土的含水率C-AHFO法现场长期分布式监测可行性研究

DISTRIBUTED FIELD SOIL MOISTURE USING C-AHFO METHOD:LONGTERM MONITORING AND FEASIBILITY

本文采用了一种碳纤维加热光缆的光纤含水率测试方法(简称C-AHFO法),解决了AHFO法监测土的含水率长期(16个月)稳定性问题,并开展了室内标定和现场原位土的含水率监测试验,确定了土中含水率与温度特征值之间的关系,建立了数值模型。室内率定试验结果表明:含水率与温度特征值之间的关系可用分段函数表述。当含水率小于0.08 m3·m-3时,可采用线性关系表述;高于0.08 m3·m-3时可采用对数函数表述。经过16个月的现场监测表明:C-AHFO法在此时间范围稳定,可对土的含水率进行分布式监测,测试误差不超过0.033 m3·m-3,可准确地反映天气和季节变化过程中表层土(深度小于20 cm)的湿度变化,监测结果与数值模拟计算结果具有一致性。该方法的研发和应用为土的大面积实时含水率分布式监测提供了一种新的手段。

In order to solve the long-term stability problem of Active Heated Fiber Optic(AHFO)in distributed soil moisture monitoring,a new method is developed on the basis of carbon fiber cable(abbreviated as C-AHFO).A laboratory calibration experiment and an in-situ field test are conducted and a numerical model is built to simulate rainfall penetration.The relationship between soil moisture and temperature characteristic values is established.The laboratory experimental results show that this relationship can be expressed by a piecewise-function.When the soil moisture is less than 0.08 m 3·m-3,a liner function is used.Otherwise,a logarithmic function is adopted.The 16 months field monitoring results indicate that C-AHFO method has a good long-term stability during this period,which can provide us with effective soil moisture data with errors less than 0.033 m 3·m-3.C-AHFO method also can record surface(less than 20 cm)soil moisture variation process which reflects weather and season changes.The development and application of C-AHFO provides a new method for achieving real-time and large scale ground moisture.