Effect Of Road Alignment Combination On Pavement Runoff Characterisrics

The combination of road alignment has an important influence on the runoff behavior of pavement during rainfall.Adverse linear combination will cause water accumulation on the road surface,affecting the normal driving and safety braking of vehicles,and even producing water skiing phenomenon.Besides,the specifications for drainage design of highway cannot consider the influence of linear combination on the spatial and temporal distribution and evolution of pavement runoff.Therefore,the study of pavement runoff behavior under different alignment combination is conducive to better optimize road design and improve driving safety in rainy days.Based on the combination of theoretical analysis,indoor and outdoor experimental research and numerical simulation,the effect of road alignment combination on pavement runoff characteristics has been studied.Firstly,the numerical model was established by using hydrodynamic software based on the two-dimensional shallow water equation.The applicability of the model was verified by comparing the simulation results with the measured data of water depth in straight line section.Therefore,the two-dimensional shallow water equation could be applied to the simulation of pavement runoff.Secondly,the orthogonal test method was used to select the geometric parameters and determine the working conditions of straight line segment,concave straight line segment and circular curve segment.The sensitivity analysis of rainfall intensity,horizontal,vertical and horizontal alignment elements and drainage mode on pavement water depth was carried out on the simulation results.The analysis showed that rainfall intensity,pavement width and transverse slope were the main factors affecting pavement water depth.Then,the spatial and temporal distributions of pavement water accumulation in straight,concave straight and circular curved sections with design speed of 120 km/h were summarized.It was concluded that under uniform rainfall conditions,the spatial distribution of pavement runoff presents strong two-dimensional characteristics,and the water depth contours within the lane were basically consistent with the longitudinal direction of the road slope.The maximum water depth of straight line section and curve section was located downstream of the road section,while the concave straight line section was located at the bottom of the vertical curve.After rainfall,the nearer the pavement was to the central partition zone,the more advanced it was to enter the steady state,and the pavement with dispersed drainage was faster to enter the steady state than the pavement with centralized drainage.Finally,the critical side water-skiing depth difference and road flooding range were used to evaluate the road alignment combination sections under uniform rainfall conditions,and the two-way six-lane combination threshold with design speed of 120 km/h that not affected driving safety in rainy days was obtained,which provided a reference for road alignment design.