The Investigation of the marbles' behaviour under compression

VII ABSTRACT In this study, deformations of metamorphosed real crystallized marble (GM1, GM2, GM3) and micritic limestone (KÇT1, KÇT2, KÇT3) samples under various pressure conditions have been examined by strain gauges. In the experiments, core samples of size B 66, h= 2R and cylindrical samples cut perpendicular to bedding plane were analysed and dynamic strain gauges of FLA 10-11, 120 Q, 2.12 gauge factor have been used. The forces applied were chosen depending of uniaxial strain of the samples, maximum forces of 5000 kgf that is applied by marble machineries of marble blocks and slabs, and about 75 % of maximum uniaxial stress values of the samples examined. Deformational variations of the samples under uniaxial strains were detected by vertical and horizontal strain gauges. The main objective of the study was to examine "time dependent deformation under constant stress (time-strain, creep)" of the samples and these accomplished by various forces applied 7-hour duration. In the time dependent deformation experiments, only vertical strain gauge were used and only the vertical strains were measured. The deformation values measured by strain gauges were transferred to a recorder and numerically plotted. Depending on numerical values of deformational path for each sample were drawn. In the time dependent deformation experiments of the group II, conducted under 5000 kgf forces, a limited elastic area has been observed. In the group II and group III in every experiments area I (transient creep) and area II (steady state creep) have been detected. Because of limited time the area III (accelerated creep) in both samples groups have not been observed. However, time dependent deformation experiments the flow area II show regularity. In both groups of the samples, the steady state creep has been reached at first 100 second under 2 toruVmin force speed.VIII In the time dependent experiments, it was found that the strain was greater in experiments under high load and, deformation and forces are proportionally related. In the same samples, the strain produced under force that was 75 % value of its uniaxial strength was bigger that produced under 5000 kgf. In the time dependent experiments, depending on load values and marble species, it was observed low values of deformations and these are shown in related graphs. In the regularly decreasing deformation graphics, the normal level under steady state creep, was called "Dynamic Level" and the level which is the lowest was called "Stable Level". The strain decreases in transient creep was later ended, and the dynamic and stable levels become equal. The time-strain curve was regular in the steady state creep and stable flow was observed. In the time dependent deformation graphics, in the steady state creep, the samples showing a linear flow and relatively regular variations are called "Stable" and ratio of stable level to dynamic level was called the "Stability Ratio". The stability ratio close to 1 means the sample flows under highest stability flow. Under 75 % load of the uniaxial stress values of the samples stability proportions was 1 except sample GM2. In the flow of the group III, the group II experiments under 5000 kgf load, the flows were more stable. It load increases the stability increases, too. The stability proportion differences are lower in different crystallized marble samples (GM1, GM2, GM3). On the other hand, in the limestone samples (KÇT1, KÇT2, KÇT3) more stable flow was observed. After deformation experiments conducted by strain gauge, we prepared thin sections from slabs cut vertically and horizontally from the samples. The thin sections examined under 400 enlarged to see general type of deformation and under 1250 enlarged to observe crystal size deformation. The limestone samples (KÇT1, KÇT2, KÇT3) are only examined under 400 times magnification.DC In thin sections it is observed that in the limestone (KÇT3 have the biggest grain, 57.82 um) with small crystal size crack openings were narrow compared the crystallized marbles (GM1 have the smallest crystal, 616.32 um) the size of cracks increase proportionally to the crystal size of the samples. The results indicate that the crack openings are correlated with the crystal size. Besides that, the crack openings increase parallel to the load. It is concluded from the investigation of the thin section obtained after the deformation experiments related with time by using 400 enlargement of the microscope, there is no any fracture trace coincide on the general structure of the samples. As a result, it is determined that there is no any deformation development which affects the usage of the micro structure related with loads. During the microscopic investigation of the thin section of the samples, flowing and figure changing were not observed. Also, there is no any changing observation of the limestone samples called as KÇT1, KÇT2, and KÇT3 having fossil and old fracture of the calcite filler. The results of the physical-mechanical experiments of the samples and the thin section pictures which were obtained after the three-dimensional experiments are presented on the Appendix. 1.