Laboratory modeling of erosion potential of earthen embankments in contact with open bedrock joint

Earth dams constructed on pre-existing jointed bedrock may be susceptible to the erosion of foundation or embankment soils that come in contact with the jointed bedrock. The mechanism analyzed in this study is contact erosion of the soils due to high velocity flows in the bedrock joint. The conditions needed to be satisfied in order for contact erosion to occur are the size of the soil particles must be smaller in diameter than the bedrock joint aperture and the soil must be able to pass through an open exit. Examples of monitored and recorded events due to this phenomenon exist for multiple dams including the Quail Creek Dike failure and deterioration of the core at Mud Mountain Dam. The objective of this research is to use a laboratory model to quantify the risk that existing dams have due to contact erosion at the interface of erodible soils and naturally occurring bedrock joints.;Tests were performed using an apparatus which was designed and constructed at Utah State University. The data obtained was used to develop a relationship for predicting the initiation of erosion and the time of progression. Key variables such as soil type, soil properties, crack aperture and flow velocity will help establish these desired correlations. Crucial values such as Critical Shear Stress and Critical Velocity are used to better understand results of testing performed and to verify results with similar research performed. Results are also compared to a Hole Erosion Test performed at Utah State University.;Conclusions of the study show how to apply the HET to data from this experiment by comparing and contrasting results from tests performed on the same material. The relationships developed are expected to be used in risk assessment toolboxes nationwide for the specific mechanism of contact erosion for existing and future dams. Further testing with the apparatus built is suggested to provide risk assessment teams with a larger database for assigning probabilities to the contact erosion mechanism in existing dams.