土木工程-建筑-道橋-外文翻譯-外文文獻(xiàn)-英文文獻(xiàn)-瀝青路面結(jié)構(gòu)設(shè)計(jì)的低成本農(nóng)村道路

1、瀝青路面結(jié)構(gòu)設(shè)計(jì)的低成本structural Design of Asphalt Pavement for Low Cost農(nóng)村道路Rural Roadsstructural Design of Asphalt Pavement for Low Cost RuralRoadsIn developing countries , rural road construction is mostly cumbered by shortage of funds。 Engineers concerns most in rural areas is how to build roads which not

2、only cost less but also meet the traffic demands. Especially in vast rural areas of China, there are a great variety of transportation patterns, and the traffic composition is very complex. Compared with other countries，the traffic composition in China rural areas have its own featuresoTherefore, th

3、ere is no experience about the rural roads construction forreference. In recent years，the central government of China has increased the strength for rural road construction。 At the same time, a lot of researches about rural road construction have been done by researchers in China, and some conclusio

4、ns about china rural roads have been made. In the authors5 opinion,the selection of the pavement structure material is the key measure to reduce the construction cost of rural roads after the route has been determined。Compared with concrete pavement，asphalt pavementrelatively costs less and is the f

5、irst choice for rural roads in China。 And then, according to the research achievements about rural roads construction，the authors have done some preliminary researches on the structure design for low-cost asphalt pavements for rural roads。Traffic Composition of Rural RoadRural roads include county r

6、oads, town roads and village roads。The traffic on rural roads is usually mixed。 On a county road, traffic volume is between 300 to 1500 veh/d in average, and in a county with a developed economy, it reaches 1000 to 2 000 veh/d。The traffic volume between county and town is 100 to 300 veh/d，and the tr

7、affic volume between towns is usually less than 100 to 300 veh/do In a mixed traffic flow , trucks account for 40 % to 70% of the traffic volume, which are mainly light trucks carrying less than 2. 5 tons(including agricultural vehicles such as electro-tricycles,walking tractors etc。)and medium-size

8、 trucks of 2。 5 to 5 tons. Most of these light or medium trucks are overloaded.The proportion of heavy truck isless than 9%。On some roads to counties, the proportion of overloaded trucks is 5% to 32 %，while on some county roads connecting to national or provincial trunk highways， the proportion of o

9、verloaded vehicles usually amounts to 20% to 32%。The traffic volume on rural roads is not heavyo However, considering the practical situation in China, as well as the exitence of overloaded vehicles, i00kN,or BZZ100 was adopted as standard axle load in the research.The pavement deflection or the fle

10、xuraltensile stress at the bottom of asphalt surface is taken as the design parameter. The axle load was calculated in accordance with the following formula：p. n和 -the axle weight of an ilevel axle in kN and the action frequency;-the axle weight of standard axle in 100 kN and the action frequency；If

11、 the distance between axles is less than 3 m, axle loads are calculated as a doubleaxle or multi-axle loads, andIf the flexuraltensile stress at the bottom of semirigid base is taken as the design parameter, the axle load is calculated in accordance with the following formula：If the distance between

12、 axles is less than 3m ,Traffic Volume on Rural RoadsMinibuses are adopted as the standard vehicle for the design of rural roads. Table 1 shows its external dimensions。Table 1 External dimensions of the passenger car mLength Width Height Front overhang Distance between axles Rear overhang60 01。82.00

13、.83。81.4The typical vehicle types on rural roads are listed in Table 2. And others such as non-powerdriven vehicles,animaldrawn vehicles,and bicycles can be taken into account in the calculation of traffic volume on rural roads,in view of their roadside interference.In accordance with the traffic co

14、mposition and volumes ,rural roads are divided into five grades. The traffic volume of each grade is shown in Table 3.Traffic volume specified in Table 3 was obtained by taking the minibus as the standard vehicle type,and converting different types vehicles according to the vehicle conversion coeffi

15、cients given in Table 2.In Table 3,Ne refers to the cumulative equivalent axle load action frequency;Ns refers to the equivalent axle load action frequency in the designed traffic lane in the beginning operation period of rural roads；y refers to the average annual growth rate of traffic volume;n ref

16、ers to lane coefficient, and 1.0 for a single lane and 0。6 一 0. 7 for a dual lane.Strength of RoadbedThe modulus of resilience of roadbed varies greatly。 For convenience, the strength of roadbed can be divided into four classes according to its moisture content and modulus of resilience，as shown in

17、Table 4.The parameters in Table 5 are determined by combining design principles with practical experience。 By applying elastic multilayer theory to the pavement structure specified in Table 5, the influence of Ne on the pavement thickness of rural roads was analyzed, and the result show that for giv

18、en h，h2，E0，the roadbase thickness for neighboring traffic classes changes in a range of 45 cm. This result indicates that the classification of traffic volume on rural roads shown in Table 3 is reasonable and feasible in terms of the design and construction of asphalt pavement structures.By using th

19、e elastic multilayer theory,the asphalt pavement structure of ordinary rural road in Table 5 is analyzed. When Ne,the cumulative equivalent axle load action frequency, the thickness of road surface(h =3 cm ), and the thickness of subbase (h2 = 20 cm ) remain the same , the influence of neighboring r

20、oadbed strength classifications on the thickness of roadbase is 3 cm 一 5 cm. This conclusion indicates that the strength classification of roadbed is reasonable and applicable to the design and construction of asphalt pavement structure。Determination of Thicknesses of Asphalt Pavement StructureSensi

21、tivity analysis of the design parameters of roadbed and pavement structures is to find out the relationship between structural strength of asphalt pavement structure and the design parameters of each layer, and determine the most sensitive layer in the pavement structure. The asphalt pavement struct

22、ure of rural roads is generally composed of a road surface, a roadbase,and a subbase,as shown in Table 6。The pavement structure was analyzed according to elastic multiplayer theory under the double circular uniform load, with an assumption that there is continuous contact between the adjacent layers

23、 of the asphalt pavement structure。 The basic parameters used in the calculation and analysis of asphalt pavement structure are listed in Table 7。 By analyzing the effects of the change of all the parameters of pavement structure on the distortion of the road surface, roadbase,and roadbed , the foll

24、owing conclusions have been drawn.Increasing the thickness of the road surface effectively decreases the road surface deflection, but raises the cost。The comparatively economical and effective method is to increase the thickness of the subbase, which is superior to increasing the thickness of roadba

25、se,while increasing the thickness of the road surface is the last choice。As the thickness of pavement structure increases, the change of road surface deflection will trend to be gentle. When the thickness of road surface reaches a certain value,the variance in the road surface deflection will not be

26、 obvious,and then it is ineffective to enhance the bearing capacity of asphalt pavement structure by increasing the thickness of road surface。 It is recommended that the thicknesses of the roadbase and the subbase should be equal to or largerthan 18 and 20 cm, respectively, in design of asphalt pave

27、ment structures of rural roads o Fig. 1 shows the effects of the changes in the thickness of each layer on road surface deflection。Road surface deflection is very sensitive to the change of modulus of the roadbed The increase in the modulus of roadbase or subbase is also effective to decrease the de

28、flection of the road surface o On the other hand,the deflection of the road surface decreases gradually when the modulus of the surface increases ,being the least effective factor o When the modulus of the road surface increases to a certain value, decrease in road surface deflection is not apparent

29、. Fig。 2 shows the effect of the modulus of each layer on road surface deflection. From the above discussion ,we conclude that the most sensitive layer for road surface deflection is subbase,and the next is roadbase. To decrease the road surface deflection of low cost rural roads,the strength and st

30、ability of the roadbed should be enhanced , and the materials with a certain thickness and relatively high density should be used to pave the subbase.The traffic volume or the accumulative equivalent axle load action times(frequency) within the designed life of road is used to determine the type and

31、 thickness of the asphalt pavement road surface, and the results are listed in Table 8,where veh/d means the number of the equivalent the passenger cars per day.For a low traffic volume rural road with Ne 500 000, graded broken stones(or gravel)can be used as a flexible base. The flexible base has g

32、ood strength and effectively prevents reflection cracks of the asphalt pavement road surface, provided the graded broken stones (or gravel ) meets the requirements for high density (degree of compaction , 100%. To ensure the sufficient strength and stability of the flexible base, its thickness is no

33、t less than 15 cm, the thickness of the aggregate subbase is not less than 20 cm，A semirigid base usually has a good bearing capacity For the rural roads with Ne) 500 000, or those with low traffic volumes but relatively, the minimum thickness of semirigid base or subbase is 1618 cmCalculation of th

34、e Thickness of Road Surface5。1 DeflectionRoad surface deflectionRoad surface deflection is a vertical distortion caused by vertical load on the road surface。 It not only reflects the whole strength and stiffness of asphalt pavement structure and roadbed , but also has a close internal relation with

35、the service condition of the pavement。Design deflectionThe design deflection is the index representing the stiffness of the pavement structure. It is also the deflection of the pavement which is established according to the accumulative equivalent axle load estimated to pass over a lane in the expec

36、ted design life, road types, road classification, and the types of road surface and roadbase. The design deflection is not only the main basis for the design thickness of the pavement structure, but also the necessary index for the examination and acceptance of the projecto Through theoretical analy

37、sis and experimental study, formulas for the design deflection value which are applicable to the pavement structure design of lowcost rural roads are as follows:semirigid base:flexible base:where A, is the type coefficient of the road surface。 The type coefficient of asphalt concrete road surface is

38、 1.0;that of hotmix asphalt macadam and that of emulsified asphalt macadam road surface are all 1。 1; and that of asphalt surface treatment road surface is1 .2。Allowable deflectionAllowable deflection is the maximum deflection allowed at the end of the roads service life under lim iting conditions i

39、n poor season. Through thoreticalanalysis and experimental study,the calculation formulas for the allowable deflection of road surfacewhich are applicable to the pavement structure designof low-cost rural roads are as follows2):When designing the asphalt pavement structure of lowcost rural roads, we

40、 should use formula (6) or (7 ) according to the types of roadbase to determine the thickness of asphalt pavement structure.5。2 Tensile stressBecause the asphalt pavement structure of lowcost rural roads is not substantial enough and the heavy vehicles are allowed to pass over them, the maximum tens

41、ile stress should be checked by computing the stresses of the semi-rigid base and subbase. The tensile stress at the bottom of semi-rigid base or subbase,would be less than or equivalent to the allowable tensile stress of the materials of the semirigid base or subbase , namely,For the stabilized agg

42、regate base with an inorganic binderFor the stabilized finegrained soil base with an inorganic binder：5。3 Pavement thicknessTo make it simple and convenient for engineers to determine the desired thickness of rural road pavement, the curves of the thickness of the roadbase of low-cost rural roads ac

43、cording to typical pavement structures and accumulative frequency of equivalent axle load are shown in Figs。 3, 4 and 5.When the accumulative frequency of equivalent axle load is within 500000 times per lane, asphalttreated or asphalt penetrated surfaces with thickness of 1. 5 cm 一 cm is recommended

44、 for road surface。 For various accumulative equivalent axle loads and the moduli (Eo)of roadbed, the equivalent thickness of roadbase is shown in Fig。 3。When the accumulative frequency of equivalent axle load is within 500 001)一 1 000 000 times per lane, asphalt macadam or asphalt concrete with thic

45、kness of 3 cm 5 cm is recommended. For various accumulative equivalent axle loads and moduli (Eo)of roadbed,the equivalent thickness of roadbase is shown in Fig. 4。When the accumulative frequency of equivalent axle load is within 1000 0002 000 000 times per lane , asphalt concrete road surface of 5

46、cm-7 cm thick is recommended。 For various accumulative equivalent axle loads and moduli(Eo)of roadbed , the equivalent thickness of roadbase is shown in Fig。S。In Figs。35,Ld is the designed deflection, Lo is the representative deflection of roadbed, E, is the modulus of resilience of the roadbase,in

47、MPa , Eo is the modulus of resilience of the roadbed, in MPa , and H, in cm, is the equivalent thickness of the base (roadbase and subbase), which can be obtained through calculation and insite investigation for a trilevel-pavement roads (including road surface, base and roadbed)。If a designed road

48、has four layers, i.e。 a subbase is added, according to the regression analysis of the extrapolated results of a number of multilayer flexible systems and the available research findings, the thickness of the roadbase , h, in cm, can be calculated from the following equation：Concluding RemarksCompare

49、d with concrete pavement, asphalt pavements have a lower construction cost, which is suitable for the roads in relatively underdeveloped rural areas in China. The research in this paper proposed a method for structural design of low cost asphalt pavements o The method is to provide an guideline for

50、the design of asphalt pavement structure in rural areas.ReferencesYuan G L , Zhang F , Chen S W , et al。 Research on technical indexes of rural highway construction in Jiangsu province J 。Highway, 2005 (6) 1135 一 I39(in Chinese).2 Research Institute of Highway , the Ministry of Communications. Final

51、 Report on Low Cost Inter-township and Rural Road Construction TechniquesR。Beijing; Resdarch Institute of Highway， 2003(in Chinese )。3 Liu Q Q. How to reduce the construction cost of the rural highway J .Journal of Highway and Transportation Research and Development, 2005 (2):41 一 44 (in Chinese)。4

52、JTG B014-97。 Specification for design of highway asphalt pavement S (in Chinese ).5 JTG BO12003. Technical Standard of Highway Engineering S (in Chinese).6 Deng X J. Engineering for subgrade and pavement M.2nd ed. Beijing; Peoples Communications Press, Beijing, 2004 (in Chinese ).瀝青路面結(jié)構(gòu)設(shè)計(jì)的低成本農(nóng)村道路在發(fā)展

53、中國家，農(nóng)村道路建設(shè)主要是因缺乏資金而受阻.工程師最關(guān)心的農(nóng)村問題是如何修 建的公路不僅成本低，而且滿足交通需求。特別是在廣大農(nóng)村地區(qū)，有各種各樣的交通方式， 交通成分非常復(fù)雜。與其他國家相比，在中國農(nóng)村地區(qū)交通組成有其自身的特征。 因此, 沒有足夠經(jīng)驗(yàn)對(duì)農(nóng)村公路建設(shè)提供參考依據(jù).近年來，中國的中央政府增加了對(duì)農(nóng)村公路建 設(shè)的力量。與此同時(shí)，在中國，研究人員已經(jīng)完成了關(guān)于中國農(nóng)村道路的大量研究和一些結(jié) 論。在作者的觀點(diǎn)，選擇不同的路面結(jié)構(gòu)材料是關(guān)鍵措施從而降低農(nóng)村道路的工程造價(jià).相 比，瀝青混凝土路面相對(duì)費(fèi)用少、是第一個(gè)在中國農(nóng)村道路的選擇.然后，根據(jù)農(nóng)村道路建 設(shè)研究成果，作者也做了一些對(duì)低

54、成本瀝青路面結(jié)構(gòu)設(shè)計(jì)的初步研究。1 農(nóng)村道路交通組成農(nóng)村道路包括縣公路、城市道路和村的道路。農(nóng)村道路上，交通通常是喜憂參半。一個(gè)平?？h的道路，交通量平均為的300至1500 輛/天；一個(gè)經(jīng)濟(jì)發(fā)達(dá)的縣，已經(jīng)達(dá)到了 1000到2000輛/天。通信量縣、鎮(zhèn)之間是100 到300輛/天，交通量之間通常低于城鎮(zhèn)是100至300輛/天。在一個(gè)混合交通流、卡車 占有4。%到70%的交通量，主要為輕型卡車攜帶小于2o 5噸(包括農(nóng)業(yè)車輛如拖拉機(jī)等)、 行走、中型卡車2o 5 5噸。大部分的輕或中等卡車超載.重型卡車的比例小于9%.某些道 路上的比例對(duì)縣、超載的卡車是5%至32%,而在一些縣公路連接到國家或省級(jí)

55、公路的比例 軀干，超載的比例通常數(shù)量的20%提高到32%o交通量對(duì)農(nóng)村道路不會(huì)很重。然而，考慮到中國的實(shí)際情況，以及車輛超載,要滿足100 kN，和BZZ-100標(biāo)準(zhǔn)軸載作用次數(shù)。人行道撓度和底部的拉應(yīng)力作為瀝青路面設(shè)計(jì)參數(shù)。軸載荷計(jì)算方式依照下面的公式：P N，和，為車軸重量和頻率R- 1 為總車軸重量和頻數(shù)如果兩軸之間的距離小于3米，軸載荷進(jìn)行了計(jì)算：如果彎拉型壓力的半剛性基層底部作為設(shè)計(jì)參數(shù)計(jì)算、軸重依下列公式：如果兩軸之間的距離小于3米：2對(duì)農(nóng)村公路交通量農(nóng)村道路以面包車為車輛的設(shè)計(jì)標(biāo)準(zhǔn)。表1顯示了其外部尺寸。典型的車輛類型農(nóng)村道路都列在表2。如電動(dòng)車，摩托車和自行車可以考慮為邊對(duì)農(nóng)村

56、道 路交通量的計(jì)算的路邊干擾.根據(jù)交通組成和卷，農(nóng)村道路被分成5個(gè)等級(jí).每一等級(jí)通信量見表3.交通量在表3規(guī)定經(jīng) 以小巴為標(biāo)準(zhǔn)的車輛類型，并將不同類型車輛的車輛折算系數(shù)記錄在所給的表2,表3中， Ne指的是累積的等效軸重行動(dòng)的頻率Ns指的等效軸重行動(dòng)的頻率在設(shè)計(jì)交通車道上開始運(yùn)行期間；r指的年增長率交通量n指系數(shù)，一個(gè)車道為為1。0,雙車道為0.6 0.7。3路基強(qiáng)度路基回彈模量的變化極大。為方便起見，路基的強(qiáng)度可以分為四類根據(jù)其含水率和模量的 韌性，顯示在表4。表5的參數(shù)確定設(shè)計(jì)原則相結(jié)合的實(shí)踐經(jīng)驗(yàn)。采用多層彈性理論對(duì)路面結(jié)構(gòu)表5中指定的 影響，在暗夜精靈，農(nóng)村道路鋪裝厚度進(jìn)行了分析，結(jié)果表

57、明，在給定的h，h2,E0、路面基層 厚度變化為周邊交通類一個(gè)范圍內(nèi)的4 - 5厘米。測(cè)試結(jié)果表明，該分類農(nóng)村道路運(yùn)輸量對(duì)顯 示在表3是合理的、可行的設(shè)計(jì)和施工條件對(duì)瀝青路面結(jié)構(gòu)。采用多層彈性理論，瀝青路面結(jié)構(gòu)的普通鄉(xiāng)村公路表5中進(jìn)行了分析。當(dāng)北東向、累積的等 效軸重行動(dòng)頻率，路面的厚度（h = 3厘米的厚度）、基層（h2 = 20厘米）保持不變，鄰近的 路基強(qiáng)度的影響分類基層的厚度為3 cm 一 5厘米。這一結(jié)論表明，路基強(qiáng)度分類是合理的、 適用于設(shè)計(jì)與施工的瀝青路面結(jié)構(gòu)。4厚度測(cè)定瀝青路面結(jié)構(gòu)設(shè)計(jì)參數(shù)的靈敏度分析路基和路面結(jié)構(gòu)之間的關(guān)系，找出瀝青路面結(jié)構(gòu)強(qiáng)度的結(jié)構(gòu)及設(shè)計(jì) 參數(shù)，并確定各層的

58、最敏感的路面結(jié)構(gòu)層。瀝青路面結(jié)構(gòu)，農(nóng)村道路通常是由一個(gè)基層路面， 和統(tǒng)一，顯示在表6.分析了路面結(jié)構(gòu)的多人游戲根據(jù)彈性理論的雙圓弧均布載荷下，假設(shè)接 觸有連續(xù)相鄰層的瀝青路面結(jié)構(gòu)。使用的基本參數(shù)的計(jì)算與分析瀝青路面結(jié)構(gòu)都列在表7. 通過分析影響所有的參數(shù)變化對(duì)路面結(jié)構(gòu)的扭曲，基層路面和路基，下面，結(jié)果顯示。（1）增加厚度路面有效減少路面的偏斜，可是飼養(yǎng)的成本。比較經(jīng)濟(jì)和有效的方法是提高 基層的厚度，優(yōu)于基層厚度的增加,而提高路面的厚度是最后的選擇。（2）隨著厚度的增加，路面結(jié)構(gòu)的變化將路面變形趨勢(shì)是溫柔.當(dāng)路面的厚度達(dá)到一定值時(shí)， 在路面撓度變化并不明顯，然后它是無效的承載力提高瀝青路面結(jié)構(gòu)通過增加厚度的路面。 建議在路面基層厚度和基層應(yīng)等于或大于18至20厘米，分別對(duì)瀝青路面結(jié)構(gòu)設(shè)計(jì)，農(nóng)村道 路。圖1顯示變化的影響各層厚度對(duì)路面偏斜。（3）路面位移的變化非常敏感對(duì)于路基系數(shù)E0。增加基層模量或基層也是有效降低路面的 變形情況。另一方面，撓度路面模量逐漸降低的時(shí)候,作為表面增加最小有效因素.當(dāng)路面模量 的增大到一定數(shù)值時(shí)，降低路面變形不明顯。圖二顯示效果