Wpływ struktury na wytrzymałość eksperymentalnie deformowanych wapieni górnej jury rejonu Częstochowy

Abstract

INFLUENCE OF STRUCTURES ON EXPERIMENTAL STRENGTH OF DEFORMED UPPER JURASSIC LIMESTONES FROM THE CZĘSTOCHOWA AREA Summary Structural differentiation of Upper Jurassic limestones from the Latosówka, Jaskrów and Złota Góra deposits in the Częstochowa area (Fig. 1) was analysed with the use of strength tests. The differentiation was traditionally analysed in uniaxial stress state and under varying rates of loading. This method leads to brittle destruction of sample so only a single strength value is obtained. A method of strength estimations in triaxial stress state and under varying pressures belongs to less popular. However, it should be noted that such tests give full characteristics of strength to compression under varying stress state and they lead to ductile deformations of samples of limestones. The deformations are reflected by reduction in height of sample at the advantage to its diameter and, therefore, a change from its cylindrical shape to the barrel- like (Fig. 6). The studies on limestones differing in structure made it possible to find influence of structure and texture on character of deformation in the two above stress states. The strength of limestones is primarily controlled by size and of grains and its variability. Moreover, it somewhat depends on porosity and, related to it, degree of lithification. Therefore, micritic limestones, which display both the finest and most uniform grains, appear to be characterized by the highest strength values under the two stress states. Moreover, the recorded differences in strength and ductility indicate influence of structure on microscopic reactions related to differentiated stress. This phenomenon is ref1ected by origin of texturally controlled microfractures in the course of deformation of sample. Such microfractures mainly originate at boundaries of grains in grainy limestones.