The 2nd Badong International Geohazards Symposium (BIGS2019)

50 / 2019-03-25 09:35:45

Analysis of Shallow Buried Oil and Gas Pipeline under Rockfall Impact Based on the Coupling of Discrete Element and Finite Element

rockfall; impact; dynamic balance; pipeline; buffer; passive protection

Prevention and Control of Reservoir Geohazards and Ecological Environmental Protection > Technologies of geohazards Prevention and Control

As an efficient and low-cost international freight transportation mode, long-distance pipeline is vulnerable to invasion when crossing the mountainous areas where geological disasters occur frequently. Because of its shallow buried pipeline, thin-shell steel tube structure, containing high-pressure flammable and explosive medium, the accident has serious consequences. Lanzhou-Chengdu-Chongqing oil pipeline has undergone several rockfall impact pipeline incidents, which seriously threaten the normal operation of gas pipeline. It is imperative and urgent to carry out research on the impact safety protection technology of rockfall on pipeline.
Based on the energy conservation law, Hertz elastic collision theory and incomplete elastic collision theory, the dynamic equilibrium formula of rockfall impact oil and gas pipeline is established to obtain the maximum impact pressure. Flac 6.0 software is used to couple the particle flow discrete element method with the finite element method. The cushioning effect of different overlying soils (sand and clay) on rockfall is studied. It is found that sand has better cushioning effect on rockfall impact, while clay has less cushioning effect on rockfall. By simulating the whole process of pipeline damage caused by falling rocks, the static load of pipeline caused by falling rocks after impact can not be ignored.
Starting from sand cushioning and stoning static load prevention, a protection project of "falling stone - buffer layer - protective structure - pipeline" is proposed. When using finite element and discrete element coupling to compare the same protective structure characteristics (buffer thickness, structure size and burial depth, etc.), the relative position (scheme 1: top-down buffer layer (sand bag) + structure (supporting beam and column) + pipeline; scheme 2: top-down structure (supporting beam and column) + buffer layer (sand bag) + pipeline) is different, and the appropriate protective effect of the two schemes is selected. Protection scheme.