Modeling of Tunnel Concrete Lining under Fire and Explosion Damage

This paper presents studies that focus on fire and explosion-induced damage of tunnel structures by employing the Discrete Element Method (DEM). By assuming a two-dimensional aggregate distribution and reconstructing the digital representation of the experimental concrete blocks, a numerical model of the tunnel lining concrete was established in the PFC2D program. The temperature distribution and the shock wave pressure at the surface of the tunnel lining were obtained by using Fluent and LS-Dyna separately; the final damage simulation of concrete section under different conditions was carried out in PFC2D. The results showed that PFC2D cooperatively provided more accurate and effective modeling and visualization of impact damage of concrete blocks. The visualizations of damage indicated the degree of damage more clearly and more intuitively. These findings also provide a potential method for further study of the damage assessment for entire tunnel lining structures.

Numerical Study on Propagation of Ice Breaking Shock Waves in Process of Breaking Ice by Double-Layer Charge Blasting

The ice-breaking process of the double-layer charge at a depth of 150 cm underwater is simulated by LS-DYNA. This paper analyzes the load type, shock wave pressure characteristics and propagation behavior of the double-layer charge during underwater explosion. By analyzing the impact of the shock wave pressure in the water under different charge intervals and time intervals on the shock wave pressure of the double charge, it is concluded that the peak pressure of the double charge explosion shock wave is jointly determined by the double charge. In this range, the second peak pressure value of the drug is greater than the pressure value of the first peak of the drug, and the attenuation is slow; the delay time of the upper charge has little effect on the peak pressure value of the shock wave in the water; the delay time is higher than that of the lower charge Initiation, at the same position, the total pressure peak of the shock wave formed by the delay of the upper charge is larger.

Frequency Dependence of a Piezo-Resistive Method for Pressure Measurements of Laser-Induced Shock Waves in Solids

A shock wave is a mechanical high-pressure pulse that travels inside a medium with a full width at half-maximum of a few nanoseconds that may be induced with a high-power laser pulse. A piezo-resistive measurement method to determine the shock wave pressure has been widely employed even though there is inner inaccuracy in the calibration process. We are interested in developing a precise theoretical model of laser material processing for applications in material sciences that includes the frequency dependence of the electronic post processing. We show an approach to determine the correction factor to frequency response at a high frequency of a piezo-resistive experimental setup and the results of the pressure measurements obtained in this experimental setup. The theoretical and experimental work demonstrates the feasibility of piezo-resistive methods to measure a laser-induced shock wave pressure in the nanosecond range. The correction factor of the frequency dependence calibration allows the technique to be applied in different shock wave experiments.

Electrical Resistivity of Aluminum under Shock Compression

Electrical resistance measurements of aluminum foil are conducted under shock compression using the electric contact technique. Shock wave pressure p dependences of the electrical resistance R and the resistivity r are obtained for pressure range up to 22 GPa. The found dependence R(p) is a monotonically increasing smooth function of the pressure. The dependence r(p) is more complex: with increasing pressure, the electrical resistivity first decreases and then increases.

CALCULATION METHOD OF UPLIFT FORCES AT PIER BASED ON GAS-LIQUID PHASE FLOW MODEL

Seaside facilities such as pier are affected by uplift forces due to storm surge and waves caused by typhoons. Therefore, detailed knowledge of external force is required for designing the pier (Tanimoto et al., 1978). Previously, the elucidation of the uplift forces and the shock wave pressure has been a major issue. Indeed, it has been clarified by experiments. Bagnold (1939) conducted an experimental study for revealing the relationship between the air layer and the pressure value, and found that air, which is a compressible fluid, reduces the pressure value. Furthermore, air has the effect for prolonging the action time. Arikawa and Yamano (2009) conducted the numerical simulation of shock breaking wave pressure by considering the inclusion of gas, and it was shown that the shock wave pressure after breaking wave can be reproduced. However, there are few cases that numerical calculation is considered for phenomena such as lifting pressure that are greatly affected by air. In this research, reproduction calculation of experiment was performed using numerical calculation for incompressible fluid. In addition, we will make a hole in the slab for calculation and investigate how the uplift forces changes.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/0o5GGt442jU