Methodology of DMC Pile Foundation
Preamble: These types of structures deep and large diameter piles are essential which can be done by direct mud circulation method supported by Bentonite slurry system.
The method is approved by British and Indian standards and used in India & abroad depending on the speed by which the project has to be completed. Tractor mounted method has got more speed when compare to DMC method and the disadvantage is that it cannot cut through hard rock’s effectively. The DMC system is widely used in India for Providing Pile foundation for buildings up to 50 stories (150 Meters) and the piles can be done up to depths of 60 meter from ground level and the diameters can vary from 500 to 1500mm.
This is cost effective and we recommend this system for Indian lab and abroad for diameters from 500-1200mm and depth up to 60meters. (Method statement- “Tractor Mounted Pile”): For executing DMC piles (Direct Mud Circulation piles) method which approved as per IS 2911 and British standards under specifications of bored cast in situ piles. The bore holes will be advanced by chisel weighing above 1000kg by circulating Bentonite slurry using a 20 HP vertical motor & pump. Because of the impact of chisel the cutting will be brought out by the Bentonite slurry and the bore holes will be advanced to the founding strata which is about 15 to 25 meters in depth. The founding strata can be rock or dense sand having N value >75 as per structural design. To prevent the side collapse and caving in a guide casing of 500-1500mm dia and 1 meter to 1.5 meter depth will be fixed on the top of the bore hole and this will be withdrawn after concreting is over.
Once the bore hole reaches the final depth the chisel will be kept for about 15 minutes to clear out all the cuttings from the bore hole. After this the chisel will be removed from the bore hole and steel cages will be inserted in to the bore as per the structural design and tremmie pipe of 6 inch (or) 8 inch diameter will be inserted to the centre of the cage. After the insertion of tremmie pipe, the bore will be thoroughly cleared by using Bentonite slurry pumped through a 20 HP pump. Once the bore is clear ready mix concrete of required specification will be poured through the funnel fitted on the top of the tremmie pipe and the concrete will be made to overflow from bore till all the laitance is removed from the bore and good concrete appears on the top.
The theoretical volume and actual concrete used will be measured and recorded including details of reinforcement etc. on a bore log which forms the basis of measurement between the contract and client.
