Supervisors info:
Αριάδνη Αργυράκη, Αναπληρώτρια Καθηγήτρια, Γεωλογίας και Γεωπεριβάλλοντος, Εθνικό και Καποδιτριακό Πανεπιστήμιο Αθηνών
Summary:
Ιn the present thesis, the results of the study of the geotechnical characteristics of natural clay materials from the western Macedonia Ventzia basin are presented. Specifically, six (6) clay samples were collected from open pit quarries of the GEOHELLAS S.A. The methods of the assays included X-ray diffraction measurement for qualitative mineralogical analysis, calculation of the cation exchange capacity of the materials by the method of methylene blue, calculation of natural moisture, liquid limit, plasticity limit, specific gravity, as well as a granulometric calibration. Furthermore, the permeability variation of these samples was measured during the interaction with a solution of low pH and high concentration of TDS, which resulted from the leaching of mining waste from the Stratoni area of Chalkidiki. The main mineralogical phases that were identified included Fe-rich smectite, nontronite and natural mixture of smectite-palygorskite. The cation exchange capacity of the samples ranged from 49-67 (meq / 100g of clay), and in particular the samples containing palygorskite had the lowest observable values. The geotechnical characterization was carried out at EDAFOMICHANIKI S.A., from which the geotechnical classification of the samples was extracted. The samples are classified into the MH Elastic Silt category, based on ASTM D2487-00. Then, the permeability coefficient was measured in the three (3) following cases. In the first case, the studied samples were used, which were added with deionized water, secondly activated samples (activation with Na2CO3) with deionized water and finally activated samples with low pH solution and high concentration of TDS. The permeability coefficient decreases due to activation of the samples and its interaction with the solution. The low pH of the solution was changed to basic (pH = 9) and the TDS concentration was increased. That occurred, because at low pH the octahedrals of the smectite were dissolved, so ions such as Si, Al, Ca and Fe were released in the solution. By means of the results and according to Greek legislation all samples are recommended for the use of clay base liners in waste disposal sites of aggregates.
Keywords:
smectite, palygorskite, XRD analysis, geotechnical characteristics, cation exchange capacity, geomembranes, low pH leachate
