桩土相互作用阻尼系数试验结果与其他结果的对比

当前如何考虑桩土之间的相互作用并将其定量化是限制基桩缺陷定量分析方法准确性的重要因素。低应变条件下将土对桩的作用以粘滞阻尼器考虑,通过桩土相互作用试验测定桩顶速度响应并结合理论分析结果确定桩侧土在不同状态下的桩土相互作用阻尼系数。在现有的一些研究中也有一些其他确定阻尼系数的方法,例如经过动力平衡分析得到桩侧土单位长度阻尼系数的理论表达式,实际测定表达式中各个参数即可确定相应阻尼系数;也有通过多次动静对比试验得到的阻尼系数经验值。由于各个阻尼系数定义并不相同,参考试验时的实际情况确定各个参数,进而将不同定义的阻尼系数转化为同一量纲,分析了不同阻尼系数的差距,发现通过多次动静对比试验得到的Case阻尼系数由于是在大应变情况下得到的,相对桩土相互作用试验得到的阻尼系数有较大差距,应用于低应变分析并不合适。而理论推导得到的阻尼系数相对试验结果虽然并不一致,但是他们之间存在一定的相关性,进而经过拟合分析发现两者之间的比值可以表示为剪切波速的函数。

Comparison between the Experimental Result of Pile-soil Interaction Damping Coefficient and Other Results

Now,the significant factor which restricts the accuracy of quantitative analysis for pile defect is how to reckon the pile-soil interaction in quantitatively.Reducing the action of soil to pile to viscous damper as strain is low,we can determine the damping coefficients of the soil around the pile in different conditions with the result of theoretical analysis and the velocity response on pile top obtained with pile-soil interaction test.There are also other methods to determine damping coefficient,such as the empirical value of damping coefficient got with static and dynamic experiments,the theoretical expression of the pile-soil interaction damping coefficient per unit length obtained with power balance analysis.As the definitions of damping coefficients are different,we should define the parameters according to the practical situation before invert the damping coefficients of different definition into the same dimension.Analyzing the difference among damping coefficients,as Case damping coefficient is obtained in high strain,it is unsuitable to use Case damping coefficient in low strain analysis.Although the damping coefficient got with theoretical derivation is inconsistent with the experimental result,there is correlation between them.With the result of fitting analysis,the ratio between them can be expressed as a function of shear wave velocity.