时域反射法(TDR)已被岩土工程领域广泛用于测量土壤体积含水率。采用延安新区和吴起县2种黄土试样分别对TDR水分测试进行试验率定,分析了TDR水分测试过程中的测试误差,探讨了黄土的干密度及塑性指数等因素对TDR水分测试率定的影响。结果表明:TDR水分传感器未进行试验率定时,测试结果误差较大;当黄土试样在质量含水率一定时,TDR水分传感器测得的体积含水率与干密度之间均呈线性增长关系;对于塑性指数Ip<10的延安新区黄土,TDR水分传感器测得的体积含水率θv均大于烘干法测得的体积含水率θw,TDR测试结果均在等值线θw=θv下方;对于塑性指数介于10~17之间的吴起县黄土,当质量含水率w<12%时,θv >θw,TDR测试结果在等值线θw=θv下方,当w>12%时,θv <θw,TDR测试结果在等值线θw=θv上方。通过比较分析2个地区θw与θv的关系,建立了TDR水分测试结果的修正公式。研究成果为TDR水分传感器测定黄土含水率这一测试技术在陕北黄土地区的岩土工程应用提供了参考。
Abstract
Time domain reflectometry (TDR) has been widely used in geotechnical engineering field as a reliable method to measure the volumetric water content of soils. In this study, TDR measuring of moisture content was calibrated. Loess samples from Yan’an New Area and Wuqi County were selected for test. The test error in the TDR measurement was analyzed, and the effects of dry density and plasticity index of loess on the calibration of TDR test were discussed. Results revealed large error of measurement before the TDR moisture sensors were calibrated. Given the same mass moisture content, the volumetric water content of loess measured by TDR moisture sensor was in a linear growth relation with dry density. For loess samples from Yan’an New Area with a plasticity index less than 10, the volumetric moisture content (θv) measured by TDR moisture sensor was greater than that (θw) measured by drying method, and the results were all below the contour line (θw=θv). For loess samples from Wuqi County with a plasticity index between 10 and 17, when the mass moisture content w was smaller than 12%, θv was greater than θw, and the test results were below the contour line (θw=θv); on the contrary when w was larger than 12%, θv was smaller than θw, and the test results were above the contour line (θw=θv). By comparing and analyzing the relations between θw and θv, a modified formula for TDR moisture measuring results was established. The research results offer reference for the application of TDR to measuring moisture content of loess in the loess area of north Shaanxi Province.
关键词
黄土 /
TDR /
水分测试 /
体积含水率 /
干密度 /
塑性指数
Key words
loess /
TDR /
moisture measuring /
volumetric water content /
dry density /
plasticity index
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基金
国家自然科学基金项目(41877278,51678484);陕西省黄土力学与工程重点实验室项目(14JS064)
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