SHEAR STRENGTH OF PTOLEMAIDA LIGNITES
Published: 29 Jul 2017
Abstract: This paper aims to investigate the shear resistance behavior of the Ptolemaida lignite. An attempt is made to determine the laws governing the development of the shear strength of lignite material and to compare it with results of research concerning the same material in Greece. This work refers initially to the geology of the region, to the natural and chemical properties of its lignites and to its quality compared to that of the Megalopolis lignite. The results of this research are listed below. Initially, the physical characteristics were determined: water content, unit (apparent) weight, unit weight, organic content. The preload tension (O.C.R) was found to be of the order of 20 Kg/m3 according to Casangrade. All of the samples examined were from the North Field of the Ptolemaida Main Lignite Ground Field. In order to determine the laws applicable to the shear strength of lignite under consideration, triaxial compression trials were conducted on isotropic consolidation specimens with undrained conditions. Resistance parameters were investigated in a wide range of pressures due to the history of loads. Systematic measurement of the rising pore pressure, deformations and proper load speed selection was performed. We outlined Mohr circles, deviatoric stress diagrams, pore pressure, and other useful diagrams to draw conclusions. In conclusion, we can deduce that the lignite material examined can generally be treated as a preloaded material in order to solve the problems of Soil Mechanics and foundations, but also at the same time take into account certain differences, which are explained on a case-by-case basis.
Keywords: lignites, preload stress, deviator of stresses, pore pressure, deformations, over consolidation ratio
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