| The area of soluble rock in China is 3.65 million km2,which has become one of the most developed countries in the world.Meanwhile,the natural gas pipelines network in China have been widely developed and it is inevitabe to cross the area of soluble rock.The most common type of geological disasters suffered along the Guangxi section of the Sino-Myanmar natural gas pipeline is karst collapse.When it happens,the pipeline will be suspended and exposed in the air with the consequence of fracture and secondary disasters,which is a serious threat to the operation.The objective of this Paper is to analyze the state of natural gas pipeline in karst section of Guangxi based on the stress.Firstly,the formation conditions,collapse mechanism and collapse principle of karst collapse are summarized.Based on the theory of elastic foundation beam,a simplified mechanical model is established and applied to analyze the properties of the collapsed pipe.Then,further analyze is conducted to study the stress characteristics of the pipeline under karst collapse with the finite element software ABAQUS which simulates the displacement,stress and strain distribution of the soil and pipeline instantaneously focusing on the major factors including the internal pressure,the diameter,the walls thickness,the depth of burial,the size of soil hole and the thickness of overburden.Finally,a practical case of a pipeline under karst section in Guangxi is proposed with the maximal suspension length of 45m obtained and its stability evaluated.Additionally,the specific measures for reducing the probability of failure and the precaution of collapse accidents are proposed for the natural gas pipelines in the karst collapse zone in Guangxi.Nowadays,there are few researches on the stress analysis of natural gas pipeline in karst subsidence area.However,the results obtained from stress analysis of natural gas pipeline in karst collapse area of Guangxi are meaningful for the design and operation in karst area. |
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