Changes

The following calculation is used to size the stone storage bed (reservoir) used as a base course. It is assumed that the footprint of the stone bed will be equal to the footprint of the pavement. The following equations are taken from the ICPI Manual <ref>Smith, D. 2006. Permeable Interlocking Concrete Pavements; Selection, Design, Construction, Maintenance. 3rd Edition. Interlocking Concrete Pavement Institute. Burlington, ON.</ref>

The following calculation is used to size the stone storage bed (reservoir) used as a base course. It is assumed that the footprint of the stone bed will be equal to the footprint of the pavement. The following equations are derived from the ICPI Manual <ref>Smith, D. 2006. Permeable Interlocking Concrete Pavements; Selection, Design, Construction, Maintenance. 3rd Edition. Interlocking Concrete Pavement Institute. Burlington, ON.</ref>

===To calculate the total depth of the foundations (all aggregate layers)===  

===To calculate the total depth of the foundations (all aggregate layers)===  

The equation for the depth of the stone foundation (''d_{f, max}'', mm) is as follows:  

The equation for the depth of the stone foundation (''d_{f, max}'', mm) is as follows:  

<math>d_{f, max}=\frac{\left[\left ( RVC_{T}\times R \right )+ RVC_{T}-\left(f'\times t\right )\right]}{V_{R}}</math>

<math>d_{f, max}=\frac{\left[\left ( RVC_{T}\times R \right )+ RVC_{T}-\left(f'\times t\right )\right]}{n}</math>

{{Plainlist|1=Where:

{{Plainlist|1=Where:

*''RVC_T'' = [[Runoff volume control target]] (mm)  

*''RVC_T'' = [[Runoff volume control target]] (mm)  

*''f''' = [[Design infiltration rate]] (mm/hr)  

*''f''' = [[Design infiltration rate]] (mm/hr)  

*''t'' = Time to fill stone bed (typically 2 hr)  

*''t'' = Time to fill stone bed (typically 2 hr)  

*''V_R'' = Void ratio for stone bed (typically 0.4 for 50 mm dia. [[reservoir aggregate|clear stone]])}}  

*''n'' = Porosity of the stone bed aggregate material (typically 0.4 for 50 mm dia. [[reservoir aggregate|clear stone]])}}  

On highly permeable soils (e.g., infiltration rate of 45 mm/hr or greater), a maximum stone reservoir depth of 2 metres is recommended to prevent soil compaction and loss of permeability from the mass of overlying stone and stored water.

On highly permeable soils (e.g., infiltration rate of 45 mm/hr or greater), a maximum stone reservoir depth of 2 metres is recommended to prevent soil compaction and loss of permeability from the mass of overlying stone and stored water.

===To calculate the invert of the underdrain from the base of the reservoir===

===To calculate the invert of the underdrain from the base of the reservoir===

For designs that include an underdrain, the maximum depth of the storage layer below the invert of the underdrain pipe (''d_{s, max}'') can be calculated as follows:  

For designs that include an underdrain, the depth of the storage reservoir below the invert of the underdrain pipe (''d_{r, max}'') can be calculated as follows:  

<math>d_{s, max}=\frac{f'\times t}{0.4}</math>

<math>d_{r}=\frac{f'\times t}{n}</math>

{{Plainlist|1=Where:

{{Plainlist|1=Where:

*''f''' = Design infiltration rate (mm/hr), and

*''f''' = Design infiltration rate (mm/hr), and

*''t'' = [[Drainage time]] (hrs), e.g. 96 hours, check local regulations for drainage time requirements.   

*''t'' = [[Drainage time]] (hrs), e.g. 72 hours, check local regulations for drainage time requirements.   

*''0.4'' = Void ratio of [[Reservoir aggregate|clear stone]]}}

*''n'' = Porosity of [[Reservoir aggregate|clear stone]]}}

----

----

When sizing the area of permeable paving based on the contributing drainage area, the following equation may be used:

When sizing the area of permeable paving based on the contributing drainage area, the following equation may be used:

<math>A_p= \frac{Q_c\times A_c}{V_R \times dp – P + q'\times t}</math>

<math>A_p=\frac{Q_c\times A_c}{V_R\times (d_p – P + (q'\times t))}</math>

 

Back to [[Permeable pavements]]

Back to [[Permeable pavements]]

[[Category:Calculations]]

[[Category:Calculations]]