YANG S K, SUN K,  DENG Z D, et al． Study on zonal fracture mechanism of surrounding rock in deep-buried multi-tunnel excavation[J]. Journal of Henan Polytechnic University( Natural Science) ， doi: 10.16186/j.cnki.1673-9787.2024040037.

doi: 10.16186/j.cnki.1673-9787.2024040037

Received： 2024-04-20

Revised： 2024-05-27

Online： 2026-03-09

Study on zonal fracture mechanism of surrounding rock in deep-buried multi-tunnel excavation (Online)

YANG Shikou, SUN Kuan, DENG Zhengding, HU Xinwei

School of Civil Engineering and Surveying & Mapping Engineering, Jiangxi University of Science and Technology, Ganzhou 341000, Jiangxi, China

Abstract: Objectives After the excavation and unloading of deep tunnels, the surrounding rock often suffers from special structural damage phenomena such as zonal fracture, which can easily cause engineering disasters such as severe deformation of the tunnel, water inrush, and large-scale collapse. At present, research on the zonal fracture of surrounding rock focuses on single tunnel, while the zonal fracture mechanism of surrounding rock in multiple tunnels in practical engineering is not yet clear. Methods In order to explore the mechanism of rock fragmentation after excavation unloading of deep buried multi-tunnels, the diversion tunnels at Jinping II Hydropower Station were used as the research background. Based on the strain softening model, a numerical model of the diversion tunnels was established. The variation patterns of the zonal fracture morphology of surrounding rock, the maximum radial distance of fracture zones, the number of fracture zones with the strength parameters, deformation parameters, and shear dilation angle after the excavation unloading of deep-buried multi-tunnels were studied, and the effects of strength parameters, deformation parameters and shear dilation angle on the fracture shape of the surrounding rock partition were compared. Results The results show that after multi-tunnel excavation and unloading, the fracturing patterns of the four caverns exhibit a certain symmetrical relationship. The signs of zonal fracturing in the surrounding rock of the 2# Tunnel are more serious, and the degree of zonal fracturing in the right side of the 1# Tunnel is more severe than that of the left side. As the internal friction angle, cohesion, and elastic modulus decrease, or the shear dilation angle increases, the zonal fracture of surrounding rock becomes more severe. The Poisson's ratio mainly affects the location of zonal fractures of surrounding rock. The smaller the Poisson's ratio is, the fractured zones on the left and right sides of the tunnel are farther away from the tunnel wall, while the closer fractured zones at the arch top and bottom are to the tunnel wall. The strength parameters have the greatest influence on the zonal fracture morphology of surrounding rock, followed by the deformation parameters, the effect of changes in shear dilation angle has relatively little effect on the zonal fracture of surrounding rock. Conclusions The research results reveal the zonal fracture mechanism of surrounding rock after excavation unloading of deep buried multi tunnels, and provide theoretical support for the design of surrounding rock support for deep underground multi-cavity excavation.

Key words: deep buried tunnel; surrounding rock; strain softening; zonal fracture; strength parameters; excavation unloading