, whether to the improvement of theoretical system, or to the construction of underground engineering are of great significance.This paper is based on the background of the Nanshan tunnel of the railway from Xiamen to Shenzhen. For the grade III surrounding rock, using the method of numerical simulation, established four models about the intersection angle between inclined shaft and main tunnel respectively in30°\60°\90°and the two holes scheme of the intersection part between the No.1inclined shaft and main tunnel of the Nanshan tunnel. Then analyzed the influences on the surrounding rock stress at the intersection part, plastic zone, sprayed concrete stress, tunnel deformation in cases of different intersection angles, and coMPared the different mechanical behaviors between the single inclined shaft orthogonal scheme and the double schemes. The research shows that for the maximum principal stress σ1of the surrounding rock in the intersection part, the smaller the intersection angle, the larger the maximum tensile stress after the excavation of the intersection part has just finishe4) When the intersection angle turns from90to60°, the maximum tensile stress increases by3%, and when it turns from60°to30°, the maximum tensile stress increases by68%, that shows that the smaller the intersection angle, the faster growth in the tensile stress. For the minimum principal stress σ3of the surrounding rock in the intersection part, the smaller the intersection angle, the larger the maximum compressive stress. After the excavation of the intersection part has just finished, when the intersection angle turns from90°to60°, the maximum compressive stress increases by49%, and when it turns from60°to30°, the maximum compressive stress increases by40%. After the tunnel has broke through, when the intersection angle turns from90°to60°, the maximum compressive stress increases by41%; and when it turns from60°to30°, the maximum compressive stress increases by30%. For the maximum plastic strain of the surrounding rock in intersection part, the intersection angle of30°is about an order of magnitude larger than that of60°or90°, and there is not much difference between60°or90°. For the vertical deformation of main tunnel in the intersection part, the smaller the intersection angle, the larger the vault crown settlement. When the intersection between inclined shaft and main tunnel is non-orthogonal, the vault crown settlement of acute angle side is greater than that of the obtuse side. In the intersection part between the No.1inclined shaft and the main tunnel of the Nanshan tunnel, coMParing the two holes scheme with the single inclined shaft scheme, the former is larger than the latter in stress of the surrounding rock, initial support stress and deformation. Therefore, it is necessary to strengthen the support on the intersection part.