Inżyniersko-geologiczna charakterystyka kredy jeziornej i gytii ze złóż środkowego Pomorza

Abstract

Opisano warunki występowania oraz charakterystykę chemiczną i petrograficzną kredy jeziornej i gytii ze złoż Grabowo, Marcelin i Prostynia z rejonu środkowego Pomorza. Analizowane osady charakteryzują się małą wytrzymałością i dużą ściśliwością. Zwrócono uwagę na szczególną rolę budowy wewnętrznej tych utworów w kształtowaniu ich cech wytrzymałościowych.

GEOLOGIC-ENGINEERING CHARACTERISTlC OF LACUSTRINE CHALK AND GYTIJA IN THE MIDDLE POMERANIA DEPOSITS

Significant occurrence of the Quaternary carbonate deposits is observed in the Middle Pomerania area. Investigations of limnic deposits occurring in the Koszalin district have been carried out in En-gineering Geology Department of Technicai University in Koszalin for several years. Detrital-calcareous gyttja from the Grabowo deposits and lacustrine chalk from the Marcelin and Prostynia deposits was chosen 10 investigation. The formations tested differ mainly in contents of organic parts and calcium carbonate, as well as internal structure, depending primarily on these two components. The mineral-organic aggregate is a basic structural element of the soil skeleton of the deposits (Tabl. IV, Fig. 9 and 10). Calcium carbonate and colloidal humus matter are the aggregate-forming substance. The presence of the mineral-organic aggregates in gyttja and lacustrine chalk determines the specific character of these deposits and caused difficulties in determination of some parameters by the use of standard methods. Mechanical testing of gyttja and lacustrine chalk have showed that there deposits are of low shear strength and of high compressible. The shear strength increases while humidity decreases (for example due to desiccation). In comparison to the compressibility of mineral soils, the compressibility of deposits is nonuniform, even step. Initial consolidation-testing carried out showed rather strong structural bonding in deposits while loading in the range 50 to 100 kPa. Exceeding of this range results in weakness the structural bonding. It may be assumed that the internal structure of the deposits tested is a significant factor determining their strength features.