Case Study of Three Bidirectional Static Load Tests for Bored Piles at Sabana Costa Rica-Paper

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The study evaluates pile capacity at four high-rise building sites in La Sabana, San José, Costa Rica, where the projects lie within roughly 1 km of one another. Researchers conducted three bidirectional static load tests (BDSLTs) on bored piles at Universal Tower and Double Tree, and three dynamic load tests (DLTs) at Cosmopolitan Tower and Secrt Tower. A three-dimensional finite-element single-pile analysis was also compared with a Double Tree test.<br /><br />The typical ground profile comprises clayey silt over a dense lahar layer, with altered tuff beneath. Groundwater is approximately 17 m below ground level. Tests and geotechnical investigations were used to assess pile load transfer and compare measured skin friction with values estimated from geotechnical correlations.<br /><br />Measured unit skin friction—particularly in the lahar and altered tuff—generally exceeded theoretical estimates. This indicates potential to optimize bored-pile design and construction in the area. Load–settlement curves from the tests were broadly consistent across sites, though differences reflect local conditions, pile depth, and how load is applied. For meaningful comparison with conventional top-down testing, BDSLT displacement estimates need to account for pile elastic compression and differences in the sequence of soil-layer mobilization.<br /><br />At Universal Tower, inadequate cleaning may have left compressible sediment beneath the pile, limiting end-bearing resistance. Nevertheless, higher-than-expected shaft friction provided the required overall capacity. The findings improve understanding of local soil–pile behavior and support more efficient foundation design, while highlighting the importance of construction quality and further refinement of finite-element model calibration.

Keywords

pile capacity

bored piles

bidirectional static load test

dynamic load test

La Sabana

San José

Costa Rica

skin friction

lahar layer

finite-element analysis