The influence of liquid nitrogen leaching time on raw coal mechanics and failure mode

Abstract

In order to study the influence of liquid nitrogen leaching treatment on the mechanical properties and failure modes of coal samples under uniaxial and triaxial loading, uniaxial and triaxial tests were carried out on coal samples with different liquid nitrogen leaching time by triaxial test device. The results show that whether liquid nitrogen leaching treatment is carried out has no obvious influence on the evolution trend of mechanical properties of coal samples during uniaxial loading and triaxial loading; with the increase of axial strain, the axial stress increases slowly at first, then increases linearly, and decreases rapidly after reaching the limit of coal samples. The peak axial stress of coal samples under uniaxial loading at different time of liquid nitrogen leaching is 4.28 MPa, 7.21 MPa, 2.32 MPa and 2.34 MPa respectively, and the peak axial stress under triaxial loading is 44.31 MPa, 25.73 MPa, 37.74 MPa and 39.78 MPa respectively. With the increase of liquid nitrogen leaching time, the peak axial stress of coal samples under uniaxial loading shows a trend of increasing first and then decreasing, and the peak axial stress under triaxial loading shows a trend of decreasing first and then increasing. The liquid nitrogen leaching coal sample is partially broken more thoroughly after uniaxial loading and triaxial loading, but the longer the liquid nitrogen leaching time is, the more the number and volume of large coal generated after the coal sample is broken.

Keywords

• raw coal
• liquid nitrogen leaching
• leaching time
• mechanical properties
• form of destruction