publications

2021

1. 

   Modelling Initial Elastic Modulus of Sand-EPS Mixtures Using Evolutionary Polynomial Regression

   Sina Lahijani Afkham, Masoud Hajialilue Bonab, and Abolfazl Najafi

   In 39th National Congress and 4th International Congress of Earth Sciences, 2021

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   Due to its low density as well as high strength/density ratio, expanded polystyrene (EPS) has gained significant popularity as a viable approach to soil stabilization. Considering the increasing use of EPS as a lightweight fill material, the development of reliable correlations for predicting its compressibility behavior would be beneficial due to the reduction of the costs connected with conventional laboratory testing. In the current study, undrained-unconsolidated (UU) triaxial compression tests were carried out on sand-EPS specimens prepared with various EPS contents and subjected to different confining pressures. Having observed and analyzed the compressibility responses of the composites, an EPR-based model was proposed and verified for the purpose of predicting the initial elastic modulus. Subsequently, in order to investigate the relative impact of each input variable on the estimated output, sensitivity analysis, as well as parametric study were carried out. The results demonstrate that although both the confining pressure and the EPS volume content have a consequential influence on the predicted initial elastic modulus, the former is a more sensitive component of the model

2020

1. 

   A polynomial model for predicting shear wave velocity from cone penetration test data

   Sina L. Afkham, and Abolfazl Najafi

   In The Third International Conference on Civil, Architecture and Urban Development Management in Iran, 2020

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   Shear wave velocity (Vs) is known to be an essential soil parameter for site characterization purposes. Although shear wave velocity can be directly measured, indirect determination using common in-situ tests, entailing cone penetration test (CPT), are often preferred by engineers. In this paper, the relation between Vs and CPT parameters is reinvestigated and a new polynomial regression form is proposed to correlate shear wave velocity with cone tip resistance, sleeve friction, and vertical effective stress. Using a dataset obtained from several sites in Canada, Japan, Norway, Italy, and China, the performance of the presented correlation is appraised through comparison with the observed data as well as formerly published CPT-Vs equations. The results demonstrate that the suggested functional form provides a more reliable approach for predicting shear wave velocity and thus, can ostensibly be regarded as an improvement to the currently adopted practices.