Experimental study on mechanical properties of Xiaojihan coal samples under plastic flow

Abstract

In order to study the plastic flow properties and hysteresis characteristics of Xiaojihan main water-bearing coal seam under the influence of mining, the axial cyclic loading and unloading tests under different confining pressures were carried out. When the axial stress after the peak drops to 70% of the peak stress, the cyclic loading and unloading axial compression test is started, and the secant modulus, width-length ratio of the hysteresis ring and the change law of the axial peak stress ratio of the adjacent hysteresis ring are analyzed. The results show that: with the increase of confining pressure, the secant modulus and width-length ratio of the axial strain-axial stress hysteresis curves and the hoop strain-axial stress hysteresis curve increase, while the axial peak stress ratio of the adjacent hysteretic loops decreases; with the increase of the number of cycles, the secant modulus and the width-length ratio of the axial strain-axial stress hysteresis curves and the hoop strain-axial stress hysteresis curves decrease. For approximately the same initial stress state, the confining pressure has a significant effect on the geometric characteristics of the hysteresis curve and the plastic flow.

Keywords

• xiaojihan coal seam
• plastic flow
• confining pressure
• cyclic loading and unloading after shear yielding
• stress-strain hysteresis