Analytical Solution For Dynamic Response Of Tunnel Subjected To Blast Loads In Saturated Soil And Partially Saturated Soil

With the rapid development of China's economy and the acceleration of urbanization, major cities are beginning to build new subways in order to alleviate the stress of ground transportation. Subway tunnel brings huge transport facilities to people, but there are some negative effects in the same time. The internal enclosed environment of subway will provide the favorable conditions for terrorist bomb attack and accidental explosion. The space of underground transportation system is always small and poor ventilation. Once a blast occurs in the tunnel, it will cause serious casualties and great economic losses. As the general subways are build in the coastal developed cities, the main subways in coastal cities are always embedded in saturated soil and partially saturated soil. So the study of blast wave propagation in the soil and dynamic response of underground tunnel in saturated soil and partially saturated soil under blast loads are very important, which is used to take protective measures to reduce the destructive effects of underground structures.In this paper, analytical method is used to study dynamic transient response of buried tunnel in the soil under blast loads. The study mainly includes the following aspects:Firstly, the transient dynamic response of buried tunnel in saturated soil under blast load is studied. Assuming that the blast occurs in the center of the tunnel, a model is established using decrease three-stage triangle loads. The motions of the. liner are considered specially based on Fliigge theory. Biot's theory is used to describe saturated soil. The analytical solutions of displacement and hoop stress induced by the blast loads are derived using Laplace transforms. Numerical results are obtained by inversion of Laplace transforms, such as the curve of displacement, hoop stress and pore water pressure with time. The influence of saturated soil parameters, the relative stiffness and thickness of the linear are emphatically analyzed.Secondly, the transient dynamic response of buried tunnel in viscoelastic soil under blast load is studied. Biot's theory is used to describe saturated soil and Kelvin-Voigt model is for soil skeleton. The motions of the liner are considered specially based on Fliigge theory. By introducing potential functions, numerical results are obtained by using the Laplace transforms and inversion of Laplace transforms. The curves of displacement and hoop stress with time for different b* on the interface between the liner and soil are presented. The influences of viscous damping coefficient are emphatically analyzed in viscoelastic saturated soil. At last, the curves of displacement and hoop stress with time of two different viscoelastic medium are given, and the influences of different model and boundary conditions are analyzed. At last, the transient dynamic response of buried tunnel in partially saturated soil under blast load is studied. The similarities and differences between Biot's theory and mixture theory are compared. The control equation of partially saturated soil based on VB theory is derived. In the calculation model, the motions of the liner are considered specially based on Flugge theory. The dimensionless permeability parameter of linear is introduced to describe the semi-enclosed tunnel. The analytical solutions of displacement and hoop stress induced by the blast loads are derived using Laplace transforms. Numerical results are obtained by inversion of Laplace transforms and the curves of displacement and hoop stress with time on the interface between the liner and soil are presented, and as also the curves of displacement and hoop stress with the distance rising. The influence of different degree of saturation to the response is analyzed and the variation of different permeability parameter of the liner is discussed in partially saturated soil.