3-D Analysis Of Transient Dynamic Response Of Lined Tunnel Under Internal Explosion Load

In engineering practice, the underground lining structure may be subject to internal transient load, for example, Huangdao oil pipeline explosion which occurred on November 22, 2013, the lining and the surrounding soil media is seriously damaged. Therefore, the propagation and attenuation law of the stress wave in the lining and the surrounding media induced by internal dynamic load is performed to direct the anti - explosion and shock absorption design of the tunnel in this paper.The main contents are as follows:(1) Transient dynamic response of lined tunnel in infinite elastic space under internal load is presented. The dimensionless dynamic transient solution of a cylindrical lined cavity under an internal blast load in an infinite elastic media is derived by Fourier transform and Laplace transform. Utilizing the inverse Fourier transform and inverse Laplace transform, the propagation and attenuation law of the vibration response induced by internal explosion load in the lining and the surrounding elastic media are calculated and analyzed. The results show that, the radial displacement, radial stress and the hoop stress at the interface between the lining and the soil reach the maximum at the explosion source center. The radial displacement, radial stress and the hoop stress decreases rapidly with z* to the right and the left of the center, and eventually decay to zero at z*= 5. The peak value of the time history curve of radial displacement, radial stress and hoop stress at the interface is the maximum at the blast source center. The farther away from the blast source center, the peak value is smaller. When t*=10, the radial displacement and the hoop stress decay to zero.(2) Transient dynamic response of lining tunnels in infinite saturated porous media under endogenous explosive load. This paper proposes a set of exact solutions for dynamic responses of a cylindrical lined tunnel in saturated soil due to internal blast loading are derived by using Fourier transform and Laplace transform. The surrounding soil is modelled as a saturated media on the basis of Biot fluctuation theory and the lining structure modeled as an elastic media. The analytic solution of the dynamic response of the lining and surrounding saturated soil under the explosive loading in the Laplace and Fourier transform domains is deduced. By utilizing a reliable and efficient numerical method of inverse Laplace transform and Fourier transform, the numerical solutions for the dynamic response of the lining and surrounding soil are then presented and discussed. The results show that compared to the simplified 2D plane strain model, the 3D model yields smaller predictions in the hoop stress, radial displacement, and pore water pressures; the dynamic responses of tunnel decrease sharply in an oscillating manner as the time elapses, while such responses attenuates exponentially with increasing distance away from the explosion source center in both radial and axial direction of the tunnel.(3) Comparison of dynamic response of tunnel lining with elastic media and saturated porous media. Assuming the porosity n in the saturated soil to be 0, the saturated porous media degenerate into the elastic media and the analytical solutions on the dynamic response of the lined tunnel surrounded by the elastic media are presented. The comparison of dynamic response of the lined tunnels caused by internal transient load between the two kinds of surrounding media. The results shown that the value of dynamic response of the lined tunnels, such as radial displacement, hoop stress and pore water pressure, surrounded by the elastic media is much larger than surrounded by the saturated porous media.