Estimation the uniaxial compressive strength of microcrystalline limestones using indentation test

Measuring of uniaxial compressive strength (UCS) of intact rocks is necessary in many engineering projects. In deep well drilling for petroleum production or exploration drilling in deep tunnels، because depth wells، obtain suitable core samples for UCS test is too extensive and sometimes impossible. Therefore indirect method for UCS determine (for example using rock particles) is common. One of these methods is known as indentation test. In this test an indenter that is hard penetrate in to rock particle which surrounded by resin is used. In this paper، 11 microcrystalline limestone block samples from carbonate Zagros formation outcrops is prepared and UCS test in laboratory is performed. Then cores are crushed and 720 rock particle samples with 2، 3 and 4 millimeters size is prepared. Indentation test with indenter 0. 6، 0. 8 and 1 millimeters diameter is done and critical transitional force (CTF) for each particles is determined. Empirical equation between UCS and CFT for different samples and indenter with R2≥0. 78 is suggested. Using multiple regression general equation between UCS، CFT، particle size (D) indenter diameter (I) with R2=0. 85 is proposed. Verification of the proposed equations with 135 indentation tests on 3 microcrystalline limestone samples and comparing measuring UCS in laboratory with estimate UCS are evaluated. This comparison showed that 88% they are similar.