ABSTRACT
Drilling techniques apply to many different fields pertinent to soils and rocks. The main applications include oil-well drilling, water-well drilling, pile driving, underpiling, sheet piling, geotechnical surveying-prospecting for ore deposits or conducting geological surveys prior to construction of dams, power-houses and tunneling, trench pipe laying, grout injection and soil mechanics. Hardness in rocks, minerals and gems is rated relatively by the capability a substance/mineral has to resist abrasion when a pointed fragment of another mineral is drawn across it. A rotary drilling rig is basically hoisting equipment necessary for well drilling. In places where overburden strata are missed, or when their drillability is not known, it is difficult for the driller to decide what tools to use in order to get the best overall results without risking the loss of equipment in the hole. Development of equipment needed for tunnelling in hard rock has progressed rapidly over the last few years.
