Failure analysis and treatments of collapse accidents in loess tunnels

Abstract

Statistical analysis of 44 loess tunnel collapse accidents in the past 15 years as related to causes and characteristics are discussed in this study. First, several statistical indicators suitable for loess tunnel collapse including loess types, causes, the burial depth, collapse form, original designs and the excavation method are proposed. Then, typical types of collapse failure in the loess tunnel are divided according to the hydrogeology factors and collapse causes: collapse failure of sandy loess: collapse failure of natural water-rich loess; collapse failure of excavation disturbance-induced water-rich loess; and collapse failure of surface infiltration water-rich loess. Finally, the causes, characteristics and mechanisms of collapse accidents in different types are analyzed and treatment schemes for different types are proposed of collapse failure. This paper aims to share practical experiences about collapse failure causes, the treatment of instability zones, and key elements of passing through the loess in tunnelling.