论文（设计）基于路面性能衰变规律的预防性养护措施和时机选择.doc

基于路面性能衰变规律的预防性养护措施和时机选择作者：任 奕 谈至明 孙明伟摘要：比选路面预防性养护措施和确定其实施时机是路面预防性养护技术的核心。在已有路面性能衰变模型的基础上，通过引入改善系数A和寿命系数B，建立了预防性养护后的路面性能衰变模型，并讨论了改善系数A和寿命系数B的内在含义；进而提出了利用该衰变模型和费用效益比最大为准则的选择预防性养护措施和确定其实施时机的方法。普及路面预防性养护观念、提高预防性养护技术水平是我国当前道路界面临的重大挑战。路面预防性养护的二大关键技术为选择经济合理的预防性养护措施和确定其实施时机，从理论上来说，这二项技术的实质是如何评估路面预防性养护的效益。采用路面性能衰变曲线围成的面积来近似表征预防性养护效益，以效益费用比最大为最佳预防性养护措施和时机的选择准则，是目前解决预防性养护措施和时机选择的可行方法。 1预防性养护后路面性能衰变模型     路面性能衰变模型应能够正确地反映路面的衰变过程和导致路面性能衰变的主要因素，随着使用年数或累计轴载作用次数的增加，各路面性能指标应逐年变差。路面使用性能预测模型主要有确定型模型和概率型模型两大类，式(1)为目前较常用的确定型路面性能衰变模型，式中a、是两个大于零的回归参数，a的大小代表了路面使用寿命的长短，决定了曲线的形状，它们的数值可由观测数据回归而得。     式中：PPId为日常养护下各使用性能指标(PCI、RQI等)；PPId0为路面新建或最近一次大中修后某路况指标的数值，一般为100：t为自路面新建或最近一次大中修到计算时的使用时间(年)。     预防性养护后路面性能衰变模型也可采用式 (1)的形式，但要确定预防性养护下的模型参数a、还面临很多困难，虽然通过预防性养护后路况数据的回归可以得到模型参数a、的值，但由于目前我国预防性养护技术的实际应用并不广泛，数据积累严重不足，这给数据回归带来很大困难。预防性养护措施仅是对路面微小损坏的修复和预防，对路面结构改变不大，同时，影响路面使用性能变化的因素，如气候条件、交通量和轴载等，也没有改变，因此在精度要求不高的情况下，可认为预防性养护后模型参数a、的值与日常养护下的值相同。但预防性养护对路面使用性能有所改善，同时延缓了路面性能的衰变，因此可在原模型的基础上引入两个新的系数A、B，预防性养护后各性能指标的衰变方程可表示如下：     式中：PPIj为预防性养护下各使用性能指标(PCI、RQI等)；t0为实施预防性养护的时间(年)；PPIa(t0)为实施预防性养护时路况指标的数值；APPI为预防性养护后路况指标的提高值。     从式(2)可以看出，系数A具有明确的数学含义，即预防性养护后路面使用性能指标的改善率，因此可称其为改善系数。改善系数A的值域为O，1，当A为0时，表示预防性养护后路面性能指标值没有任何提升；当A为1时，表示预防性养护后路面性能指标值达到了路面新建或最近一次大中修后的水平PPId0。     系数B的大小决定了预防性养护后的路面性能曲线的衰变速度，可称为寿命系数，其值域为0，1。当B=O时，即图2中的曲线4，这说明预防性养护后路面使用性能曲线的衰变速度没有任何延缓，与日常养护下t0时刻后的曲线衰变速度相同，仅是t时刻后各时间点的路面性能指标值较日常养护下的值有同比例的提升。当B=1时，即图2中的曲线1，预防性养护后路面使用性能曲线的衰变速度得到了最大程度地延缓，此时路面使用性能曲线的衰变速度同新建或最近一次大中修后的路面使用性能衰变速度相同。当B在01之间时，说明预防性养护不同程度地延缓了路面使用性能曲线的衰变速度，增加了路面的使用寿命，预防性养护后路面性能曲线的衰变速度在日常养护下0时刻后和t0时刻后的衰变速度之间。     改善系数A和寿命系数B值与采用的路况指标、预防性养护措施和实施预防性养护时的路况指数有关。在路况较好时采取预防性养护措施，虽然路面使用性能指标的提高值不大，但其改善程度较大，预防性养护措施的使用寿命也较长，因此A和B值均较大。某种预防性养护措施对某项路况指标起到很明显的改善作用时，A取较大值，如石屑封层对路况指标SFC有很明显的提升，A值可取1；而石屑封层在延缓路面损坏、增加路面使用寿命上的作用并不十分突出，所以相应的B取较小值。相反，在某种预防性养护措施对某项路况指标并没有明显改善作用时，如板底灌浆并不能有效地提升路况指标PCI的值，A取较小值；但板底灌浆可以有效预防路面出现错台、唧泥等病害，从而延缓路面损坏，增加路面使用寿命，因此B值应取较大值。 2预防性养护措施初选     预防性养护措施初选主要从预防性养护措施的技术特点出发，即考虑各预防性养护措施的技术特点和路面各种损坏形式的匹配情况，可通过预防性养护对策矩阵来实现。     在对国内外常用路面预防性养护措施进行详细调研的基础上，根据各预防性养护措施的技术特点和路况的匹配情况，归纳出沥青和水泥混凝土路面预防性养护对策矩阵，如表1和表2所示。     根据路面的损坏及交通量情况，可很容易从表1和表2中选择出所有合适的预防性养护措施，之后再对所有适合的预防性养护措施进一步进行分析，从中选择最佳措施。 3预防性养护效益分析 31预防性养护比选方案     在进行费用效益分析之前，需先确定一系列预防性养护比选方案。不同预防性养护措施在不同的时机实施所对应的预防性养护效益是不同的，因此将初选后所得到的m种预防性养护措施和n个时间方案进行组合，从而得到m×n种预防性养护比选方案。时间方案的制定是以实施预防性养护的适宜时间范围为基础的，在这个适宜的时间范围内，在不同的时间点应用预防性养护措施，即可得到多种不同的时间方案。 32效益面积     若已知表征路面性能的指标，如路面平整度指数IRI、横向力系数SFC、路面状况指数PCI等衰变规律，则指标衰变曲线与上下效益基线围成的面积称之为该指标的效益面积。当采用预防性养护措施后，效益面积的增量称之为预防性养护效益面积，预防性养护效益可用效益面积来表征。     就单一效益指标PPI而言，预防性养护效益面积为如图3中所示Ai。时间零点为路面新建或大、中修的初始时间，图3中的PPId(t)为日常养护时PPI的衰变曲线方程，PPIi(t)为在第j个比选方案下采取进行预防性养护措施后的衰变曲线方程，分别见式(1)和式(2)。时刻Tj0为第j个比选方案的预防性养护起始时间点，Ta1、Tjl为PPId(t)和PPIj(t)与效益计算基线的交点，即效益计算的终止时间点；y为效益计算基线，它是计算效益面积的下边界，反映在效益计算指标和时间关系图上为平行于时间t轴的直线2。则预防性养护效益面积Aj计算公式如式(3)所示。     将式(1)和式(2)代入式(3)，便可得到预防性养护效益面积Aj，即： 4最佳比选方案     算得第j个比选方案的预防性养护效益面积Aj，同时确定该方案中预防性养护措施的费用Cj后，可进一步求出其效益费用比(Benefit-Cost  Ratio，简称BCR)，其中，效益费用比最大的方案即为最佳比选方案，其效益费用比计算如式(4)所示，该方案所对应的措施和时间即为最佳预防性养护措施和时间。 5结论     比选路面预防性养护措施和确定其实施时机是路面预防性养护技术的核心。文章阐述利用路面性能衰变曲线来选择预防性养护措施和确定其实施时机的过程，在已有路面性能衰变模型的基础上，通过引入改善系数A和寿命系数B，建立了预防性养护后的路面性能衰变模型，并讨论了改善系数A和寿命系数B的内在含义；进而归纳了路面预防性养护对策矩阵，介绍了预防性养护效益面积计算方法；最后，提出了最佳预防性养护措施及其实施时机的选择准则。 Editor's note: Judson Jones is a meteorologist, journalist and photographer. He has freelanced with CNN for four years, covering severe weather from tornadoes to typhoons. Follow him on Twitter: jnjonesjr (CNN) - I will always wonder what it was like to huddle around a shortwave radio and through the crackling static from space hear the faint beeps of the world's first satellite - Sputnik. I also missed watching Neil Armstrong step foot on the moon and the first space shuttle take off for the stars. Those events were way before my time.As a kid, I was fascinated with what goes on in the sky, and when NASA pulled the plug on the shuttle program I was heartbroken. Yet the privatized space race has renewed my childhood dreams to reach for the stars.As a meteorologist, I've still seen many important weather and space events, but right now, if you were sitting next to me, you'd hear my foot tapping rapidly under my desk. I'm anxious for the next one: a space capsule hanging from a crane in the New Mexico desert.It's like the set for a George Lucas movie floating to the edge of space.You and I will have the chance to watch a man take a leap into an unimaginable free fall from the edge of space - live.The (lack of) air up there Watch man jump from 96,000 feet Tuesday, I sat at work glued to the live stream of the Red Bull Stratos Mission. I watched the balloons positioned at different altitudes in the sky to test the winds, knowing that if they would just line up in a vertical straight line "we" would be go for launch.I feel this mission was created for me because I am also a journalist and a photographer, but above all I live for taking a leap of faith - the feeling of pushing the envelope into uncharted territory.The guy who is going to do this, Felix Baumgartner, must have that same feeling, at a level I will never reach. However, it did not stop me from feeling his pain when a gust of swirling wind kicked up and twisted the partially filled balloon that would take him to the upper end of our atmosphere. As soon as the 40-acre balloon, with skin no thicker than a dry cleaning bag, scraped the ground I knew it was over.How claustrophobia almost grounded supersonic skydiverWith each twist, you could see the wrinkles of disappointment on the face of the current record holder and "capcom" (capsule communications), Col. Joe Kittinger. He hung his head low in mission control as he told Baumgartner the disappointing news: Mission aborted.The supersonic descent could happen as early as Sunday.The weather plays an important role in this mission. Starting at the ground, conditions have to be very calm - winds less than 2 mph, with no precipitation or humidity and limited cloud cover. The balloon, with capsule attached, will move through the lower level of the atmosphere (the troposphere) where our day-to-day weather lives. It will climb higher than the tip of Mount Everest (5.5 miles/8.85 kilometers), drifting even higher than the cruising altitude of commercial airliners (5.6 miles/9.17 kilometers) and into the stratosphere. As he crosses the boundary layer (called the tropopause), he can expect a lot of turbulence.The balloon will slowly drift to the edge of space at 120,000 feet (22.7 miles/36.53 kilometers). Here, "Fearless Felix" will unclip. He will roll back the door.Then, I would assume, he will slowly step out onto something resembling an Olympic diving platform.Below, the Earth becomes the concrete bottom of a swimming pool that he wants to land on, but not too hard. Still, he'll be traveling fast, so despite the distance, it will not be like diving into the deep end of a pool. It will be like he is diving into the shallow end.Skydiver preps for the big jumpWhen he jumps, he is expected to reach the speed of sound - 690 mph (1,110 kph) - in less than 40 seconds. Like hitting the top of the water, he will begin to slow as he approaches the more dense air closer to Earth. But this will not be enough to stop him completely.If he goes too fast or spins out of control, he has a stabilization parachute that can be deployed to slow him down. His team hopes it's not needed. Instead, he plans to deploy his 270-square-foot (25-square-meter) main chute at an altitude of around 5,000 feet (1,524 meters).In order to deploy this chute successfully, he will have to slow to 172 mph (277 kph). He will have a reserve parachute that will open automatically if he loses consciousness at mach speeds.Even if everything goes as planned, it won't. Baumgartner still will free fall at a speed that would cause you and me to pass out, and no parachute is guaranteed to work higher than 25,000 feet (7,620 meters).It might not be the moon, but Kittinger free fell from 102,800 feet in 1960 - at the dawn of an infamous space race that captured the hearts of many. Baumgartner will attempt to break that record, a feat that boggles the mind. This is one of those monumental moments I will always remember, because there is no way I'd miss this.