GROUND RESPONSE TREATED WITH MINIGROUTED PILES

Abstract

Small diameter piles having diameters between 150 mm to 250 mm are known as minigrouted piles. The depth of these piles are usually 10 m but may be increased to 30 m where as the conventional piles are generally 300 mm diameter or more. Weak ground reinforced with mini-grouted piles results into a composite mass of soil which provides higher bearing capacity with corresponding very small settlement. Primary purpose of a mini-grouted pile is to work as a reinforcing element. The present investigation consisted of a model experimental study of mini grouted piles installed in medium sand (relative density 50%) and dense sand (relative density 80%). The mini-grouted piles were cast through an aluminum casing pipe of external diameter 18.5 mm with a '600 wooden conical shoe at the bottom. The piles were provided with a 3 mm diameter re-inforcing. mild steel rod. The piles were grouted with cement slurry of water cement ratio 0.5 which was made to flow through the pipe under gravity. Both single and groups of mini-grouted piles were tested. The single piles were tested under three different cement slurry heads of 30 cm, 60 cm. and 90 cm. and the groups under two slurry heads of 30 cm and 90 cm. The piles consisted of three length /diameter ratios of 15, 30 and 42. Pile groups of four piles with spacing varying from twice to six times the pile diameter were. tested. All the single piles and pile groups were (;t) subjected to vertical compressive loads only and tested as free standing vertical piles. Analysing the test results the following conclusions have been drawn : Both in case of single piles and group piles ultimate pile load increases with increase in length/diameter ratio of the pile from 15 to 42. The increase in grout head used for pile grouting influences the ultimate pile load. Increase in relative density of sand results in increase in ultimate pile capacity of minigrouted piles. The results of group efficiency indicates that minigrouted piles tend to function as friction piles.