Influence Analysis of Crack Depth and Position on Asphalt Pavement Structure with 3D Finite Element

Abstract:

In recent years the research on Surface-initiated longitudinal cracking along wheelpath (or Top-Down cracking) is become a fresh hotspot in the field of pavement damage focused by international asphalt pavement engineering.Because the traditional load is the vertical surface load with uniform tire pressure, this loading is applied at only one position and no effort is made to distinguish between tire pattern.The traditional method can’t explain the mechanism of the top-down cracking. In order to discuss the mechanism of TDC, this paper establish a 3D finite element model of semi-rigid pavement structure and use the large finite element software Abaqus. The analysis shows that, in the crack beginning stage, the main tensile stress appears under the center of the load on the sub-base of the pavement,and its value increases with the time. When cracks appear in the base, the position of the main tensile stress appears at the bottom of the surface layer, under the outside edge of wheel path. The value of the main shear stress increases at the stage of the cracks beginning, but the increase is small. The value of the main shear stress decreases when the cracks appear in the middle of the surface layer, and the position of the main shear stress changes with the depth of the cracks. With the increase of the cracks’ depth, the adverse influence of the shear stress becomes weaker and weaker.So the key of controlling the cracks in the surface layer is prevention. To prevent the development of the cracks, the tensile strength of the layer’s material should be enhanced in any way. The stress and its value resulted from the vehicle loaded on the structure layer is bigger than the other cases when the position of the cracks is at the edge of wheel path, and the stress is much bigger than the shear strength and the fracture toughness of the material of the layer. As the shear strength of the material is not enough, the vertical cracks are easier to appear at the edge of wheel path under the load of the vertical. Once it appearing, the cracks will extended into the layer because of the load of vertical. Eccentric load generates greater stress in the structure than the load loaded upright. In fact, though, non-channeling can reduce the appearance of the tracks, eccentric load enhance the development of the cracks in the surface because of the existence of the cracks in the surface layer.

• Periodical: Advanced Materials Research (Volumes 450-451)
• Pages: 267-272
• DOI: https://doi.org/10.4028/www.scientific.net/AMR.450-451.267
• Online since: January 2012
• Authors: Peng Wang, Can Cui
• Keywords: Asphalt Pavement, Eccentric Load, Finite Element Method (FEM), Highway Engineering, Surface-Initiated Cracking, Tire Pattern

References

[11] loading generates longitudinal cracks on the surface which appear in the outside edge of wheel path .Once it appearing, the cracks will develop into the layer because of the load of vertical. Influence of eccentric load Eccentric load Fig. 4 Eccentric load Road traffic in the lane has a horizontal swing, in order to further simulate actual impact of traffic, changing the symmetrical loading pattern into the eccentric loading pattern and the load at one side of the cracks, as shown in Figure 4 . Chosen crack is 7.5cm, and the model parameter is consistent with the former ones. Table4 shows calculation of maximum stress and stress intensity factors, which are under symmetric load and eccentric load . Table4 Stress intensity factor value under upright load and eccentric load Position of crack Maximum tensile stress Maximum shear stress Stress intensity factor value/Pa position/m value /Pa position /m KI/Mpa.m1/2 KII/Mpa.m1/2 Upright load 4.048E+04 -0.11,1.65,2.5 5.627E+05 0.14,2.5,2.355 -0.0593 0.00008 Eccentric load 1.318E+05 0.14,2.43,2.5 5.545E+05 0.28,2.47,2.355 -0.0394 0.1 The results shows that, in the structure,the stress response of eccentric loads are bigger than that of the upright load. As for cracks structure under eccentric loads, the maximum tensile stress which appeared at the crack tip reached 1.318E +05 Pa, eccentric load in the stress intensity factor for Type II is larger than the upright road KII reach 0.1, Thus in actual traffic,though, non-channeling can reduce the appearance of the tracks, but because of the presence of Surface-initiated cracking, partial loads exacerbated the development of Surface-initiated cracking Conclusion According to the analysis of generates of stress in the structure of the pavement with cracks, analysis of the crack depth, crack location, and the influence of stress in the structure under eccentric load , the analysis obtained: 1.When crack initiated, the maximum tensile stress occurs straightly below the bottom of the center of the load on the subbases of the pavement, and its value is constantly increasing. When the crack extended to the subgrade, the maximum tensile stress shift to the bottom of the surface layer, and it is below the outside edge of wheel path. 2.At the beginning of cracks, the maximum shear stress is increased, but the increase is small, when the crack extends to the 1 / 2 depth of surface layer, the maximum shear stress begins to become small, and the appearing location of maximum shear stress changes with the change of crack depth. 3.With the extension of the crack depth, the adverse effects of the shear continues to weaken, therefore, so the key of controlling the cracks in the surface layer is prevention. To prevent the expansion of cracks, we should try to increase the tensile strength of the material of layer structure. 4.The stress and its value resulted from the vehicle loaded on the structure layer is bigger when the position of the cracks is at the edge of wheel path than the other cases. And the stress is much bigger than the shear strength and the fracture toughness of the material of the layer.As the shear strength of the material is not enough, the vertical cracks are easier to appear at the edge of wheel path under the load of the vertical. Once it appearing, the cracks will develop into the layer because of the load of vertical. 5. Eccentric load generates greater stress in the structure than the load loaded upright. In fact, though, non-channeling can reduce the appearance of the tracks, partial load enhance the development of the cracks in the surface because of the existence of the cracks in the surface layer. Referencr books:

[1] Sha Qinglin.Early failure phenomenon and precaution of asphalt pavement of expressway[M].Peking:China communications press,(2001)

[2] Lu Hui,Sun Lijun.Analysis on asphalt pavement under tyre load by 3D finite element method[J].China civil engineering journal, 2004，37（7）：64-67

[3] Sun Lijun.Theory of behavior of asphalt pavement structure[M].Shanghai:Tongji university press: 2003,109-122

[4] Xie shui-you. Zheng Chuanchao. Effects of tire contact pressure on asphalt pavement structure[J].Journal of Chang'an University(Natural Science Edition), 2004, 24(1) :12-16

[5] Hu Xiaodi,Sun Lijun.Analysis of asphalt pavement structure under non-uniform distributed tire pressure with 3D finite element method[J]. Journal of Chang'an University(Natural Science Edition), 2003,5(3):15－20

[6] Yue，Zhong Qi，Svec，Otto J．.Effects of tire-pavement contact pressure distributions on the response of asphalt concrete pavements[J]．Canadian Journal of Civil Engineering，1995，22(5)：849—860

DOI: 10.1139/l95-103

[7] Sebaaly， Peter，Tabatabaee，Nader．Effect of tire pressure and type on response of flexible pavement[Z]．Transportation Research Record,1989，No．1227：ll5—127

[8] Wang Yang,Liu Zhaojin.The influence of characteristics of vehicle load on pavement structure [J]．Liaoning construction material，2004，3(3)：69-70

[9] Bi Yufeng,Sun Lijun. Research on Test Method of Asphalt Mixture's Shearing Properties[J],Journal of Tongji University(Natural Science Edition) ,2005,33(8): 1036-1040

[10] Lu Weimin. Asphalt Mixture Design Theory and Method[M],Shanghai: Tongji University Publishing Company,(2001)

[11] Li Feng, Sun Li-jun. Finite Element Analysis of Top-Down Cracking in Asphalt Pavement[J], Journal of Highway and Transportation Research and Development, 2006，23(6)：1－4