Determination of uniaxial compressive strength of microcrystalline limestone using single particles load test

摘要

The uniaxial compressive strength (UCS) of intact rock is an important mechanical parameter which is required for many engineering projects. In some engineering projects such as well drilling for petroleum production, due to the depth of the well, there are some limitations for obtaining rock core samples and determining the UCS. Nevertheless acquiring such parameter is essential for well wall stability analysis and wells development program. Accordingly, the idea of using drilling cuttings has been proposed to determine the UCS. In this study in order to investigate the relationship between UCS and single particles compressive strength (SCS), 10 block samples of microcrystalline limestone from Asmari formation outcrops were used. Then UCS test was performed and uniaxial compressive strength was determined. Next, these samples were crushed and 600 single particles were prepared. Then the SCS of each particle was determined by using the apparatus made for this purpose. Since the shape of particles affects the strength of them, therefore their shape was modified and all particles used for determining SCS turned into spherical ones. For studying size effect of them, particles with 2, 3, and 4 mm diameters were prepared and SCS for each particle was determined. Along with increasing diameter of particles, SCS increased accordingly. To eliminate the effect of particles' size, variable sizes were defined and the empirical equation between UCS, SCS and particles' diameter (D) was proposed. The coefficient of correlation between SCS and UCS was more than 0.91 which indicated an existing reliable correlation among them. To verify the empirical equation, some other samples were selected and the UCS measured in laboratory was compared with UCS estimated from SCS. This comparison showed they are more than 88% identical.