Vízügyi Közlemények, 1970 (52. évfolyam)

4. füzet - Rövidebb közlemények és beszámolók

(14) densities were checked by nuclear methods and cylinder samples taken simultaneously ( Fig. 1 ). The density of existing older, or recent earth structures is measured using depth probes in lined boreholes, sunk by manual augers. The results are presented in a highly visual form (Fig. 2). Nuclear methods yield information even in stratified soils, where actual densities and moistures could not be determined by conventional methods (Fig. 3). Nuclear depth probes have been used successfully also in field experiments of flood control research, where a basin of about 25,000 cu.m capacity has been enclosed by levees. In the basin artificial flood waves were created and continuous moisture- and density measurements were run in pre-established control sections in the levees. In the course of two such experiments, each of which lasted for about 3 months, altogether round 40,000 density- and moisture readings were taken. In the course of these experiments comparative density- and moisture measurements were performed to evaluate the relative merits of nuclear and conventional methods ( Fig. 4). In order to obtain information on the accuracy, reliability and reproducability of nuclear measurements a great number of observations has been performed in a 5.5 m deep borehole sunk within a building ( Fig. 5). As a result of experiments aimed at the improvement of measurement methods the range of the moisture probe could be extended by structural modification to higher moisture contents (Fig. 6). For the calibration of surface probes concrete standards of different bulk densities, while for that of the depth probes a layered standard sunk into the ground has been constructed ( Fig. 7). To make the instruments intended for wider use in the hydraulic service more easy to handle several modifications have been introduced, as a result of which the weight of devices for surface measurements was reduced considerably and their output increased nearly twofold over the earlier design.