The effect of increasing the water content on rocks characteristics from Şuior, Romania
M. Toderas1, R. Moraru2
1Mining Engineering, Surveying and Civil Engineering Department, University of Petrosani, Petrosani, Romania
2Management and Industrial Engineering Department, University of Petrosani, Petrosani, Romania
Min. miner. depos. 2017, 11(3):1-14
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Purpose.Generation of relative humidity fluctuations lead to a further decrease in the resistance of rocks, which involves the swift evacuation of groundwater from mining works. For andesitic rocks strongly hydrothermal altered it was found an irreversible phenomenon of the effect of humidity upon their strength, while this phenomenon is accompanied by an alteration. Natural humidity content at saturation and absorption coefficient of rock specimens studied ranged within large limits, average kinetics absorption by changing from one type of rock to another, some rocks could not reach the degree of saturation because they were disaggregated.
Methods. Establishing the rocks characteristics from Şuior mine, in the context of underground microclimate conditions and their interaction with water taking into account the determinative anisotropy and the degree of heterotrophy.
Findings. Some of the mining works with straight walled profiles, vaulted ceiling and unsupported floor were executed in rocks with pronounced trends towards deterioration and swelling of floors; given that, the rocks contain insertions of kaolin andesite, have shown a tendency to swelling of floor, which required the use of circular profiles and horseshoe-shaped profiles with enclosed floor. Observations have highlighted that the deformations of the floor are not due only to the fact that the works are located in rocks with low resistance, but also because the water is accumulated in the floor of these works, changing in a short time the mechanical properties of the rocks. Swelling of the floor is the consequence of intensive water-rock action, having the effect of misalignment of the floor, destructive effect upon the foundation and of support base, this attempt a horizontal displacement towards the interior of the gallery, unbalancing the support.
Originality. For the rocks from Şuior, protecting with synthetic resin is the optimal method, which is confirmed by the good behavior of the resins as insulating protection in order to maintain the characteristics of these unaltered rocks.
Practical implications. Under the influence action of water and underground climate, most of the rocks, with the exception of porphyritic andesite with hipersten, degrades and reduces its mechanical strengths and elastic characteristics. In order to maintain these rocks to initial parameters, methods will be used to protect, to strengthen. Alteration created by water effect has a significant influence on the characteristics of strength and deformation, effect that has direct implications on the stability of the mining works performed in the rocks from Şuior.
Keywords: anisotropy, alteration, humidity, swelling, stability, pressure, microclimate
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