考虑桩土相互作用的低应变基桩缺陷的定量分析

Low Strain Quantitative Analysis of Pile Defects with Pile-Soil Interaction

为了在低应变条件下建立考虑桩土相互作用的基桩缺陷定量分析方法,研究了不同桩土相互作用阻尼系数时速度波沿桩身的衰减规律.应用一维波动理论求解了瞬态锤击作用下桩土相互作用的定解问题,得到了不同桩侧土阻尼系数时桩的速度响应,论证了速度波的衰减是时间和桩侧土阻尼系数的函数.利用速度波的衰减规律和缺陷处能量的分配规律,得到考虑了桩土相互作用影响的缺陷定量分析关系式.为了验证这个关系式的适用性,分别对完整桩、缩颈桩和扩颈桩进行了不同纵向应力下的模型试验.通过完整桩试验反演阻尼系数,利用得到的阻尼系数和缺陷桩桩顶速度响应曲线进行缺陷定量分析,结果得到的桩缺陷程度与实际缺陷程度基本一致,误差在6%以内.结果证明,缺陷定量分析关系式确定的桩缺陷程度与实际缺陷程度是基本一致的,建立的基桩缺陷定量分析方法是可行的.

In order to establish a low strain method of quantitative analysis of pile defects considering pile-soil interaction,the attenuation rule of velocity wave along pile shaft was studied under different pile-soil interaction damping coefficients. In the research, the fixed solution problem of pile-soil interaction under transient impact was solved with one-dimensional wave theory. Then the velocity responses of pile under different damping coefficients were obtained, The results show that the attenuation rule of velocity wave was a function of time and damping coefficient. With the attenuation rule and the energy distribution rule at the defect, the relational expression for quantitative analysis of pile defect considering pile-soil interaction was obtained. To validate the applicability of the relation, the model tests of an integrity pile, a necked pile and an enlarged pile were carried out under different longitudinal stress. The damping coefficients were inversed from the test results of the integrity pile.Based on the damping coefficients and the testing curves of defect piles, the quantitative analyses of pile defects were performed. The results show that the defect degrees obtained from the analyses are consistent with the reality, and the errors are lower than 6%. Therefore the method of quantitative analysis of pile defects established here is feasible.