饱和土剪切波速在基桩缺陷定量分析中的应用研究

在基桩缺陷定量分析中准确定量地描述桩土之间的相互作用是非常重要的。以黏滞阻尼器模拟桩土之间的相互作用,对6种饱和土进行了桩土相互作用模型试验和剪切波速试验。试验结果表明,可以对这些饱和土在土剪切波速与阻尼系数之间建立一致的相关关系。同样依据试验结果分析了试验阻尼系数和理论值的差别,得到了以剪切波速的函数表示的理论值修正系数。由桩身纵向振动响应解析解利用正交试验方法分析了阻尼系数、瞬态冲击力的脉冲宽度和幅值、桩弹性模量、桩密度、桩长以及桩截面积对速度波衰减过程的影响,确定了阻尼系数是影响速度波衰减的唯一显著因素,得到了速度波沿桩身的衰减规律。进而结合土剪切波速与阻尼系数之间的相关关系和桩身缺陷处的能量分配特性建立了利用土剪切波速和桩顶速度响应进行基桩缺陷定量分析的关系式。根据建立的关系式分析了利用剪切波速确定阻尼系数所带来的误差,结果证明由剪切波速最终得到的缺陷程度相对利用试验阻尼系数得到的结果误差一般在10%以内,所以利用剪切波速确定阻尼系数是可行的。

Application of saturated soil shear wave velocity in quantitative analysis of pile defects

It is very important to describe the pile-soil interaction accurately and quantitatively in quantitative analysis of pile defects.Simulating the pile-soil interaction with a viscous damper,the pile-soil interaction model experiment and the shear wave velocity experiment of six kinds of saturated soils are performed.The test results show that the consistent relation between soil shear wave velocity and damping coefficient can be established for these saturated soils.The difference between experimental damping coefficient and rational damping coefficient is also analyzed with the results,and the coefficient for correction for rational damping coefficient,which is a function of shear wave velocity,is achieved.With the analytical solution of pile response under longitudinal vibration,the influence of factors on the attenuation rules of velocity wave along pile shaft is studied.The factors include the damping coefficient,the impulse duration and amplitude of transient impact force,and the elastic ratio,density,length,sectional area of piles.With the result,it is confirmed that the only significant factor which influences the attenuation rules of velocity wave is the damping coefficient,and the attenuation rule of velocity wave is obtained.Then,the relational expression is established with the relation between the soil shear wave velocity and the damping coefficient and the energy distributing character at the defect to analyze pile defect quantitatively with soil shear wave velocity and velocity response of pile top.With the expression,the error of determining the damping coefficient with shear wave velocity is analyzed.The results show that most of the final errors in defect degrees are lower than 10% and it is feasible to determine the damping coefficient with shear wave velocity.