The Effect of an Intermediate Inclusion in Soil on a Buried Lined Tunnel Due to a Nearby Explosion

Abstract

The paper presents the analysis of a buried explosion in the proximity of a tunnel in a soil medium. The soil is modeled as an elastic plastic material with irreversible bulk and deviatoric strains. The tunnel lining is modeled as an elastic plastic Timoshenko shell. An inclusion is placed in soil between the explosion source and the tunnel and its effect on the tunnel response is investigated. A coupled approach is proposed to allow to perform stable calculations of that complex problem and to follow the development of the large deformations and distortions of the tunnel lining's shape, as well as the large deformations of the explosive cavity. The effect of the rigid single inclusion or of the set of rigid inclusions located between the charge and the lined tunnel on the tunnel lining's response has been studied. When the inclusion is relatively distant from the lining, even a small inclusion improves the state of displacement and pressure of the lining, while when the inclusion is placed close to the lining, the lining's displacements increase. When the inclusion is small, its size slightly affects the lining shape while for middle sized inclusion the permanent displacement sharply decreases. Compared to the case of a single inclusion, a set of intermediate inclusions of the same size slightly decrease the peak stress at the front point and more significantly protects the periphery zone. The usage of larger inclusions yields better protection of the lining front part.