ABSTRACT
Most urban tunnels are located at shallow depths which pass through stratified rockmass and are extremely vulnerable to impact loads such as falling heavy objects and projectiles. The present study aims to comprehend the behaviour and deformation pattern of twin tunnels in stratified rockmass under impact loads using finite element method (FEM) based numerical simulation. The analysis was carried out for various stratified rockmasses such as homogeneous, stratified horizontal layers of two, and three at an impact load of 20kg, 30kg, and 40kg. Deformation at the crown of a homogeneous rockmass is less than that at the spring line, and similar behaviour is observed in stratified horizontal layers of two and three. In comparison to stratified rockmass, homogeneous model exhibits the most damage and deformation. In the case of stratified horizontal layers of three, there was relatively less damage and deformation. This paper establishes that rockmass properties and formation thickness influences deformation under impact loads.
