DFI Journal - The Journal of the Deep Foundations Institute

Volume 9, Issue 1, January 2015
DOI: 10.1179/1937525514Y.0000000004

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Load Tests on Drilled Shaft Foundations in Moderately Strong to Strong Limestone
Article Type: Research Paper

Race, M. L. & Coffman, R. A.


Three drilled shaft foundations (DSFs) were constructed in moderately strong to strong limestone at the Siloam Springs Arkansas Test Site (SSATS). The embedment lengths within the limestone were 3-0, 1-5 and 2-1 m for the DSFs with diameters of 1-2, 1-8 and 1-2 m, respectively. The DSFs were instrumented to facilitate cross-hole sonic logging testing and full scale load testing using bidirectional load cells (BLCs). Lessons learned from construction included the: (1) proper concrete pouring techniques; (2) ability to retrofit improperly installed telltale instrumentation; and (3) influence of rock socket length within moderately strong to strong limestone. Recommended design, construction and testing techniques in moderately strong to strong limestone are presented. Based on the full scale testing, t–z model recommendations for weathered limestone and moderately strong to strong limestone are presented and discussed. Comparisons between measured unit side resistance and current design recommendations are also considered.

drilled shaft foundations, strong limestone, full scale load test