Settlement Property And Dynamic Compaction Improvement Parameters Study For High Crushed Stone Embankment

With the rapid development of expressway,more and more high embankment was constructed and how to improve compaction quality or decrease post-construction settlement of embankment should be solved quickly.Dynamic compaction has been adopted to improve embankment for its wide adaptation to the soils,remarkable effects,economical building material even no mateatical,low cost and short construction period etc.However,some problems in the reinforcement mechanism and design theory was exised due to the shortage of the design standard and theoretical basis of dynamic compaction,and the design of its construction parameters has been experiential and confused.In this case,it has to be determined by means of small scale tests and caused the result for the architects act blindly and randomly.In combination with the dynamic compaction construction for Changde-Jishou expressway,dynamic compaction methed to improve crushed-stone embankment is systematically studied.Firstly,based on comprehending the recent study of dynamic compaction technique and engineering practice,deepcutting study on tamping-strengthening principle,mechanism of tamping-energy transmission and mechanism of faster consolidation settlement combining dynamic compaction with roller compaction is carried out.Secondly,considering the characteristic of non-perfect elastic collision and the theory of dynamic foundation in half space, vibration equilibrant equation of hammer is established and the process of impact is analyzed.Solutions of impact stress and deformation are also abtained,furthermore, the influence factors and orderliness of impact stress and deformation are researched in theory.Thirdly,the paper determines the parameters of dynamic compaction and analyzes the improvement effect and deformation orderliness via a novelty in-situ experiment.The strengthening effect on Crushed Red-sandstone embankment is analyzed comparing with Crushed Limestone embankment.Finally,3D FEM model of dynamic compaction is established.The numerical simulation of whole dynamic process is carried out and the coutours of displacement & stress are obtained with explicit dynamic finite element program Ansys/Ls-dyna.The results show that the orderliness of stress & strain are quite consistant with the experiment results and theoretical analysis results.All above results illuminate the correctness of theoretical analysis,rationality of experiment method,reliability of experiment results and the accuracy for numerical simulation by Ansys/Ls-dyna.