This study considers the saturated soil around the tunnel as a transversely isotropic medium and derives the dynamic response solutions of the tunnel lining and its surrounding medium under explosive loads in the Laplace and Fourier transform domains. When the transverse isotropic coefficient equals 1.0, this solution simplifies to the case where the tunnel is surrounded by a uniform medium. By performing inverse Fourier and Laplace transforms on the solution, we obtain the time domain solution. Compared with the results for a uniform medium surrounding the tunnel, it was found that the peak values of stress and pore water pressure increased, while the peak displacement slightly decreased. In addition, the peak arrival time is advanced, and the fluctuation attenuation is accelerated. The transverse isotropy of soil in engineering cannot be ignored.

In the modern world, the demand for bunkers has grown significantly as a vital means of protection against blast loads. This study investigates the structural response of underground bunkers subjected to surface blast loads using finite element (FE) analysis in ABAQUS/Explicit. The model uses the Mohr-Coulomb model for soil, Concrete Damage Plasticity (CDP) for the bunker liner, and Johnson-Cook for steel and aluminum. Five dome curvatures (flat, D/8, D/4, 3D/8, and D/2) were analyzed under a 1000 kg TNT explosion. Results show higher stress, deformation, and tension damage with increasing curvature, especially for D/2. Organic sandy clay caused maximum stress and deformation. Two mitigation strategies were proposed: upgrading concrete from M40 to M50 and adding an aluminum 2024-T3 liner. M50 concrete reduced stress by 19.23%, deformation by 5.09%, and damage by 2.63%, while the aluminum liner provided greater protection, reducing stress by 83.12%, deformation by 58.03%, and damage by 67.07%.

A non-linear simulation of a shallow buried cut-and-cover tunnel exposed to extreme surface blast conditions was performed utilizing finite element-based dynamic explicit analysis. The Mohr-Coulomb plasticity model was employed to simulate the soil, the concrete damaged plasticity model depicted the behavior of concrete, and the Johnson-Cook model was utilized for the steel reinforcement. The conventional weapons blast function simulated the trinitrotoluene charge weight. The parametric simulations encompassed four vehicular explosions, two soil types, the inclusion of sheet pile walls, and variable depth-to-height ratios (d/h) of the tunnel. The investigation focused on mitigation through the application of an energy-absorbing material, specifically steel-fiber-reinforced concrete. Results showed that the displacement of the upper slab escalates with an increase in charge weight. The existence of a sheet pile wall enhances the structure's stiffness, resulting in increased displacement and tensile damage, but the displacement of the top slab diminishes as the d/h ratio escalates. The extent of damage has been noted to decrease with an increase in the d/h ratio, or cover thickness. These findings underscore the significance of structural configuration and mitigation strategies in reducing the impact of surface blasts on cut-and-cover tunnels.

The present study investigates blast-induced deformations in the ground surface and lining of shallow tunnels. Using a 2D finite element method (FEM), numerical simulation of the interaction effect of factors such as depth, shape (circular and square), tunnel diameter, the modulus of elasticity of the soil, the size of the blast loading, and the distance from the explosion site to the center of the tunnel on maximum ground surface settlement, maximum deformation in tunnel crown, and maximum bending moment in tunnel lining are discussed. The results show that circular tunnels perform better than square tunnels under blast loadings. The tunnel's behavior is more suitable in soils with high elasticity. The improvement in the system's performance would be more significant for tunnels with smaller sections and deeper locations due to a larger distance from the center of the blast.

All Nuclear power plants consist of several structures of varying importance that have to be designed for dynamic loading like earthquakes and impacts that they might be exposed to. Research on the influence of dynamic loading from blast events is still crucial to address to guarantee the general safety and integrity of nuclear plants. Conventional structural design approaches typically ignore the Soil-Structure Interaction (SSI) effect. However, studies show that the SSI effect is significant in structures exposed to dynamic loads such as wind and seismic loads. The present study is focused on evaluating the Soil-Structure Interaction effects on G + 11 storied reinforced concrete framed structure exposed to unconfined surface blast loads. The SSI effect for three flexible soil bases (i.e., Loose, Medium, and Dense) is evaluated by performing a Fast Non-linear (Time History) Analysis on a Two-Dimensional Finite Element Model developed in (Extended Three-Dimensional Analysis of Building System) ETABS software. Unconfined surface blast load of three different charge weights (i.e., 500 kg TNT, 1500 kg TNT, and 2500 kg TNT) at a standoff distance of 10 m are applied on the structure. Blast wave parameters are evaluated based on technical manual TM-5-1300. The blast response of the structure with and without the SSI effect is studied. It is concluded from this study that, there is a significant variation in dynamic response parameters of the structure with flexible soil bases compared to rigid or fixed base. For all magnitudes of surface blasts and soil base conditions, the ground floor is the most vulnerable floor against collapse. The study recommends measures to mitigate the damage due to unconfined surface blasts on multi-storey reinforced concrete structures.

This study investigates the dynamic response of RC lined rectangular tunnel in soil subjected to internal blast load. For this purpose, a three-dimensional non-linear finite element model comprising of tunnel lining, reinforcement, and soil is analyzed in Abaqus/Explicit. The behaviors of soil, concrete, and steel are simulated using Drucker-Prager plasticity, concrete damaged plasticity, and Johnson-Cook (J-C) plasticity models, respectively. The effect of various grades of concrete (C30, C40, and C50) and lining thickness (300 mm, 400 mm, and 500 mm) on the dynamic response of the tunnel structure and the surrounding soil is investigated. It is observed from the results that deformations of tunnel lining increase with a decrease in the grade of concrete and decrease with an increase in lining thickness. The results suggest it is advantageous to increase the thickness of the liner for a certain grade of concrete, rather than increasing the grade of concrete for the same liner thickness for better blast response. The vulnerability of the tunnel liner is high at the roof-sidewall junction suggesting the need for better reinforcement detailing.

In order to evaluate the damage characteristics of buried natural gas pipelines with circular dent defects subjected to blast loading, based on pressure -impulse damage theory, explosion experiment and numerical simulations were implemented to evaluate the damage of a natural gas with circular dent defects buried in soil under blast loading in this research. The ALE method was used to develop a coupled pipeline-soil simulation model using LS-DYNA software, and the validity of the established model was verified correctly compared with experimental results and empirical theory equations calculations. Furthermore, according to regulations in the Assessment and Management of Pipeline Dents (American Petroleum Institute Recommended Practice 1183), the effect with different circular dent defect diameter on the mechanical properties of natural gas was also investigated and analysed. The results showed that, under the blast loading, plastic deformation happened on the surfaces of the pipeline facing the explosive, and the high-stress zone appeared in the circumferential direction with 32.27 degrees . The range of the high-stress zone firstly expanded along the axial direction of the pipelines and then along the circumferential direction. The larger diameter of the circular dent defects had, which resulted in a failure at the defects under the condition of the depth of the defects keeping constant. The effect of the size of defect diameter on the amount of pipeline deformation was further investigated, and the mathematical formula described the maximum plastic deformation with different defect diameter was established. Meanwhile, a finite element model of pipeline with a diameter of 457 mm was established for numerical analysis, which implied that the larger diameter of pipeline with the same defect had, the lower risk of pipeline in failure subjected to blast loading had. And through mathematical analysis and considering the feasibility of the actual situation, the curve described the maximum plastic deformation of the natural gas pipeline with three different defects varying in diameter were established respectively. In addition, a formula to express the relationship between pipeline defect diameter and maximum plastic deformation was established, which can effectively predict the critical plastic dent deformation of pipelines with different defect diameter subjected to blast loading. Besides, based on the pressure-pulse damage theory and with the damage assessment criterion of dent depth -dent length ratio of 0.072, the pressure -impulse diagrams of buried natural gas pipelines with defect diameters of 30 mm, 40 mm and 50 mm were defined, which can be used to predict the damage of pipelines with different defect diameters. Moreover, with the pressure -impulse damage evaluation curves, mathematical formula for the buried natural gas pipeline with the circular defects were established. Furthermore, the critical circular defect diameters with 30 mm was confirmed and the unique formula was also established, which could be effectively used to evaluate the safety of buried natural gas pipelines with the critical circular defects.