Abstract:

The purpose of the paper is to realize the dynamic modification and management of the full course of the assessment on the karst water inrush risks. In the paper, first, the distance between the karst caves and the tunnel in the profile map is estimated by means of semiquantative analysis method on basis of the development and distribution rules of the karst; secondly, the prediction of the safe thickness of the karst water inrush resisting rock strata is divided into three stages, i.e., the preliminary estimation stage, the secondary estimation stage and the dynamic calculation stage, for which effective modification methods are adopted so as to obtain more accurate and more appropriate prediction values for the safe thickness of the karst water inrush resisting rock strata; thirdly, the evaluation standard for the probability level of the karst water inrush risks is proposed on basis of the safe thickness of the water inrush resisting rock strata and the disturbance depth of the excavation blasting, the evaluation standard for the consequence level of the karst water inrush risks is proposed by means of classifying the water inrush volumes and the water pressures in the karst chamber, and the assessment matrix for the grades of the karst water inrush risks is established; Finally, the assessment model for the karst water inrush risks based on the karst distribution pattern and the karst water inrush resisting rock strata is established. The comparison and contrast between the theoretical result and the actual conditions in the engineering cases verifies the rationality and feasibility of the karst water inrush risk assessment model. 

Key words: karst tunnel, karst water inrush, fissure, safe thickness of rock strata, threestage predictive calculation, risk level, risk assessment