Water-sand inrush risk assessment method of sandy dolomite tunnel and its application in the Chenaju tunnel, southwest of China

Abstract

Sandy dolomite strata are widely distributed in the diversion tunnel of the Yuxi section of the Water Diversion Project in Central Yunnan (WDPCY). The water-sand inrush is the main failure phenomenon in the construction of sandy dolomite tunnel, which has seriously and commonly threatened the safety of the Chenaju (CNJ) tunnel in the WDPCY. In this paper, we established the discriminant matrix of the water-sand inrush risk assessment by consulting the experts, including the designers and construction personnel of the CNJ tunnel. Then, the risk assessment of water-sand inrush in the CNJ tunnel is carried out based on the proposed Fuzzy-AHP method. The results show that (1) a hierarchical model for risk assessment of water-sand inrush in sandy dolomite tunnel is constructed by criterion and index including thirteen factors. (2) The main criterion layer factors affecting water-sand inrush in the sandy dolomite tunnel are dolomite’s sandy degree and water yield. (3) The risk grade of water-sand inrush in the sections of YX49 + 089∼YX49 + 099 and YX51 + 637∼YX51 + 647 in the CNJ tunnel is V, which indicates very high risk. The assessment results are consistent with the actual engineering situation, which indicate the proposed method can provide the reference for the risk management in a similar project. Key Policy Highlights Thirteen main factors induce water-sand inrush in sandy dolomite tunnel. Characteristics of sandy dolomite mass and groundwater condition play a decisive role in sandy dolomite tunnel for water-sand inrush. A water-sand inrush risk assessment system established based on Fuzzy-AHP method is suitable for sandy dolomite tunnel.