The purpose of this study was to determine the effect on side shear resistance in limestone when temporary casing is used. Due to testing in actual limestone being an unrealistic goal, simulated limestone mixes were prepared and cast into 6 – 42 in. diameter beds. Limestone throughout Florida can be quite varied (e.g. 50-5000 psi) but where stronger limestone is not likely to be penetrated by casing installation. Therefore, target unconfined compressive strengths of the study specimens ranged between 60 psi to 850 psi. A simulated limestone material was developed based on over 200 cylinders cast for unconfined compression testing where the binder (cement or lime), water to binder ratio, aggregate types (sand, coquina, and oyster shells), and binder content were all varied. Results of the laboratory tests were used to establish simulated limestone mixes for 42 in. diameter specimen beds in which 1/10th scale drilled shaft rock sockets were cast. Drilled shaft casing installation techniques were adapted to 1/10th scale where driven casing and oscillated/rotated casing methods were simulated. Within each of the simulated limestone test beds, 5 shaft specimens were cast with and without temporary casing where at least one of the specimens was cast without temporary casing (control specimen). Pullout tests of each specimen revealed that the presence of temporary casing reduced the side shear by 25 to 28 percent depending on the casing installation/extraction method. However, in all cases representative of weaker limestone, the measured reduction did not affect the anticipated design side shear resistance.

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