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Compressive deformation characteristics of crushed sandstone based on multiple experimental factors

Sun Yanan, Zhang Peisen, Yan Wei, Yan Fenqian, Wu Junda

Archives of Mining Sciences

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2020

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Vol. 65, no. 1

129--146

EN

In this study, the compressive deformation of crushed sandstone was tested using a crushed rock deformation-seepage test system, and the effects of various factors, including crushed rock grade, grade combination, water saturation status, and stress loading method (i.e., continuous loading or cyclic loading and unloading), on the compressive deformation of crushed sandstone was analyzed from four perspectives including stress-strain, bulking coefficient, deformation mechanism and energy dissipation. The results indicate that the stress-strain relations of crushed sandstone are closely associated with all factors considered, and are well represented by exponential functions. The strain observed for a given applied stress increased with increasing crushed rock grade throughout the loading period. Crushed sandstone grades were combined according to a grading index (n), where the proportion of large-grade rocks in the sample increased with increasing n. The bearing capacity of a water-saturated crushed sandstone sample with n = 0.2 was less than that of an equivalent dry sample for a given applied stress. The stress-strain curve of a water-saturated crushed sandstone sample with n = 0.2 under cyclic loading and unloading was similar to that obtained under continuous loading. Observation and discovery, the deformation mechanism of crushed sandstone was mainly divided into four stages, including crushing, rupture, corner detachment and corner wear. And 20% of the work done by testing machine is used for friction between the crushed sandstone with the inner wall of the test chamber, and 80% is used for the closing of the void between the crushed sandstone, friction sliding, crushing damage.

2

Evaluation of Strength and Failure of Brittle Rock Containing Initial Cracks under Lithospheric Conditions

Li X., Qi C., Shao Z., Ma C.

Acta Geophysica

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2018

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Vol. 66, no. 2

141--152

EN

Natural brittle rock contains numerous randomly distributed microcracks. Crack initiation, growth, and coalescence play a predominant role in evaluation for the strength and failure of brittle rocks. A new analytical method is proposed to predict the strength and failure of brittle rocks containing initial microcracks. The formulation of this method is based on an improved wing crack model and a suggested micro-macro relation. In this improved wing crack model, the parameter of crack angle is especially introduced as a variable, and the analytical stress-crack relation considering crack angle effect is obtained. Coupling the proposed stresscrack relation and the suggested micro-macro relation describing the relation between crack growth and axial strain, the stress-strain constitutive relation is obtained to predict the rock strength and failure. Considering different initial microcrack sizes, friction coefficients and confining pressures, effects of crack angle on tensile wedge force acting on initial crack interface are studied, and effects of crack angle on stress-strain constitutive relation of rocks are also analyzed. The strength and crack initiation stress under different crack angles are discussed, and the value of most disadvantaged angle triggering crack initiation and rock failure is founded. The analytical results are similar to the published study results. Rationality of this proposed analytical method is verified.

3

Duże koparki zgarniakowe

Kozioł W., Kawalec P., Machniak Ł.

Surowce i Maszyny Budowlane

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2006

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nr 1

41-46

PL

Duże koparki zgarniakowe wykorzystuje się do urabiania zwałowania różnego rodzaju skał: od sypkich, miękkich i kruchych, po skały średniozwięzłe i zwięzłe (po wstępnym rozluzowaniu materiałami wybuchowymi). W niektórych przypadkach używa się również koparek zgarniakowych do urabiania i załadunku kopaliny użytecznej na środki transportu technologicznego (głównie duże samochody). Znajdują one zastosowanie w górnictwie odkrywkowym przede wszystkim w USA, Kanadzie, Australii, Rosji, Kolumbii, Wielkiej Brytanii i Indiach. Koparki te wykorzystywane są głównie do zdejmowania nakładu i bezpośredniego przemieszczania go za zwałowisko wewnętrzne.