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

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 m³·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 m³·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.