Abstract: To study the stability of the surrounding rock of nonequalsection crossed caverns, stress concentration phenomena at the intersection are theoretically deduced. Failure laws of the surrounding rock at the triangle area of crossed caverns with various diameter differences and crossed angles are analyzed, and the stress variation law of the surrounding rock is obtained. Comparisons and contrasts are made between the theoretical calculation and numerical simulation results of a civil defense enlargement project in Guiyang, and the results show the following. (1) The stress concentration coefficient K of the surrounding rocks distributed on the side of the cavern with a large section diameter. (2) With an increase in the crossed angle (from 30° to 90°), the vertical stress of the surrounding rock in the triangle area decreases, and the construction condition is the safest when the caverns vertically intersect. (3) When the hole diameter difference is two, three, and four times, the maximum value of K in the surrounding rock at the crossed top is 3.83, 3.60, and 3.21, respectively, indicating that the possibility of failure in this part of the actual project is the highest. (4) The vertical stress of the surrounding rock in the triangle area shows an obvious bias distribution and presents a curved triangle distribution shape.

Key words: underground engineering, crossed caverns, surrounding rock stress in triangle area, stress concentration, sectional difference