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This paper presents the theoretical investigation on the damage of the submerged floating tunnel (SFT) under extreme loads. Water was modeled by smoothed-particle hydrodynamics (SPH). Anchor cables, SFT, and submarine were modeled by the finite element method (FEM). Penetrating phenomenon in the calculation process was achieved by the penalty function, and the fluid-solid coupling effect was also considered in the simulation. The process of a submarine striking on the SFT was studied based on the commercial software. The relationships between the energy of the water, submarine, and SFT were studied. The structural and human damages were evaluated using the kinematics and kinetic parameters of the SFT according to the relevant criterion. The results indicate that the SPH-FEM coupling method is suitable to investigate the impact of the SFT in the water. The initial kinetic energy of the submarine is mainly converted into kinetic energy of the water and internal energy of the tunnel. The kinematic parameters at the impact point reach a peak value. The kinematic parameters at the anchor cables reach the minimum value, so the anchor cables can inhibit the development of disaster significantly. The SPH-FEM coupling method can be helpful for collision and explosion analysis of the SFT.

In order to study on the vibration effect of the blasting in the upper and lower cross tunnels, depress the impact of blasting vibration on existing adjacent tunnel and acquire the sound way of tunnel blasting construction, the finite element software LS-DYNA was adopted to calculate what vibration effect of existing tunnel would be generated by the different detonation modes (simultaneous initiation and hole-by-hole initiation) and the different cut modes (parallel cut and oblique cut). In general, the results of numerical simulation compared with the results measured in real, they are generally consistent. Results show that the vibration velocity of hole-by-hole initiation of digital electronic detonator is 40% lower than ordinary simultaneous initiation of millisecond detonator, and the vibration acceleration is reduced by 24%. As regards vibration displacement, the distinction between the two detonation modes is small. The rule of velocity decay with increasing distance from the initiating position is similar in this two cases. Meanwhile, the vibration velocity of oblique cut is lower than parallel cut. But, for the vibration acceleration, the oblique cut is 15% higher than parallel cut. For oblique cut, the seismic waves show a pronounced periodicity and the energy is relatively concentrated. The fact is quite opposite when the parallel cut applied. In the case of explosion of hard rock strata, the effect of oblique cut is better than parallel cut. KEY WORDSTunnel engineering, Explosion vibration, Numerical simulation, LS-DYNA In recent years, with the rapid economic growth in China and the booming development of the national transport industry, the subway construction has become an essential development project in large and medium-sized cities. In that cities, such as Chongqing, Xiamen and Qingdao, the drilling and blasting method usually used to subway construction in hard rock strata. In addition, Article no. 16 THE CIVIL ENGINEERING JOURNAL 2-2019-` due to the outward expansion of the city and the characteristics of the original terrain, a lot of "mountain city" appeared. As a result, many mountain hard rock tunnels have emerged in the construction of municipal roads and subway traffic. So, the surrounding buildings, especially cultural building relics, will be impacted by blasting construction in central urban area. How to choose a reasonable tunnel blasting method to reduce the impact of blasting vibration on the surrounding buildings is a considerable issue.As the science and computer technology progressed, the method of numerical simulation of blasting vibration effect and evaluating structural safety is widely used. Singh P K (2002) delved into the destruction problems of underground tunnels in the effect of adjacent tunnel blasting [1] . There are research results indicate that blasting vibrations induced by a new tunnel excavation might cause spalling, fissures, or even collapse of existing tunnel linings [2] . Yao et al. (2004) conducted numerical simulations on the blasting construction process ...

In this study, a single-span submerged floating tunnel (SFT) is simplified as an elastic supporting beam model with movable ends. This model is used to analyze the displacement response of the SFT subjected to an underwater explosion in an ocean environment. The effects of the shock wave pressure and bubble pressure are considered simultaneously. The dynamic equilibrium equation was established based on D’Alembert’s principle. When the pipe segment of the SFT vibrates, the additional inertia force and the damping force of the surrounding water to the pipe are calculated using the Morison equation. The motion differential equation of an SFT under the load of an underwater explosion is obtained using the Galerkin method. The displacement analytical expressions of an SFT under four different stages of load are derived, and a comprehensive analysis is performed to assess the influence of key parameters, including the brace stiffness, damping, scaled distance, and bubble oscillation frequency, on the displacement of the SFT. It was observed that the key parameters mentioned above all significantly influence the displacement response of the SFT. Some reasonable suggestions for different parameters are proposed to provide a reference for the SFT design.