Drainage capacity of pervious pavement mixtures is commonly measured using a falling head permeameter at hydraulic heads much higher than expected in the field. Recent advancements in computational fluid dynamics (CFD)- and X-ray computed tomography (XRCT)-based modeling eliminates the laboratory challenges of maintaining lower hydraulic heads. However, improper characterization in digital image processing (DIP) and finite-volume simulations resulted in significant errors in permeability measurements and fluid flow behavior. In addition, past studies have identified non-Darcy fluid flow characteristics in pervious pavement mixtures following the Izbash and Forchheimer laws. This paper attempts to bridge this research gap by comparing the Darcy and non-Darcy permeability parameters at different laboratory and field hydraulic heads using advanced XRCT-based modeling. It was found from the analyses that the use of laboratory hydraulic head could result in significant underestimation of permeability parameters compared with the field hydraulic heads for Darcy and Izbash equations (by up to 73%), and overestimation for Forchheimer equations (by up to 216%). Fluid flow behavior in pervious mixtures was found to be in transition flow regime (neither laminar nor turbulent) at both laboratory and field hydraulic gradients. Overall, this study can help in a better fundamental understanding of the current limitations of laboratory measurements and the need for XRCT-based numerical modeling to bridge field and laboratory permeabilities of pervious pavement mixtures.

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Grooving of pavement surface and tire tread has been accepted as good practice to enhance road travel safety against wet weather skidding and hydroplaning. Many guidelines on this practice have been derived from findings of experimental studies and field experience. However, theoretical studies to provide insights into the factors and mechanisms involved are lacking. A theoretically derived analytical simulation model was used to study the relative effectiveness of pavement grooving and tire grooving in reducing vehicle hydroplaning risk. Three basic grooving configurations were considered: ungrooved, longitudinally grooved, and transversely grooved. There are nine different combinations of grooving configurations. To form a common basis for comparison, constant values of groove width, groove spacing, and water-film thickness were considered in the computation of hydroplaning speeds for different groove depths. Transverse grooves performed better than longitudinal grooves in raising hydroplaning speed (i.e., reducing hydroplaning risk), and pavement grooving was a more effective measure than tire tread grooving in reducing hydroplaning risk. Further detailed examinations of the results were conducted to study the practical implications of the findings. For longitudinal grooving, which is commonly adopted in highways, pavement and tire grooving are of equal importance in their contributions toward reducing hydroplaning risk. In the case of runways where transverse grooving is the standard practice, pavement grooving is the dominating component in guarding against hydroplaning.

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Grooving of tire tread is necessary to provide sufficient skid resistance for wet-weather driving and to reduce the risk of hydroplaning. Many different groove patterns of tire tread are found in the market. However, their relative effectiveness in reducing hydroplaning risk is generally not known to motorists and highway engineers. The effects of changes in the groove depth of a tire tread's groove pattern also deserve further investigation. This paper presents an analytical study that aims to characterize quantitatively the influence of different tire-tread patterns and groove depths on the hydroplaning behavior of passenger cars. The analysis is performed by means of a computer simulation model with a three-dimensional finite element approach. The following six forms of tire-tread groove patterns are considered: (a) longitudinal groove pattern, (b) transverse groove pattern, (c) V-groove pattern with 20° V-cut, (d) V-groove pattern with 40° V-cut, (e) combined groove pattern consisting of longitudinal grooves and edge horizontal grooves, and (f) combined groove pattern consisting of longitudinal grooves and 20° V-cut grooves. The analysis shows that a parameter computed as the groove volume per tread area of the tire is a useful performance indicator to assess the effectiveness of various tire-tread groove patterns in reducing vehicle hydroplaning risk. The significance of V-shape grooves is discussed. For vehicular operations involving both forward and lateral movements, the analysis indicates that a combined pattern would provide a good compromise in lowering hydroplaning risk sufficiently in different modes of vehicle movements.@en

This paper presents an analytical study performed to analyze the effectiveness of different pavement grooving patterns in reducing vehicle hydroplaning potential (i.e. raising hydroplaning speed). Grooves are man-made macrotexture formed in pavement surface to increase resistance to skidding and hydroplaning. In pavement engineering, the mean texture depth (MTD) is commonly adopted to characterize macrotexture and used as a controlling parameter to help ensure that sufficient skid resistance is maintained for safe traffic operations. This practice has been established based on the knowledge that pavements with better macrotexture (i.e. higher MTD) suffer less skid resistance loss as vehicle speed increases. In contrast, the exact benefits of pavement macrotexture in reducing hydroplaning potential are not well understood. This study attempts to offer some explanations by using a validated computer simulation model to analyze the variation of hydroplaning speeds on pavements having different groove patterns and depths. Three patterns of grooved surface are examined: two patterns of unidirectional flow channels, i.e. transversely grooved and longitudinally grooved surface, and grid-pattern grooved surface that has two-directional flow channels. The results show that they display different hydroplaning-related behaviors, and the relationships between MTD and hydroplaning speed for the three cases also differ. Possible causes of the differences are identified by examining the development of hydrodynamic uplift forces, and the flow characteristics of the water-film at tire-pavement interface at the onset of hydroplaning.@en