GROUND SURFACE RESPONSE TO THE TRANSPORT LOADS IN THE TUNNEL REINFORCED WITH A THREE-LAYER LINING

Abstract

Based on mathematical modelling, effective methods have been developed for studying the dynamics of tunnels under transport loads (from an object moving through the tunnel). For a tunnel with a circular three-layer lining, such a method has only been developed in the case of a deep-buried tunnel. This article focuses on a similar shallow-buried tunnel, modeled as a circular cylindrical three-layer shell, composed of a thick middle layer (filler) and thin outer layers (cladding), embedded in an elastic half-space. The horizontal boundary of the half-space (the ground surface) is parallel to the shell axis. The motion of the filler and the half-space is described by the dynamic equations of elasticity theory in Lamé potentials, while the motion of the cladding layers – by the classical equations of shell theory. The equations are represented in a moving coordinate system associated with a uniformly moving load along the inner surface of the shell. Based on the obtained solution and numerical experiments, the stress-strain state of the ground surface was investigated under the influence of a transport normal load acting symmetrically relative to the vertical diametral plane of the tunnel on the three-layer steel-concrete lining, as well as when the intensity of one of its symmetric halves was doubled. This asymmetric load distribution leads to significant changes in the displacements and stresses of the ground surface, with horizontal displacements increasing by more than an order of magnitude. Thus, the transport load must be symmetrical in the operation of shallow-buried tunnels in urban areas.