Abstracts Category : Other

Constitutive modelling of fibre-reinforced sands under cyclic loads

by Anderson Peccin Silva

Cyclic loads are induced by several sources, such as traffic, waves, wind and earthquakes. Particularly in the last years, more attention has been given to such loading conditions due to the development of the offshore engineering. Additionally, ground improving techniques have been employed to alter the characteristics of natural soils in order to increase its strength and delay or avoid liquefaction. Previous studies have developed complete constitutive laws for fibre-reinforced sands under monotonic loading conditions, but no previous work on modelling granular soils under cyclic loading has been reported. Hence, this research develops and validates a new constitutive modelling which is capable to fully assess the behaviour of fibre-reinforced soils under cyclic loads for undrained conditions. This model is based on two previous models developed by Diambra et al. (2013) and Diambra and Ibraim (2014), which employed a homogenisation technique to scale sand and fibre contribution. The behaviour of the sand follows the Severn-Trent Sand Model proposed by Gajo and Muir Wood (1999). Once the model is structured and its calculation procedure is defined, a parametric analysis is carried out in order to show the influence of each fibre and sand parameter in the composite response. An adjustment factor to account for the change in the interparticle forces caused by the fibres is proposed. Finally, the model is calibrated with experimental results and an analysis of its competences and limitations is performed. The calibration process showed that the model is able to capture important trends caused by the fibre reinforcement, such as a reduction in axial strain and in pore pressure generation, delaying the occurrence of liquefaction. The proposed model was shown to be more effective in reproducing the response of loose sands, i.e. those whose stress states are above the critical state line. Carregamentos cclicos so causados de diversas maneiras, como trfego de veculos, ondas, vento e terremotos. Nos ltimos anos, particularmente, tem-se aumentado o nmero de estudos para este tipo de carregamento devido ao desenvolvimento da engenharia offshore. Alm disso, tcnicas de melhoramento de solos granulares tm sido empregadas para alterar as caractersticas dos solos naturais, com o objetivo de aumentar sua resistncia e retardar - ou evitar - a ocorrncia de liquefao. Alguns estudos anteriores desenvolveram leis constitutivas completas para areias reforadas com fibras sob carregamento monotnico, mas no so encontrados na literatura trabalhos sobre a modelagem deste tipo de solos sob carregamentos cclicos. Sendo assim, essa dissertao desenvolve e valida um novo modelo constitutivo capaz de avaliar o comportamento de solos granulares reforados com fibras sob carregamento cclico sob condies no-drenadas. Este modelo baseado em dois modelos previamente desenvolvidos por Diambra et al. (2013) e Diambra e Ibraim (2014), que utilizam uma tcnica de homogeneizao para considerar a contribuio da areia e dasAdvisors/Committee Members: Consoli, Nilo Cesar, Festugato, Lucas.