Abstract
dc:descriptionDue to the increasing need in hydrology for techniques which could measure partial saturation of soils in a non-invasive way, the development of a low-field NMR sensor has been undertaken in this dissertation. Based on prior designs of low-field NMR instruments like the NMR-MOUSE and the well logging tools, two conceptual designs has been evaluated. One of these designs was chosen for construction of a cylindrical sensor labelled the Slim-Line Logging (SLL) Tool. It is shown that, in a well shielded experimental setup, the SLL tool can reliably measure partial saturation of soils with a uncertainty of 3% in a measurement time of 3 min. To demonstrate its capability to supply data of hydraulic interest, the SLL tool is deployed in two experimental setups, which respectively contain the model soils FH31 and FH31/W3. In these setups a One-Step Outflow (OSO) experiment is performed. Measurement of the saturation before, during and after the OSO experiment permits to follow the dynamic of flow in the model soil under known boundary conditions. Therefore, the obtained data could be analyzed using the Van Genuchten-Muallem model for the soil hydraulic conductivity and the Richard equation for the water flow in partially saturated media. The result of this analysis is the determination of the hydraulic parameters of the soil. Furthermore, with data acquired from the model soils in hydraulic equilibrium, it is demonstrated that the whole decay of the NMR signal, analyzed through the Inverse Discreet Laplace (ILD) transformation, also helps to form a picture of the processes the water is subjected to when the saturation decreases. Therefore, the sensor is not only capable of measuring water content but also to provide data related to the microscopicalconditions under which the water is retained in the soil. As a final application the sensor was deployed also in the test site Selhausen, Germany to measure the saturation on-field. To make the measurement feasible some provisions were made to decrease the influence of external noise on the final measurement. Profiles of saturation in depth up to 1.20 mt were made during aweek-long measurement campaign.
Degree
thesis:*- Grantor dc:publisher
- Publikationsserver der RWTH Aachen University
- Year dc:date
- 2011
Author and committee
dc:creator, dc:contributor.*- Author dc:creator
-
- Sucre, Oscar Elías
- Contributors dc:contributor
-
- Blümich, Bernhard
Subjects
dc:subject × 16Rights
dc:rights- Statement dc:rights
-
- info:eu-repo/semantics/openAccess
- Language dc:language
- eng
Identifiers
dc:identifier.*- OAI identifier oai:identifier
- oai:publications.rwth-aachen.de:63078