| Summary: | 碩士 === 國立交通大學 === 土木工程系所 === 94 === Suspended sediment concentration (SSC) measurement is critical for water resource, flood control, and sediment discharge. However, an efficient and automated technique for high SSC monitoring are yet to be discovered. This thesis introduces a new method based on time domain reflectometry (TDR) that may lead to an effective solution for high SSC monitoring with high spatial and temporal resolution.
TDR method measures apparent dielectric constant from travel time and electrical conductivity from steady state response, both have high correlation with SSC. Considering the influence of parameters, such as soil type, soil particle size, water salinity, and temperature, various probe types and analyses methods are designed to evaluate the TDR measurement performance. Experimental results reveal that using short-uncoating probe with reference line travel time analysis can greatly reduce water salinity effect on dielectric estimation. The laboratory calibration result of Shihmen sediment showed that the mean error of SSC estimation from travel time is 4300 ppm with a standard deviation of 950ppm. The maximum SSC measurement range is theoretical unlimited. The travel time decreases linearly with increasing temperature. But this temperature dependency can be compensated by a simultaneous temperature measurement. Furthermore, the TDR SSC measurement is relatively independent of soil type and particle size, making it much more advantageous than optical and supersonic method.
TDR has the advantage of high SSC measurement ability, low-cost, and high spatial and temporal resolution. Future research is directed to optimizing reference line analysis with temperature compensation and dielectric spectroscopy for further improving the SSC measurement accuracy.
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