A Case History of Expansive Clays in Southwest Puerto Rico

This investigation involves characterizing and evaluating the expansion potential of several clayey soils from the area of Boquerón, Cabo Rojo, in southwest Puerto Rico. The samples were collected from two test pits excavated as part of this project and were also obtained from a geotechnical consultant that had performed a study in the vicinity of the test pit locations. The experimental program involved in- situ field tests and laboratory tests on selected representative samples. The laboratory program involved geotechnical classification of the soils, gradation, Atterberg limits, mineralogy characterization, and specialized tests for assessing swell potential of clayey soils. The mineralogy characterization involved determination of specific surface area, cation exchange capacity, and X-Ray diffraction. Results from these tests revealed significant presence of montmorillonite. The mineralogy combined with test results of swell pressure and free swell revealed that some of the soils tested from the test site Cabo Rojo can experience free swell volume changes greater than 40%, and swell pressures greater than 32,000 psf. The results of this investigation confirmed presence of highly expansive soils in this test area located in the southwest region of Puerto Rico.