Abstract

Info

Title:: Effects of Bottom Karst Caves on Tunnel Structure Stability Using Orthogonal Test

Author(s):: LAI Jin-xing; WANG Ke; GUO Chun-xia; LIU Bang-zhe; 1. School of Highway, Chang’an University, Xi’an 710064, Shaanxi, China; 2. School of Science, Xi’an University of Architecture and Technology, Xi’an 710055, Shaanxi, China

Keywords:: tunnel; karst cave; orthogonal test; displacement; stress; non-safety distance; envelope diagram

Abstract:: Based on orthogonal test and elastic plastic finite element method, the effect of the size and distance of karst cave on displacement and axial force of tunnel structure were discussed with MIDAS NX finite element software; the changes and function relationships of displacement and axial force to vertical distance from the top of karst cave to the bottom of tunnel under the conditions of different span ratios were calculated; non-safety distances of karst cave beneath the tunnel under the conditions of different span ratios were calculated; non-safety distance envelope diagrams of tunnel were drawn. The results show that the displacements of different parts of tunnel are significantly influenced by span ratios; when the span ratio is certain, the changes of displacement to the increase of vertical distance from the top of karst cave to the bottom of tunnel are logarithmic function; axial force of inverted arch center is significantly influenced by karst cave beneath the tunnel, and is logarithmic function of vertical distance; non-safety distance calculated by the vertical displacement of tunnel structure is large, while non-safety distance calculated by the horizontal displacement and axial force is small, so that the former should be taken as the main basis for the karst cave treatment because of the safety.