Rockfall impacts have seriously threatened the operations of buried pipelines in geologically unstable regions. In this book, mechanical behaviour of oil and gas pipeline impacted by a rockfall was investigated by numerical simulation. In chapter 1, collapse reasons of rockfalls and impact force of buried pipeline impacted by a rockfall were introduced. In chapter 2, mechanical behavior of a ground pipeline impacted by a rockfall (normal impact, longitudinal inclined impact, transverse inclined impact and eccentric impact) was investigated. In chapter 3 and 4, buckling behavior of a buried pipeline in soil stratum and rock stratum impacted by a rockfall were studied. Effects of pipeline parameters, rockfall parameters and surrounding soil parameters on the pipeline¿s mechanical behavior were researched. In chapter 5, mechanical behavior of a buried pipeline under surface load caused by rockfalls were investigated. In chapter 6¿a protective device of buried pipelines is designed for preventing rockfalls impact. Those results can be used for laying construction, safety evaluation and protection engineering of oil and gas pipelines in bad geological regions.