Mechanical properties of deep sandstones under loading rate effect

Abstract

The advance speed of the working face in coal mines can significantly affect the fluctuation frequency of abutment pressure in front of the coal body. Moreover, it has a certain correlation with the change of axial loading rate in coal and rock mechanics test. Therefore, uniaxial compression tests under various loading rates of 0.05, 0.1, 0.15, 0.25, 0.5 MPa/s were conducted using 2000 kN triaxial testing machine and PCI-2 acoustic emission test system to study the loading rate effect on the mechanical properties of deep sandstones. The results show that 1) the peak strength and elastic modulus of the deep sandstone increase with the loading rate increasing; 2) with the loading rate increasing, the deep sandstone transforms from plastic-elastic-plastic to plastic-elastic and moreover, the failure mode gradually transfers from type I to type III; 3) With the loading rate increasing, the total input strain energy, elastic strain energy, and dissipated strain energy generally increase; 4) the damage variable presents the evolution characteristics of inverted “S” shape with time, and with the loading rate increasing, the damage degree of the deep sandstone is aggravated. The conclusion obtained can provide the theoretical basis for the stability control of the surrounding rock in deep engineering.

Keywords

loading rate effect / failure mode / energy evolution / damage evolution / mechanical properties / deep sandstone

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