仲甡,李杰,黃敏*
1.云南建工集團(tuán)有限公司,云南 昆明 650000;2.武漢工程大學(xué)資源與土木工程學(xué)院,湖北 武漢 430074
層間接觸狀態(tài)和橫向力大小對(duì)車轍貢獻(xiàn)率的影響
仲甡1,李杰2,黃敏2*
1.云南建工集團(tuán)有限公司,云南 昆明 650000;2.武漢工程大學(xué)資源與土木工程學(xué)院,湖北 武漢 430074
車轍貢獻(xiàn)率是反映瀝青路面各結(jié)構(gòu)層車轍病害程度的一個(gè)主要參數(shù),可用于指導(dǎo)瀝青路面的設(shè)計(jì)和施工.利用三維有限元計(jì)算軟件建立三維有限元模型用于理論分析,將有限元計(jì)算結(jié)果與理論解進(jìn)行對(duì)比,驗(yàn)證了該三維有限元模型的可靠性.采用實(shí)測(cè)的輪胎接地壓力,考慮不同層間接觸狀態(tài)和橫向力大小,結(jié)合有限元計(jì)算的數(shù)據(jù),分析了瀝青路面結(jié)構(gòu)層的車轍貢獻(xiàn)率.結(jié)果表明:在層間完全連續(xù)狀態(tài)下,橫向力大小的選取不能簡單地選取最大垂直輪胎接地壓力的一定比例,而是要根據(jù)所研究的具體情況具體分析.在對(duì)瀝青路面車轍貢獻(xiàn)率的研究中,可以忽略層間接觸狀態(tài),即假定層間完全連續(xù).
瀝青路面;車轍貢獻(xiàn)率;層間接觸狀態(tài);橫向力大小
很多學(xué)者對(duì)瀝青路面車轍貢獻(xiàn)率的問題進(jìn)行過研究,也采取了很多方法,例如室內(nèi)車轍試驗(yàn)和現(xiàn)場(chǎng)鉆芯實(shí)測(cè)并結(jié)合統(tǒng)計(jì)學(xué)原理、圓形均布荷載理論分析、以及實(shí)測(cè)輪載有限元理論分析等[1-6].本文采用實(shí)測(cè)輪載并考慮不同層間接觸狀態(tài)和橫向力大小,通過有限元分析來研究有關(guān)瀝青路面車轍貢獻(xiàn)率的問題.
計(jì)算用路面結(jié)構(gòu)及其參數(shù)見表1,文中所采用模量均為動(dòng)態(tài)模量.標(biāo)準(zhǔn)軸載BZZ-100的輪載P=25 kN,p=700 kPa,當(dāng)量直徑d=0.213 m(雙圓荷載);層間接觸條件考慮完全連續(xù).由于車轍是在壓應(yīng)變和橫向剪應(yīng)變共同作用下引起的[7],故本文在建立三維有限元計(jì)算模型時(shí),考慮的對(duì)比計(jì)算指標(biāo)為壓應(yīng)變?chǔ)舲和橫向剪應(yīng)變?chǔ)脁z.
瀝青路面車轍貢獻(xiàn)率有限元計(jì)算模型根據(jù)經(jīng)驗(yàn)[7]初定為:單元類型:plane82,solid45;尺寸:4 m×4 m×8 m;邊界條件:沿行車方向的前后側(cè)沒有Y方向的位移,左右側(cè)沒有X方向的位移,底部沒有Z方向的位移.有限元的計(jì)算模型見圖1.
表1 路面結(jié)構(gòu)計(jì)算參數(shù)Table 1 Pavement structure calculations
圖1 三維有限元計(jì)算模型Fig.1 Three-dimensional finite element calculation model
為保證所建立的計(jì)算模型的可靠性,本文將三維有限元計(jì)算模型與多層彈性體系理論解按上述指標(biāo)進(jìn)行對(duì)比,結(jié)果如圖2所示.
圖2 有限元計(jì)算模型和多層彈性理論的剪/壓應(yīng)變響應(yīng)Fig.2 Finite element model and the shear/compressive strain response of the multi-layer elastic theory
通過圖2有限元計(jì)算模型和多層彈性體系理論的壓應(yīng)變和剪應(yīng)變響應(yīng)趨勢(shì)對(duì)比分析,可驗(yàn)證該計(jì)算模型的可靠性.
瀝青路面車轍貢獻(xiàn)率是指瀝青路面面層各層的車轍量占總車轍量的比例.車轍是一種累積變形量;而應(yīng)變則是具有一定尺寸(長度、角度)的物體在該尺寸方向發(fā)生的變形與該物體原有尺寸的比值.每一層的應(yīng)變乘以該層的厚度就是車轍量,這樣就能建立應(yīng)變與車轍量的關(guān)系.假設(shè)不考慮回彈恢復(fù)等,即每個(gè)量都是絕對(duì)量.
壓/剪應(yīng)變車轍貢獻(xiàn)率,如圖3所示.圖3中,A1ε/A1γ分別表示上面層壓/剪應(yīng)變與上面層厚度的乘積A2ε/A2γ表示中面層壓/剪應(yīng)變與中面層厚度的乘積,A3ε/A3γ表示下面層壓/剪應(yīng)變與下面層厚度的乘積,則有:
SA1ε=A1ε/(A1ε+A2ε+A3ε)表示上面層壓應(yīng)變車轍貢獻(xiàn)率,%;
ZA2ε=A2ε/(A1ε+A2ε+A3ε)表示中面層壓應(yīng)變車轍貢獻(xiàn)率,%;
XA3ε=A3ε/(A1ε+A2ε+A3ε)表示下面層壓應(yīng)變車轍貢獻(xiàn)率,%;
SA1γ=A1γ/(A1γ+A2γ+A3γ)表示上面層剪應(yīng)變車轍貢獻(xiàn)率,%;
ZA2γ=A2ε/(A1γ+A2γ+A3γ)表示中面層剪應(yīng)變車轍貢獻(xiàn)率,%;
XA3γ=A3γ/(A1γ+A2γ+A3γ)表示下面層剪應(yīng)變車轍貢獻(xiàn)率,%.
圖3 壓/剪應(yīng)變車轍貢獻(xiàn)率示意圖Fig.3 Pressure/shear strain rut contribution
層間接觸狀態(tài)是指瀝青路面各層之間的接觸情況.由于瀝青路面面層之間,以及面層與基層之間不是完全連續(xù)的,故在本文研究中考慮兩種層間接觸狀態(tài).第一種是理想狀態(tài),即考慮層間完全連續(xù);第二種考慮層間有摩擦,且瀝青路面面層之間的摩擦系數(shù)為0.7,面層與基層之間的摩擦系數(shù)為0.5[8].
計(jì)算采用標(biāo)準(zhǔn)荷載(后軸總重100 kN,胎壓600 kPa,單輪負(fù)荷25 kN),走向花紋輪胎的實(shí)測(cè)豎向接地壓力作為計(jì)算荷載[9],且考慮水平荷載作用.研究表明,橫向輪胎接地壓力一般為最大垂直輪胎接地壓力的15%~50%[10].為了使計(jì)算結(jié)果更具一般性,分別取橫向輪胎接地壓力為最大垂直輪胎接地壓力的0、15%、30%和50%進(jìn)行計(jì)算分析.縱向輪胎接地壓力一般為最大垂直輪胎接地壓力的12%.采用表2中的路面結(jié)構(gòu)參數(shù)進(jìn)行計(jì)算,其中模量為實(shí)測(cè)模量.
表2 路面結(jié)構(gòu)計(jì)算參數(shù)Table 2 Pavement structure calculations
3.1 不同層間接觸狀態(tài)下橫向力大小對(duì)車轍貢獻(xiàn)率的影響
不同層間接觸狀態(tài)下橫向力大小對(duì)車轍貢獻(xiàn)率的影響計(jì)算結(jié)果如表3、表4所示,從表中可以看出:
a.在層間完全連續(xù)狀態(tài)下,隨著橫向力大小的變化,中面層剪應(yīng)變車轍貢獻(xiàn)率變化較小,且表現(xiàn)為中面層占優(yōu),無論橫向力如何變化,中面層剪應(yīng)變車轍貢獻(xiàn)率維持在40%~43%之間;在層間有摩擦條件下,各面層剪應(yīng)變車轍貢獻(xiàn)率變化均較小,且中面層占優(yōu)趨勢(shì)不再明顯.
b.無論層間接觸狀態(tài)如何,隨著橫向力大小的變化,各面層壓應(yīng)變車轍貢獻(xiàn)率變化均較小,且各面層壓應(yīng)變車轍貢獻(xiàn)率相當(dāng).
c.在層間完全連續(xù)狀態(tài)下,橫向力大小的選取不能簡單的取最大垂直輪胎接地壓力的隨意比例,例如30%,而是要根據(jù)所研究的具體情況具體分析.
表3 層間完全連續(xù)狀態(tài)下不同橫向力下瀝青層各層剪應(yīng)變和壓應(yīng)變車轍貢獻(xiàn)率Table 3 Rutting contribution of shear strain and compressive strain in each layer at the different transverse forces under the completely continuous state of layers
表4 層間有摩擦條件下不同橫向力下瀝青層各層剪應(yīng)變和壓應(yīng)變車轍貢獻(xiàn)率Table 4 Rutting contribution of shear strain and compressive strain in each layer at the different transverse forces under conditions of interlayer having friction
3.2 不同橫向力大小下層間接觸狀態(tài)對(duì)車轍貢獻(xiàn)率的影響
不同橫向力大小下層間接觸狀態(tài)對(duì)車轍貢獻(xiàn)率的影響計(jì)算結(jié)果如表5所示,從表中可以看出:
a.層間接觸狀態(tài)由完全連續(xù)到考慮摩擦,無論橫向力大小如何,中面層剪/壓應(yīng)變車轍貢獻(xiàn)率均減小,但減小幅度不大.
b.層間接觸狀態(tài)由完全連續(xù)到考慮摩擦,無論橫向力大小如何,各面層的剪/壓應(yīng)變車轍貢獻(xiàn)率變化幅度均比較小.由此可以看出,在各種水平的橫向力大小情況下,層間接觸狀態(tài)對(duì)瀝青路面車轍貢獻(xiàn)率的影響較小.
通過以上研究得出如下結(jié)論:
a.在層間完全連續(xù)狀態(tài)下,橫向力大小的選取不能簡單的取最大垂直輪胎接地壓力的一定比例,例如30%,而是要根據(jù)所研究的具體情況具體分析.
b.在各種水平的橫向力大小情況下,層間接觸狀態(tài)對(duì)瀝青路面車轍貢獻(xiàn)率的影響較小.在以后的研究中,為了減小計(jì)算量同時(shí)又不影響研究的準(zhǔn)確性.在適當(dāng)?shù)那闆r下,可以忽略層間接觸狀態(tài),即假定層間完全連續(xù).
表5 不同橫向力下層間接觸狀態(tài)下瀝青層各層剪應(yīng)變和壓應(yīng)變車轍貢獻(xiàn)率Table 5 Rutting contribution of shear strain and compressive strain in each layer at the different transverse forces under the contact between layers
致謝
感謝云南建工集團(tuán)直屬總承包二部為本研究提供的支持和幫助!
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Influence of interlayer contact state and lateral tire-pavement contact pressure on rutting contribution rate
ZHONG Shen1,LI Jie2,HUANG Min2
1.Yunnan Construction Engineering Group Co.LTD,Kunming 650000,China;2.School of Resource and Civil Engineering,Wuhan Institute of Technology,Wuhan 430074,China
The rutting contribution rate,as a main parameter which can reflect the degree of rutting disease of each structural layer on asphalt pavement,can be used to guide the design and construction of asphalt pavement.In this paper,the three-dimensional finite element calculation software was used to establish three-dimensional finite element model for theoretical analysis.With the comparison of the result of the finite element calculation with the theoretical solution,the reliability of the 3D finite element model was verified.Considering the different interlayer contact state and the lateral force,the rutting contribution rate of Asphalt Pavement was analyzed by using the data of measured tire contact pressure and finite element calculation.According to the results,if the interlayer is completely continuous,the size of lateral force can not be simply decided by a certain proportion of the largest vertical value of tire grounding pressure,instead,it should be analyzed on the specific situation.The interlayer contact condition can be ignored in the research of rutting contribution rate on asphalt pavement,that is,the interlayer contact condition can be assumed completely continuous.
asphalt pavement;rutting contribution rate;interlayer contact state;magnitude of lateral tire-pavement contact pressure
U411
A
10.3969/j.issn.1674-2869.2015.02.002
1674-2869(2015)02-0005-05
本文編輯:龔曉寧
2015-01-22
仲甡(1990-),男,河南駐馬店人,碩士研究生,研究方向:道路工程.*通信作者