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By K.W. Hau, G.R. McDowell, G.D. Airey and S.F. Brown

Predicting the Repeated Load Behaviour of Pavement Subgrades Using the Three-surface Kinematic Hardening Model. By K.W. Hau, G.R. McDowell, G.D. Airey and S.F. Brown. Presentation Outline. Introduction Finite element analysis of a 3-layer pavement Model predictions under cyclic loading

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By K.W. Hau, G.R. McDowell, G.D. Airey and S.F. Brown

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  1. Predicting the Repeated Load Behaviour of Pavement Subgrades Using the Three-surface Kinematic Hardening Model By K.W. Hau, G.R. McDowell, G.D. Airey and S.F. Brown

  2. Presentation Outline • Introduction • Finite element analysis of a 3-layer pavement • Model predictions under cyclic loading • Conclusions

  3. Introduction • Current pavement design methods are empirical based • Objective: apply fundamental soil mechanics principles to pavement engineering • FE analysis of 3-layer pavement • Capability of the 3-SKH model in predicting soil behaviour under cyclic loading

  4. Cross-section of a Pavement Moving wheel load Bituminous Granular Sub-base Subgrade

  5. FE Mesh • 8-noded quadrilateral elements • Wheel load of 600 kPa • 50 cycles

  6. Results

  7. Problem • Common nodes at the subgrade interface • Elastic layer will pull the soil in tension • Overcome by applying equivalent stress • Permanent strain obtained by assuming the top two layers will follow the surface of the clay

  8. Problem • Comparison between CRISP and layered elastic theory • The 3-SKH model poorly predicts shear strain under low stress pulses

  9. Model Predictions • Simple triaxial simulation on isotropic normally consolidated soil • Model parameters • 20 isotropic cycles with p' =100 kPa

  10. Results

  11. Results

  12. Problem • Isotropically normally consolidated soil • Accumulation of negative permanent shear strain for low stress pulses

  13. Results

  14. Results u u u u u u = unloading

  15. Results • Load pulses cycle in the way shown Kinematic surface

  16. Conclusions • The 3-SKH model predicts essential features of soil behaviour under cyclic loading • Poor prediction of shear strain for small stress pulse • Should not be a serious problem in pavement modelling

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