Freezing core sampling and CT analysis of the Danube riverbed

Rövid leírás: 

In case of bank infiltration drinking water supplies (e.g.. Szentendrei-island) the composition (grainsize distribution) and structure (porosity) of the riverbed are really important parameters, since the water goes through physical and biological filtering processes during its travel in the sand and gravel riverbed, before reaching the wells. Furthermore, the upper layer of the bed is in constant interaction morphologically with the river flow, and this is also where the local hydraulic losses emerge when the water enters the riverbed. In this study we are focusing on this upper layer and apply novel measurement techniques in order to attain undisturbed samples and data (in contrast with the traditional methods which are not able to do that). First of all, we will gather samples from the field with the so-called freezing core method (Figure 1.). This provides a relatively undisturbed, 1-1.2 m long sample, which will be taken to a laboratory, while maintining its temperature and state, to analyze them with CT (computer tomography). The X-rays will reveal the inner and outer structure of the sample and retrive its 3D modell, presenting its sand-, gravel- and pore structures (Figure 2.,3. and 4.). Finally, the sample will be sieved and weighted to get the grainsize distribution as well. The study will go along the mentioned steps and reveal their limitations and good practices, to try to give useful scientific information for future drinking water management.

 Figure 1: Freezing core sampling and a core sample.
Figure 2: 2D-slice of the sample from CT.