Study On The Soil Erosion Around Underground Pipe Leakage

The leakage and pipe burst in underground pipelines lead to the disruption of water and ground collapse,posing significant impacts on resident life as well as social economy.The erosion cavity formed by leakage orifice has great relationship with the pipe burst and ground collapse.The soils around the pipe also affect the pipe leakage.However,the traditional orifice formula does not take the surrounding soil into consideration.This study has research on the process of erosion in soil around the pipe leakage and the three-dimensional leakage formula considering the surrounding soil with experiments.Chapter 1 analyzed the problem of ground collapse induced by pipe leakage,summarized the erosion process and leakage flow rate calculation,and concluded the necessity of studying the soil erosion around the leakage as well as leakage formula.Chapter 2 introduced the theories about the interaction between the fluid and soil and reviewed the state of experiments about the soil erosion by leakage and effect of soil on leakage,which provided the reference for the following experiments.Chapter 3 studied the soil erosion process with a vertically upward leakage.The experiment showed that the soil erosion process was divided into three stages obviously with the increase of flow rate.When the flow increased to the critical flow rate for the full fluidization,the soil damage zone was an inverted cone shaped.In addition,the erosion orifice critical flow was obtained by critical Reynolds number and the formula of the critical flow rate for the full fluidization was developed based on the point-source model.Chapter 4 developed the soil erosion process with vertically downward leakage.Different from the upward pipe leakage,the fluidization zone was cylinder shaped when increased to the critical flow.Furthermore,an empirical formula for the size of erosion cavity,fitting the experimental data well,was derived by dimensionless analysis.Chapter 5 presented the soil erosion process considering the fixed pipe with vertically downward leakage.It was reported from the experiment that the erosion cavity turned to be widen and deeper due to the existence of pipe.The formula for erosion cavity considering the fixed pipe was then derived by dimensionless analysis.What’s more,with the increase of pipe diameter,the critical flow rate for the full fluidization decreased.Chapter 6,an approximate solution for three-dimensional pipe leakage assessment considering the surrounding soil was derived.A series of experiments were carried out under steady-state conditions to validate the solution.The experimental results agreed well with the derived solution.This study focused on the noncohesive soil,and the cohesive soil without considered.Future work may need to consider the impact of cohesion force on the erosion process.