<p><p><strong>References:<br></strong><em>Christopher et al. (2010)</em></p><p><strong>Method Summary</strong></p><p>Permeability is the ability of a material to conduct water. It is defined as the quantity of fluid flow through a unit area of soil under a unit pressure gradient. Permeability of the subgrade is rarely an issue for pavement design, but may be of interest in terms of dewatering requirements for excavations or installation of interceptor drains to lower groundwater. For rehabilitation projects, permeability of existing base and subbase may be of interest in order to evaluate drainage characteristics (e.g., time to drain) of in-place materials. Field permeability tests may be conducted on natural soils (and rocks) by a number of methods, including simple falling head, packer (pressurized tests), pumping (drawdown), slug tests (dynamic impulse), and dissipation tests. Simple falling head tests are typically used for evaluating the permeability of in-place base and subbase materials.</p></p>