A brief introduction of Eccentric Casing system: 1. When drilling starts,the reamer swings out and reams the pilot-hole wide enough for the casing tube to slide down behind the drill bit assembly. 2. When the required depth is reached,rotation is reversed carefully.where upon the reamer swings in,allowing the drill bit assembly to be pulled up through the casing. 3.Casing Tubes are to be left in the drill hole should be sealed at the bottom of the hole by means of cement grout or some other sealing agent. 4.Drilling continues to the desired depth in the bedrock using a conventional drilling.