基于体应变的强夯加固范围研究

Reinforcement range of dynamic compaction based on volumetric strain

通过数值模拟分析地基的强夯加固效果,把夯后地基土的体应变与工程要求的干密度联系起来,用控制体应变作为评价加固范围的标准。通过对数值模拟及试验数据的分析发现,夯击冲量越大,加固效果越好。相同夯击能可以产生不同加固效果的规律,得出了用夯击冲量替代夯击能作为施工参数的控制标准更为合理的结论。改进了夯锤尺寸影响强夯加固效果的研究方法,分析时固定夯锤厚度比固定夯锤质量更具归一性。研究表明,在土性参数相同的条件下,夯击沉降量仅与单位面积夯击冲量有关,而加固深度不仅与单位面积夯击冲量有关,还与夯锤半径有关。在以控制体应变作为加固范围的评价标准、研究各参数影响规律的基础上,采用量纲分析法得到了加固范围的计算公式,并与工程实例进行对比分析,得到了强夯作用下土的干密度分布特征。所得结论对类似工程具有一定的参考价值。

The numerical simulation method is used to analyze the reinforcement effect of dynamic compaction. The volumetric strain of reinforced foundation and the required dry density are linked. The required volumetric strain is proposed as an evaluation standard to determine the reinforcement range. It can be found from both the numerical simulation and test data that the larger impulse leads to the better reinforcement, while a fixed tamping energy can lead to different reinforcement effects. Hence, it can be concluded that the tamping impulse is more suitable to be used as a control standard of construction parameters than tamping energy. In order to study the hammer size, a modified method is proposed. Besides, it is shown that if the parameters of soil are given, settlement will be only concerned with impulse per unit hammer area; while reinforcement depth will be concerned with both the impulse per unit hammer area and the radius of hammer. The influence of tamping number is also studied. On the basis of setting the required volumetric strain as the evaluation standard and analyzing the influences of major parameters, the formulas of reinforcement range are developed with dimensional analysis method. The proposed procedure is used to predict the reinforcement range of a foundation by dynamic compaction, it is found that the calculated dry density distribution of reinforced foundation is in agreement with measurements, which demonstrates the proposed procedure is applicable.