冲击荷载作用下地基土变形及动力特性

为研究冲击荷载作用下地基土变形及动力特性,在ABAQUS框架内,采用Mohr-Coulomb模型、刚体冲击荷载、非线性大变形有限元算法及ALE(arbitrary lagrangian eulerian)自适应技术,计算了变形、应力和加速度。计算与现场试验结果基本一致,验证了模型的合理性。以该模型为基础,研究了不同能级、不同冲击次数、不同土体弹模对地基土体变形、应力、速度及加速度的影响。结果表明:夯沉量、隆起高度与夯击能呈线性关系,夯沉量和弹性模量近似呈线性关系;冲击荷载作用下土体呈弹塑性变形→弹性变形逐渐恢复→仅剩塑性沉降变形;冲击能量沿40°～45°向下传递且不断衰减,在施工过程宜合理确定夯间距,分遍错位夯实,确保土体得以有效处理;竖向应力时程曲线呈近似三角形形状,仅出现一次峰值应力。

Deformation and Dynamic Characteristics of Foundation Soil under Impact Loads

In order to study the deformation and dynamic characteristics of foundation soil under impact loads, Mohr-Coulomb model, rigid body impact loads, non-linear large deformation finite element method and ALE adaptive technology in ABAQUS finite element program are used to analyze the deformation, stress and acceleration. Comparing with the actual monitoring data, the results indicate that the calculated results acquired in the analysis are close to the actual data,which verifies the rationality of the model.Based on the model, the effects of different energy levels, different impact times and different elastic modulus of soil on the deformation, stress, velocity and acceleration of foundation soil are studied. The results show :1) there is a linear relationship between tamping energy deformation and deformation elastic modulus; 2) under impact loads, the soil presents elastic-plastic deformation to elastic deformation and gradually recovers only residual plastic settlement deformation; 3) impact energy transfers downward and decreases continuously from 40~45°. In the construction process, it is advisable to determine the compaction spacing reasonably and to tamp the soil in dislocation in order to ensure the effective treatment of the soil mass. 4) The vertical stress time history curve is approximately triangular, and only one peak stress appears.