Ił zawęglony – właściwości geologiczno-inżynierskie mioceńskiego gruntu organicznego występującego w deformacjach glacitektonicznych na terenie Zielonej Góry

Abstract

Lignite clay – some properties of the Miocene organic soil from glaciotectonic deformation in Zielona Góra.A b s t r a c t. The paper presents the characteristic of peculiar Miocene soil which occurs in Zielona Góra. Geological structure of Zielona Góra is determined by glaciotectonic disturbances. Shallow occurrence of Miocene sediments, as clays or lignite, is connected with a structure called Wał Zielonogórski. This is a moraine formed in Warthe glaciation and built from Miocene and old-Pleistocene sediments. The height of the moraine is about 150 m. Lignite clay contains high amount of lignite silt (organic material); hence should be classified as an organic soil. Some laboratory tests (oedometer tests, organic material content, index of swelling) and field tests (Cone Penetration Test) were done. The results show that the strength parameters of lignite clay are close to “clear” clay. The findings show that lignite clay cannot be recognized as a non-carrying soil although high amount of organic material. Oedometer test results allow to design building foundation with standard continuous footing. The occurrence of lignite clay in subsoil in Zielona Góra always indicates the glaciotectonic deformation and high soil variety, hence such area should be investigated more carefully, with an increased number of drilling and probing points.