Laserfiche WebLink
<br /> <br /> <br /> <br />17 <br />breakdown) and in-place density are performed to <br />confirm the method specification achieves the desired <br />results. <br /> <br /> <br /> <br /> <br /> <br />Photo 3. Test Pad for Granular Filter Materials <br />Below is an example excerpt from a specification for <br />placement and compaction of a sand filter. It is not all <br />encompassing, and only provides an example portion <br />of typical requirements, and would be tailored for <br />project specific requirements by the design engineer. <br />“Place, spread, and compact Zone 2 material <br />parallel to the embankment axis and in such a <br />manner as to avoid cross contamination of <br />adjacent zones…Place and spread Zone 2 <br />material in level, continuous, approximately <br />horizontal lifts that do not exceed 12 inches in <br />thickness before compaction….Thoroughly wet <br />Zone 2 material at the time of compaction in <br />such a manner as to achieve uniform moisture <br />throughout the lift…compact each lift on Zone 2 <br />with 4 coverage’s, as is defined in these <br />specifications, of an approved 20-ton smooth <br />drum vibratory roller, or with the number of <br />passes based on the test pad program result…” <br />End-result (or QC-based) specifications are more <br />typically and effectively used to control the compacted <br />density of fine-grained, especially cohesive, <br />embankment materials. Verification of the desired <br />outcome is obtained by QA/QC testing of the <br />completed product against a required minimum <br />standard, such as a percentage of standard Proctor <br />maximum dry density within a range of acceptable <br />moisture contents. This is the most common type of <br />earthwork control specification for clay and silt core <br />materials where in-place density testing can be readily <br />performed with real-time results using nuclear density <br />testing gauges. <br />Below is an example excerpt from a specification for <br />placement and compaction of a core material. It is not <br />all encompassing, only provides an example portion of <br />typical requirements, and would be tailored for project <br />specific requirements by the design engineer. It does <br />not present associated requirements including, but <br />perhaps not limited to, protection from cold and wet <br />weather, limits on exposure time of unworked <br />surfaces, discing of clumps, scarifying for adequate tie- <br />in of layers, special compaction at contacts, etc. <br />“Place, spread and compact Zone 1 material <br />parallel to the embankment axis… Place and <br />spread Zone 1 material in level, continuous, <br />approximately horizontal lifts that do not <br />exceed 8 inches in thickness before <br />compaction…compaction water content of Zone <br />1 shall be between minus 1 and plus 3 of the <br />optimum water content in accordance with <br />ASTM D698… moisture conditioning shall be <br />performed in the borrow area or at the stockpile <br />to the extent possible…Zone 1 material shall be <br />compacted to at least 98 percent of the <br />maximum dry density (unit weight) as <br />determined by ASTM D698. <br />References <br />FEMA (2011), Filters for Embankment Dams - Best Practices for Design <br />and Construction (FEMA). <br />Montana Department of Natural Resources (2010), Chimney <br />Filter/Drain Design and Construction Considerations (Technical Note 4) <br />New Mexico Office of the State Engineer (2008), Technical <br />Specifications for Dams <br />Montana Department of Natural Resources (2012), Specification <br />Requirements for Dams (Technical Note 8) <br />American Society for Testing and Materials (ASTM), various reference <br />standards <br />FEMA (2005), Technical Manual: Conduits Through Embankment <br />Dams (FEMA 484) <br />Colorado Division of Water Resources (2007), Rules and Regulations <br />for Dam Safety and Dam Construction