Chapter 1 Introduction and Literature Review 1.1 Background and Research Objective 1.2 Literature Review 1.2.1 Responses of Underground Structures Subjected to Blast Loading 1.2.2 Pore Pressure and Soil Liquefaction Induced by Blast 1.2.3 Multi-hazard Engineering for Tunnel Lining 1.2.4 Centrifuge Modeling Technique 1.2.5 Numerical Simulation of Explosion 1.2.6 Numerical Simulation of Soil-Tunnel Interaction 1.3 Research Approaches 1.4 Chapter Contents Chapter 2 Blast Simulation Involving Air-Structure Interaction 2.1 Blast Wave Propagation in Air 2.1.1 Theoretical Background 2.1.2 Blast Wavelength and Finite Element Size 2.2 Simulation of Blast Loading in LS-DYNA 2.2.1 Modeling of Air and Explosives 2.2.2 MM-ALE Approach 2.2.3 LBE+MM-ALE Approach 2.3 Simulation of Free Air Blast 2.3.1 Effects of Initial Air Density 2.3.2 Simulation of Free Air Blast with Different Locations of Ambient Layer 2.3.3 Amount of Explosive and Element Size 2.4 Centrifuge Technique 2.5 Reflected Blast on a Rigid Surface 2.6 Simulation of Blast Effect on a Steel Plate 2.7 Size of Air Domain Inside the Tunnel 2.8 Conclusions and Discussions Chapter 3 Numerical Modeling of Soil-Tunnel Interaction 3.1 Modeling of Tunnel Lining 3.2 Modeling of Soil Tunnel Interfaces 3.3 Modeling of Unsaturated and Saturated Soils 3.4 Evaluation of FHWA Soil Model 3.4.1 Introduction 3.4.2 Evaluation 3.5 Conclusions Chapter 4 Response of Circular Tunnels Subjected to Medium Internal Blast Loading 4.1 Base-Case Finite Element Model 4.2 Simulation Results with 200kg TNT 4.2.1 General Response of Tunnel 4.2.2 Response in Soil-Tunnel Interface 4.2.3 Response in Soil 4.2.4 Analysis Results with Simplified Blast Load 4.2.5 Equivalent Triangle Impact Load 4.3 Simulation Results with 100kg TNT 4.3.1 Response of Tunnel 4.3.2 Impact Loading on Tunnel Lining 4.3.3 Response in Soil 4.4 Simulation Results with 50kg TNT 4.4.1 Response of Tunnel 4.4.2 Response of Soil 4.5 Conclusions ����