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目的:建立含水率与介电常数间的经验关系模型是利用时域反射(TDR)技术测试土体含水率的关键。通过收集并建立包含45种土样418个试验数据点的数据库,提出一个土体质量含水率与表观介电常数间的经验公式,分析经验公式误差随土体类型、干密度、击实功、孔隙水电导率和温度等因素的变化规律,并提出考虑干密度影响的修正方法。创新点:1.基于电磁波相互作用理论,直接建立土体质量含水率和介电常数间的关系模型;2.通过数据拟合得到通用型经验公式,可在现场无标定快速高效地实现含水率测试。方法:1.通过理论分析,直接建立土体质量含水率和介电常数间的关系模型(公式(9));2.通过试验数据收集和回归分析得到通用型经验公式(图2和公式(10));3.通过影响因素分析,对公式的适用性和有效性进行分析(图3~7)。结论:1.该经验公式对常见的土体类型均能给出误差在±0.05 g/g以内的结果;2.在1.3~2.3 g/cm3的干密度范围内,该经验公式具有较好的适用性;在工程中常见的击实功和孔隙水电导率变化范围内,含水率测试精度可满足工程要求;4~30°C温度变化范围对本经验公式的计算结果无明显影响;3.利用该经验公式,对于特殊场地,可以不通过标定实现TDR现场测试,具有较好的实用性。
OBJECTIVE: To establish an empirical relationship model between moisture content and dielectric constant is the key to testing soil water content with time-domain reflectometry (TDR). By collecting and establishing a database containing 418 experimental data points of 45 kinds of soil samples, an empirical formula between soil water content and apparent dielectric constant was proposed. The error of empirical formula was analyzed with the types of soil, dry density, , Pore water conductivity and temperature and other factors, and propose a correction method considering the effect of dry density. Innovative points: 1. Based on the theory of electromagnetic wave interaction, directly establish the relationship between the soil moisture content and dielectric constant; 2. Through the data fitting to get the general empirical formula can be quickly and efficiently without calibration on the spot water content test. Through the theoretical analysis, the direct relationship between soil water content and dielectric constant is established (formula (9)); 2. The general empirical formula (Figure 2 and formula 10)); 3. Through the analysis of influencing factors, the applicability and validity of the formula are analyzed (Figures 3 to 7). The empirical formula can give the result that the error is within ± 0.05 g / g for the common soil types; 2. The empirical formula has the better performance in the dry density range of 1.3 ~ 2.3 g / cm3 Applicability; in the project common compaction and pore water conductivity within the range, the moisture content test accuracy to meet the engineering requirements; 4 ~ 30 ° C temperature range of the empirical formula of the calculation results no significant impact; The empirical formula, for special venues, TDR field test can not be achieved through calibration, has good practicality.