Physical Modeling on Sand Erosion around Defective Sewer Pipes under the Influence of Groundwater

This paper studies soil-erosion problem around cracked sewer pipes, which is usually associated with groundwater infiltration in sewer systems. Four factors (soil-particle size, defect size, water head, and soil height) that are associated with the erosion process were investigated experimentally. Two experimental setups were used: a cylindrical bin with a circular outlet at the bottom center to simulate the erosion process and a rectangular box with the outlet on the side wall to show the internal erosion process. The quantitative influences of the four factors on the erosion-void shape, volume, and length were analyzed. It is found that the geometry of the erosion void is determined by water head and soil height. Relationships were developed for calculating the water-discharge rate, sand-discharge rate, and erosion-void diameter.