# Difference between revisions of "Permeable pavements: Sizing"

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 [1]

### For full infiltration design, to calculate the total depth of clear stone aggregate layers needed for the water storage reservoir

The equation for the maximum depth of the stone reservoir (dr, max, m) is as follows:

${\displaystyle d_{r,max}={\frac {(RVC_{T}\times A_{p})+(RVC_{T}\times A_{i}\times C)-(f'\times D\times A_{p})}{n}}}$

Where:

${\displaystyle RVC_{T}=D\times i}$

• D = Duration of the design storm event event (hr)
• i = Intensity of the design storm event (m/hr)
• Ai = Impervious contributing drainage area (m2
• R = Ai/Ap; the ratio of impervious contributing drainage area (Ai) to permeable pavement area (Ap). Note that the contributing drainage area should not contain pervious areas. R should not exceed 2.
• n = Porosity of the stone bed aggregate material (typically 0.4 for 50 mm dia. 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.

### For partial infiltration design, to calculate the depth of the storage reservoir needed below the invert of the underdrain pipe

For designs that include an underdrain, the depth of the storage reservoir below the invert of the underdrain pipe (dr) can be calculated as follows: ${\displaystyle d_{r}={\frac {f'\times t}{n}}}$

Where:

• t = Drainage time (hrs), e.g. 72 hours, check local regulations for drainage time requirements.
• n = Porosity of the stone bed aggregate material (typically 0.4 for 50 mm dia. clear stone)

Where the total area of the pavement (Ac) and total depth of clear stone aggregate needed for load bearing capacity are known (i.e., storage reservoir depth is fixed) or if available space is constrained in the vertical dimension due to water table or bedrock elevation, the minimum footprint area of the water storage reservoir, Ar can be calculated as follows:
${\displaystyle A_{r}={\frac {D(i-f')\times A_{c}}{d_{r}\times n}}}$

Where:

Ac = Ai + Ap

Then increase Ar accordingly to keep R between 0 and 2, which reduces hydraulic loading and helps avoid premature clogging. This assumes that the water storage reservoir area and permeable pavement area are the same (Ar = Ap).

Back to Permeable pavements

1. Smith, D. 2006. Permeable Interlocking Concrete Pavements; Selection, Design, Construction, Maintenance. 3rd Edition. Interlocking Concrete Pavement Institute. Burlington, ON.
The text passage provides equations and guidelines for calculating the depth and area of stone storage beds used in permeable pavement systems, including both full and partial infiltration designs.
no_question

the passage does not contain a specific mathematical question or request for a calculation. it provides formulas and parameters for calculating the depth and area of stone storage beds but does not ask the reader to solve a particular problem or provide an answer to a specific question.
Given a text passage, determine:
    1. If it contains a mathematical question (including word problems or calculations)
    2. If an answer to that mathematical question is provided in the text

First, describe the content structure you found in 1-2 sentences.

Then provide your analysis in the following format:
TYPE: <one of the following values>
- NO_QUESTION
- SINGLE_QUESTION
- SINGLE_QUESTION_WITH_ANSWER
- MULTIPLE_QUESTIONS
- MULTIPLE_QUESTIONS_WITH_ANSWERS
system
# Difference between revisions of "Permeable pavements: Sizing"

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 [1]

### For full infiltration design, to calculate the total depth of clear stone aggregate layers needed for the water storage reservoir

The equation for the maximum depth of the stone reservoir (dr, max, m) is as follows:

${\displaystyle d_{r,max}={\frac {(RVC_{T}\times A_{p})+(RVC_{T}\times A_{i}\times C)-(f'\times D\times A_{p})}{n}}}$

Where:

${\displaystyle RVC_{T}=D\times i}$

• D = Duration of the design storm event event (hr)
• i = Intensity of the design storm event (m/hr)
• Ai = Impervious contributing drainage area (m2
• R = Ai/Ap; the ratio of impervious contributing drainage area (Ai) to permeable pavement area (Ap). Note that the contributing drainage area should not contain pervious areas. R should not exceed 2.
• n = Porosity of the stone bed aggregate material (typically 0.4 for 50 mm dia. 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.

### For partial infiltration design, to calculate the depth of the storage reservoir needed below the invert of the underdrain pipe

For designs that include an underdrain, the depth of the storage reservoir below the invert of the underdrain pipe (dr) can be calculated as follows: ${\displaystyle d_{r}={\frac {f'\times t}{n}}}$

Where:

• t = Drainage time (hrs), e.g. 72 hours, check local regulations for drainage time requirements.
• n = Porosity of the stone bed aggregate material (typically 0.4 for 50 mm dia. clear stone)

Where the total area of the pavement (Ac) and total depth of clear stone aggregate needed for load bearing capacity are known (i.e., storage reservoir depth is fixed) or if available space is constrained in the vertical dimension due to water table or bedrock elevation, the minimum footprint area of the water storage reservoir, Ar can be calculated as follows:
${\displaystyle A_{r}={\frac {D(i-f')\times A_{c}}{d_{r}\times n}}}$

Where:

Ac = Ai + Ap

Then increase Ar accordingly to keep R between 0 and 2, which reduces hydraulic loading and helps avoid premature clogging. This assumes that the water storage reservoir area and permeable pavement area are the same (Ar = Ap).

Back to Permeable pavements

1. Smith, D. 2006. Permeable Interlocking Concrete Pavements; Selection, Design, Construction, Maintenance. 3rd Edition. Interlocking Concrete Pavement Institute. Burlington, ON.
user
The text passage provides equations and guidelines for calculating the depth and area of stone storage beds used in permeable pavement systems, including both full and partial infiltration designs.

TYPE: NO_QUESTION

The passage does not contain a specific mathematical question or request for a calculation. It provides formulas and parameters for calculating the depth and area of stone storage beds but does not ask the reader to solve a particular problem or provide an answer to a specific question.