Interaction And Back-Analysis Of Multi-Slabs On Layered Foundation

To the engineering problem of nondestructive testing and evaluation for rigid pavement and airfield pavement,an efficient and reliable numerical procedure for back calculating material properties of multiple slabs on multi-layered foundation through the data measured from in-situ falling weight deflectometer (FWD) tests is presented.As the preliminary step,a simplified approach based on spline semi-analytical method is proposed for evaluating flexibility coefficient of layered plane (or space) elastic foundation. At the second step,the semi-analytical method is combined with a finite element method (four nodal element,three nodal element and cubic spline element),and a computational method is developed to analyze the response of multiple,jointed slabs subject to static load. Thirdly,as for dynamic multi-slabs model,a simplified visco-elastic foundation that is modeled by a series of distributed springs and dashpots is adopted to conduct dynamic analysis of multi-slabs. In the case of infinite media,according to the complex-damping principle,the dynamic flexibility coefficient can be obtained by solving Lagrange's equation. And the spline semi-analytical method and the finite element method are combined through equilibrium and compatibility considerations at the soil-foundation interface to analyze the dynamic response of multi-slabs on visco-elastic soil.Furthermore,the data of falling weight deflectometer (FWD) and the system identification method are jointly used in conjunction with the proposed procedure for estimating material properties from responses of multi-slabs on foundation. The analysis is based on quasi-static linear elastic,dynamic frequency domain fitting and dynamic time domain fitting. The theoretical results show that (I) System identification method is an efficient back calculationapproach that can converge to a solution quickly in a wide rang of initial values of modulus.(2) Good agreement between measurement and prediction can be achieved. On the ground of above work,the deflection data from in-situ falling weight deflectometer(FWD) tests are used to determine the pavement material,which include rigid pavement,airfield and flexible pavement It has been shown that the back-calculating program can beadapted to these situations. Therefore a practical and versatile analysis methodology isestablished for the future study on evaluation of capacity of pavement. This work described herein has been conducted as part of National Outstanding YouthScience Fund and Trans-Century Training Program Foundation for the Talents offered by theMinistry of Education of China.