GEOSTATISTICAL MODELING OF SPT DATA TO DETERMINE THE MINIMUM NUMBER AND DEPTH OF FUTURE BOREHOLE INVESTIGATIONS
Keywords:Geotechnical, Kriging, Geostatistics, SPT, GIS
The standard of determining the minimum required number and depth of boreholes is currently governed by professional judgment and is not scientifically justified in the local structural code. In this study, previous Standard Penetration Test (SPT) reports within the University of the Philippines – Los Baños Science and Technology Park Complex were used to perform geostatistical modeling using the simple kriging interpolation of GIS software to predict the SPT N-values, uncertainties, and soil type in 22.5x 22.5m cell sizes, or blocks, within the study area with depths of down to 10 meters. Statistical measures such as mean error, mean average error, root mean square error and coefficient of determination were used to validate the accuracy of the models. A superimposed raster map of the maximum SPT N standard errors of 1-10m and 6-10m layers were created, and the blocks with at most ±5 N-values as their 95% confidence interval were identified as 0-blocks, which suggests that no borehole exploration will be necessary. Guidelines to determine the minimum required number and depth of boreholes in a specific area using these interpretations were then developed. Finally, this study established a method that requires fewer boreholes and explorations with lesser depths compared to the current code and produced a total of 401 0-blocks that may save up to 20.30 hectares of land that needs geotechnical investigations.