【国外标准】 Standard Test Method for Saturated Water Permeability of Granular Drainage Media [Falling-Head Method] for Vegetative (Green) Roof Systems

5.1 This test method addresses performance characteristics for vegetative (green) roof systems with respect to the water permeability of the drainage media.5.1.1 Water permeability of coarse materials is highly influenced by the head conditions under which it is measured. In vegetative (green) roofs, coarse materials are frequently used to create drainage zones for percolated rainfall.5.1.2 This test method is intended to provide water permeability data that is relevant to this design condition that is characterized by horizontal flow under low-head. This will also allow the performance of granular drainage layers in vegetative (green) roof systems to be compared directly to alternative components, such as geocomposite drain layers.5.2 Determining the performance characteristics of vegetative (green) roof systems provides information to facilitate the assessment of related engineering aspects of the facility. Such aspects may include structural design requirements, mechanical engineering and thermal design requirements, and fire and life safety requirements.5.3 Determining the performance characteristics of vegetative (green) roof systems provides information to facilitate assessment of the performance of one vegetative (green) roof system relative to another.1.1 This test method covers a procedure for determining the water permeability of coarse granular materials used in the drainage layers of vegetative (green) roof systems.1.2 This test method addresses water permeability under the low-head conditions that typify horizontal flow in vegetative (green) roof applications.1.3 This test method is suitable for coarse-grained materials with 100 % of the material retained on the U.S. #8 [2.25 mm] sieve. It is not suitable for finer-grained materials.1.4 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard.1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and to determine the applicability of regulatory limitations prior to use.1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.