二級(jí)公路畢業(yè)設(shè)計(jì)外文文獻(xiàn)(共7頁(yè))

1、精選優(yōu)質(zhì)文檔-傾情為你奉上外文資料及翻譯Effects of Design Features on Rigid Pavement PerformanceThe performance of rigid pavements is affected by a variety of design features, including slab thickness, base type, joint spacing, reinforcement, joint orientation, load trans fer, dowel bar coatings, longitudinal joint des

2、ign, joint sealant, tied concrete shoulders ,and subdrainage . A study was made by ERES Consultants, Inc. under FHWA contract on the effects of these features on rigid pavement performance . Ninety-five pavemen tsections located in four major climatic regions were thoroughly evaluated . The followin

3、g conclusions, which provide some revealing insights into pavement performance, are abstracted from the report (Smith et al., 1990a).Slab Thickness The effect of slab thickness on pavement performance was significant.It was found that increasing slab thickness reduced transverse and longitudinal cra

4、cking in all cases. This effect was much more pronounced for thinner slabs than fo rthicker slabs . It was not possible to compare the performance of the thinner slabs and the thicker slabs directly, because the thick slabs were all constructed directly on th esubgrade and the thinner slabs were all

5、 constructed on a base course .Increasing the thickness of slab did not appear to reduce joint spalling or join tfaulting . Thick slabs placed directly on the subgrade, especially in wet climates an dexposed to heavy traffic, faulted as much as thin slabs constructed on a base course .Base Type Base

6、 types, including base/slab interface friction, base stiffness, base erodibility, and base permeability, seemed to have a great effect on the performance of jointed concrete pavements . The major performance indicators, which were affected by variations in base type, were transverse and longitudinal

7、 cracking, joint spalling, and faulting .The worst performing base type, consisted of the cement-treated or soil cementbases, which tended to exhibit excessive pumping, faulting, and cracking. This is mostlikely due to the impervious nature of the base, which traps moisture and yet can brea- k down

8、and contribute to the movement of fines beneath the slab .The use of lean concrete bases generally produced poor performance . Large curl -ing and warping stresses have been associated with slabs constructed over lean concrete bases. These stresses result in considerable transverse and longitudinal

9、cracking of the slab . The poor performance of these bases can also be attributed to a bathtub design, in which moisture is trapped within the pavement cross section .Dense-graded asphalt-treated base courses ranged in performance from very poor to good. The fact that these types of bases were often

10、 constructed as a bathtub design contributed to their poor performance . This improper design often resulted in severe cracking, faulting, and pumping.The construction of thicker slabs directly on the subgrade with no base resultedIn a pavement that performed marginally. These pavements were especia

11、lly susceptible to faulting, even under low traffic levels.Pavements constructed over aggregate bases had varied performance, but weregenerally in the fair to very good category. In general, the more open-graded the aggregate,the better the performance . An advantage of aggregate bases is that they

12、contribute the least to the high curling and warping stresses in the slab . Even thoughaggregate bases are not open-graded, they are more permeable and have a lower friction factor than stabilized bases .The best bases in terms of pavement performance were the permeable bases . Typical base courses

13、have permeabilities ranging from 0 to less than 1 ft/day (0 .3 m/day) ; good permeable bases have permeabilities up to 1000 ft/day (305 m/day) . Specific areas of concern were the high corner deflections and the low load transfer exhibited by the permeable bases . These can affect their long-term pe

14、rformance, so the use of dowel bars might be required . An unexpected benefit of using permeable bases was the reduction in D cracking on pavements susceptible to this type of distress .Slab Length For JPCP, the length of slabs investigated ranged from 7 .75 to 30 ft(2.4to9.1m). It was found that re

15、ducing the slab length decreased both the magnitude of the joint faulting and the amount of transverse cracking. On pavements with random joint spacings, slabs with joint spacings greater than 18 ft (5.5 m) experienced more transverse cracking than did the shorter slabs .For JRCP, the length of slab

16、s investigated ranged from 21 to 78 ft (6 .4 to 23 .9 m) .Generally, shorter joint spacings performed better, as measured by the deteriorated transverse cracks, joint faulting, and joint spalling . However, several JRCP with long joint spacings performed quite well . In particular, the long jointed

17、pavements in New Jersey, which were constructed with expansion joints, displayed excellent performance .An examination of the stiffness of foundation was made through the use of the radius of relative stiffness, f . Generally speaking, when the ratio L/E, where L is the length of slab, was greater t

18、han 5, transverse cracking occurred more frequently . This factor was further examined for different base types . It was found that stiffer base courses required shorter joint spacings to reduce or eliminate transverse cracking .Reinforcement The amount of steel reinforcement appeared to have an eff

19、ect in controlling the amount of deteriorated transverse cracking . Pavement sections with less than 0.1% reinforcing steel often displayed significant deteriorated transverse cracking.A minimum of 0 .1% reinforcing steel is therefore recommended, with larger amounts required for more severe climate

20、 and longer slabs.Joint Orientation Conventional wisdom has it that skewed joints prevent the application of two wheel loads to the joint at the same time and thus can reduce load-associated distresses . The results from the limited sample size in this study were ambiguous, but all of the nondoweled

21、 sections with skewed joints had a lower PSR than similar designs with perpendicular joints . The available data provide no definite conclusions on the effectiveness of skewing transverse joints for nondoweled slabs . Skewed joints are not believed to provide any benefit to doweled slabs.Load Transf

22、er Dowel bars were found to be effective in reducing the amount of joint faulting when compared with nondoweled sections of comparable designs. The diameter of dowels had an effect on performance, because larger diameter bars provided better load transfer and control of faulting under heavy traffic

23、than did smaller dowels.It appeared that a minimum dowel diameter of 1 .25 in . (32 mm) was necessary to provide good performance .Nondoweled JPCP slabs generally developed significant faulting, regardless of pavement design or climate . This effect was somewhat mitigated by the use of permeable bas

24、es. However, the sections in this group had a much lower number of accumulated ESAL, so no definite conclusions can be drawn yet .Dowel Bar Coatings Corrosion-resistant coatings are needed to protect dowels from the adverse effects of moisture and deicing chemicals .While most of the sections in thi

25、s study did not contain corrosion-resistant dowel bars, those that did generally exhibited enhanced performance. Very little deteriorated transverse cracking was identified on these sections. In fact, one section in New Jersey with stainless steel-clad dowel bars was performing satisfactorily after

26、36 years of service .Longitudinal Joint Design The longitudinal joint design was found to be a critical design element.Both inadequate forming techniques and insufficient depths of joint can contribute to the development of longitudinal cracking . There was evidence of the ad vantage of sawing the j

27、oints over the use of inserts . The depth of longitudinal joints is generally recommended to be one-third of the actual, not designed, slab thickness, but might have to be greater when stabilized bases are used .Joint Sealant Joint sealing appeared to have a beneficial effect on performance . This w

28、as particularly true in harsh climates with excessive amounts of moisture . Preformed compression sealants were shown to perform well for more than 15 years under heavy traffic.Except where D cracking occurred, pavement sections containing preformed sealants generally exhibited little joint spalling

29、 and were in good overall conditions.Rubberized asphalt joint sealants showed good performance for 5 to 7 years.Tied Concrete Shoulders It is generally believed that tied concrete shoulders can reduce edge stresses and corner deflections by providing more lateral supports to the mainline pavement, t

30、hus improving pavement performance . Surprisingly, this study showed that, although tied concrete shoulders performed better than asphalt shoulders,many of the tied shoulders were not designed properly and actually contributed to poor performance of the mainline pavement . The tiebars were spaced to

31、o far apart ,sometimes at a spacing of 40 in.(1016 mm), and were not strategically located near slab corners to provide adequate support . In some cases, tied concrete shoulders were constructed over a stabilized dense-graded base in a bathtub design, resulting in the poor performance of mainline pa

32、vement.Subdrainage The provision of positive subdrainage, either in the form of longitudinal edge drains or the combination of a drainage layer and edge drains, generally reduced the amount of faulting and spalling related to D cracking . With few exceptions, the load-associated distresses, especial

33、ly faulting and transverse cracking, decreased as the drainage characteristics improved . The overall pavement performance can be improved by using an open-graded base or restricting the percentage of fines . A filter layer must be placed below the permeable base, and regular maintenance of the outl

34、ets must be provided .譯文 結(jié)構(gòu)特點(diǎn)對(duì)剛性路面性能的影響剛性路面的性能受種種結(jié)構(gòu)特點(diǎn)的影響，如板厚、基層類(lèi)型、接縫間距、鋼筋用量、接風(fēng)方向、荷載傳遞、傳力桿涂層、縱縫設(shè)計(jì)、接縫填封料、有拉桿混凝土道肩和地下排水等。ERES咨詢(xún)公司于聯(lián)邦公路局（FHWA）簽訂合同，研究這些結(jié)構(gòu)特點(diǎn)對(duì)剛性路面的影響。對(duì)四個(gè)主要?dú)夂騾^(qū)內(nèi)95個(gè)路面段作了詳細(xì)的評(píng)定。從研究報(bào)告（Smith等，1990a）摘錄了以下結(jié)論，以便對(duì)路面性能有一透徹的理解。一、板 厚板厚對(duì)路面性能的影響很大。發(fā)現(xiàn)在所有的實(shí)例中，增加板厚，是縱向和橫向開(kāi)裂減小。這種影響對(duì)對(duì)薄的路面板，比厚板更為明顯。不可能直接將薄板的想能

35、與厚板進(jìn)行比較，因?yàn)榘搴穸贾苯愉佒谕粱?，而薄板都鋪筑在基層上。增加板厚并不能減少接縫剝落及接縫錯(cuò)臺(tái)。厚板直接鋪在土基上，尤其是氣候潮濕交通繁重的情況下，產(chǎn)生的錯(cuò)臺(tái)同鋪筑在基層上的薄板同樣也很多。二 、基 層 類(lèi) 型基層類(lèi)型，包括基層與板的界面摩擦力、基層剛度、基層抗沖刷能力和基層透水性，看來(lái)對(duì)有接縫混凝土路面性能有很大影響。受各種基層類(lèi)型影響的主要性能指標(biāo)是橫向額縱向開(kāi)裂、接縫剝落和錯(cuò)臺(tái)。性能最差的基層類(lèi)型是水泥穩(wěn)定或水泥土基層，最容易于楚翔很對(duì)唧泥、錯(cuò)臺(tái)和開(kāi)裂。這很可能是因?yàn)榛鶎硬煌杆?，它吸收水分，易于斷裂，使得板下的?xì)顆粒發(fā)生移動(dòng)。應(yīng)用貧混凝土基層，一般工作性能都很差。很大的翹曲應(yīng)力是

36、與貧混凝土基層上鋪筑路面板有關(guān)系的。由于這些應(yīng)力，使得面板產(chǎn)生很多橫向和縱向的裂縫。這些基層的性能差，還可能是由于路面橫截面按盆狀設(shè)計(jì)，造成水分集中。密級(jí)配瀝青穩(wěn)定基層的性能從很差到好都有。性能低劣的原因是這些基層類(lèi)型經(jīng)常采用盆狀設(shè)計(jì)，這種錯(cuò)誤設(shè)計(jì)結(jié)果將產(chǎn)生嚴(yán)重的開(kāi)裂、錯(cuò)臺(tái)和唧泥。厚的面板直接鋪筑在不舍基層的土基上，路面勉強(qiáng)合格。這些路面特別容易錯(cuò)臺(tái)，即使交通量不大也是如此。鋪筑在集料基層上的路面具有不同性能，但是一般屬于良好到很好等級(jí)。通常，集料開(kāi)集配空隙越多。性能越好。集料基層的優(yōu)點(diǎn)是由于基層引起的面板翹曲高應(yīng)力是最小的。即使集料基層不是開(kāi)集配的，也比穩(wěn)定基層具有較好的透水性和較低的摩擦系

37、數(shù)。在路面性能方面最好的基層是透水基層。常用基層的滲透率在0至0.3m/d(1ft/d)，而好的透水基層滲透率達(dá)305m/d(1000ft/d)。需要特別考慮的問(wèn)題是透水基層板角部位撓度大，且傳荷能力低。由于這將影響其長(zhǎng)遠(yuǎn)性能，要應(yīng)用傳力桿是必不可少的。應(yīng)用透水基層有一種意想不到的好處，它能夠是容易產(chǎn)生“D”裂縫的路面，裂縫數(shù)量減少。三、板長(zhǎng)調(diào)查的JPCP路面板長(zhǎng)度在2.4-9.1m（7.75-30ft）之間，發(fā)現(xiàn)板長(zhǎng)減小，接縫錯(cuò)臺(tái)的大小和橫向開(kāi)裂的數(shù)量?jī)烧叨紲p少。在接縫間距不規(guī)則的路面上，接縫間距大于18ft（5.5m）的板，橫向開(kāi)裂多余較短的板。對(duì)于調(diào)查的JRCP路面板長(zhǎng)度在6.423.9m（21-78ft）之間。一般地，從調(diào)查損壞的橫向裂縫、接縫錯(cuò)臺(tái)和接縫剝落來(lái)看，接縫間距有短的一些的路面性能好些。然而，有些接縫間距長(zhǎng)的JRCP，性能也很好。尤其是新澤西州的長(zhǎng)接縫路面，筑有膨脹縫，呈現(xiàn)出極好的性能。通過(guò)相對(duì)剛度半徑l調(diào)查了地基的剛度。一般來(lái)說(shuō)，當(dāng)L/l比值（L為板長(zhǎng)）大于5，橫向開(kāi)裂較多。這一因素對(duì)不同基層類(lèi)型作了進(jìn)一步研