Laboratory Testing

Continuing Erosion Filter (CEF) Testing

Continuing Erosion Filter (CEF) testing provides a direct laboratory evaluation of the compatibility between a base soil and filter. Developed through the work of Foster and Fell (2001) and Foster (2007), the test evaluates the extent of erosion that may occur through a filter under controlled hydraulic loading.

Evaluating Base-Filter Compatibility

Filters are a fundamental defence against internal erosion in embankment dams. While gradation-based filter criteria provide the primary basis for assessing compatibility, laboratory testing can provide additional evidence where material characteristics or base-filter relationships introduce uncertainty.

CEF testing places a prepared base soil in contact with a candidate filter and applies controlled hydraulic loading. The erosion response is monitored to determine whether erosion is limited through self-filtering or continues to a greater extent.

Testing can be particularly valuable for broadly graded, gap-graded, or otherwise complex materials, and for existing dam materials where conventional filter criteria do not provide a definitive understanding of expected behaviour.

Applications to Embankment Dams

CEF testing can support dam safety assessments, evaluation of existing filter systems, rehabilitation and upgrade projects, and selection of proposed filter materials.

Results are best considered as one line of evidence within a broader internal erosion assessment, alongside material gradations, dam zoning, seepage conditions, construction history, and observed performance.

Test Program Development

Stratem develops each CEF testing program around the materials being evaluated and the engineering question the results are intended to address. Programs can be developed collaboratively with dam owners, consultants, and engineering teams to establish appropriate material combinations and testing objectives.