Anisotropy on the ductile-to-brittle transition for rock in process of drilling

Anisotropy is an inherent property of rocks. It refers to the different response of the rock properties in each direction. Understanding the anisotropy characteristics of rock failure by drilling has practical applications in improving drilling efficiency, especially for engineering applications. In this paper, a criterion is established to clarify the ductile-to-brittle transition in the drilling process of rock. Moreover, a new anisotropy index has been proposed to evaluate the effect of anisotropy on the critical state of the ductile-to-brittle transition. The digital drilling tests are conducted on six types of rock to study the drilling mechanical performance in the X, Y, and Z directions. The anisotropy characteristics of drilling parameters and mechanical specific energy (MSE) are analysed at the critical state of ductile–brittle failure. The results show that the critical state of ductile–brittle failure is manifested as an inflection point of the depth of cut. The evolution of MSE is fitted as two linear functions, which corresponds to the two stages. The order of anisotropy in MSE is obtained as: gneiss > slate > red sandstone > granite > argillaceous sandstone > sandstone. The anisotropy in the uniaxial compressive strength and MSE for different rock types has the same sequences. The advantages of the proposed method in determining rock anisotropy are illustrated.

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Opracowanie rekordu ze środków MNiSW, umowa nr SONP/SP/546092/2022 w ramach programu "Społeczna odpowiedzialność nauki" - moduł: Popularyzacja nauki i promocja sportu (2024).