Dynamic Elastic Modulus Estimation of Granular Soils Using Group Method of Data Handling (GMDH)

Elastic modulus is one of the most important parameters in geotecal engineering that is usually measured through laboratory or in situ testing. Cyclic triaxial testing is a well-known laboratory test to determine the dynamic and static parameters of soils. In the current study, the dynamic elastic modulus of sand-gravel mixture at very small strain levels (about 10-5) has been studied using a triaxial cyclic apparatus along with local axial strain measurement. Influence of grading characteristics (curvature and uniformity coefficients), gravel content, mean effective confining stress and relative density on dynamic elastic modulus have been investigated. Based on the results of the tests, a comprehensive database including 120 records was established. Based on the database, two models have been developed to predict the dynamic elastic modulus using the group method of data handling (GMDH). In the first model the curvature coefficient (Cc) and in the second model the uniformity coefficient (Cu) is used as input parameter of soil grading charecteristics. Comparison of the RMSE in the two models indicates that the second model has better predictions than the first model. However, the coefficients of correlation (R) of models are satisfactory which indicates the GMDH has a good ability to predict the dynamic elastic modulus.