발파로 인한 암반거동의 확률론적 접근
Probabilistic Analysis of Blasting Loads and Blast-Induced Rock Mass Responses
디커플링 암반거동 발파하중;
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The drilling and blasting method for excavating rock mass is widely used in tunnel and underground construction. However, this method has some disadvantages such as rock damage in remaining rock and overbreak. Blast-induced rock damage and overbreak in tunneling construction cause increasing construction costs and declining the stability of tunnel. Therefore, it is important to properly assess rock mass responses induced by blasting loads. In this study, the blasting loads propagated in rock mass under decoupled charge condition is derived, and the rock mass behavior due to blasting loads is analyzed by using the continuum damage model and the fuzzy-random probabilistic theory. The blasting loads can be probabilistically represented by its maximum pressure and rise time and shape. The maximum blasting pressure was a function of detonation velocity, adiabatic exponent, explosive density, rock density, and velocity of elastic wave in rock mass. Meanwhile the rise time was governed by explosive properties such as detonation velocity, adiabatic exponent and explosive density. Sensitivity analysis was conducted to find influential parameters that affect the maximum blasting pressure and the rise time. The detonation velocity is the most sensitive parameter to both the maximum blasting pressure and the rise time among others. The probabilistic distribution of each parameter is investigated through experiments including explosion and rock property tests. These results show that the uncertainty of natural rock properties is much larger than the uncertainty of explosive properties. Therefore, the uncertainty of blasting loads is more affected by rock properties than explosive properties, although detonation velocity is the most sensitive parameter. The statistical estimation of blasting loads and randomly damaged rock mass properties, which can be presented by initial damage and critical tensile strain, were evaluated by the Rosenblueth's point estimate method. A numerical continuum damage model with initial damage and the fuzzy-random probabilistic theory was suggested to assess the rock mass behavior under blasting loads. The suggested model was coded and linked with a commercial program ABAQUS/Explicit through user's subroutine. And also, the fuzzy failure probability of rock mass was discussed through numerical analysis.