The Impact Of Collapsed Rockfall On The Crossing Pipeline Of The Minjiang River And Its Prevention And Control

Lantsang Bridge and Tunnel Crossing Project is one of the largest crossing projects of the Sino-Myanmar Pipeline Project. The mountains are high and steep, and the terrain is precipitous in crossing region. Up in the cliff, there distribute many unstable rocks and collapse-slide accumulations. During the pipeline operation stage, rock fall situation had already occurred in this region. The following reasons have determined collapse and rock fall hazards are not acceptable in Lantsang Bridge and Tunnel Crossing Project. Firstly, the crossing section of this project adopts overhead laying method. Secondly, three pipelines (natural gas, crude oil and product oil pipeline) are parallel laid on the crossing bridge. Thirdly, its geographical location is vulnerable to collapse or rock fall hazards. Therefore, it is one of the most important tasks to do research on the influences falling rocks can cause to the crossing pipeline and the prevention and control of rock fall. Given this, the paper takes crossing section pipeline and falling rock exists on both sides as research objects. On the basis of consulting and analyzing a large number of literature materials, rock kinematics theory, dynamics theory and pipeline stress theory are combined with numerical simulation software (RocFall and CAESAR ?).According to the actual circumstance of Lantsang crossing pipeline project and the research data, numerical stimulation models of rock motion path and pipeline stress analysis on the most unfavorable section are established. By rock motion path numerical stimulation model, rock mass and falling heights are studied as well as the influence on the various characteristic parameters (such as the impact scope of the pipeline, the largest kinetic energy when it hits the pipe).Based on the database of impact force and impact angle,1056 times stress simulation analysis are conducted on these three crossing pipelines, and the changes of pipe stress caused rock fall under different condition are analyzed and it identifies that how heavy of these rocks can be to put these pipelines in a dangerous or completely destroyed state.Finally, the paper presents an arrangement of "two layer type" fence. And by applying RocFall, the corresponding relationship curves between rock fall bounce height and the total kinetic energy are being obtained, based on which the position of the SNS passive fence layout, setting height, length of layout and intercept kinetic energy can be determined. And through simulation and site verification, it proves reasonable and protective effects.This research method could provide scientific recommendation to the Lantsang crossing pipeline rockfall protection and pipeline security, and it can also offer guidance and reference to the pipeline engineering which has similar geographic conditions with Lantsang crossing pipeline, such as its design, laying construction and rock protection planning.