The Anisotropy of Rock Drilling in Marble Quarry Mining Based on the Relationship between Vertical and Horizontal Drilling Rates

Abstract

There is a high correlation between rock engineering behavior and the anisotropy index, which is crucial for the safety assessment of rock properties. In rock drilling, rock anisotropy significantly affects the cost and efficiency of the drilling project. Therefore, the anisotropy during the rock drilling process is investigated in this study. First, measurements of horizontal and vertical drilling rates were conducted at a marble quarry. Then, experimental tests were conducted to measure the physical and mechanical properties of collected minor rock blocks corresponding to the major under-drilling marble blocks. Through this process, a total of 40 data sets comprising vertical and horizontal drilling rates and 12 different rock properties were provided. The results showed that the vertical drilling rate correlates more with rock mechanical properties, while the horizontal drilling rate is associated more with physical characteristics. Also, sensitivity analysis confirmed that porosity and dry density are the most and least effective variables on both vertical and horizontal drilling rates, respectively. Based on the analysis of variance, the polynomial equation was found to be the optimum relationship between vertical and horizontal drilling rates. Based on the comparative analysis and using actual data sets, the accuracy of the proposed equation was proved. Finally, a drilling anisotropy index was proposed based on the ratio of vertical to horizontal drilling rates. The results showed that the drilling anisotropy index is more prominent in rock blocks with high-strength properties. Also, it was proved that the drilling anisotropy index has an inverse relation with vertical and horizontal drilling rates. As the vertical and horizontal drilling rates are inherently affected by different rock properties, it can be concluded that the suggested relationship between vertical and horizontal drilling rates and the proposed drilling anisotropy index could be effectively applied to assessing the interaction of drilling rates with rock properties in anisotropic rocks. This study investigated the relationships between rock properties and vertical and horizontal drilling rates, which is one of the main issues in rock drilling operations. According to the field and laboratory results, the correlation between the physical and mechanical properties of rocks with vertical and horizontal drilling rates was achieved, which can be considered during the drilling operation to enhance the drilling efficiency. Also, a new drilling anisotropy index was proposed, which can help identify a good interaction between drilling tools and the rock environment in anisotropic rocks. In addition, a new relation was proposed between vertical and horizontal drilling rates, which can be applied in practice to predict one of them based on the other. Generally, the outputs of this research could be applied to specifying the relationship between rock properties and vertical and horizontal drilling rates, emphasizing the drilling anisotropy index. In practice, the study outputs can lead to enhanced drilling efficiency and mine productivity in marble quarry mining by providing a deep knowledge of rock interaction with drilling tools while drilling in both the vertical and horizontal directions and choosing proper drilling tools for the under-drilling rock type.