不同FDR传感器和计算模型测量土体质量含水率和干密度的对比研究

Comparison of the determination of soil gravimetric water content and dry density by using different FDR sensors and calculation models

频率反射技术(FDR)能够快速测得土体介电常数和电导率,并通过模型计算压实土体的质量含水率和干密度,是一种具有较好应用前景的土体压实质量快速检测方法。为此,通过标定试验和模型试验,研究了不同FDR传感器以及计算模型对压实土体质量含水率和干密度测量精度的影响。结果表明:不同厂家生产的FDR传感器测量数据差异较大,尤其对于土体电导率的量测结果,因此开展参数标定试验十分重要;对于采用电磁波反射和交流电桥法测土体介电常数和电导率的FDR传感器,其测得的数据对Yu与Drnevich、Bhuyan两种模型的拟合程度较高;Yu与Drnevich模型的计算结果较Bhuyan模型更接近烘干法与环刀法的测试结果,其计算得到的质量含水率绝对误差在±0.03以内,干密度相对误差在±6%之内。本研究可为FDR传感器和计算模型的选取提供参考,以推动FDR法的工程应用。

Frequency Reflection technology(FDR)is a method with a good application prospects to evaluate soil compaction quality quickly,which can measure the soil dielectric constant and electric conductivity directly by using FDR sensor,and calculate soil gravimetric water content and dry density subsequently.In this study,the calibration test and model test were conducted to investigate the influences of different FDR sensors and calculation models on the accuracy to determine gravimetric water content and dry density for compacted soils.The results show that the measured values for the sensors manufactured by different companies have a relatively large difference,especially for the value of electric conductivity.Thus,it is very important to carry out calibration tests before the use of FDR method to determine soil gravimetric water content and dry density.For the FDR sensor that integrates reflection technology of electromagnetic wave and AC bridge method to measure the soil dielectric constant and electric conductivity,the measurement data fit well to both models proposed by Yu-Drnevich and Bhuyan.Compared to Bhuyan’s model,the calculation result by using Yu-Drnevich′s model agrees better with the actual value measured by methods of cutting ring and oven,such as the absolute error of gravimetric water content is within±0.03,while the relative error for the dry density is within±6%.Finally,the results of this study are expected to provide reference for the selection of FDR sensor and calculation models,which could promote the application of FDR method in the engineering.