Research on stress arching effect of surrounding rock in excavation of inclined layered jointed rock mass tunnels

The stress arching effect of rock excavation in underground engineering has an important influence on the self-stability of the surrounding rock in the underground excavation space. Aiming at the stress arching effect of surrounding rock in inclined layered jointed rock mass tunnel, a series of numerical tests are carried out using a two-dimensional discrete element program （UDEC） to simulate the stress arching characteristics of surrounding rock after tunnel excavation. The correctness of the numerical program is verified by comparing the results of laboratory model tests, and then the variation of stress arch zone of surrounding rock is studied under different strata inclination angle, single block size and lateral pressure coefficient. At the same time, the mechanism of these factors on the stress arching of the surrounding rock of inclined layered joint is discussed based on the structural mechanics model of masonry beam and the thrust line theory. The results show that the axial direction of the stress arch of the roof of the inclined layered jointed rock mass tunnel is roughly perpendicular to the inclined bedding plane, and it rotates counterclockwise with the increase of the inclination angle. When the inclination angle of the strata is more than 60°, the effect of the stress arch basically disappears, and the block group between two laminar surfaces at the top of the tunnel is inclined to undergo a monolithic sliding. The stress arch zone decreases approximately linearly with the increase of single block size and lateral pressure coefficient. The camber of the thrust line of the joint stratum increases with the increase of overlying load and the span of the stratum, but increasing the horizontal thrust on the stratum will reduce the camber of the thrust line, which is conducive to the stability of the masonry beam structure and the stress arch. This study can provide theoretical support for the stability assessment and control of tunnel excavation of jointed rock mass.