A STUDY ON THE COMPRESSIVE STRENGTH OF THE BASE BULB OF BORED PILES AFFECTED BY CONSTRUCTION METHODS

Abstract

To investigate the influence of construction methods on the strength of soil-cement in the base bulb of bored piles, laboratory mixing tests are carried out for in-situ soil obtained from base layers of piles and for soil controlling grain size and water content. Unconfined compression tests are conducted for these specimens and those of fresh soil-cement mixture sampled from the base bulb under construction of bored piles. It is found that the strength of the base bulb is determined mainly by the effective cement-water ratio which considers the water content in the original ground. To insure the strength of the base bulb a practical measure is proposed in regard to the quantity of the cement grout mixed into the base bulb.