强夯法是一种加固某些土体的施工操作较为简单的方法,合理分析其夯击作用在土体中产生的动应力是工程实践中的关键环节之一.针对成都平原地区的典型土-石混合填土,通过现场夯击试验,测得了在4 000 kN·m的夯击能作用下土体中不同深度处的竖向夯击动应力,鉴于既有算法与试验值的差异,从两个方面确定了适于土-石混合填土夯击动应力的简单计算方法.一方面针对较为复杂的既有理论公式问题,采用敏感性分析与回归分析法,建立了以夯锤质量、夯锤落距、夯锤半径、土体密度、土体动力剪切模量、土体泊松比、土体阻尼比、夯锤入土的速度损失率等8个参数表征夯击点冲击应力的线性回归方程;另一方面采用竖向动应力传递指数对理想弹性静力学理论公式进行修正,得到了基于拟静力法的土体中夯击动应力计算表达式,进而可分析确定强夯有效加固深度.试验结果显示,土-石混合填土的竖向动应力传递指数约为1.673 57,土-石混合填土地层的强夯有效加固深度约为8.0 m.
Abstract
Dynamic compaction is one of the most convenient methods of ground improvement.It is crucial to reasonably analyze additional dynamic compressive stress on the compacted soil in practice.The typical mixed soil-rock fill in Chengdu plain is investigated in this study.The vertical dynamic stress at different depths in the soils subjected to dynamic compaction with an impact energy of 4 000 kN·m is tested in situ.Considering the difference between the observed results and those using the existing calculation methods,simplified and modified algorithms for the dynamic compressive stress are developed.On the one hand,parameter sensitivity analysis and linear regression analysis are conducted to simplify the existing complicated formula via eight parameters characterizing the surface impact stress including the mass of rammer,fall height,radius of the rammer,soil density,dynamic shear modulus,Poisson's ratio,damping ratio,as well as impact velocity loss rate of the rammer.On the other hand,based on the pseudo-static method,a modified formula of the vertical dynamic stress at different depths of the soil is provided via introducing a transfer index into the elastic static stress dispersion equation,and the modified formula can be employed to analyze the effective impact depth.The example of the mixed soil-rock fill from the field test demonstrates a transfer index of 1.673 57 and an effective impact depth of approximately 8.0 m..
关键词
强夯/现场试验/土-石混合填土/动应力/应力分布
Key words
dynamic compaction/field test/mixed soil-rock fill/dynamic compressive stress/stress distribution
维普
万方数据