Abstract
This paper presents an innovate approach to simulate the stress-strain behaviour of sands subjected to large amplitude regular cyclic loading. New prediction correlations were derived for damping ratio (D) and shear modulus (G) of sand utilizing linear genetic programming (LGP) methodology. The correlations were developed using several cyclic torsional simple shear test results. In order to formulate D and G, new equations were developed to simulate hysteresis strain–stress curves and maximum shear stress (τmax) at different loading cycles. A genetic algorithm analysis was performed to optimize the parameters of the proposed formulation for stress-strain relationship. A total of 746 records were extracted from the simple shear test results to develop the τmax predictive model. Sensitivity and parametric analyses were conducted to verify the results. To investigate the applicability of the models, they were employed to simulate the stress-strain curves of portions of test results that were not included in the analysis. The LGP method precisely characterizes the complex hysteresis behaviour of sandy soils resulting in a very good prediction performance. The proposed design equations may be used by designers as efficient tools to determine D and G, specifically when laboratory testing is not possible.
Highlights
Introduction and backgroundAn important concern to design engineering geosystems is to provide precise estimations of stress-strain response of soils under cycling loading
The behaviour of soil under the state of unloading and reloading is important in many cases such as foundation excavation and cyclic loading
The linear genetic programming (LGP) paradigm was employed for the analysis of the stress-strain behaviour of sands under large amplitude regular cyclic loading
Summary
An important concern to design engineering geosystems is to provide precise estimations of stress-strain response of soils under cycling loading. Three major categories are considered for the models developed to predict stress-strain relationship of soil under cyclic loading (Ishihara 1996; Shahnazari et al 2010):. (3) Numerical procedures involving step-by-step integration techniques are employed to simulate the stress-strain response of soil in large range of shear strain (i.e. shear strain >10–2) In this case, the shear modulus and damping ratio change with both the shear strain and the progression of cycles. This is usually done through extensive trial studies (Alavi et al 2011) To cope with this issue, more robust tools are required to formulate the cyclic stress-strain behaviour of soils. There is no need to perform laboratory tests before the implementation of the LGP models
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