基于时域反射技术(TDR)的黄土湿陷原位评价研究

In-situ evaluation of collapsible loess through time-domain reflectometry

现有黄土湿陷评价方法具有取样扰动、耗时和费用高等缺点,急需探索原位评价黄土湿陷的新技术。基于时域反射技术(TDR)原位测试黄土介电常数和电导率,计算干密度和质量含水率。依据原位所测黄土干密度、质量含水率以及物性指标(相对质量密度、液塑限),采用经验模型对黄土进行湿陷评价。结果表明,TDR原位测试黄土干密度和室内烘干法结果相对误差在±6%以内,测试黄土质量含水率和室内烘干法结果绝对误差在±0.02以内。另一方面,基于经验的湿陷评价模型,利用TDR原位所测干密度、质量含水率以及物性指标不仅可判定黄土有无湿陷,且具有区分强烈和中等湿陷程度的潜力。本研究丰富了黄土地区勘察技术手段,为黄土湿陷原位勘察提供有益探索。

It is urgent to propose a new technique for the in-situ evaluation of collapsible loess,as the existing methods are time-and cost-consuming,and may lead to inevitable sampling disturbance.The gravimetric water content and dry density of loess are computed by the dielectric permittivity and electrical conductivity measured by the time-domain reflectometry(TDR)in the field.The collapsibility of loess is evaluated using the computed gravimetric water content,dry density of loess and physical properties of soil(i.e.,specific gravity,plastic and liquid limits)through empirical relationships.Comparing with those obtained by the oven-dried method,the dry density and gravimetric water content of loess by the TDR are within a relative error of±6%and an absolute error of±0.02,respectively.On the other hand,empirical relationships relating the gravimetric water content,dry density and soil physical properties to the collapsibility show a good performance to evaluate collapsible loess.Moreover,the strong and medium collapsible loess may also be characterized.This study extends the techniques of site investigation in loess regions and provides beneficial explorations for the in-situ evaluation of collapsible loess.