Estudo do modelo constitutivo BBM. Influência da sucção na resistência ao corte

Abstract

In the present dissertation, a study of the Barcelona Basic Model, BBM, is realized. The mathematical formulation is presented and developed, referring the assumptions and simplification assumed in each step. A set of laboratory tests that enable the determination of the model parameters is suggested and some considerations are elaborated about the influence that some parameters have on the model and the range of values that they should adopt. It is adapted to the BBM and implemented in MATLAB programming language two explicit integration algorithms, without proceedings to the error control, to strain and stress tensor increments, respectively, together with suction increments. A third explicit integration algorithm with proceedings to the error control, more effective for the implementation in automatic calculation programs, is also adapted. The formulation of the CODE_BRIGHT program is presented, indicating the necessary simplifications to the modelling of geotechnical structures. Comparative analyses are made between CODE_BRIGHT program and the implemented drivers, in order to validate the explicit integration algorithms adapted to the BBM and illustrate the main phenomena of the unsaturated soils that the BBM is capable of modelling. Some limitations of the model are presented and discussed. Finally, some general considerations are made about the evolution of the volumetric and deviatoric strain with the occurrence of the collapse phenomenon and the influence that the suction decrease may have in the evolution of the shear strength.