Model Test of Seepage Erosion Around Defective Buried Pipelines
In recent years, the cave-in on roads frequently occurs in urban area to threaten the city safety, which is usually initiated by the ground cavity due to internal erosion around defective buried pipelines. In order to study the mechanism of internal erosion inducing cavity, the model tests are performed using gap grading soil samples. The effects of soil saturation, hydraulic head, initial soil grading and defect size of the pipeline on the internal erosion are studied with eight model tests. The erosion is characterized in terms of the erosion area and cavity formation during erosion. The test results show that the erosion can get stable due to the support of coarse particle skeleton in gap grading soil. The erosion areas can be classified into three forms of gravel area, flow area and cavity according to erosion state. Furthermore, the erosion area especially the cavity in saturated soil is more extensive than that in unsaturated soil. Besides, no hidden cavity forms in unsaturated soil, but the surface settlement. The higher hydraulic head induces bigger erosion area and cavity forms at the water table. More initial fine-sand content means more sand loss, leading to more significant soil deformation. While bigger defect size may cause a little more erosion amount, the effects on cavity is not significant. Finally, the mechanism of internal erosion and cavity formation are interpreted from the microscopic and macroscopic aspects.
KeywordsPipeline leakage Internal erosion Model test Influential factors
This study is financially supported by National Natural Science Foundation of China (Grants No. 41772295). The support is gratefully acknowledged.
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