New apparatus for evaluating filter performance for dams containing cracks

A new test apparatus has been developed to evaluate filter performance when both the filter and the core (base) material have been cracked. This apparatus allows the orientation of the crack to be horizontal or vertical, and accommodates flow in the horizontal and vertical directions as well. The applied hydraulic gradient and the thickness of the crack can also be varied. Two apparatuses have been constructed and tested. The smaller apparatus allows testing of truncated cylindrical test specimens that are 10 cm in diameter by 20 cm long. The larger apparatus allows testing of specimens that are approximately 30 by 30 by 30 cm. An automated data acquisition system was developed to measure the pressures and flow rates through the test specimens as well as obtaining a video record of the filter performance. In successful tests, the filter slumped to fill the crack, the flow rate decreased, and the head water pressure increased. In failed tests, the filter never slumped to fill the crack, the flow rate remained high, and the head water pressure stayed very low. The relative success of failure of a filter system could be assessed by the video record as well. Copyright © 2007 by ASTM International.