Application of rock hardness and abrasive indexing to rock excavating equipment selection
The work carried out in this thesis outlines some of the problems associated with abrasive wear in machines and other mechanical equipment used to excavate or process natural rock material. It has been stated that if the problems associated with abrasion are to be better understood, then a sound knowledge of the abrasive potential of rocks is essential. A number of common wear mechanisms are described together with existing hardness and abrasive tests. The author has investigated rock hardness and abrasiveness by the use of existing methods and subsequently, developed new correlated with the well tests which can be established methods of determining physical and mechanical properties of rock. A project on hard rock drilling has been conducted to determine the rate of wear on expensive diamond impregnated coring drill bits. A detailed investigation which involved the design and manufacture of special measuring equipment to accurately measure and record changes in the profile shape of the bit during its life span. This has permitted a study of the wear characteristics related to the various drilling parameters employed. A collaborative project was carried out with DeBeers, UK, to attempt to discover methods of predicting the rate of specific wear on diamond impregnated saw blades and the cutting forces required with the sawing of hard stone materials. This project has led to a new statistical approach to the analysis of the acquired test data for this purpose. A number of case histories have been discussed and recommendations made. As a result of these investigations together with the work covered in this thesis, the author has developed two new abrasive tests. These tests can be used to test materials such as unconsolidated rocks which otherwise, could not be satisfactorily tested by the established tests already in existence. The new tests have been tried and proved by correlating the test data by combining multiple regression analysis with the results obtained from physical and petrological rock property tests with actual rock cutting data. Conclusions have been drawn and recommendations for future work suggested.