Various methods are currently used to increase penetration rate into hard rock for all kinds of applications such as drilling, tunneling, underground excavations and so on. Mechanical tools, because of their simplicity, have been the most popular for many years and have been developed to have the most efficient penetration rates. Other novel methods are being investigated, to assist mechanical tools as well. Microwave energy is one novel technique, generating in-depth heat which leads rocks to be highly fractured. It can also assist mechanical tools and allow the tool to penetrate more effectively by reducing the strength of rocks. A short summary of related methods will be discussed, followed by a brief explanation of experiments done to date, regarding the way.
Human beings started breaking rocks using basic handmade tools. At the beginning of 19th century, horizontal drilling started being done by a method named "single- and double-handed hammer drilling" [1]. In single-handed hammer drilling, a man carried a hammer weighting 1.6 to 2 kilograms in one hand and a steel bar, which acts as a bit, in the other. The man pounds the hammer against the steel bits' head while rotating it after each blow of the hammer in order to penetrate the bit into the rock. Doublehanded hammer drilling is the same as the single-handed method with the addition of a second man holding a hammer to pound on the same steel bit, with the second hammer weighing about 4.5 kilograms. To penetrate hard rocks, one man carries the steel bar, which acts as a drill bit, and two hammer-men each hammer against the head of the same drill bit [1]. During the 19th century, drilling systems evolved to mechanized drilling machines. More recently, the technology of drilling soft to hard rock has developed quickly. Today, drilling machines can penetrate to significant depths in hard rock within a time frame of a few minutes. Although drilling technology was initially developed mechanically, today new technology assists mechanical drilling system in order to improve penetration rates. Microwave energy is a novel kind of technology, which can assist mechanical drilling by reducing the strength of rock ahead of the mechanical tool. In this report, various drilling methods will be presented along with an explanation of the way microwave energy can assist mechanical tools to improve their penetration rate into hard rock
The term rock breakage describes freeing and detaching hard pieces of a rock mass from its parent deposit. Advancement of projects in mining and civil applications is strongly dependent on rock breakage efficiency. Early on, humans understood that heating rocks and quenching it with cold water could reduce the rock Later, he discovered that 88 chemical energy derived from detonating various mixtures such as black powder, dynamite or bulk explosives could be more effective in breaking rocks [2]. In order to break the rock most efficiently, blasting materials must be confined within the rock mass.
