Constitutive Model for 1-D Cyclic Soil Behaviour Applied to Seismic Analysis of Layered Deposits

A phenomenological constitutive model, 'BWGG', is developed for the non-linear one-dimensional ground response analysis of layered sites. The model reproduces the nonlinear hysteretic behaviour of a variety of soils, and possesses considerable flexibility to represent complex patterns of cyclic behaviour such as stiffness decay and loss of strength due to build-up of pore-water pressure, cyclic mobility, and load induced anisotropy. It also has the ability of simultaneously generating realistic modulus and damping versus strain curves, by a simple calibration of only three of its parameters. The model is implemented through an explicit finite-difference algorithm into a computer code which perform integration of the wave equations to obtain the nonlinear response of the soil. The code, 'NL-DYAS', is then applied to study the seismic response of a soft marine normally-consolidated clay. The results are compared with those of widely used codes. Finally, the records of the Port Island array during the Kobe 1995 earthquake, are utilized, and the model is shown to “predict” the observed response with sufficient accuracy.