动力固结的显式非线性数值分析

Explicit Non-linear Numerical Analysis of Dynamic Compaction

动力固结是一种有效的地基加固方法,应用显式瞬态非线性有限元分析了动力固结时夯锤对地基土的冲击碰撞过程,分析中考虑了碰撞中出现的材料非线性、几何非线性、接触非线性、运动非线性以及它们之间相互耦合的特性,得到了不同落距和不同锤重条件下夯锤的动能迁移、撞击力时间历程、夯锤下应力分布及土的能量吸收、变形和密度的时间历程,并得到了它们之间的相互关系,分析结果表明:位移时程与应力时程并不同步,位移滞后于应力;夯坑深度与夯锤动能的自然对数成正比;夯锤的初始动能与最大撞击力并不一一对应;有限元分析反映了动力固结过程的基本规律,再现了夯锤与土体碰撞的整个过程。

Dynamic compaction is an efficient ground improvement technique.The collision process of dynamic compaction （DC） is studied using nonlinear explicit dynamic finite element. In this study many characters are taken into account, such as material nonlinearity,geometric nonlinearity, contact nonlinearity, movement nonlinearity and coupling characters of them, etc.The variation processes of kinetic energy losing and collision force of hammer and energy transference, strain and density of soil have been obtained at different height and weight of hammer. Comparisons are made of the energy transference of hammer, collision force of hammers with different initial kinetic energy, strain and stress of soil.The analysis results indicated that strain is nonsynchronous with stress; cavity depth is proportional to the natural logarithm of hammer＇ s kinetic energy; the relationship of hammer＇ s initial kinetic energy and maximum collision force isn＇ t one-to-one correspondence. The regularity of DC is revealed by the simalation, the whole process of hammer and soil body collision is reappeared as well.