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First name, Middle name, Last name, Scientific degree, Scientific rank, Current position. Full and brief name of the organization, The organization address.Ofrikhter V.G. – candidate of technical sciences, associate professor E-mail: This e-mail address is being protected from spambots. You need JavaScript enabled to view it Ofrikhter I.V. – student E-mail: This e-mail address is being protected from spambots. You need JavaScript enabled to view it Perm National Research Polytechnical University The organization address: 614990, Russia, Perm, Komsomolsky av., 29
Title of the articleEstimation of the mechanical creep of fibrosand by the results of compression testing
Abstract.Settlement of fibrosand in consolidation testing is determined by two processes – direct compression and mechanical creep. Traditional approaches for compression estimation, based on filtration consolidation theory are unsuitable for unsaturated specimens of pseudo-cohesive soil. Testing results for such soils could be estimated by first order rate equations. Sand reinforced by randomly oriented short (6-12 mm) fibers (further – fibrosand) is a specific type of artificial soil for which the properties of as cohesive as non-cohesive soils are intrinsic. Mechanical characteristics of fibrosand are angle of internal friction and cohesion, but at the same time the permeability coefficient is measured in order of 1 m/day. Settlement of fibrosand is caused by the physical mechanisms and determined by two processes – direct compression and mechanical creep. Initial rapid development of settlements is direct compression. The term «direct compression» is proposed to use for fibrosand in contrast to the primary consolidation, used in soil mechanics because of the fact that material of fibrosand is generally unsaturated, while the primary consolidation in soils conforms to the compression of cohesive soils at pore pressure dissipation. Further settlement increase continues at constant load as a result of mechanical creep. Mechanical creep is a physical process of compression at which the volume of voids decreases with time because of separate components of fibrosand are shifted under the load and slipping appears on the contact of the particles. Methodologies applied in soil mechanics for determination of the transition from the primary to secondary consolidation (for example methods of Taylor and Casagrande, founded on one – dimensional theory of filtration consolidation are inapplicable to the fibrosand as the material is unsaturated and pore pressure is not dissipated. In this situation the method of compression evaluation and determination of void ratio to the ending of each of two phases of compression (direct compression and mechanical creep), based on the first order rate equation was applied. In all performed experiments on the study of fibrosand creep at each step of load application the rapid increase of settlement was observed initially (direct compression), followed by the reduction of the speed of deformations (mechanical creep). Using the first order rate equation anyone can prognosticate the value of void ratio to the ending of secondary compression. Established rules allow verifying the mechanism of behavior of unsaturated non-cohesive fibro-reinforced soils and soil-like materials to which, except fibrosand, municipal solid waste is related. Compression of unsaturated sand specimens, reinforced by randomly oriented fibers consists of two phases – direct compression and mechanical creep. Compression testing of fibro-reinforced sand specimens allows understanding the mechanism of mechanical creep of non-cohesive fibro-reinforced soils and soil-like materials. Application of first order rate equation allows estimating the rheological processes in unsaturated fibro-reinforced soils and soil-like materials under continuous loading.
Keywords.fibro-reinforced unsaturated non-cohesive soil, mechanical creep, first order rate equation.
For citations:Ofrikhter V.G., Ofrikhter I.V. Estimation of the mechanical creep of fibrosand by the results of compression testing // Izvestiya KGASU. 2014. №4(30) P.222-229.


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