CHARACTERISTICS OF THE ALLUVIAL DEPOSITS IN KARST CONDUITS AT BAZILING TUNNEL OF YIWAN RAILWAY

In the course of the tunnel construction at the karst mountain area,the karst conduit connectivity has a great importance to determine the quantity of welling water and water pressure,and to protect the tunnel construction.This paper presents a case study during Baziling tunnel construction of Yiwan railway.It systematically analyzes the characteristics of grain size,the rock and minerals component,roundness of karst conduit deposits.It applies the theory of sedimentation to study hydraulic characteristic of fragmental deposits.Finally it examines the source of the deposits.According to this result,it analyzes karst conduit connectivity of thee area,and provides the references for the design of the tunnel construction.