Simulation of Water Flow Path Length (WFPL) and Water Film Depth (WFD) for Wide Expressway Asphalt Pavement

This paper simulates actual rainfall conditions and raindrops flowing to form a water flow path (WFP) on the pavement surface of the wide expressway. Then, the different linear combination conditions, including longitudinal slope (LS), transverse slope (superelevation, TS), gradual change rate of TS, and pavement width (PW), were simulated and analyzed. The results show that (1) the influence of each linear index on the maximum water film path length (WFPLmax) and maximum water flow depth (WFDmax) differs (according to the absolute values of Beta, LS has the greatest influence on WFPLmax, and PW has the greatest influence on the WFDmax for both straight-line and circular-curve sections); (2) when the design value of LS is between 1.1% and 4%, the WFDmax can be effectively reduced by lowering the value of LS; (3) in the case of a high design value of LS, it can be considered to increase the TS of the pavement arch from 2% to 2.5% to effectively reduce the WFPLmax, and the wider PW, the better the reducing effect; (4) while widening the expressway, adjusting the TS from 2% to 2.5% can effectively offset the increasing effect of PW on the WFDmax. This research aims to fill the research gap in the simulation of runoff characteristics of wide expressway asphalt pavements and to improve the alignment design of expressways from the drainage perspective for the improvement of driving safety.