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Estimation of fractured rock permeability around excavations from the viewpoint of rock mechanics

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Category: Mining

Last Updated on 16 May 2013

Published on 15 November 2012

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Authors:

D.V. Rudakov, Dr. Sci. (Tech.), Associate Professor, State Higher Educational Institution “National Mining University”, Senior Lecturer of the Department of Hydrogeology and Engineering Geology, Dnipropetrovsk, Ukraine

Ye.S. Ivanova, State Higher Educational Institution “National Mining University”, Postgraduate Student of the Department of Hydrogeology and Engineering Geology, Dnipropetrovsk, Ukraine

Abstract:

Purpose. To estimate changes in the fractured rocks permeability caused by the disturbances in the stress-strain state of rocks appeared during driving of an underground excavation. The studied site is a local zone in rock mass around a horizontal working at depths down to 900 m, which is characteristic for ore deposits of central part of Ukraine.

Methodology. A method of estimation of permeability of fractured rocks around underground excavations was developed. It was based on numerical simulation of the stress-strain state of rocks and allows calculating hydraulic conductivity according to fracture parameters. The model was verified in the mining and geological conditions of Pivdenno-Bilozerske deposit. The deviations in hydraulic conductivity up to 2–3 times from the mean undisturbed value were established. They depend on fractured rock parameters such as tilt angle and distance between joints. The more significant changes were predicted for tilt angle of 45°, with extension of these zones reaching 3–5 excavation radiuses.

Findings. The nature of changes in the active zone of fractures at different depths, rock properties and parameters of joints such as length, the disclosure value, the distance between joints, tilt angle have been investigated. Permeability changes both within the mined out zone and around the single excavations are of practical interest. However, the local excavation impact on shaping the field permeability has not been investigated properly yet.

Originality. Numerical modeling of the stress-strain state was used in analysis of local changes of fractured rock permeability in the zone around underground excavations of circular cross section at different fracture inclination angles.

Practical value. More exact values of conductivity in the zone affected by underground excavation allow for more reliable predictions of the hydrodynamic behavior in mined out rocks in the mines to be flooded.

References:

1. Шашенко О.М. Геомеханічні процеси у породних масивах / Шашенко О.М., Майхерчик Т., Сдвижкова О.О. – Дніпропетровськ: НГУ, 2005. – 319 с.

Shashenko, O.M., Maikherchik, T. and Sdvizhkova, O.O. (2005), Geomekhanіchnі protsesy u porodnykh masyvakh [Geomechanical Processes in Massif], National Mining University, Dnіpropetrovsk, Ukraine.

2. Teutsch, G. (2005), Flow and Transport in Fractured Porous Media, Springer Verlag.

3. Садовенко И.А. Научные основы управления геофильтрационным состоянием породного массива вокруг горных выработок: автореф. дис… д-ра техн. наук / Садовенко Иван Александрович // Днепропет-ровский горный ин-т. – Днепропетровск, 1992. – 455 с.

Sadovenko, I.А. (1992), “Scientific base for massif filtration properties control around mine workings,” Abstract of Dr. Sci. (Tech.) dissertation: 05.15.04; 05.15.11, National Mining University, Dnepropetrovsk, Ukraine.

4. Рудаков Д.В. Обоснование модели инфильтрационных потоков в неоднородном подработанном массиве горных пород / Рудаков Д.В., Садовенко И.А. // Сб. науч. трудов ДНТУ – Донецк, 2005. – №13. – С. 3–15.

Rudakov, D.V. and Sadovenko, I.А. (2005), “Substantiation of seepage model in undermined heterogeneous massif”, Sb. nauch. trudov DNTU, Donetsk, no.13, pp. 3–15.

5. Громадка II.Т. Комплексный метод граничных элементов в инженерных задачах / Громадка II Т., Лей Л. – М.: Мир, 1990 – 303 с.

Gromadka, II.T. Ley, L. (1990), Kompleksnyy metod granichnykh elementov v inzhenernykh zadachakh [The Complex Boundary Elements Method in Engineering Problems], Mir, Moscow, Russia.

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