Study on Micro-Mechanism of Concrete Hydraulic Fracturing Using DEM
The micro-mechanism of hydraulic fracturing of concrete was investigated by using the discrete element method . A bonded-particle model was employed to simulate the mechanical behavior of the cement among aggregates. Coarse aggregates were modeled as unbr
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Abstract The micro-mechanism of hydraulic fracturing of concrete was investigated by using the discrete element method. A bonded-particle model was employed to simulate the mechanical behavior of the cement among aggregates. Coarse aggregates were modeled as unbreakable clusters composed of several particles. The initial bonded contacts is assumed to be a parallel-plate channel that is the fluid flow path, and the element of fluid is characterized by domain, which is defined as a closed chain of particles and receives flows from the surrounding channels. Hydraulic pressure applied to the particles was increasing gradually until micro-cracks were developed. The number of micro-crack caused by normal stress and shear stress were recorded during the hydraulic fracturing test. After the test was finished, the macro-crack propagation direction was obtained. The results showed that the direction of macro-crack is almost in horizontal plane and hydraulic fracturing of concrete is due to tensile cracks between aggregates.
1 Introduction The problem of Hydraulic fracturing has been becoming one focus of geotechnical engineering since Teton dam failed in 1976 and a great deal of research on hydraulic fracturing was carried out over the past decades. Among these studies, some results showed that differential settlement and internal load transfer is probably the leading cause of hydraulic fracturing occurring in embankment or zoned dams [6, 8]. Based on laboratory testing results, a wedging mechanism created by water pressure in the initial discontinuity was hypothesized [4]. In recent years, acoustic emission is used for investigating the source mechanisms in geotechnical engineering. Acoustic emission data indicated that viscosity of fracturing fluid is the Y. Yang (&) Z.Z. Wang Z.L. Li Northwest A&F University, Yangling 712100, China e-mail: [email protected] T.-T. Ng University of New Mexico, Albuquerque 87131, USA © Springer Science+Business Media Singapore 2017 X. Li et al. (eds.), Proceedings of the 7th International Conference on Discrete Element Methods, Springer Proceedings in Physics 188, DOI 10.1007/978-981-10-1926-5_36
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factors of hydraulic fracturing [1, 2] and shear type fracture mechanism was observed [1]. However, the mechanism of hydraulic fracturing in earth and rock-fill dams has not been obtained yet because of the complication of geomaterial behavior. On the other hand, hydraulic fracturing occurs not only in earth and rock-fill dams but also at the heels of concrete gravity dams, especially if the concrete gravity dam is higher than 200 m [5]. Nevertheless, only a few studies on hydraulic fracturing in concrete gravity dam were performed [5], thus further research need to be done to reveal the mechanism. The purpose of this paper is to explore the micro-mechanism of hydraulic fracturing of concrete based on DEM. First, cluster models of concrete are created by using parallel bonds. Then fluid-solid coupling model is proposed and hydraulic fracturing test is carried out. Finall
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