An experimental study of calibration of soil moisture content by using the frequency domain reflectometry
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摘要: 对滑坡体土壤含水率进行长期和连续的监测，有利于对滑坡体的变形分析和安全预警。为了提高频域反射分析法（FDR法）测量土壤含水率的精度，通过室内标定和现场标定相结合的方式，对使用FDR法测定野外现场滑坡土壤含水率进行了标定。通过对比分析FDR法和烘干法测得的土壤含水率数据，探讨电压信号、含水率、绝对误差和相对误差之间的对应关系，并建立函数模型。试验结果表明：FDR法测定的土壤含水率较烘干法偏高；通过线性、多次曲线及指数形式对试验数据进行拟合和回归分析，最终确定四次曲线作为标定方式，标定后测得的土壤含水率精度明显提高，平均绝对误差可控制在2%以内。该方法可用于类似条件下FDR法测定土壤含水率的标定。Abstract: Long-term and continuous monitoring of soil moisture content in a landslide body is important for the analysis and safety warning of landslides. Based on the frequency domain reflectometry (FDR), the principle of measuring soil moisture content is described in this paper. In order to improve the accuracy of soil water content measured by the FDR method, the soil moisture content of the landslides near the Jietai Temple is calibrated by the combination of indoor and field calibration methods, respectively. By comparing and analyzing the data of soil moisture measured by the FDR method and drying method, the corresponding relationship between the voltage signal, water content, absolute error and relative error is discussed, and a function model is established. The test results show that the soil moisture content measured by the FDR method is higher than that of the drying method. Through fitting and regression analyses of the test data with linear, multiple power curves and exponential forms, the four power curve is determined as the calibration method. The accuracy of soil moisture content measured after calibration is obviously improved, and the mean absolute error can be controlled within 2%. The calibration curve can be applied to the determination of soil moisture content with the FDR method in the landslide near the Jietai Temple and other similar areas.
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