To design mat foundation, there are certain values which are required for calculations and analyses, one of which would be the vertical modulus of subgrade reaction. It can be obtained through various deterministic testings such as the Plate Load Test. On the other hand, the study calculated this factor through the use of Standard Penetration Test (SPT) results by using four methods that were obtained from the review of related literature, namely, by definition of the said parameter (Das, 2008), by standard equation (Vesic, 1961), by empirical models (Moayed & Naeini, 2006 Ou, 2006), and by the equation formulated by Bowles (Bowles, 1995). Comparative study and validation were also performed to confirm the most recommendable method to be used to compute for the soil spring constant, given the limitations of the SPT results, by correlation of this parameter to the California Bearing Ratio (CBR) test results. Through this, the study considered and used the equation formulated by Bowles to calculate for the vertical modulus of subgrade reaction. Then, a Geographic Information Systems (GIS) software was utilized to generate maps of these values by the method of ordinary kriging. These maps presented the locations with the predominantly high and low values of the soil spring constant. They were also used to create a digitized reference of the values of the vertical modulus of subgrade reaction for the design of mat foundations for preliminary design through the use of Visual Basic Applications 2010
