Measurement of uniaxial compressive strength of rocks using reconstructed cores from rock cuttings

摘要

Uniaxial compressive strength of intact rock is an important mechanical parameter required for the design of geo-technical, mining engineering and petroleum reservoir projects. In geotechnical and mining projects, rock cores are usually available to be tested for such purposes. In the petroleum reservoirs, however, the extreme high cost and time-consuming of coring operation is a main issue and thus, rock core for mechanical destructive testing are rarely available. In this study, a new technique is proposed for measuring the uniaxial compressive strength of reconstructed cores from rock cuttings. For this purpose, a total of 23 blocks of limestone having different densities including Asmari and Sarvak Formations from Western part of Iran and also Cretaceous limestone from Northern part of the country were used. After preparing appropriate cores from the blocks, uniaxial compressive strength test was performed on rock cores. Next, rock cuttings were produced from the same blocks and were reconstructed into artificial cylindrical specimens. The size of the rock cuttings varied between 0.075 mm and 0.4 mm, since it proved promising in preparing specimens with a maximum density of about 80% of the intact rock. Thus, cylindrical specimens with the diameter of 38 mm and the length of 76 mm were built from the cuttings using standard compaction test. Cores with the same dimensions were taken from the same rock blocks. The two sets of samples were next subjected to the uniaxial compression test Results showed an acceptable relationship between uniaxial compressive strength (UCS) of rock cores and the unconfined compressive strength of reconstructed cores (q_u). A correlation coefficient of about or higher than 0.85 was obtained between UCS and q_u for all samples tested. The proposed method can be used for determining the UCS of rocks whenever no cores are available.