This method is used where the areas are congested and noise is forbidden. Initially the bore is made by desanding using an auger, chisel or by a bailer. The bailer is used for boring with a provision for passing bentonite solution through pressure.
DMC Direct mud circulation is used, that is by pouring bentonite solution into the pile along with water to wash the bentonite solution at the top. This makes the surface hard in layers, then a suitable chisel is used to drill through these layers for socketing necessities.
The chisel that is chosen is based on pile diameter and the capacity to be mobilized. The layering is ended after determining of the penetration of the chisel for the amount of energy utilised. This is completed by pouring bentonite solution to wash the bored hole. The specific gravity for the solution to come out is measured to make sure that the bore is cleansed properly. Following this the reinforcement is brought down following by tremmie and the concreting.
MECHANICALLY OPERATED DMC RIG FOR BORED PILE
The mechanically operated auger has more advantages than using the hydraulically operated rotary rigs. In hydraulic rigs, when the auger is being removed it produces greater force of suction after the bore is drilled that might lead to the bore being destroyed. In addition the hydraulic rigs does not allow the cleansing of the bored holes. While on the other hand, there is a possibility for DMC that can ensure efficient cleansing of the bore hole, where bentonite is circulated using some pressure. Furthermore pulling the auger out is done gradually so that the auger comes out with so much ease and with very minimalto neglible suction effect.
- 1) The state of compaction is assessed as the tube is driven by observing the number of blows required for a constant depth of penetration
- 2) The energy imparted to the soil by driving the tube compacts the surrounding soil which helps in the increase of friction capacity of the pile
- 3) The tamping of the tube while extraction creates serrations in the pile shaft which ensures the mobilization of the shaft friction.