Study On The Permanent Deformation Prediction Model Of Graded Crushed Stone Through Simulations

The thsis is supported by National Natural Science Foundation Project (No.50608007), Western Transportation construction Science and Technology Project of Ministry of Communication (No.2004 318 000 04) and China's postdoctoral Foundation Project (No.20060400673).Graded crushed stone is a kind of unbound material, which has the characteristics of having big plastic deformation, small stiffness and poor stress diffusivity, and in the situation of heavy traffic (big volume of traffic or more heavy vehicles), the unbound granular material will lead much more residual deformation or post-deformation. Many studies have shown that the rutting of granular material layer account for 59% of the total permanent deformation, so to control the rutting damage of flexible pavement, the study of the deformation characteristic of granular layer is of great significance.The basic test result of the raw materials indicated that the materials were good for research. Using the laboratory test methods to get the parameters of the graded crushed stone's resilient modulus of compression and the shear performance parameters. The result would be used in the ABAQUS simulate.The graded crushed stone permanent deformation test simulation scheme is developed by referring to foreign unbound granular material permanent deformation, resilient modulus test scheme and Chinese regulations of compactness and moisture content for base material. The diameter and height of simulation specimen was 100 mm and 200 mm respectively; the compactness was 96%, 98% and 100%; and the moisture content was OMC and OMC+2%; the type of load was haversine; the frequency was 1 HZ; the loading time was 0.1s and the interval time was 0.9s; the confining pressure was 35 kPa and 69kPa, the deviator stress was 1,3,5 multiple of the confining pressure respectively; the plastic parameters are tested in laboratory.The repeated load triaxial tests of graded crushed stone were simulated by the finite element software ABAQUS and a 2D finite element model was adopted. ABAQUS Mohr-Coulomb model was used to graded crushed stone for the high nonlinear characteristics of the constitutive relation of geotechnical. The paper took the evaluation of the forecast model of the permanent deformation at home and abroad, and compared the Tseng and Lytton model, Ayres model and the AASHTO 2002 model with the fitting curve of simulation results. Then we find it was correct of the simulationm, and the three kind of models are all not fit for the prediction of the unbound materials'permanent deformation. At the same time, we chose the Perez model which was based on the shakedown theory, using least square method to fit the simulation curve, and the correlation coefficient R2 was all more than 0.99. At last, we did regression analysis of the model parameters, and then we can get the forecast model of granular material permanent deformation.