The objective of this project is to assess the applicability of current field-based liquefaction approaches for calcareous sands. This is of importance because there are many coastal communities in areas of high seismicity founded on calcareous sands (e.g. Haiti, Puerto Rico, Hawaii, etc.), and existing field-based approaches were developed almost entirely for case studies in silica sands. We will perform a combined in situ and laboratory-testing program at two sites in western Puerto Rico, which is an ideal site because of the extent of calcareous deposits throughout the island, the relatively high seismicity of the region, the high population density, and the expertise of the research team with these particular soils. The in situ testing program will consist of conventional drilling and sampling techniques, Standard Penetration Tests with hammer energy measurements, and Cone Penetration Testing with shear wave velocity measurements. The laboratory-testing program will consist of cyclic triaxial and cyclic simple shear tests with shear wave velocity measurements. Research by the PIs has shown that the relationship between cyclic resistance and shear wave velocity (CRR-Vs) is soil specific and can be used to link in situ test results with laboratory determined values of CRR. Shear wave velocity (Vs) has been shown to be a good measure of the combined effects of stress and fabric, and it is hypothesized that samples consolidated or prepared to in situ values of Vs yield the in situ CRR. This approach will be used to estimate the in situ CRR at each site by linking the shear wave velocity in the laboratory and the field, and then comparing this with values of CRR predicted from existing field based approaches (SPT, CPT).
This research will lead to a better understanding of how existing field based correlations for the assessment of liquefaction potential, which is the state-of-the-practice in geotechnical earthquake engineering, applies to calcareous sands that can be found in many tropic and subtropical coastal regions. In addition, this project will build upon existing research that shows that shear wave velocity measured appropriately in the laboratory and in situ can provide a link between laboratory testing and field measurements for characterizing the in situ behavior of soils that are difficult to sample. The primary societal impact of this research will be to help minimize losses from earthquakes by improving the current methods for liquefaction potential assessment in calcareous sands. Another important component of this project is the inclusion of students from underrepresented groups in the STEM fields of research. Three Hispanic American students from Puerto Rico will be working on this research project. One Hispanic American from Puerto Rico is currently a Ph.D. student at the University of Rhode Island and will complete her dissertation on the proposed research. Two undergraduates will work on this project as summer research assistants through an existing collaboration between the PI, University of Puerto Rico Mayaguez, and the University of Rhode Island Transportation Center as part of the Federal Highway Administration Dwight D. Eisenhower Fellowship Program.
