scholarly journals Numerical Method of Flexible Pavement considering Moisture and Stress Sensitivity of Subgrade Soils

2019 ◽  
Vol 2019 ◽  
pp. 1-10 ◽  
Author(s):  
Jue Li ◽  
Jianlong Zheng ◽  
Yongsheng Yao ◽  
Junhui Zhang ◽  
Junhui Peng
Keyword(s):  
Tensile Stress ◽  
Compressive Strain ◽  
Flexible Pavements ◽  
Fatigue Cracking ◽  
Flexible Pavement ◽  
Stress Sensitivity ◽  
Fem Model ◽  
Moisture Condition ◽  
Subgrade Soils ◽  
Moisture Variation

Weaknesses of the subgrade structure induce the asphalt surface diseases and shorten the service life of flexible pavement. However, the resilient modulus (Mr) of subgrade soils is difficult to be evaluated directly since the subgrade is hidden and covered by the granular or asphalt layer. This study aimed to establish a numerical approach to predict the dynamic behavior of flexible pavements considering the stress sensitivity and moisture variation of subgrade soils. Firstly, 2D FEM simulations of flexible pavements were performed with half-sine loadings. A constitutive model of subgrade soils was proposed to incorporate soil suction and octahedral shear stress. It was validated using the laboratory triaxial test data of 3 selected soils. Then, the developed model was programmed by the user-defined material subroutine (UMAT) in the software ABAQUS. Subsequently, the validity of FEM model was verified by the laboratory tank model. Finally, the effect of moisture contents on the dynamic response of pavement structures was studied by tensile stress and vertical compressive strain. Results show that the surface deflection of the FEM model is similar to that of the actual pavement structure with the R2 of 98.44%. The developed UMAT program is reliable since the distribution of Mr in the FEM model is influenced by the stress and moisture condition of subgrade soils. When the moisture content is increased by 63%, the average Mr of subgrade soils is decreased by 18.7%. Meanwhile, the stiffness softening of subgrade soils increases vertical compressive strain at the top of the subgrade and the tensile stress at the bottom of the surface layer. It is interesting that the developed model can be applied to analyze the fatigue cracking of both subgrade and surface layers in the future.

Mechanistic–empirical damage analysis and impacts of reduced tire pressure on thaw weakened flexible pavements using the AI and MEPDG models

2012 ◽  
Vol 39 (7) ◽  
pp. 812-823
Author(s):  
Leonnie Kavanagh ◽  
Ahmed Shalaby
Keyword(s):  
Fatigue Damage ◽  
Flexible Pavements ◽  
Fatigue Cracking ◽  
Flexible Pavement ◽  
T Test ◽  
Pavement Design ◽  
Damage Analysis ◽  
Confidence Limits ◽  
Tire Pressure ◽  
Design Guide

A damage analysis was conducted on a spring weight restricted flexible pavement to quantify the effects of reduced tire pressure on pavement life and to compare the damage predictions from the Asphalt Institute (AI) and the Mechanistic Empirical Pavement Design Guide (MEPDG) models. The models were used to predict the number of repetitions to fatigue and rutting failure at three maximum loads and at high and low tire pressures. Based on the results, the AI and MEPDG predictions were statistically different for both fatigue cracking and rutting damage, based on the t-test at 95% confidence limits. The AI model predicted 31% lower fatigue damage than the MEPDG, but 56% higher rutting damage. However, both models produced similar trends in predicting the relative effects of reduced tire pressure and load levels on pavement life. The methodology and results of the analysis are presented in this paper.

Mechanical Response of Asphalt Pavement under Overloading

2013 ◽  
Vol 361-363 ◽  
pp. 1869-1872 ◽  
Author(s):  
Sheng Jie Liu ◽  
Qing Long You
Keyword(s):  
Tensile Stress ◽  
Mechanical Response ◽  
Asphalt Pavement ◽  
Compressive Strain ◽  
Flexible Pavement ◽  
Load Application ◽  
Rigid Base ◽  
Linear Elastic ◽  
Application Procedure ◽  
Surface Increase

This paper examines theoretically the possible mechanical response changes on both bituminous pavement structure using linear elastic method, the change regulation of deflection,stress on the bottom of base and subbase and compress strain on the top of subgrades between semi-rigid base and flexible pavement pavement. In the load application procedure, a dual wheel with the a series of pressure was chosen.The results have shown that the deflection tensile stress and subgrade compressive strain on the surface increase with the increase of axle load and they would result in serious effect of overloading on the earlier damage of asphalt pavement.

scholarly journals Experimental Investigation on Design of Thickness for Flexible Pavement Subgrade Soils using CBR Approach

2020 ◽  
Vol 184 ◽  
pp. 01087
Author(s):  
Y. Kamala Raju ◽  
C. Vivek Kumar
Keyword(s):  
Experimental Investigation ◽  
Bearing Capacity ◽  
Flexible Pavements ◽  
Flexible Pavement ◽  
California Bearing Ratio ◽  
Cement Concrete ◽  
Wheel Load ◽  
Subgrade Soils ◽  
Pavement Thickness

This paper aim’s to ensure that the transmitted stresses due to wheel load are adequately reduced, so that they will not exceed bearing capacity of the sub- grade. This present study deals with the design thickness of flexible pavements, where majority of the Indian roads are flexible pavements having bituminous layer. Earlier, due to the scarcity of cement and India went for flexible pavements with bituminous toppings. This flexible pavement is preferred over cement concrete roads as they have a great advantage that these can be strengthened and improved in stages with the growth of traffic. With a major advantage of this roads and their surfaces milled and recycled for rehabilitation. The flexible pavements are less expensive also about initial investment and maintenance. In this present study, the flexible pavement thickness is designed for both sub grade soils as per IRC:37-2001 code and its pavement thickness is calculated by California Bearing Ratio (CBR)method.

Middle-Up Cracking Potential in Flexible Pavements with Stabilized Foundations

2021 ◽  
pp. 036119812199069
Author(s):  
Mostafa Nakhaei ◽  
David H. Timm
Keyword(s):  
Tensile Strain ◽  
Elevated Temperatures ◽  
Compressive Strain ◽  
Flexible Pavements ◽  
Fatigue Cracking ◽  
Full Scale ◽  
Computational Simulations ◽  
Cracking Potential ◽  
Maximum Tensile Strain ◽  
New Perspective

This investigation presents a new perspective on the structural behavior of stabilized foundation pavements through full-scale testing and simulation where the historical premise of bottom-up fatigue cracking has been challenged. Two full-scale pavement sections were constructed at the National Center for Asphalt Technology Test Track in 2018. One section featured a stabilized foundation under the asphalt layers while the other was a thick-lift asphalt section on conventional base and subgrade materials. Both sections were embedded with pavement response instrumentation and their behavior was observed over time under accelerated truck trafficking. In addition, computational simulations were executed to explain the observed behavior. The strain measurement at the bottom of the asphalt concrete (AC) for the thick-lift section showed a familiar trend in which the tensile strain at the bottom of the AC increased exponentially with temperature. In contrast, the strain at the bottom of the AC in the stabilized foundation pavement was predominantly in compression at elevated temperatures. Further analysis revealed that compressive strain at the bottom of the AC increased exponentially with temperature similar to conventional flexible pavements but with a reversed sign. The results were confirmed by falling weight deflectometer testing that was conducted directly above the embedded pavement sensors. Computational simulations confirmed the behavior and suggested that the maximum tensile strain could occur at shallower depths, possibly mid-depth of the AC, in stabilized foundation pavements. This indicates stabilized foundation pavements could be prone to middle-up cracking and subsequent precautions should be taken to avoid middle-up fatigue cracking.

Consideration of the Cross-Anisotropy of Different Materials of the Asphalt Surface Layer and Temperature to Determine Pavement Responses

2021 ◽  
Vol 13 (1) ◽  
pp. 140-151
Author(s):  
Minrui Guo ◽  
Xinglin Zhou
Keyword(s):  
Surface Layer ◽  
High Temperatures ◽  
Low Temperatures ◽  
Compressive Strain ◽  
Fatigue Cracking ◽  
Element Model ◽  
Rate Of Change ◽  
Temperature Relationship ◽  
The Cross ◽  
Cross Anisotropy

The effects of the cross-anisotropy of different materials of the asphalt surface layer and the depth-temperature relationship on pavement responses and damage are investigated. A three-dimensional Finite-Element Model (FEM) of the pavement, which considers the depth-temperature relationship of the surface layer under moving tire load, is developed. Pavement damage models are established to evaluate the damage ratio for primary rutting and fatigue cracking. The results show that the compressive strain at the bottom of the surface layer increases as the temperature increases, and the cross-anisotropy (n-value) decreases, indicating that a decrease in the horizontal modulus of different materials of the surface layer increases the damage ratio for primary rutting at high temperatures. The tensile strain at the bottom of the surface layer declines as the n-value increases to 1. For the same change in the n-value, the rate of change of the damage ratio for fatigue cracking is greater at low temperatures than at high temperatures, demonstrating that the number of allowable load repetitions is more sensitive at low temperatures. In addition, the effect of cross-anisotropy and temperature on the vertical stress are larger on the top of the base than in the subbase and subgrade.

scholarly journals Fatigue Resistance and Cracking Mechanism of Semi-Flexible Pavement Mixture

Materials ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5277
Author(s):  
Shiqi Wang ◽  
Huanyun Zhou ◽  
Xianhua Chen ◽  
Minghui Gong ◽  
Jinxiang Hong ◽  
...  
Keyword(s):  
Low Temperature ◽  
Fatigue Resistance ◽  
Stress Ratio ◽  
Asphalt Binder ◽  
Asphalt Mixture ◽  
Fatigue Cracking ◽  
Flexible Pavement ◽  
The Poor ◽  
Grouting Material ◽  
Cracking Mechanism

Semi-flexible pavement (SFP) is widely used in recent years because of its good rutting resistance, but it is easy to crack under traffic loads. A large number of studies are aimed at improving its crack resistance. However, the understanding of its fatigue resistance and fatigue-cracking mechanism is limited. Therefore, the semi-circular bending (SCB) fatigue test is used to evaluate the fatigue resistance of the SFP mixture. SCB fatigue tests under different temperature values and stress ratio were used to characterize the fatigue life of the SFP mixture, and its laboratory fatigue prediction model was established. The distribution of various phases of the SFP mixture in the fracture surface was analyzed by digital image processing technology, and its fatigue cracking mechanism was analyzed. The results show that the SFP mixture has better fatigue resistance under low temperature and low stress ratio, while its fatigue resistance under other environmental and load conditions is worse than that of asphalt mixture. The main reason for the poor fatigue resistance of the SFP mixture is the poor deformation capacity and low strength of grouting materials. Furthermore, the performance difference between grouting material and the asphalt binder is large, which leads to the difference of fatigue cracking mechanism of the SFP mixture under different conditions. Under the fatigue load, the weak position of the SFP mixture at a low temperature is asphalt binder and its interface with other materials, while at medium and high temperatures, the weak position of the SFP mixture is inside the grouting material. The research provides a basis for the calculation of the service life of the SFP structure, provides a reference for the improvement direction of the SFP mixture composition and internal structure.

AYMA: Mechanistic Probabilistic System To Evaluate Flexible Pavement Performance

1998 ◽  
Vol 1629 (1) ◽  
pp. 137-148 ◽  
Author(s):  
Manuel Ayres ◽  
Matthew W. Witczak
Keyword(s):  
Low Temperature ◽  
Mechanistic Model ◽  
Permanent Deformation ◽  
Probabilistic Approach ◽  
Fatigue Cracking ◽  
Flexible Pavement ◽  
Analysis And Design ◽  
Mechanistic Approach ◽  
Low Temperature Cracking ◽  
User Friendly

A new rational mechanistic model for analysis and design of flexible pavement systems has been developed. Furthermore, a fundamental probabilistic approach was incorporated into this system to account for the uncertainty of material and environmental conditions. The system was integrated in a user-friendly Windows program with a variety of user-selected options that include widely used models and those recently developed in the Strategic Highway Research Program project. Three basic types of distress can be investigated separately or all together, including fatigue cracking, permanent deformation, and low-temperature cracking. The mechanistic approach makes use of the JULEA layered elastic analysis program to obtain pavement response. The system provides optional deterministic and probabilistic solutions, accounts for aging and temperature effects over the asphalt materials, variable interface friction, multiple wheel loads, and user-selected locations for analysis. Tabular and graphical results provide expected distress values for each month as well as their variability, probability of failure, and assessment of the overall reliability of the pavement relative to each type of distress for a user-selected failure criterion. Only the load-associated module of AYMA is presented; a separate work describes the low-temperature cracking analysis.

Highly flexible and stretchable MWCNT/HEPCP nanocomposites with integrated near-IR, temperature and stress sensitivity for electronic skin

2018 ◽  
Vol 6 (22) ◽  
pp. 5877-5887 ◽  
Author(s):  
Mei Li ◽  
Yunming Wang ◽  
Yun Zhang ◽  
Huamin Zhou ◽  
Zhigao Huang ◽  
...  
Keyword(s):  
Tensile Stress ◽  
High Sensitivity ◽  
Stress Sensitivity ◽  
Near Ir ◽  
Electronic Skin

MWCNT/HEPCP nanocomposites realized high sensitivity to IR, temperature and tensile stress, together with outstanding flexibility and stretchability for electronic skin.

Sign in / Sign up

Export Citation Format

Share Document