Modification of TDR Penetrometer for Water Content Profile Monitoring
| Autor: | Shih-Kai Wei, 魏士凱 |
|---|---|
| Rok vydání: | 2019 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 107 Taiwan is featured with subtropics monsoon climate and has many typhoons and rainfall annually. Heavy rainfall always causes lots of landslides and changes landforms around the slopes. Great quantities of unstable sand and soil on the slopes may be washed down by subsequent typhoon and flood events, as well as the soil yields from the shallow landslides. The consequence will affect the safety of residents nearby and raise the pollutant issue to environment. To efficiently verify the safety of the slope, soil water content is one of the most important factors for monitoring, therefore, it is better to automatically capture the water content profile of the soil slope during rainfall events. Time Domain Reflectometry (TDR) can achieve the demands of continuously measuring the volumetric water content () and the electrical conductivity (EC) of the soil slope simultaneously. Previous study has reported the unique relationship between the soil and EC for the shallow landslide monitoring. Therefore, observations by TDR penetrometer at Zengwun Reservoir Watershed were firstly retrieved for the relationship in different soil wetting-drying rates, but apparent variations led unsatisfied results because of the instability of the TDR device and limited sampling volume of the current TDR penetrometer. Based on the aforementioned measurements in the field, this study further improved the existed TDR penetrometer from one-side to dual-sides by using COMSOL numerical software for electromagnetic field simulations, as well as the electrical energy density and the strain in response to stress of each different design. Considering all factors, this study attempted to obtain the optimal design of the TDR penetrometer. Although the improvement of the TDR penetrometer is determined, a sandbox physical test was further arranged to confirm the feasibility and aimed to find out the relationship between soil , EC and matric suction. The existing TDR penetrator and the improved TDR penetrator were penetrated into the sandbox, as well as the traditional TDR probe to observe the measurement performance with each different TDR sensors and the possible hysteresis effect during the rainfall event. At last, transforming the electrical conductivity profile obtained by ERT to the water content profile, trying to point out the importance of the water content monitoring in slope stability. Finally, this study revealed the close relationship between soil water content, electrical conductivity and matric suction, and this study also found the characteristics of different soil may affect the measurement of TDR sensors, and the hysteresis effect found in the TDR sensor measurement process echoes the issue that the soil water content and electrical conductivity will have different relationship in different rainfall events. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
| Externí odkaz: |
|