Full Scale Field Performance of Drilled Shafts Constructed Utilizing Bentonite and Polymer Slurries

Three 6-ft (1.83-m) diameter, 120-ft (36.6-m) long test drilled shafts were constructed and load tested to evaluate the effects of using bentonite and polymer slurry on full-scale drilled shaft load carrying capacity. Ground conditions at the Miami, Florida site consisted of alternating layers of soft sedimentary rock and sand. Load tests were performed using embedded multi-level Osterberg-type loading jacks (O-cells) where maximum equivalent top loads of as much as 12,200 kips (54.3 kN) were applied. This paper presents the test drilled shaft construction procedures, and the load test procedures and results. Shaft drilling procedures, equipment, and bottom cleaning methods; slurry mixing and testing procedures; and construction time are also presented. Conclusions are drawn regarding the effects of construction methods and drilling slurries on observed side shear and end bearing load transfer.