Experimental and analytical study of a frustum confining vessel

Abstract

<p>A Frustum Confining Vessel (FCV) was developed by McMaster University and Berminghammer Foundation Equipment Ltd., which provides an environment for the testing of reduced-scale piles (physical model). This vessel is intended to produce stress distributions within sand specimens, which resemble field conditions, however at a smaller geometric scale. This thesis presents the findings of the experimental and analytical investigations conducted on the FCV device. A technique for measuring normal stresses in dry sand is developed, and the stresses and displacements measured at specific locations within the sand specimens are used to calibrate the finite element model. Finite element simulations are used to evaluate different aspects of the responses, which cannot be directly measured in the experiments. The fundamentals of dimensional analysis are reviewed and a set of primitive variables for the pile-soil system is presented. Using the Buckingham-π theorem, a derived set of dimensionless groups is thereby proposed for the study of pile-soil interaction. The scaling factors necessary for the extrapolation of results from model to prototype conditions are obtained via similarity analysis. It is suggested that the lack of gravity scaling in the FCV device does not introduce significant distortions in the physical model provided that stress distributions, particularly horizontal stresses, are properly controlled by FCV loading. In relation to physical modeling of piles, a criterion for the acceptance of testing conditions is established, and the suitability of the current device is assessed in terms of the mentioned criterion. It is found that the current device does not completely meet the acceptance criteria. The improvement on testing condition is thereby sought by redesigning the vessel's shape. Alternative shapes for the vessel are investigated by means of finite element modeling. A redesigned shape, which offers optimal stress conditions for the purposes of physical modeling, is presented.</p>