驻波比法测定黄土含水量的标定试验研究

CALIBRATION OF STANDING-WAVE RATIO SENSORS FOR DETERMINING WATER CONTENT OF LOESS

为提高驻波比(SWR)法测定黄土含水量的精度,对SWR土壤水分传感器进行标定试验,分别通过SWR法与烘干法测定Q3黄土和古土壤的含水率并进行对比分析,探讨干密度、结构性和土质差异对SWR土壤水分传感器测试结果的影响,并建立相关数学修正模型。试验结果表明,SWR法含水率测量值较烘干法偏高,干密度变化对SWR法测量结果的影响不可忽略;通过建立考虑干密度影响的经验修正模型对SWR法测量值进行修正,当体积含水率9.2%≤θw≤39.9%时,误差可控制在2%以内;当39.9%≤θw≤46.3%时,误差可控制在3%以内,总体修正效果优于SWR法与烘干法测量数据通过三次曲线拟合建立的修正公式;土的结构性对SWR法测量结果影响不明显,可采用重塑土的室内标定试验代替现场标定试验;黄土与古土壤因土质差异,应分别建立修正模型。

The calibration test was carried out to improve the measurement accuracy of the standing-wave ratio(SWR) sensor. The effect of dry density,structure properties and soil texture on soil-water content measured with the SWR sensor was explored. The mathematic correction models were established on the basis of the measured soil-water content of Q3 loess and paleosol with the SWR sensor and the oven-drying method. The use of the factory-supplied parameters resulted in an overestimation of soil-water content compared to the one measured with oven-drying method. The effect of the variation of dry density on the measurements of sensor should not be neglected. The correction model of soil-water contents for SWR sensor was established considering the effect of dry density. The corrected results with the model were proved better than those based on the cubic fitting equation of regression analysis between θv and θw determined in the laboratory. When the volumetric water content was in the range of 9.2% to 39.9%,the adjusted soil-water content was within 2%. While the volumetric water content was 39.9% to 46.3%,the adjusted soil-water content was within 3%. No statistically significant difference of soil-water contents was observed between the undisturbed and the remoulded samples. There were notable differences between the loess and the paleosol in soil texture and therefore the corresponding calibration models should be established separately.