Different methods of boring are in vogue for the construction of drilled shafts in the world. The most commonly used methods include rotary drilling, rotary bucket auger, percussion, continuous flight auger etc. It is widely reported in the literature as well as supported by some design codes that the load carrying capacity of drilled shafts depends a lot on the local construction practices in addition to the soil parameters. In Pakistan, recently about twenty thousand drilled shafts have been constructed for the first ever Metro Electric Train and RLNG power projects. A host of boring methods have been used in different contract packages, for drilling in the wet as well as in the dry conditions. The subsequent performance of full-scale static load tests on the selected drilled shafts has divulged variable load carrying capacities of drilled shafts constructed by different techniques. This paper is based on a study of different factors involved during the construction of drilled shafts by different methods and their effect on load carrying capacity as ascertained from pile load tests. Practical conclusions have been drawn and recommendations have been made for the sound construction of drilled shafts in alluvial conditions as in Punjab Province, Pakistan.
Subjects: Drilled shafts performance, rotary bucket auger, reverse rotary, pile load tests
Author: Sohail Kibria Vice President and Sajid Iqbal Senior Geotechnical Engineer
Publisher: DFI, EFFC