Strength gain of fine tailings/slimes resulting from secondary compression

The offset upstream construction method consists of constructing tailings impoundment dams on top of previously deposited fine tailings/slimes. The undrained shear strength of iron ore fine tailings/slimes underlying offset dams has been observed to increase over time, which is referred to as strength gain. The strength gain consists of two components: (1) increase in undrained shear strength due to increasing confining stress from fill placement and (2) increase in undrained shear strength under constant effective stress, which occurs after the end of primary consolidation (EOP). The second component of strength gain can be explained using the secondary compression concept. This paper presents field and laboratory testing used to characterize the strength gain of fine tailings/slimes due to secondary compression. Results of cone penetration test (CPT) soundings in addition to laboratory vane shear and consolidation tests are presented. Findings based on this testing are described, and recommendations for implementing strength gain due to secondary compression in tailings dam design are included.Applied Science, Faculty ofMining Engineering, Keevil Institute ofUnreviewedOthe

Sketching Free-Forms in Semi-Immersive Virtual Environments

In spite of the widely used sophisticated software tools for mechanical design, serious difficulties are encountered in the styling phase of the design process when free-form surfaces (shortly free-forms) have to be modelled. In this paper we extend the ideas of Sachs' pioneering 3-Draw which allowed curve sketching in 3D space in several ways: we support the creation of NURBS surfaces (not only curves), we use a semi-immersive environment centered around a table-like stereoscopic back-projection display (also know as Virtual Table or Responsive Workbench) and we give the user an immediate preview while he sketches free-form surface. This combination of features makes our approach unique in comparison to similar systems. Some of them only work on polyhedral models and others are restricted to indirect 3D interaction with control points. Our approach follows the Walk-Up VR concept: the user can just step in front of a Virtual Table and work on his task intuitively