Evaluation of dynamic analyses and static pile load tests from bored cast-in-situ piles in dense sands and sandstones

As part of a large-scale development project in the United Arab Emirates (UAE), more than a thousand bored cast-in-situ reinforced concrete piles, 1.2 m diameter and 20 to 40 m long, were constructed in dense sands and sandstone (calcarenite) formations. The foundation system consisted of a raft supported on piles where all piles were designed to work in compression at the initial construction stages. Currently, after project completion, part of the foundation system is working to resist the strong uplift forces due to the high groundwater table level. Prior to the start of construction, preliminary static pile load tests were carried out to 2.5 times the design loads under compression and tension in order to confirm the design capacities. During construction, as part of the quality control and quality assurance testing procedure, non-destructive pile integrity testing was performed on all working piles. In addition, close to a hundred of the working piles were statically tested under compression and tension to 1.5 times the design loads. Some of the preliminary and working test piles were instrumented with vibrating wire gages from which load resistance curves were obtained. Finally, high-strain dynamic testing was performed on more than 30 working piles spread throughout the project site. This paper focuses on the results obtained from the static and dynamic pile load tests. A comparison is made between the measured and Calculated static pile resistances using common state of practice design methods. Comments and observations are drawn regarding their adequacy in assessing the axial pile capacities. In particular, attention is given to the shaft side resistance (f(s)) derived from the static load test results. The derived values of f(s) are compared to the shaft side resistance data found in relevant soil/rock databases available in the literature. Finally, the dynamic test results are analyzed and the inferred static resistances are compared to the measured values obtained from the static load tests.