【国外标准】 Standard Practice for Measurement of the Kinetic Energy of Simulated Rainfall

5.1 When a raindrop impacts the surface of a soil, it expends its energy and begins the impact-induced soil erosion process. This kinetic energy of the raindrop is one factor influencing soil erosion. This practice provides a method to quantify the kinetic energy produced by rainfall simulators.5.2 Soil erosion is a concern that affects many industries. The highway and road construction industry is particularly interested in slope protection. There are many ECP manufacturers that rely on testing of their products using rainfall simulators to meet certain specifications set forth by different agencies.5.3 Laboratories that offer testing of ECPs use rainfall simulators. Many laboratories are able to adjust their rainfall simulators, the drop height of the raindrops, and even the slopes of the test plots they use to model expected, anticipated, or actual field conditions. The kinetic energy associated with the specific configuration of the simulator should be measured.5.4 Knowing the kinetic energy for the given simulator configuration will provide a way to set minimum and upper limit values so that comparisons between laboratories can be made as well as having a way to account for the differences between the laboratories. If there are minimum and upper limit values and the raindrop size is in the same range between laboratories, the kinetic energy between the laboratories should be similar. Once the kinetic energy is established for a given rainfall simulator configuration according to a specific standard, comparisons of the results for those specific standards can be made.NOTE 2: The quality of the result produced by this standard is dependent on the competence of the personnel performing it, and the suitability of the equipment and facilities used. Agencies that meet the criteria of Practice D3740 are generally considered capable of competent and objective testing/sampling/inspection/etc. Users of this standard are cautioned that compliance with Practice D3740 does not in itself assure reliable results. Reliable results depend on many factors; Practice D3740 provides a means of evaluating some of those factors.1.1 This practice is used to measure the kinetic energy of rainfall simulators used by laboratories to evaluate soil erosion. The kinetic energy of raindrops is an important factor that should be considered when conducting soil erosion studies. Using the data collected from determining the raindrop size, this practice provides a method to uniformly calculate the kinetic energy which can be used to compare results from different laboratories.1.2 Many types of Erosion Control Products (ECPs) are evaluated for their ability to reduce soil erosion in laboratory and field settings using rainfall simulators. Rainfall simulators are used with test plots to simulate a specific condition that is or may be expected in the field. Rainfall simulators typically use drop emitters, sprinklers, or nozzles to create the raindrops. Each device produces different drops and since the rainfall simulators can be configured to produce different raindrop sizes and fall heights, the kinetic energy will be different. Therefore, the kinetic energy must be calculated for a given set of conditions in order to properly understand the impact of erosion for bare soil and the ECP.1.3 The upper limit of the size of a raindrop is generally accepted to be 7 mm. While it is possible to get a raindrop size between 6 and 7 mm occasionally, it is not common to get raindrop sizes above 6 mm.1.4 Units—The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. Reporting of test results in units other than SI shall not be regarded as nonconformance with this standard.1.5 All observed and calculated values shall conform to the guidelines for significant digits and rounding established in Practice D6026.1.5.1 The procedures used to specify how data are collected/recorded or calculated in the standard are regarded as the industry standard. In addition, they are representative of the significant digits that generally should be retained. The procedures used do not consider material variation, purpose for obtaining the data, special purpose studies, or any considerations for the user’s objectives; and it is common practice to increase or reduce significant digits of reported data to be commensurate with these considerations. It is beyond the scope of this standard to consider significant digits used in analysis methods for engineering design.1.6 This practice offers a set of instructions for performing one or more specific operations. This document cannot replace education or experience and should be used in conjunction with professional judgment. Not all aspects of this practice may be applicable in all circumstances. This ASTM standard is not intended to represent or replace the standard of care by which the adequacy of a given professional service must be judged, nor should this document be applied without consideration of a project’s many unique aspects. The word “Standard” in the title of this document means only that the document has been approved through the ASTM consensus process.1.7 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 determine the applicability of regulatory limitations prior to use.1.8 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.