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1.
Measurement and interpretation of the small strain stifness of Boštanj silty sand
Gregor Vilhar, Vojkan Jovičić, 2009, original scientific article

Abstract: This paper presents measurements, and an interpretation of these measurements, based on the use of bender-element probes for Boštanj silty sand. The samples were prepared at different initial void ratios and isotropically compressed up to 5 MPa. The bender-element technique was used to determine the dynamic shear modulus ($G_0$) of the soils at very small strains. The multiple bender-element probes were shot at different excitation frequencies in order to increase the reliability of the measurements. The $G_0$ stiffness was determined by using three different techniques: a) the first-time arrival, b) the phase-change method and c) the cross-correlation method. The systematic differences observed between the $G_0$ values, calculated using the three techniques, are discussed. The variation of $G_0$ in the log$G_0$ - log$p'$ plane was evaluated for the Boštanj silty sand and compared with other sands.
Keywords: silty sand, triaxial testing, small strain stiffness, bender elements, time-domain and frequency-domain, measurements
Published in DKUM: 06.06.2018; Views: 1194; Downloads: 160
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2.
Development of a conceptual material model for structured materials - S_BRICK
Vladimir Vukadin, Jakob Likar, Vojkan Jovičić, 2005, original scientific article

Abstract: Materials known in literature as Soft Rocks & Hard Soils such as claystones, siltstones, flysh, hard soils, marls, etc. received a lot of attention in research community in recent years. It was demonstrated that some of these materials can be described through general theoretical framework (Cotecchia & Chandler [1]), which takes into account the structure as an intrinsic material property that is present in all natural geological materials. The influence of the structure is manifested as an increase in strength and stiffness in a material. Based on a laboratory results and existent theoretical frameworks, a further step was taken with the development of a conceptual constitutive model for structured materials. A model formulated in strain space named BRICK (Simpson [2]) was chosen as a base model and was further developed with the inclusion of structure and destructuring. The new model was named S_BRICK and was tested on a conceptual level where the results of numerical tests on structured and structure less (reconstituted) materials at different stress paths were compared. The results showed that S_BRICK was able to capture stress-strain behavior typical for structured material and could be potentially used for the modeling of Soft Rocks and Hard Soils.
Keywords: geomechanics, soft rocks, hard soils, constitutive material models, structure, destructuring, numerical modeling
Published in DKUM: 15.05.2018; Views: 1438; Downloads: 165
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