Permeability Measurement of Base Materials Using Falling-Head Test Apparatus

The development of a new falling-head procedure for laboratory permeability measurement of pavement base materials is described. The main advantage of the falling-head test over the conventional constant-head test is its ability to determine permeability properties of the test material at different levels of hydraulic gradients in a single test. The test setup is simpler and the test duration is much shorter. Each test takes only a few minutes to complete. A large number of tests have been conducted with the proposed procedure on different materials, including compacted crushed stones, glass spheres, and cement stabilized base materials. The falling-head test results were verified by performing constant-head permeability tests on the same specimens at different hydraulic gradients. Analysis on the falling-head test data revealed that the relationship between specific discharge and hydraulic gradient over the range studied could not be represented by a single linear relationship as stated by Darcy’s law. The proposed approach can be a useful tool for determining the drainage properties of base materials within the range of hydraulic gradients encountered in actual pavements.