Numerical Analysis On Dynamic Responses Of Buried Pipeline Structures Considering Multiphase Coupling By Blast Loading

As rapid economic development of China, pipeline transportation with unique and irreplaceable advantages has obtained fast development. Pipeline transportation is an important means of transportation because of its economic, safe, fast, and convenient characteristic, and it is widely used in a variety of industries. But in recent years, the terrorist attacks are becoming more frequent with the serious harm. As an important means of transportation, buried pipeline structures subjected to blast loads will bring not only casualties and property losses, but also seriously damage for the public image and impact. Therefore, the security of the buried pipeline structures under the explosive load is an urgent problem to be solved.The study on the explosion problem has substantially three methods:theoretical analysis, experimental research and numerical simulation. Theoretical analysis of the explosion issue is quite difficult because of the need for accurate models and appropriate decomposition, and the simplification also requires a large amount of calculation. The experimental study has its limitations because of the explosion characteristic. Therefore, the numerical simulation as a new research method is widely used to study the explosion problem. In this dissertation, the finite element software ANSYS/LS-DYNA is used for a buried pipeline structure to perform numerical simulation by using a variety of material models such as air, soil, liquid and TNT charge. These material models have good fluidity which is applicable to Euler mesh, and pipeline structure belonging to the solid material has poor fluidity which is applicable to Lagrange mesh. The ALE algorithm is applied in the dissertation to solve the fluid solid coupling problem.This dissertation mainly studies the following aspects:(1) the analysis on transmission of the blast wave in soil and pipeline is performed;(2) through the numerical simulation analysis of pipeline structure under the explosive load along the transverse section and the longitudinal direction of pipeline stress characteristic, the vulnerable area of the pipeline structure is found out, and the effective range of the buried pipeline structure subjected to explosion is defined.(3) the responses of the buried pipeline structure such as stress, velocity, acceleration and displacement are numerically analyzed, focusing on the differences of the pipeline filled with gas or liquid under the explosive load.The numerical results show that it is simple and effective to analyze explosion problem by using the method of numerical simulation. The area in the range of the pipeline facing blast with45degrees is relatively dangerous, and the effective area can be determined based on the scaled distance. The failure possibility of the pipeline will increase with the increment of the explosive weight and the decrement of the standoff to the explosion. Through the comparative analysis of the responses differences between gas pipeline and liquid on, it is found that the pressure in the pipeline has a certain influence on the force of the pipeline, and less influence on the displacement, velocity and acceleration. But the liquid in the pipeline has less impact on the force of the pipeline, but obvious influence on the displacement, velocity and acceleration. These analyses will provide a basis for engineering structure design in the future.The summary is finally concluded and some prospects for the future research are put forward at the end of the dissertation.