Laboratory Modeling of Internal Erosion in Dam Foundations-Paper

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The study used two bench-scale laboratory devices to investigate internal erosion where dam soils interact with bedrock defects. The Joint Erosion Testing Device (JETD) modeled contact erosion along flowing bedrock joints, while the Foundation Void Test Cell (FVTC) modeled soil erosion into open joints or solution cavities under different hydraulic conditions.<br /><br />Nine soils were tested in the JETD. Measurements of flow, pressure, and erosion progression were used to estimate critical shear stresses. Results varied substantially with soil type and with small differences in compaction and water content. In some cases, JETD critical shear stresses differed from those measured using hole erosion tests, likely because the devices produce different flow patterns and test durations. Greater compaction water content generally appeared to increase erosion resistance.<br /><br />Six FVTC tests examined four soil types, using constant downward flow or cyclic flow from below. Constant flow produced discrete piping channels; in granular soil, natural filters formed and slowed erosion without preventing its progression. Cyclic upward loading generally produced slow initial erosion followed by rapid upward stope development and widening. Low-cohesion soil did not sustain a tall, narrow stope, while a larger initial void accelerated failure. Pressure measurements indicated that drainage could create a low-permeability, unsaturated zone above a stope, generating high hydraulic gradients that may drive its upward advance.<br /><br />The experiments demonstrate that erosion mechanisms depend on soil properties, defect geometry, and hydraulic loading history. The devices provide a way to observe and measure these processes, potentially improving dam foundation design, monitoring, remediation, and risk assessment. The authors caution that small differences in soil preparation can materially affect test outcomes.

Keywords

internal erosion

dam foundation

bedrock defects

Joint Erosion Testing Device

Foundation Void Test Cell

contact erosion

critical shear stress

piping channels

hydraulic gradients

soil properties