Concept
Boring is drilling a hole, tunnel, or well in the Earth. It is used for various applications in geology, agriculture, hydrology, civil engineering, and mineral exploration. Today, most Earth drilling serves one of the following purposes: return samples of the soil and/or rock through which the drill passes access rocks from which material can be extracted access rocks which can then be measured provide access to rock for purposes of providing engineering support Unlike drilling in other materials where the aim is to create a hole for some purpose, often the case of drilling or coring is to get an understanding of the ground/lithology. This may be done for prospecting to identify and quantify an ore body for mining, or to determining the type of foundations needed for a building or raised structure, or for underground structures, including tunnels and deep basements where an understanding of the ground is vital to determining how to excavate and the support philosophy. Drilling is also used in vertical and inclined shaft construction. Borehole drilling has a long history. Han dynasty China (202 BC – 220 AD) used deep borehole drilling for mining and other projects. Chinese borehole sites could reach as deep as 600 m (2,000 ft). When drilling in stone, one must pay particular attention to the type of material. There are three different classifications of drill bits used for drilling into stone: soft, medium, and hard. Soft formation rock bits are used in unconsolidated sands, clays, and soft limestones, etc. Medium formation bits are used in dolomites, limestones, and shale, while hard formation bits are used in hard shale, mudstones, granite, limestones and other hard and/or abrasive formations. Soft ground drilling can be undertaken using a rotary auger or wash boring techniques, while rock drilling often use methods such as NMLC which allow for recovery of a core of material which can be examined to determine the strength, degree of weathering, understanding of any how intact the rock is (RQD) and identify any discontinuities or other planes of weakness.
