Method for determining safe thickness of cave roofs under a tunnel

doi:10.16265/j.cnki.issn1003-3033.2019.04.017

Abstract

Abstract: To solve the difficult problem of how to determine the safe distance between karst caves and tunnels, the vibration differential equation of fixed-supported beam was established on the basis of the study of the existing methods for determining the safe thickness of roofs under dynamic load, and the double cusp catastrophe model of rock stratum instability between tunnels and karst caves was deduced. Then, its instability mechanism and failure conditions were analyzed, the nonlinear equation of the safe thickness was obtained before Matlab programming-based iteration method was utilized to solve the equation. What's more, analysis was also made on the impact of blasting vibration intensity, frequency, features of surrounding rocks and tunnel span on the safe thickness. It was found that the safe distance between tunnels and karst caves was determined by the internal and external factors of the rock strata; in addition, under the same amplitude of vibration load, the safe thickness has a nonlinear relationship with vibration frequency, while it has a linear relationship with blasting vibration amplitude when at the same vibration frequency; meanwhile, the safe thickness gradually decreases with the increase of elastic modulus, and was approximately proportional to increase along with the increase of the karst cave span.

Key words: tunnel, karst cave, catastrophe theory, instability, safety thickness of roof

CLC Number:

X913.4

LIU Bo, XIAO Hongfei. Method for determining safe thickness of cave roofs under a tunnel[J]. China Safety Science Journal, 2019, 29(4): 104-111.

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