| Collapsible loess, a special kind of soil, is widely distributed in Northwest, North China, Shandong, Liaoning Province and other areas, which accounts about 450,000 square kilometers. With the advance of western development and construction of major energy engineering projects in western China, it has become an urgent issue to treat deep collapsible,loess economically and efficiently and to change the traditional layer-wise dynamic compaction, rolling compaction, lime-soil compaction pile and other foundation treatment with high cost and long construction time. Based on this, the present study has a theoretical and practical significance.The paper is based on a 800,000-square kms dynamic compaction foundation treatment in a moving and reconstruction project of CNPC(China National Petrolem Corporation),which is the first project to use the 15000kN.m-ultra-high dynamic compaction to treat deep collapsible loess. The paper introduces the dynamic compaction parameter, construction requirements, laboratory test, the static load test, cone penetration test, permeability test before and after compaction, which reaches a good achievement. And it also derives the predicted formula of high energy dynamic compaction in effective depth consolidation. It aims to provide experiences to promotion of dynamic compaction in loess areas and reference data to revise of dynamic compaction in the present foundation treatment norms.On the base, the paper builds a finite element numerical model, ABAQUS analysing the stress and strain of soil and effect of foundation solidation. This model is a explicit dynamic analysis model and can precisely solve problems similar to dynamic compaction and other complex problems of non-linear dynamics. In this model, the dynamic compaction is simplified into an axisymmetric problem. It considers the large-deformation effect and applies the analysis of erosion units to make sure the stability of meshing in computation process and remove the influence of unit distortion. |
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