含管黄土渗流变形规律模拟研究

Simulated study on seepage deformation of the pipe-containing loess

黄土地区油气长输管道管沟回填土及附近区域中发育有洞穴灾害,对管道安全的威胁日益严重.尽管原状黄土、公路与铁路路堤中黄土洞穴的成因机理研究较多,但对含管黄土的渗透变形及洞穴灾害研究却较为匮乏.文章在厘清含管黄土渗流变形流固耦合方程的基础上,构建由原状土、回填土与管道组成的含管黄土渗流变形计算模型.利用Ansys Workbench中Fluent和Transient Structural耦合求解,模拟分析含管黄土中雨水渗流和土体变形规律.结果表明:约3 m宽的管沟回填黄土的渗流速度和变形量明显大于原状土;入口流速、回填土孔隙率与密度的增加均会以不同方式加快管沟回填黄土的渗流变形,进而加速管周黄土洞穴的形成与发展;微地貌起伏汇水区、管沟回填土、原状土与回填土的接触面是管周黄土洞穴灾害易发区.研究结果对揭示管周黄土洞穴成因机理有重要的理论意义,为管周黄土洞穴灾害防治提供参考.

There are a large number of caves in the backfill soil of the oil and gas pipeline trenches and the neighboring areas of the loess regions,and the threat of cave hazards to pipeline safety is increasingly serious.There are many researches on the mechanism of loess-cave formation in undisturbed loess,and along highway and railway embankments,but there are few researches on seepage deformation and cave disasters of pipe-containing loess.On the basis of clarifying the fluid-structure coupling equation of seepage deformation of pipe-containing loess,the research constructs a seepage deformation calculation model of the pipe-containing loess composed of undisturbed soil,backfill soil and pipes.The coupling solution of Fluent and Transient Structural in Ansys Workbench was used to simulate and analyze the laws of rainwater seepage and soil deformation in the pipe-containing loess.The results show that the seepage velocity and displacement deformation of the backfill soil with a width of about3 m are significantly greater than that of the undisturbed soil.Meanwhile,the increase of inlet velocity,porosity and density of backfill soil can promote the seepage deformation of the backfill loess in different ways,hence accelerating the formation and development of loess caves around the pipes.Loess cave disasters are prone to occur in the micro-geomorphologic undulating catchment areas,backfill soil and the contact surface of undisturbed soil and backfill soil.The project is of great theoretical significance to reveal the genetic mechanism of the loess caves and provides some references for preventing and controlling the loess cave disasters along the pipelines.