Towards Restoring Infiltration in Permeable Pavers—Initial Demonstration of Rapid Clean-out Concepts

Abstract

Where clogging of drainage cells in permeable interlocking concrete pavers (PICPs) is dominantly in the upper parts of the filter media, as it is in most cases, infiltration rates in special PICPs may be rapidly restored if the PICP design is dovetailed to the fluid mechanics of the street cleaning equipment. PICPs described in this paper have special purpose cupules (shaped filter recesses in the upper surface of the block) for rapid cleaning, which are connected to drainage conduits. These cupules facilitate rapid removal of filter media and filtrate by routine street cleaning equipment at economical speeds. Below the cupules, the drainage conduits are designed to provide specified maximum or controlled drainage flow rates. Further, geometry of the resulting drainage cell also meets the requirements of the Americans with Disability Act as well as certain requirements for mass production. To develop these special PICPs-here denoted RCPPs (rapidly cleaned permeable pavers)-experiments were carried out in Guelph, Southern Ontario. This paper describes initial RCPP demonstrations using a rig designed to reveal the fluid mechanics and performance of a regenerative air cleaner moving horizontally over test blocks having the same geometry as the RCPPs, and filled with non-cohesive filter aggregate. Note that these tests were designed to examine the dynamic fluid mechanics of the removal of filter media by a moving pickup head, as affected by geometrical variables only. In our continuing experiments, the independent variables are: V, speed of cleaning equipment over the pavement; θ, angle of the cleaning jets; v, air velocity in the cleaning jets; d and φ, geometry of the cupules; w, width of drainage conduit; and G, gradation of the filter media. S, the ratio of the mass of removed and captured to the original mass of cupule filter media (plus filtrate), is the dependent variable. S is measured by weighing the aggregate added when replacing that removed by the regenerative air vortices, and dividing by the original weight of the aggregate in the cupule. Our laboratory experiments demonstrated that, for the chosen geometries and filter aggregate, complete removal (S ≥ 1.0) is easily achieved in one pass at reasonable speed. The paper describes our experimental rig and demonstrates the cleanout concepts, and includes CAD files of detailed drawings of the components of the rig and test blocks, as well as slow motion video clips of the clean out processes. In essence, the new RCPP promises ready capture of particulates and pollutants attached to them by routine (routine meaning conventional, or off-the-shelf, non-special-purpose) regenerative-air street cleaning equipment. Evidently these RCPPs could significantly advance environmental protection, by rendering clean-out more effective and more economical.

Permeable Pavers Designed for Rapid Renewal by Considering Sweeper Mechanics: Initial Field Tests

“…For the RASS used in this study we published details of the pick-up head in our previous paper (James and von Langsdorff 2016). Many details can be gleaned from information held by the U.S. Patent Office.…”

“…An earlier paper (James and von Langsdorff 2016) described laboratory tests of a new PICP designed to be readily cleaned out. Where clogging of drainage cells in PICPs is dominantly in the upper parts of the filter media, as it is in most cases, infiltration rates in special PICPs may be rapidly restored if the PICP design is dovetailed to the fluid mechanics of the street cleaning equipment.…”

“…Furthermore, the geometry of these cupules also meets the requirements of the Americans with Disability Act (ADA 2010), as well as certain requirements for mass production. Our earlier paper (James and von Langsdorff 2016) demonstrated that infiltration rates in these new PICPs, denoted RCPP, may be rapidly restored if their design is dovetailed to the aerodynamics of the regenerative air street sweeper (RASS) at the pavement surface. In that earlier paper, we describe experiments carried out in Guelph, in Southern Ontario, using a rig designed to reveal the air flow at the pavement surface of a simulated RASS pickup head moving horizontally over test blocks having geometry similar to the RCPPs.…”

“…In later studies the issue of cohesiveness in the filter aggregate in the cupules will be taken up. The earlier paper described our experimental rig and demonstrated the cleanout principles, and included CAD files of detailed drawings of the components of the rig and test blocks, and a slow-motion video clip of the cleanout processes (James and von Langsdorff 2016). In the present paper we describe tests on a real PICP pavement constructed in Ayr, Ontario using RASSs and mechanical street sweepers (MSSs) with stiff bristles rotating vertically in the plane of the direction of sweeper travel.…”

A Prediction Model to Cost-Optimize Clean-Out of Permeable Interlocking Concrete Pavers

“…Replacing the top 2.5 cm of clogged material with fresh aggregates in the PICPs resulted in a complete restoration to the original infiltration rate of 200 mm/h. Accelerating and simplifying cleanout procedures would allow PICPs to be used more frequently for stormwater treatment [34,41,43,44].…”