Implementation and application of bounding surface model in ABAQUS

In most dynamic analyses of geotechnical problems, an iterative equivalent linear approach is usually used to model the nonlinear strain dependent modulus and damping properties of the soils. However, the computed seismic response can not reflect the effects of the induced pore pressure during earthquake shaking and the permanent deformations can not be predicted directly. So it is important to adopt an appropriate elastic-plastic model to simulate soil behaviors under the cyclic loading conditions. The integration algorithm of bounding surface model and the consistent tangent matrix were derived first, and then the procedure to write a UMAT subroutine in ABAQUS for bounding surface model was described in detail. Finally, the undrained triaxial shear tests were simulated using ABAQUS with the developed model, and the computed results were found to be reasonable and reliable. The developed user subroutine can make use of the advantages of ABAQUS such as convenient preprocessor and postprocessor, high solution precision and high ability to handle complex problems. Therefore it provides an alternative method for dynamic analysis of geotechnical problems.