Seepage barriers have been used extensively to mitigate seepage problems in dams andlevees. Although the design of many of these dams and levees has been based on intactbarriers, seepage barriers have been shown to be susceptible to deformation and crackingwhen high differential hydraulic pressures act across the barrier. Under certainconditions, these cracks can lead to serious seepage problems which could potentiallylead to the development of a low-resistance seepage pathway. Three scenarios have beenidentified where there is the potential for erosion to occur adjacent to a crack in a barrier:1) erosion at the interface between a fine grained soil and a course grained soil, 2) erosionof overlying soil due to flow along a joint in bedrock, and 3) erosion of the barriermaterial. The objective of this study is to investigate the first mode of erosion andidentify the conditions at which more serious seepage problems can develop. Theresearch has been performed using a laboratory model to simulate conditions near aseepage barrier crack under the scenarios described above. The results from thelaboratory testing were compared to finite element seepage models for each scenario toestimate the flow velocities near the crack. The flow velocities were compared to criticalvelocities of the soil estimated from published relationships to estimate where erosion islikely to occur. A comparison was made between the observed behavior in the model andthe behavior predicted with the computer model. Although not presented in this paper,the results of the research will be used to develop a method to assess the potential forerosion to occur and develop into a failure mode based on conditions near seepage barriercracks.
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