Optimization Of Key Geometric Design Parameters Of Sponge Road And Study On Driving Safety In Rainy Days

Drainage pavement can improve the skid resistance and noise reduction,reduce hydroplaning and spray in rainy days due to its good drainage capacity,which has been widely used in the deepening and promotion of the concept of sponge city for the significant improvement of traffic safety.Abundant research has been carried out on the performance of drainage and noise reduction with the structure and material design of drainage pavement.However,few have been devoted to the geometric design parameters of sponge road.Hence,the objective of this paper is to construct the optimization system of key geometric design parameters of sponge road.By establishing the drainage layer model of sponge road,the quantitative model of spray and its influence on visibility,the optimization values of geometric and pavement structure design parameters of sponge road were obtained.The visibility change analysis under the coupling effect of spray and raindrop during rainfall was realized,and the correction model of stopping sight distance was studied.Firstly,a two-dimensional drainage and seepage model with cross slope only was established by Seep/w software based on the runoff generation mechanism and seepage law of drainage pavement.The simulation results showed that 1)the fewer the number of lanes,the better the seepage condition;2)when the number of lanes increased,the greater the cross slope,the better the drainage function of the pavement;3)for the two-way eight-lane road,0.5%~2.0% of the cross-slope settings could not meet the drainage needs of the pavement,and to thicken the road drainage layer to 10 cm could solve this problem.In addition,Seep 3D software was employed to establish the three-dimensional seepage model considering resultant gradient,and it was found that the drainage and seepage capacity of pavement increased with the increase of cross slope.When the cross slope is constant,the larger the longitudinal gradient,the larger the resultant gradient,the longer the drainage route,and the worse the drainage performance of pavement.Secondly,in order to determine the widening width of multi-lane horizontal curve section with superelevation,the pavement structure was optimized.By increasing the thickness of the surface layer,adding a drainage point in the road,adding two drainage points,and setting an unequal thick surface layer,the maximum allowable pavement width for different pavement combinations was suggested.Then,in this paper,a quantitative model of spray caused by high-speed vehicles with the existence of water film on wet pavement was constructed.The influence of splashing on visibility was simulated by principle of multiple scattering of photons,which could obtain the change of visibility under the coupling effect of spray and raindrops.It was found that visibility decreased with the increase of vehicle speed and water film depth when driving on wet pavement after or during rainfall.When the speed was high,the visibility affected by the coupling visibility was higher than the single spray,however when the speed was low,the difference of visibility was not obvious.Finally,the stopping sight distance model of sponge road under low visibility was analyzed and discussed.Based on the stopping sight distance of vehicles at different speeds and the change of visibility,the recommended safety-speed values for different combinations of sponge road after or during rainfall were suggested,and the reasonable safety strategies of vehicles under low visibility in rainy days were proposed.This study achieved the optimization for geometric design parameters of sponge road,quantified the coupling influence of spray and raindrop on visibility,and obtained the correction model of stopping sight distance,which will provide a better guidance for the safe operation on sponge road.