Description: Hand sludging (also known as Asian, or Indian sludging) is a traditional technique used in parts of Nepal, India and Bangladesh. It involves reciprocating a steel pipe (of 25 to 40mm diameter) vertically in a shallow pit, which is kept full of water. The reciprocating action is achieved by a lever, which is attached to a bamboo frame. One operator operates the lever while the other uses his hand over the top like a flap valve. On the up-stroke the hand covers the pipe, while on the down stroke it lifts off. This action enables the cuttings to be carried up through the drill pipe and exit at the top.

The water in the pit flows back down the drilled hole and then up the inside of the pipe, carrying the cuttings. This provides a continuous circulation of water for the removal of the spoil as a sludge (hence the name of the technique). Thickeners or stabilisers can be added to the water in the pit to prevent collapse of the hole and reduce lost circulation. Cow dung and sawdust are commonly used thickening materials.

Capability: Hand sludging is an excellent method for drilling silts, sands and certain clays. Hard layers can reduce speed of penetration or halt progress completely. Some clays can block the sludging pipe. Coarse gravels and sands can result in lost circulation and thus failure to remove spoil from the hole. Depths of up to 15m are common.

Locations: Extensively used by private artisans (mistries) India, Bangladesh, Tchad.

Availability: Hand sludging equipment is made locally in parts of India, Nepal and Bangladesh.

Documentation:

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