Die Time Domain Reflectometry in der Geotechnik Messung von Wassergehalt, elektrischer Leitfaehigkeit und Stofftransport

This thesis concentrates on the time domain reflectometry, an electromagnetic technique for the determination of water content in porous media, which is based on the measurement of the dielectric constant of the materials. Development, theories and measurement principles are presented, advantages and disadvantages compared to other measurement methods of water content are discussed. A new TDR-technique (TRIME) was investigated in laboratory and field experiments. The new method was calibrated with different soil materials, giving a wide range from heavy clays to fine sand. Only little dependence of soil type was found and a universal empirical calibration function was established. The clays and soils with high organic content showed a more pronounced deviation, which is due to a different dielectric behaviour of bound soil water. Influences of soil structure, density, temperature and salinity on the measurement were discovered and recommendations to avoid or correct these effects are given. The possibility to simultaneously measure the electrical conductivity with this technique was demonstrated. The results indicated a higher soil type dependence which - beside dielectric characteristics of the materials - was caused by technical specifications. In laboratory soil columns as well as in a loessy field plot the application of TDR in the measurement of soil transport properties was tested and break through curves of solutes (KCl) could be measured. The method showed a good temporal and spatial resolution and data could be collected automatically with only small perturbation of the soil. (orig.)145 refs.Available from TIB Hannover: RO 6603(40) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman