Effect of anisotropy on drilling mechanical properties for rock in process of drilling

The anisotropic characteristics of rock have important value for construction safety and evaluation of rock properties. The purpose of this article is to study the variation law of drilling parameters in different rocks and their anisotropy characteristics. This article investigates drilling characteristics by conducting digital drilling experiments on six different types of rocks in three different directions. The variation law of drilling parameters (drilling speed, torque, rotational speed, thrust force) and the special energy with drilling depth are analyzed as well as the anisotropy variation of six types of rocks. The influence of anisotropy on the specific energy of six types of rocks is investigated. A special energy index f is proposed to characterize the anisotropy for evaluating different rocks. The test results show that the anisotropy of granite, slate, gneiss, red sandstone, argillaceous sandstone, and sandstone is weakened accordingly by using the special energy index f. The specific energy index after data normalization can better judge the anisotropy difference for different rocks, such as granite, slate, gneiss, and red sandstone.