Coupled infiltration and filtration behaviours of concrete porous pavement for stormwater management

Cementitious porous pavement (CPP) is a structural low‐impact development material for rainfall–runoff management. Both infiltration and filtration are critical functions for CPP stormwater quality and quantity control. In this study, three groups of CPP specimens exposed to rainfall–runoff for 4 years and experienced with different maintenance intervals (6, 12 and 48 months, respectively) were used to examine CPP infiltration and filtration performance. Particle mass strained on CPP surface, saturated infiltration rate I_f, temporal infiltration rate I(t), suspended sediment concentration (SSC) and turbidity (τ) were measured to evaluate the process of filtration/infiltration. I(t), SSC and τ were examined less than 50 mg/l of the suspended particle loading. It was found that the CPP surface cleaning methods used in the past 4 years, namely, high pressure wash followed by vacuuming with one atmosphere (100 kPa), were effective, and a 12‐month maintenance interval was verified suitable to maintain the pore structure an acceptable infiltration rate for stormwater management. It was also found that CPP infiltration and filtration process affect each other, and the two properties are coupled in urban stormwater quality and quantity control. On the basis of the experimental measurements, the temporal infiltration rate of the cleaned CPP under a certain particle loading could be simulated by a first‐order nonlinear rational model, and effluent turbidity–SSC relationship was found following a power law. Copyright © 2012 John Wiley & Sons, Ltd.     

银川市路面温度预报与爆胎指数预报方法研究

利用7月份银川市沥青、水泥2种路面温度实测资料,研究了银川市水泥、沥青城市道路路面温度特征及其与气温、相对湿度、风等气象要素的关系,采用统计回归方法,建立了路面温度统计预报模型。在此模型基础上,分析了气温、车速和路面温度之间的关系,继而建立了爆胎指数分级预报方法和标准。结果表明：导致汽车爆胎的因素有很多,但当气温低于25℃时,即使是高速行驶的汽车,也不易因路面温度导致爆胎;而当气温高于35℃时,路面温度可高达70℃以上,此时车速在66km／h以上就有可能爆胎,车速超过82km／h时,爆胎的可能性非常大。通过对路面温度预报模型的检验表明,尽管建立的模型比较简单,也不能完全反应气象要素和路面温度之间更深层的关系,但是该模型的求解过程简单易懂,输人参数少且易于获得,可操作性强,预测精准度已满足业务需要,值得在业务中使用,在以后的业务中,通过不断的改进和完善,预报效果将得到进一步提升。     

沥青混凝土路面工程病害及防治技术浅析

本文根据我国的公路越来越多地采用沥青混凝土或改性沥青混凝土路面的实际情况,论述了沥青路面早期病害的原因,指出了我国沥青路面规范的不足,介绍了沥青路面病害因素的分析及预防措施。     

Sustainable Construction Case History: Fly Ash Stabilization of Recycled Asphalt Pavement Material

A case history is described where Class C fly ash was used to stabilize recycled pavement material (RPM) during construction of a flexible pavement in Waseca, MN, USA. The project consisted of pulverizing the existing hot-mix asphalt (HMA), base, and subgrade to a depth of 300 mm to form RPM, blending the RPM with fly ash (10% by dry weight) and water, compacting the RPM, and placement of a new HMA surface. California bearing ratio (CBR), resilient modulus (M_r), and unconfined compression (q_u) tests were conducted on the RPM alone and the fly ash stabilized RPM (SRPM) prepared in the field and laboratory to evaluate how addition of fly ash improved the strength and stiffness. After 7 days of curing, SRPM prepared in the laboratory had CBR ranging between 70 and 94, M_r between 78 and 119 MPa, and q_u between 284 and 454 kPa, whereas the RPM alone had CBR between 3 and 17 and M_r between 46 and 50 MPa. Lower CBR, M_r, and q_u were obtained for SRPM mixed in the field relative to the SRPM mixed in the laboratory (64% lower for CBR, 25% lower for M_r, and 50% lower for q_u). In situ falling weight deflectometer testing conducted 1 year after construction showed no degradation in the modulus of the SRPM, even though the SRPM underwent a freeze–thaw cycle. Analysis of leachate collected in the lysimeter showed that concentrations of all trace elements were below USEPA maximum contaminant levels.     

Analysis on spatial distribution and correlation of pavement distress along the Xinjiang-Tibet Highway北大核心CSCD

The Xinjiang-Tibet Highway（XTH）is a transportation corridor of manpower and supplies from inland regions to Tibet. The XTH has the highest altitude in China,which also has complex geological conditions and high distress ratio. The pavement distress was investigated completely to analyze the spatial distribution of pavement distress along the XTH and reveal the relationship among different types of distress. The distress ratio of 7 types of pavement distress was obtained and the relationship of pavement distress and ground surface temperature,altitude and vegetation cover was quantitatively fitted along the XTH. The result shows that,distress occurrence ratio of racking is has the largest percentage,which is the main reason to reduce the road condition. Pavement distress has a positive correlation and interaction with each other. One type of distress appears with the formation and development of other types of distress. The pavement cracking of the roadway with high altitude was obviously influenced by solar radiation and freeze-thaw cycle,which has a larger occurrence scale and development ratio than other regions. This paper reveals the relationship of each pavement distress and environmental factors,and provides a scientific basis and theoretical reference for the operation,maintenance and distress treatment of the XTH and planning Xingjiang-Tibet transportation corridor. © 2022 Science Press (China).     

Surface water flow over a pervious pavement

This work investigates the profiles of surface water flow over a pervious pavement, for example, highway, during a uniform rainfall. The pavement, such as porous asphalt or open‐graded asphalt friction course, is regarded as a porous medium, and the flow inside the layer is porous media flow. At first, the velocity distributions are solved based on the simplified Navier–Stokes equations and Biot's theory of poroelasticity for the water layer and the permeable layer, respectively. Then, the flow profiles can be found via the continuity equation. Because the closed form of the water depth cannot be obtained, a numerical technique is employed to find the flow profiles on the pavement surface. A critical permeability factor related to the material and structure of pavement is illustrated to be η = 1.36 × 10^{? 4}m as the half road width L = 20 m, the cross slope S = 0.02,the pavement thickness H = 0.05 m, and rainfall intensity i = 100 mm/h. The water on the road surface can be drained very fast, whereas the parameter is greater than the critical value. Another illustration of allowable/safety water depth is made for the design of the pavement thickness. Copyright © 2012 John Wiley & Sons, Ltd.     

Backcalculating pavement structural properties using a Nelder–Mead simplex search

A structural integrity assessment technique of pavements that considers the backcalculation of material properties is herein proposed. In order to carry out the backcalculation, a Nelder–Mead simplex (NMS) search is applied to estimate the elastic moduli of layered structures using the deflection data simulated by falling weight deflectometer (FWD) tests. In order to utilize a forward calculation engine of the numerical simulation in the FWD testing, a wave analysis program of layered pavement systems is used based on a spectral element method. The performance of the NMS inversion technique is evaluated based on a comparison with the Levenberg–Marquardt method. Copyright © 2009 John Wiley & Sons, Ltd.     

"冰臼"是古地貌面上的流水侵蚀遗迹——壶穴——就韩同林《发现冰臼》一书中的资料谈华北北部的"冰臼"

分布在华北北部山顶面上的“冰臼”,无论从地理环境、地貌演化,还是从海拔高度方面分析,都不是第四纪大冰盖的证据,而是古地貌面上流水侵蚀的遗迹。它分布在3个海拔高度不同的山地夷平面上和现代河流谷地内,与当时的地理环境和山地的地貌演化密切相关。未构成山地夷平面前准平原上的河流以河网密集的曲流河为主。随着准平原的抬升,河流也开始下切,下切的河流以溯源侵蚀为主。在源头地区的顺直型谷地中,一是河流流速较急,且挟有数量不多、颗粒较粗的砂砾石;二是源头地区大块石较多,容易形成涡流;三是河水不深,丰水期刚刚没过块石,枯水期块石露出水面。在质地不均的岩体(特别是花岗岩)中,挟带砂砾石的涡流在岩面上形成了壶穴。准平原及壶穴最后被抬升到山地的顶部,构成了山地夷平面。     

热反射技术及其在多年冻土区道路热保护中的应用

热反射技术是一项被广泛应用于建筑物及道路表面降温的主动冷却技术, 国内外很少对此技术在多年冻土区道路热保护方面进行研究。针对多年冻土区气候及工程环境特点, 综述了热反射技术在冻土区道路中的应用现状和研究成果, 阐述了热反射涂层的基本成分、 反射机理和测试方法, 分析了路用热反射涂层的材料性能、 反射效果和路用性能, 简要介绍了热反射涂层在路基边坡应用方面的研究进展。指出在当前条件下利用热反射涂层保护多年冻土区道路所遇到的问题及可行的解决方案, 并在此基础上提出了今后研究的重点： 从材料选择、 理论分析和试验方法入手, 对路用热反射涂层的颜色、 反射性能、 路用性能和区域适用性进行改进和研究, 加强多年冻土区道路热反射涂层的野外试验和分析, 深入研究复杂气候和工程环境下的热反射涂层性能。     

青藏高原冻土区路面类型对路基温度场影响的非线性分析

采用焓模型, 建立含相变的冻土路基温度场, 综合考虑气温、太阳辐射、风速风向、坡面蒸发等气象因素, 将诸多气象因素归结为第二、三类边界条件的叠加组合, 对不同气温地区的沥青路面及水泥路面路基温度场进行了有限元计算. 结果表明: 路面类型对冻土路基温度场有着重要影响, 水泥路面的采用可有效地降低路面温度, 延缓冻土上限下降速率, 从而可以有效保护基底多年冻土; 从对基底冻土上限影响的角度来看, 路面类型、外部气温与路基高度三者间存在一定的动态等效关系.