|Alternative Title||Study on Dynamic Response of Buried Pipeline Caused by Rock Fall Impaction|
|Place of Conferral||北京|
|Keyword||岩块 埋地管道 冲击响应 Eps垫层 耗能减振|
|Abstract||输油气管道穿越山区时多沿坡脚敷设，崩裂岩块对管道造成的安全问题日渐突出。崩裂岩块对管道的主要危害是岩块自高空坠落对管道产生的冲击荷载，尤其是在高程差比较大的地段，冲击载荷使管道承受的应力超过其安全规定的许用应力，从而引起管道破坏。为保障埋地管道的安全运营，本论文采用理论分析和数值仿真方法开展了崩裂岩块冲击作用下埋地管道的动力学响应研究，主要研究内容有：1）崩裂岩块岩土工程稳定性评价及冲击力计算；2）岩块冲击荷载下埋地管道的受力分析和强度计算；3）埋深对埋地管道承受冲击力影响规律的研究；4）垫层防护机理及效果分析。通过对以上内容的研究，取得以下研究结论： （1）推荐最符合实际的岩块最大冲击力计算方法。 （2）岩块冲击载荷作用下埋地管道应力和应变分析：1）管道纵向受力分析时可将管道视为弹性地基上的无限长梁，冲击载荷视为集中力，按照弹性地基梁法进行内力计算。2）横向受力分析时可将冲击载荷简化为均布载荷，按照弹性理论方法和结构力学方法计算横向内力。3）对于崩裂岩块这种会使埋地管道产生大变形的灾害类型，引入了更为适合设计使用的基于应变的设计方法。4）以某输油管道在甘肃阳坝遭受崩塌灾害为例，采用理论计算和有限元数值模拟相结合的方法，对管道进行荷载分析、应力分析和应变分析后，得出管道破坏结果与现场相吻合的结论。 （3）岩块冲击载荷在土层中的传播规律：1）岩块冲击荷载作用时间极短，最大冲击力与速度近似成正比。2）岩块冲击力在土层中的传播是一个过程，各深度出现最大冲击力的时间随着深度而延迟。 （4）在岩块冲击作用下土体竖向应力在管顶将出现应力集中现象，其分布形式与静力学荷载分布形式相似，但是应力更加集中。冲击中心正下方为管道最危险截面处，最大位移和最大有效应力均出现在管道顶部。 （5）增加埋深可以有效减弱岩块冲击荷载对管道的冲击效应，埋深对管体承受的峰值有效应力有较明显的影响，但是这种影响是在一定埋深范围内的，当超过这个范围时，增加埋深将变得毫无意义。以文中的工况为例，当埋深在1.0m~2.0m范围内时管道峰值有效应力急剧下降，且与埋深成近似线性关系；当埋深在2.0m~3.0m范围内时，增加埋深对减弱管道峰值有效应力的效果不再显著；当埋深超过3.0m时，管道峰值有效应力几乎不随埋深的增加而减小。 （6）EPS板垫层对冲击能量的耗能隔振效应显著，在同种条件下其耗能隔振效果可达5倍左右。EPS板垫层的初始密度越小，其对岩块冲击应力耗散作用越明显。|
|Other Abstract||Laying oil and gas pipelines through the mountains mostly distributed along foot of the|
slope, the pipeline security issues caused by rock fall have become increasingly prominent. The impact load on the pipelines is the major hazard on the pipelines exerted by bursting rocks when falling from the upper air. This is more remarkable in the sections with relatively large difference of elevation, where the stress on the pipelines imposed by the impact load exceeds the allowable stress in safety requirement and causes pipeline destruction. This thesis is about the study on the dynamic response of the buried pipelines under the impact of bursting rocks, by means of theoretical analysis and numerical simulation, in order to guarantee the safe running of buried pipelines. The research mainly covers: 1) Cracked rock geotechnical stability evaluation and impact force calculations; 2) force analysis and strength calculation of buried pipelines under the impact load of rocks; 3) Laws about influence of burial depth on the impact force endured by the buried pipelines; 4) protective mechanism and effect analysis of cushion ply. The above research leads to the following conclusions:
(1) Recommend the most realistic rock maximum impact force calculation methods.
(2) Stress and strain analysis of buried pipelines under the impact load of rocks: 1) In the
longitudinal stress analysis of the pipelines, the pipelines can be regarded as the infinite
beams on the elastic foundation, and the impact load as the concentrated force, and then the internal force calculation is done according to Elastic Foundation Beam Method. 2) In the transverse force analysis, the impact load can be simplified as uniformly distributed load, and the calculation of transverse internal force is done according to elastic theory method and structural mechanics method. 3) For the disaster category that can cause major deformation of the buried pipelines such as the bursting rocks, the designing method based on strain more suitable for designing use is introduced. 4) Taking certain oil pipeline in Yangbei, Gansu Province, which suffered the dilapidation, as the example, the author, after load analysis, stress analysis and strain analysis of the pipelines, reached the conclusion that the destruction of the pipelines coincides with the scene.
(3) Laws about the transmission of the impact load of the rocks in the soil layer: 1) The
period during which the impact load of the rocks exerts effects is pretty short. The maximum impact force is almost in direct ratio to the rate. 2) The transmission of the impact force of rocks in the soil layer is a process in which the time the maximum impact force occurs in each depth is delays according to the depth.
(4) Under the impact of the rocks, the vertical stress of the soil mass is quite oncentrated on the top of the pipelines, whose form of distribution is similar to that of statics load, but with more concentrated stress. The most dangerous cross section area in the pipelines is located below the center of the impact. And the top of the pipelines is the area where the maximum displacement and the maximum effective stress occur.
(5) The increase of burial depth can effectively weaken the shock of impact load of rocks
on the pipelines, because the burial depth exerts remarkable effects on the maxima effective stress the pipelines can endure. However, this effect is restricted by the range of burial depth. When exceeding the range, the increase of burial depth becomes meaningless. In different situation, for example, when the depth in the range of 1.0m to 2.0m, pipeline’s peak effective stress falling sharply, and approximately linear relationship with depth. When the depth in the range of 2.0m to 3.0m, increase the depth to weak pipe’s peak effective stress effect was no longer significant. When the depth exceeds 3.0m, pipe’s peak effective stress almost does not change with the increase in depth decreases.
(6) EPS plate cushion layers exert remarkable energy dissipating and vibration isolating
effect on the impact energy, 5 times as much as that under the same circumstances. The less the initial density of the EPS plate cushion layers, the more remarkable its dissipation of the impact force of the rocks.
|王东源. 崩裂岩块冲击埋地管道的动力学响应研究[D]. 北京. 中国科学院研究生院,2013.|
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