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Why can’t normal Reversed Circulation Drills function in shallow rock conditions?

Reversed Circulation Drill (RCD) is normally used for forming large diameter rock socket. The method involves the exertion of a download force of roller cutter bits on rock, together with the action of rotation and grinding of bits on rock. The cuttings are then removed by reverse circulation. The water and cuttings are airlifted through a central drill pipe, which is also used for rotating the drill bits.

To facilitate the grinding action on the rock, about 15 tons of force is used for each cutter. With such a high bit force, the drill frame has to be stationed by attaching to pile casing of bored piles. Therefore, during the drilling operation, the pile casing is prevented from lifting up by the weight of drill rig and pile casing and the frictional forces developed between the ground and pile casing. Hence, in shallow rock conditions with short length of pile casings, it may affect the stability of RCD drill rig.

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This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.

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Kanwarjot Singh

Kanwarjot Singh is the founder of Civil Engineering Portal, a leading civil engineering website which has been awarded as the best online publication by CIDC. He did his BE civil from Thapar University, Patiala and has been working on this website with his team of Civil Engineers.

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