LABORATORY EXPERIMENTS ON A LARGE SCALE-FULLY MONITORED PERMEABLE PAVEMENT SYSTEM

Permeable pavements (PPs) are one of the so called Sustainable Urban Drainage Systems used to face the consequences deriving from the ever-increasing urbanization and to changing in climatic forces (Burns et al., 2013) that jeopardize the management of stormwater in existing urban drainage networks. Indeed, these solutions have received increasing attention from scientific communities looking for new ways to manage stormwater and restore as much as possible pre-urbanized conditions according to new regulations. Among other solutions, PPs can be easily retrofitted into the urban environment: roads, parking lots, bike-lanes surfaces which are impermeable, in many cases can be replaced with permeable surfaces without the need of changing the end-of-use of the area, allowing for infiltration and retention of water into the ground during rainfall events. PPs are characterized by a permeable surface layer made of either porous concrete/asphalt or impermeable/pervious paver blocks with joints filled with permeable materials, laid on a filter package usually made of coarse aggregates. The filter package is used to store infiltrated runoff during rainfall events, which in turn is slowly released into the underlying ground or collected by a drain. Consequently, runoff peak discharges as well as the total runoff volume conveyed to the drainage system and to nearby water bodies, is reduced. Moreover, PPs act as filters for trapping particulate matter and pollutants accumulated on the surfaces during dry periods and washed off during rainfall events. Although PPs seem to be a suitable solution for improving stormwater runoff control and even though there has been a worldwide increase of their use in urban areas, their application remains relatively new and concerns regarding their efficiency over time have rose, prompting researchers at investigating their efficiency over time and at assessing the factors affecting their performance. To this aim, both real-scale and laboratory scale PPs have been monitored, and numerical models have been realized (e.g. Brown & Borst, 2014; Palla et al., 2014, Elliot & Trowsdale., 2007). Assessing the hydraulic performance of PPs using modelling techniques has been proven to be a complicated task due to several factors: the need of assigning accurate unsaturated hydraulic properties to the aggregate materials and assessing the highly heterogeneous properties of the filter layer package. Thus, to this aim, instrumented laboratory models are fundamental to gain information regarding the unsaturated hydraulic properties of the materials, as well as to provide insights on the physical processes occurring in a PPs. With respect to small scale ones, large scale laboratory models (e.g. VanVuuren et al., 2022), although expensive, allow to reproduce physical processes occurring on PPs near to real scale experiments, for which monitoring is usually very complex. Here we present a new large scale laboratory model of a PP, equipped with several sensors for the continuous monitoring of water level, water content and both runoff and subsurface discharges. The hydraulic performance of the system subjected to rainfall events with different rainfall intensities has been investigated and results are here discussed.