Abstract:
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 about 3 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.