【作者】 刘伟；

【导师】 赵永利； 孙一兵；

【作者基本信息】 东南大学 ， 道路与铁道工程（专业学位）， 2018， 硕士

【摘要】 沥青路面是城市道路建设中运用最为广泛的一种形式,其通常为不透水结构,这易引发城市内涝,同时造成水资源大量浪费。此外,沥青路面夏季高温时容易产生车辙病害,并加剧城市热岛效应。为此,引入海绵城市理念,对沥青路面进行优化设计。首先,根据海绵城市具体要求,考虑实际降雨条件,给出了基于芝加哥雨型设计法的南京设计降雨强度:2.47×10^-3（88）/。通过分析排水路面的降水入渗过程,总结了路面产流机制。结合降雨强度和路面排水机理,引入裘布依假定,建立了排水路面渗流计算模型。运用龙格库塔四阶段法在MATLAB软件中计算该模型的数值解,以不产生径流为标准,得出1cm/s的渗透系数、南京设计降雨条件下,2年重现期要求排水层厚度为6cm,3年重现期要求排水层厚度为6.5cm,5年重现期要求排水层厚度为7cm。以不产生明显径流为评价依据,得出2年重现期南京设计降雨条件下,排水层厚度为4cm时,最小渗透系数为0.92cm/s;厚度为4.5cm时,最小渗透系数为0.79cm/s;厚度为5cm时最小渗透系数为0.70cm/s。其次,根据计算流体力学等理论知识,建立了大孔隙沥青路面补水降温的物理模型和数学模型。运用Fluent软件中的VOF模型、多孔介质模型以及层流模型,分析在2%路面横坡、8米路面宽度、25%孔隙率、4×10^-4kg/（m?s）的补水强度下沥青路面补水时水流运动范围以及温度场分布。上述分析得到以下结论:（1）通过路面横坡的作用,在道路一侧设置补水口,可对大孔隙路面内空隙进行补水填充,稳态时含水层高度为2.18cm,不产生路表径流。（2）大孔隙沥青路面在补水时不能够均匀降低路表温度,且路表温度降低的效果要明显滞后于内部含水量范围的增加,为了充分利用水流的作用,可将传统路面横坡形式改为中间低两端高的设计。（3）在7月典型气候条件下,当大孔隙沥青路面多孔层内空隙被水完全填充时,同等辐射强度下,24h路表最高温度可比传统沥青路面降低达22℃,排水层底部（距多孔层5cm处）最高温度也可下降近18℃,降温效果显著。再次,借鉴土壤蒸发的原理和计算,给出了南京全年补水降温路面的需水量为1060mm。通过实验和软件模拟的对比,验证了软件模拟的可行性和准确性。通过比较不同工况下的补水方式,得到以下结论:（1）在不产生路表径流的前提下,将进水速度由2.0×10^-48)/改为4.0×10^-48)/,补水3h,空隙含水率可由39.01%增加到71.58%;（2）提高渗透系数,可以加快水流流动速度;（3）在控制单位进水流量的基础上,改变补水方向和补水管高度,对补水降温效果几乎没有影响。（4）改变路面宽度,对于4.0×10^-48)/的进水速度,2%的坡度,得到右侧出口产生水流所需的时间t随路面宽度B变化情况公式:t=1.931B+37.058,²=0.9958。右侧出口产生水流时空隙含水率随路面宽度B变化情况公式:?=781.35B-911.7,²=0.9995。（5）对于满足南京设计降雨强度下的最小设计排水层厚度和孔隙率,可拟定单位长度进水量为7.0×10^-68)³/（?8）)。比较二维和三维模拟结果,发现设置小间距补水口时,二者模拟结果几乎完全相同,此时二维模拟可代替三维模拟。最后,结合海绵城市在雨水处理方面的要求,提出道路水循环设计具体措施,包括通过水量平衡分析以确定雨水管渠、储水池、弃流池以及补水管的设计尺寸;制定LID附属设施设计方案以应对特大暴雨天气。基于上述措施,结合路面补水方法,搭建水循环系统,实现排水、蓄水和用水的目标。更多还原

【Abstract】 Asphalt pavement is the most widely used form of urban road construction.It is usually an impervious structure.This can easily lead to urban hail and cause massive waste of water resources.In addition,asphalt pavements are prone to rut diseas during high temperatures in summer and increase urban heat island effects.To this end,the concept of a sponge city was introduced to optimize the design of asphalt pavement.First of all,design rainfall intensity of 2.47×10^-3（88）/is developed on the basis of the method of Chicago rain type design,according to the specific requirements of the sponge city,combined with the actual rainfall conditions in Nanjing.The mechanism of pavement runoff generation is summarized by means of analyzing the precipitation infiltration process of drainage pavement.The model of seepage calculation on drainage pavement is established by the rainfall intensity and pavement drainage mechanism in Nanjing analyzed before,as well as the Dupuit assumption.The Runge Kutta four-phase method is applied to compute the numerical solutions of the model in MATLAB software,namely design permeability coefficient corresponding to different pavement thicknesses on condition that the road surface does not generate obvious runoff.The numerical solutions conclude that the drainage layer thickness is required to be 6 cm in 2-year recurrence period,6.5 cm in 3-year recurrence period and 7 cm in 5-year recurrence period,under the condition of 1 cm/s permeability coefficient and Nanjing design rainfall.Based on the evaluation that no obvious runoff is generated,it is concluded that the minimum permeability coefficient is 0.92 cm/s when the thickness of drainage layer is 4 cm and 0.79 cm/s when the thickness is 4.5 cm,and 0.70 cm/s when the thickness is 5 cm in the two-year return period in Nanjing.Secondly,a physical model and a mathematical model for water-filling and temperature-reducing of large-pore asphalt pavement were established based on the theoretical knowledge of computational fluid dynamics.The VOF model,porous media model,and laminar flow model in the Fluent software are used to analyze the flow range and temperature distribution of the large-pore asphalt pavement under the condition of 2%pavement cross slope,8 meters pavement width,25%porosity and 4×10^-4kg/（m?s）water supplement strength.The following three conclusions are drawn from the above analysis.（1）With the water replenishing port provided on one side of the road through the action of the road surface cross-slope,the gaps in the large-pore road pavement are filled with water without generating road surface runoff and the aquifer height is 2.18 cm at steady state.（2）Large-pore asphalt pavement cannot lower the surface temperature evenly when filling water and the effect of road surface temperature reduction is obviously lagged behind the increase of internal water content range.In order to make full use of the function of water flow,traditional pavement cross slope can be changed into the design with low middle and high two ends.（3）Under typical weather conditions in July,when the pores in the porous layer of large-pore asphalt pavement are completely filled with water,the cooling effect is obvious which can be proved by that under the same radiation intensity,the maximum surface temperature during 24hours can be reduced by 22°C compared to traditional asphalt pavement and the highest temperature at the bottom of the drainage layer（5cm from the porous layer）can also be reduced by nearly 18°C.Thirdly,it is given that the water demand of Nanjing water replenishing and cooling pavement is1060 mm throughout the year by the referring to the principle and calculation of soil evaporation.The feasibility and accuracy of software simulation are verified by the comparison between experiment and software simulation.The following five conclusions are drawn by comparing the water supply methods under different working conditions.（1）When the inflow rate was changed from2.0×10^-48)/to 4.0×10^-48)/,the void water content can be increased from 39.01%to 71.58%after 3 hours replenishment without generating surface runoff.（2）The increase of permeability coefficient can accelerate the flow velocity of water.（3）It has weak influence on the effect of water-filling and temperature-reducing by changing water-filling direction and the height of water-filling pipe on the basis of controlling the unit water inflow.（4）Under the condition of 4.0×10^-48)/water inflow speed and 2%slope,the formula of time t needed to generate water flow at the right exit with respect to road width B can be obtained by changing road width and is=1.931B+37.058,²=0.9958.The corresponding void moisture content?with respect to road width B is the formula that?=781.35B-911.7,²=0.9995.（5）It can be drawn out that the water inflow per unit length is7.0×10^-68)³/（?8）)for the minimum design drainage layer thickness and porosity that meet the design rainfall intensity in Nanjing.Comparing the two-dimensional and three-dimensional simulation results,it is found that both of the simulation results are almost identical with the small-pitched water inlet provided.At this time,the two-dimensional simulation could replace the three-dimensional simulation.Finally,combined with the requirements of sponge city in rainwater treatment,the specific measures of road water cycle design are put forward,including determining the design dimensions of rainwater drainage channels,reservoirs,abandonment flow pools,and makeup pipe through water balance analysis,as well as developing LID ancillary facilities design plan to cope with heavy rain weather.The water circulation system is built to achieve the goals of drainage,water storage and water use on the basis of the above measures.更多还原