Paria Afsharchi; Ali Asghar Mirghasemi
Abstract
Tailings dams, due to methods and materials used in their construction are vulnerable structures to earthquake. In many cases storage of water over tailings is required to prevent aerial pollution or reduction in water consumption by the means of a recycling system, therefore failure of these kinds of ...
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Tailings dams, due to methods and materials used in their construction are vulnerable structures to earthquake. In many cases storage of water over tailings is required to prevent aerial pollution or reduction in water consumption by the means of a recycling system, therefore failure of these kinds of dams not only induce affects similar to conventional water dams, but also may lead to irreversible damage to their surrounding environment due to toxic content of tailings. Sarcheshmeh Tailings dam, a rockfill dam with an inclined clay core, is 70 m height and necessity for increasing reservoir capacity has led to dam upgrading to a minimum level of 90 m; using downstream method. Different options have been studied in order to get the safest and most economical alternative. Vulnerability of dam site to earthquake has considerably affected the design issue. This paper represents the results of dynamic and pseudo-static analyses of this tailings dam. Dynamic analysis is carried out using the finite difference code FLAC (Fast Lagrangian Analysis of Continua, ITASCA).This code is able to take into account pore water pressure generation during construction and earthquake. Different acceleration time history records and soil models are used and results have been compared.
Ali Asghar Mirghasemi; Helia Rahmani
Abstract
In some natural events such as soil failure the deformations are localized in narrow restrictions, which are called shear bands. This event which is a fundamental phenomenon in granular material, has been widely investigated during recent decades within expensive experimental tests and also some numerical ...
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In some natural events such as soil failure the deformations are localized in narrow restrictions, which are called shear bands. This event which is a fundamental phenomenon in granular material, has been widely investigated during recent decades within expensive experimental tests and also some numerical simulations. Most of previously used numerical methods are based on continuum theories describing shear bands as interfaces along which solid masses move like rigid blocks. In this interpretation many physical events such as changes of the soil structure around failure line are neglected. In this paper the discrete element method is used to simulate the shear bands. Since in this method some of the problems of experiments and simulations are solved,
It would be an ideal method to obtain the stresses and strains, and also to investigate the behavior of shear bands in a granular media, while exposing to external forces. In this research by the use of DEM and conducting series of biaxial tests on assemblies of two-dimensional ellipse shaped particles, the effect of different factors such as average grain size, particle shape and confining pressure on the shear bands are studied and the results show that some investigated factors like average grain size and confining pressure have considerable effect on the shear bands characteristics.
The main results can be summarized as follows:
• The amount of rotation is a very sensitive characteristic and it changes considerably by all of the factors measured in this research.
• The most affecting factors on the displacement of the particles across the shear bands are the loading rate and confining pressure. Moreover by increasing the particle size the displacements increase with a great amount but if these values are divided by the particle radius, no significant changes in the particle displacement will be observed. Other factors do not seem to have any effects on this issue.
• 6-13d50 seems to be the best estimation for the shear band thickness, and other controlled factors affect this value within this restriction. The width of the shear bands seems to increase by the loading rate and confining pressure increase.
• The inclination of this localization is mostly affected by confining pressure (which increase leads to angle decrease), porosity (which increase leads to angle decrease), grading (its uniformity causes smaller shear band angles), and size (greater sizes of grains would result in failure with lower angles of sear band). Among these factors grain size has the least effect.