Difference between revisions of "Reservoir aggregate"
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| − | [[File: | + | [[File:Clear stone.jpg|thumb|Note the uniform size and angularity of this clear stone sample. |
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| − | + | Note also that the fragments all appear to have a film of fine particles adhering; this material would be improved by being washed prior to use.]] | |
| + | This article gives recommendations for aggregate to be used to store water for infiltration. This is usually called 'clear stone' at aggregate yards. | ||
| − | The clean wash to prevent rapid accumulation of fines from the aggregate particles in the base of the reservoir. The uniform grading and the angularity are important to maintain pore throats and clear voids between particles. (i.e. achieve the | + | To see an analysis of Ontario Standard Specifications for granular materials, see [[OPSS aggregates]]. |
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| + | For advice on decorative surface aggregates see [[Stone]] | ||
| + | ---- | ||
| + | Gravel used for [[underdrains]] in [[bioretention]], [[infiltration trenches]] and [[infiltration chambers|chambers]], and [[exfiltration trenches]] should be 20 or 50 mm, uniformly-graded, clean (maximum wash loss of 0.5%), crushed angular stone that has a porosity of 0.4<ref>Porosity of Structural Backfill, Tech Sheet #1, Stormtech, Nov 2012, http://www.stormtech.com/download_files/pdf/techsheet1.pdf accessed 16 October 2017 </ref>. | ||
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| + | The clean wash to prevent rapid accumulation of fines from the aggregate particles in the base of the reservoir. The uniform grading and the angularity are important to maintain pore throats and clear voids between particles. (i.e. achieve the porosity). Porosity and permeability are directly influenced by the size, gradation and angularity of the particles <ref name = Judge>Judge, Aaron, "Measurement of the Hydraulic Conductivity of Gravels Using a Laboratory Permeameter and Silty Sands Using Field Testing with Observation Wells" (2013). Dissertations. 746. http://scholarworks.umass.edu/open_access_dissertations/746</ref>. See [[jar test]] for on-site verification testing protocols. | ||
Gravel with structural requirements should also meet the following criteria: | Gravel with structural requirements should also meet the following criteria: | ||
*Minimum durability index of 35 | *Minimum durability index of 35 | ||
*Maximum abrasion of 10% for 100 revolutions and maximum of 50% for 500 revolutions | *Maximum abrasion of 10% for 100 revolutions and maximum of 50% for 500 revolutions | ||
| + | Standard specifications for the gradation of aggregates are maintained by ASTM [https://www.astm.org/Standards/D2940.htm D2940] | ||
| + | <gallery> | ||
| + | File:Particle void ratio.png|The highest porosity is found in uniformly graded aggregate, as there are no smaller particles to occupy the inter-particle pores. <ref name = Judge/> | ||
| + | File:Particle permeability.png|Higher permeability is found in larger, angular, uniformly graded aggregate. This is due to larger pore sizes and lower tortuosity. <ref name = Judge/> | ||
| + | </gallery> | ||
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[[category:materials]] | [[category:materials]] | ||
Latest revision as of 17:15, 27 July 2020
This article gives recommendations for aggregate to be used to store water for infiltration. This is usually called 'clear stone' at aggregate yards.
To see an analysis of Ontario Standard Specifications for granular materials, see OPSS aggregates.
For advice on decorative surface aggregates see Stone
Gravel used for underdrains in bioretention, infiltration trenches and chambers, and exfiltration trenches should be 20 or 50 mm, uniformly-graded, clean (maximum wash loss of 0.5%), crushed angular stone that has a porosity of 0.4[1].
The clean wash to prevent rapid accumulation of fines from the aggregate particles in the base of the reservoir. The uniform grading and the angularity are important to maintain pore throats and clear voids between particles. (i.e. achieve the porosity). Porosity and permeability are directly influenced by the size, gradation and angularity of the particles [2]. See jar test for on-site verification testing protocols.
Gravel with structural requirements should also meet the following criteria:
- Minimum durability index of 35
- Maximum abrasion of 10% for 100 revolutions and maximum of 50% for 500 revolutions
Standard specifications for the gradation of aggregates are maintained by ASTM D2940
The highest porosity is found in uniformly graded aggregate, as there are no smaller particles to occupy the inter-particle pores. [2]
Higher permeability is found in larger, angular, uniformly graded aggregate. This is due to larger pore sizes and lower tortuosity. [2]
- ↑ Porosity of Structural Backfill, Tech Sheet #1, Stormtech, Nov 2012, http://www.stormtech.com/download_files/pdf/techsheet1.pdf accessed 16 October 2017
- ↑ 2.0 2.1 2.2 Judge, Aaron, "Measurement of the Hydraulic Conductivity of Gravels Using a Laboratory Permeameter and Silty Sands Using Field Testing with Observation Wells" (2013). Dissertations. 746. http://scholarworks.umass.edu/open_access_dissertations/746