Advanced Modeling in Civil Engineering
Evaluation of Initial Shear Stiffness Empirical Models for Unsaturated Soils with In-situ Down-Hole Tests
Document Type : Original Article
Authors
1 Master of Science in Civil Engineering - Earthquake Engineering, Civil engineering Department, Faculty of Engineering, Razi University, Kermanshah, Iran
2 Associate Professor, Civil Engineering Department, Faculty of Engineering, Razi University, Kermanshah, Iran
Abstract
Initial shear stiffness is one of the critical parameters in geotechnical investigations. It mainly applies to evaluating the seismic ground response analysis and the seismic design of earthen structures. Laboratory and in-situ geophysical tests are standard methods for measuring shear stiffness parameters; however, particularly for unsaturated soils, these methods are expensive because of the use of advanced equipment and professional labor. Empirical equations could be used to estimate the shear stiffness modulus effectively. Although the proposed equations for estimating the shear stiffness modulus for saturated soils have been studied for years, these equations have a short history due to the complexities of dynamic tests on unsaturated soils. In recent years, numerous research studies have been performed to provide models for estimating the initial shear modulus of unsaturated soils. This research compares the results of a series of empirical initial shear stiffness estimating models for unsaturated soils with the down-hole test results. The study includes utilizing empirical soil-water retention curves from the site borehole geotechnical properties and estimating the initial shear stiffness from existing empirical models. Each model's constant parameters have been determined using the particle swarm optimization (PSO) method. Finally, the estimated shear modulus is compared with the measured shear modulus from down-hole test results, and a series of calibrated parameters is presented for studied borehole soils.
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