道路工程(路橋)畢業(yè)設(shè)計(jì)外文文獻(xiàn)翻譯

1、精選優(yōu)質(zhì)文檔-傾情為你奉上外文文獻(xiàn)翻譯原文：Asphalt Mixtures-Applications, Theory and Principles1 . ApplicationsAsphalt materials find wide usage in the construction industry. The use of asphalt as a cementing agent in pavements is the most common of its applications, however, and the one that will be considered here.Asp

2、halt products are used to produce flexible pavements for highways and airports. The term “flexible” is used to distinguish these pavements from those made with Portland cement, which are classified as rigid pavements, that is, having beam strength. This distinction is important because it provides t

3、hey key to the design approach which must be used for successful flexible pavement structures.The flexible pavement classification may be further broken down into high and low types, the type usually depending on whether a solid or liquid asphalt product is used. The low types of pavement are made w

4、ith the cutback, or emulsion, liquid products and are very widely used throughout this country. Descriptive terminology has been developed in various sections of the country to the extent that one pavement type may have several names. However, the general process followed in construction is similar

5、for most low-type pavements and can be described as one in which the aggregate and the asphalt product are usually applied to the roadbed separately and there mixed or allowed to mix, forming the pavement.The high type of asphalt pavements is made with asphalt cements of some selected penetration gr

6、ade. Fig. 1 A modern asphalt concrete highway. Shoulder striping is used as a safely feature.Fig. 2 Asphalt concrete at the San Francisco International Airport.They are used when high wheel loads and high volumes of traffic occur and are, therefore, often designed for a particular installation. 2 .

7、Theory of asphalt concrete mix designHigh types of flexible pavement are constructed by combining an asphalt cement, often in the penetration grade of 85 to 100, with aggregates that are usually divided into three groups, based on size. The three groups are coarse aggregates, fine aggregates, and mi

8、neral filler. These will be discussed in detail in later chapter.Each of the constituent parts mentioned has a particular function in the asphalt mixture, and mix proportioning or design is the process of ensuring that no function is neglected. Before these individual functions are examined, however

9、, the criteria for pavement success and failure should be considered so that design objectives can be established.A successful flexible pavement must have several particular properties. First, it must be stable, that is to resistant to permanent displacement under load. Deformation of an asphalt pav

10、ement can occur in three ways, two unsatisfactory and one desirable. Plastic deformation of a pavement failure and which is to be avoided if possible. Compressive deformation of the pavement results in a dimensional change in the pavement, and with this change come a loss of resiliency and usually a

11、 degree of roughness. This deformation is less serious than the one just described, but it, too, leads to pavement failure. The desirable type of deformation is an elastic one, which actually is beneficial to flexible pavements and is necessary to their long life.The pavement should be durable and s

12、hould offer protection to the subgrade. Asphalt cement is not impervious to the effects of weathering, and so the design must minimize weather susceptibility. A durable pavement that does not crack or ravel will probably also protect the roadbed. It must be remembered that flexible pavements transmi

13、t loads to the subgrade without significant bridging action, and so a dry firm base is absolutely essential.Rapidly moving vehicles depend on the tire-pavement friction factor for control and safety. The texture of the pavement surfaces must be such that an adequate skid resistance is developed or u

14、nsafe conditions result. The design procedure should be used to select the asphalt material and aggregates combination which provides a skid resistant roadway.Design procedures which yield paving mixtures embodying all these properties are not available. Sound pavements are constructed where materia

15、ls and methods are selected by using time-tested tests and specifications and engineering judgments along with a so-called design method.The final requirement for any pavement is one of economy. Economy, again, cannot be measured directly, since true economy only begins with construction cost and is

16、 not fully determinable until the full useful life of the pavement has been recorded. If, however, the requirements for a stable, durable, and safe pavement are met with a reasonable safety factor, then the best interests of economy have probably been served as well.With these requirements in mind,

17、the functions of the constituent parts can be examined with consideration give to how each part contributes to now-established objectives or requirements. The functions of the aggregates is to carry the load imposed on the pavement, and this is accomplished by frictional resistance and interlocking

18、between the individual pieces of aggregates. The carrying capacity of the asphalt pavement is, then, related to the surface texture (particularly that of the fine aggregate) and the density, or “compactness,”, of the aggregates. Surface texture varies with different aggregates, and while a rough sur

19、face texture is desired, this may not be available in some localities. Dense mixtures are obtained by using aggregates that are either naturally or artificially “well graded”. This means that the fine aggregate serves to fill the voids in the coarser aggregates. In addition to affecting density and

20、therefore strength characteristics, the grading also influences workability. When an excess of coarse aggregate is used, the mix becomes harsh and hard to work. When an excess of mineral filler is used, the mixes become gummy and difficult to manage.The asphalt cement in the flexible pavement is use

21、d to bind the aggregate particles together and to waterproof the pavements. Obtaining the proper asphalt content is extremely important and bears a significant influence on all the items marking a successful pavement. A chief objective of all the design methods which have been developed is to arrive

22、 at the best asphalt content for a particular combination of aggregates.3 . Mix design principlesCertain fundamental principles underlie the design procedures that have been developed. Before these procedures can be properly studied or applied, some consideration of these principles is necessary. As

23、phalt pavements are composed of aggregates, asphalt cement, and voids. Considering the aggregate alone, all the space between particles is void space. The volume of aggregate voids depends on grading and can vary widely. When the asphalt cement is added, a portion of these aggregate voids is filled

24、and a final air-void volume is retained. The retention of this air-void volume is very important to the characteristics of the mixture. The term air-void volume is used, since these voids are weightless and are usually expressed as a percentage of the total volume of the compacted mixture.An asphalt

25、 pavement carries the applied load by particle friction and interlock. If the particles are pushed apart for any reason , then the pavement stability is destroyed. This factor indicates that certainly no more asphalt should be added than the aggregate voids can readily hold. However ,asphalt cement

26、is susceptible to volume change and the pavement is subject to further compaction under use. If the pavement has no air voids when placed, or if it loses them under traffic, then the expanding asphalt will overflow in a condition known as bleeding. The loss of asphalt cement through bleeding weakens

27、 the pavement and also reduces surface friction, making the roadway hazardous. Fig. 3 Cross section of an asphalt concrete pavement showing the aggregate framework bound together by asphalt cement.The need for a minimum air-void volume (usually 2 or 3 per cent ) has been established. In addition, a

28、maximum air-void volume of 5 to 7 per cent should not be exceed. An excess of air voids promotes raveling of the pavement and also permits water to enter and speed up the deteriorating processes. Also, in the presence of excess air the asphalt cement hardens and ages with an accompanying loss of dur

29、ability and resiliency.The air-void volume of the mix is determined by the degree of compaction as well as by the asphalt content. For a given asphalt content, a lightly compacted mix will have a large voids volume and a lower density and a greater strength will result. In the laboratory, the compac

30、tion is controlled by using a specified hammer and regulating the number of blows and the energy per blow. In the field, the compaction and the air voids are more difficult to control and tests must be made no specimens taken from the compacted pavement to cheek on the degree of compaction being obt

31、ained. Traffic further compact the pavement, and allowance must be made for this in the design. A systematic checking of the pavement over an extended period is needed to given factual information for a particular mix. A change in density of several per cent is not unusual, however.Asphalt content h

32、as been discussed in connection with various facets of the ix design problem. It is a very important factor in the mix design and has a bearing an all the characteristics ld a successful pavement: stability, skid resistance, durability, and economy. As has been mentioned, the various design procedur

33、es are intended to provide a means for selecting the asphalt content . These tests will be considered in detail in a future chapter ,but the relationship between asphalt content and the measurable properties of stability, unit weight, and air voids will be discussed here. Fig.4 Variations in stabili

34、ty, unit weight, and air-void content with asphalt cement content.If the gradation and type of aggregate, the degree of compaction, and the type of asphalt cement are controlled, then the strength varies in a predictable manner. The strength will increase up to some optimum asphalt content and then

35、decrease with further additions. The pattern of strength variation will be different when the other mix factors are changed, and so only a typical pattern can be predicted prior to actual testing.Unit weight varies in the same manner as strength when all other variable are controlled. It will reach

36、some peak value at an asphalt content near that determined from the strength curve and then fall off with further additions.As already mentioned, the air-void volume will vary with asphalt content. However, the manner of variation is different in that increased asphalt content will decrease air-void

37、 volume to some minimum value which is approached asymptotically. With still greater additions of asphalt material the particles of aggregate are only pushed apart and no change occurs in air-void volume.In summary, certain principles involving aggregate gradation, air-void volume, asphalt content,

38、and compaction mist be understood before proceeding to actual mix design. The proper design based on these principles will result in sound pavements. If these principles are overlooked, the pavement may fail by one or more of the recognized modes of failure: shoving, rutting, corrugating, becoming s

39、lick when the max is too rich; raveling, cracking, having low durability when the mix is too lean. It should be again emphasized that the strength of flexible is, more accurately, a stability and does not indicate any ability to bridge weak points in the subgrade by beam strength. No asphalt mixture

40、 can be successful unless it rests on top of a properly designed and constructed base structure. This fact, that the surface is no better than the base, must be continually in the minds of those concerned with any aspect of flexible pavement work.譯文：瀝青混合料的應(yīng)用、理論和原則1、應(yīng)用瀝青材料如今在建筑行業(yè)廣泛使用。瀝青最常見(jiàn)的應(yīng)用是作為的瀝青路面

41、的粘結(jié)劑使用。然而，這一點(diǎn)必須在這里予以介紹。瀝青產(chǎn)品常用于生產(chǎn)公路和機(jī)場(chǎng)柔性路面。所謂“柔性”是用來(lái)區(qū)分與硅酸鹽水泥制成的路面，它被列為剛性路面，也就是這些路面具有剛性強(qiáng)度。這個(gè)區(qū)別很重要，因?yàn)樗岢隽顺晒M(jìn)行柔性路面結(jié)構(gòu)設(shè)計(jì)的方法的關(guān)鍵。柔性路面的分類可進(jìn)一步細(xì)分為高、低的類別，分類通常取決于是否有使用固體或液體瀝青產(chǎn)品。低類型路面結(jié)構(gòu)類型通過(guò)減少瀝青用量或使用乳化劑、液體瀝青，是非常廣泛的應(yīng)用在全國(guó)范圍內(nèi)。在全國(guó)的范圍內(nèi)各地區(qū)已開(kāi)發(fā)各自的描述性術(shù)語(yǔ)，一個(gè)路面類型可能有好幾個(gè)名字。但是，一般對(duì)大多數(shù)低型路面其施工方法確是相似，可描述為瀝青產(chǎn)品通常單獨(dú)或其混合結(jié)構(gòu)應(yīng)用于行車(chē)道，形成路面。高級(jí)

42、瀝青路面用經(jīng)過(guò)選擇的具有好的滲透性的瀝青混凝土制成。圖1 現(xiàn)代瀝青混凝土公路 路肩設(shè)置路標(biāo)線具有安全地特點(diǎn) 圖2 舊金山國(guó)際機(jī)場(chǎng)瀝青混凝土跑道它們被用于重荷載和大交通量道路，因此，人們會(huì)進(jìn)行特殊的結(jié)構(gòu)設(shè)計(jì)。2、瀝青混凝土設(shè)計(jì)原理高等級(jí)柔性路面是用瀝青混凝土建造而成，通常根據(jù)集料的85%-100%通過(guò)率將其分為三種類型。這三種分別為粗集料、細(xì)集料和礦粉。這些將在后面的章節(jié)中進(jìn)行詳細(xì)討論。瀝青混合料的每一個(gè)組成部分都有特定的功能，混合料配合比設(shè)計(jì)是確保沒(méi)有功能被忽略的過(guò)程。然而，在這些個(gè)別功能檢查之前，對(duì)于路面的成功和失敗的標(biāo)準(zhǔn)應(yīng)該考慮，這樣路面的設(shè)計(jì)目標(biāo)才能確定。一個(gè)成功的柔性路面必須有幾個(gè)特定

43、的屬性。首先，它必須是穩(wěn)定的，即抵抗負(fù)荷下的永久位移。瀝青路面變形的可能發(fā)生在三種方式，二個(gè)是不理想的形變，一個(gè)是可以接受的。塑性變形對(duì)路面來(lái)說(shuō)是要盡量避免的失敗。路面的壓縮變形導(dǎo)致的路面鋪裝的尺寸變化，這種變化將引起路面彈性和粗糙度的損失。這種變形沒(méi)有剛剛描述的那種那么嚴(yán)重，但它也同樣導(dǎo)致路面破壞。理想類型的變形是一種彈性變形，這實(shí)際上有利于柔性路面，并對(duì)于其長(zhǎng)壽命是十分必要的。路面應(yīng)該耐用并能夠保護(hù)路基。瀝青混凝土是受環(huán)境的影響的，因此設(shè)計(jì)必須降低對(duì)氣候敏感性。一個(gè)耐用的路面要不開(kāi)裂或擁包才能保護(hù)路基。我們必須記住，柔性路面將荷載直接傳至路基，所以堅(jiān)實(shí)的基礎(chǔ)是絕對(duì)必要的?？焖僖苿?dòng)的車(chē)輛依靠

44、的輪胎路面摩擦力實(shí)現(xiàn)控制和保證安全。路面表面紋理必須保證足夠的防滑性否則將產(chǎn)生不安全的后果。設(shè)計(jì)過(guò)程通過(guò)瀝青材料的選擇和集料的組合設(shè)計(jì)提供了防滑路面。設(shè)計(jì)程序放棄鋪面結(jié)合料所有這些表面特性都無(wú)法使用。合理的路面建造所需的材料和方法是經(jīng)過(guò)使用時(shí)間考驗(yàn)和規(guī)范和工程判斷和在一起所稱的設(shè)計(jì)方法選定。對(duì)于任何路面最后一個(gè)要求是經(jīng)濟(jì)性。經(jīng)濟(jì)性不能一開(kāi)始就確定，準(zhǔn)確的經(jīng)濟(jì)是從開(kāi)始建設(shè)直到路面整個(gè)壽命期的成本。然而，如果對(duì)于路面穩(wěn)定，耐久，安全性的要求都達(dá)到一個(gè)合理的安全系數(shù)，那么對(duì)經(jīng)濟(jì)的最佳利益或許已經(jīng)實(shí)現(xiàn)。考慮到路面的這些要求，可通過(guò)檢查各組成部分的功能如何有助于現(xiàn)在已經(jīng)確定的目標(biāo)或要求。瀝青混凝土功能是

45、承擔(dān)路面上施加的負(fù)荷，這是由混合料各材料之間相互咬合和摩擦阻力實(shí)現(xiàn)。也就是瀝青路面的承載能力與路面的表面紋理（尤其是細(xì)集料）和密度或者混合料的“密實(shí)度”相關(guān)，表面結(jié)構(gòu)隨集料的不同而不同，雖然理想的表面具有粗糙紋理，但在有些情況下卻不能實(shí)現(xiàn)。密級(jí)配混合物通過(guò)使用自然或人為的連續(xù)級(jí)配集料得到。這意味著細(xì)骨料的存在填補(bǔ)了粗骨料的空隙。這除了影響混合料的密度和強(qiáng)度特性之外，也影響施工性能。當(dāng)粗骨料使用過(guò)量時(shí)，混合料將變得堅(jiān)硬而且難以施工；當(dāng)?shù)V物填料使用過(guò)多時(shí)，混合料將變得較軟，影響使用性能。柔性路面中的瀝青膠結(jié)材料用于將集料粘結(jié)在一起并充當(dāng)防水材料。選取適當(dāng)?shù)臑r青含量是非常重要的，它對(duì)于成功的路面在項(xiàng)目的整個(gè)評(píng)分過(guò)程中具有重要的影響。設(shè)計(jì)的首要目標(biāo)是對(duì)于特定的集料組合確定瀝青的最佳用量。3 、混合料配合比