Calculation of Surrounding Rock Pressure Based on Pressure Arch Theory

摘要

Study on the surrounding rock pressures of rail tunnel is conducted based on pressure arch theory by performing numerical simulation in this paper. Two concepts: the critical burial depth of arching and the boundary calculation of pressure arch, are proposed by analyzing the stress state above the vault. Based on the universal reference drawings of rail tunnel, influences of the span and buried depth of tunnel, as well as the physical and mechanical parameters of surrounding rock, on the critical buried depth and calculation boundary of pressure arch are investigated. Results indicate that the critical buried depth and calculation boundary of pressure arch increase with the increases in tunnel span and surrounding rock level, and certain laws are presented. The formulas of critical buried depth and calculation boundary of pressure arches are obtained by nonlinear multivariate regression analysis, and then, the formula of surrounding rock pressure is proposed based on the basic theory of pressure arch. Results of surrounding rock pressure predicted with the proposed formula and the formula in code for design of railway tunnel are compared. Comparison results indicate the surrounding rock pressure predicted with the proposed formula is larger than that with the formula in Chinese code; with the increase in surrounding rock level, the difference of predictions with the two formulas decreases, and is the smallest for surrounding rock with level V.