Reaearch On Characteristics Of Water Damage Along Oil And Gas Pipelines On Collapsible Soil Site

There is about 414.5km pipeline of Sebei-Xi’ning-Lanzhou Gas Transmission Pipeline deposited on the loess. Most loess has strong collapsibility in this area. Collapsible loess will likely cause washout and other geological disasters due to seasonal rainfall and pressure. Washout often causes pipe bareness, suspension, and even crack, so due attention must be paid to it. Based on it, the following research work is done in this paper.According to the field work, three different types of water damage along pipeline are preliminarily analysed, and whose sensitive factors are identitied.Three different pipe mechanics models are established, and the stress calculation formula is derived. Then common models of water damage along pipeline are established by using the ABAQUS finite element analysis tool: models of suspended pipe due to loess settlement and models of pipe under the impact of river water. For suspended pipe. At first, based on simulation calculation, it works out the limit length of pipeline is about 40 m, and the distribution law of stress field distribution by selecting the pipeline. Then through changing parameter, the influence of pipe diameter, wall thickness, diameter, buried depth and internal pressure on the stress, strain and displacement of the pipeline is calculated, it draws such a conclusion that buried depth, wall thickness and outside diameter affect it greatly, and internal pressure has a minor effect on it. As for pipeline under the impact of river water. At first, based on simulation calculation, it works out the limit velocity of flow is about 7m/s when the suspended length is 60 m, and the distribution law of stress field distribution by selecting the pipeline. Then through changing parameter. The influence of pipe diameter, wall thickness, diameter, buried depth and internal pressure, pipe-soil friction coefficient on the stress, strain and displacement of the pipeline is calculated, it draws such a conclusion that buried depth, wall thickness and outside diameter affect it greatly, and internal pressure, buried depth, pipesoil friction coefficienton has a minor effect on it.In the last part of this paper, based on laboratory experiment, standard sand, lime, cement, soluble silicate are adopted as modified materials, the result reveals collapsibility of modified loess in different compaction coefficient and different mixture ratio. The result shows that modified loess can reduce collapsibility of the loess. Under the condition of certain degree of compaction coefficient, the collapsibility of loess is eliminated basically, which can meet the needs of safety reqiurements. The analysis of the improvement effect shows that water glass is the best modified material, which is followed by the lime and cement, and the standard sand is the least effective.