Experimental study on evolution of mechanical parameters of coal containing gas under unloading confining pressure

Taking briquette samples as object of study, evolution of mechanical parameters of coal containing gas is studied under unloading confining pressure by triaxial servo-controlled seepage equipment for thermo-fluid-solid coupling of coal containing gas. The results show: the common law of evolution of mechanical parameters of coal containing gas under unloading confining pressure is a two-stage characteristics, and nonlinear characteristics is very obviously. In process of unloading confining pressure, there is one value of confining pressure points so that the mechanical parameters of coal samples are abnormal changes, and all of axial load, radial strain and deformation coefficient are significantly reduce, but axial strain will have a slight increase, the relation between confining pressure and radial strain can be expressed by improved logarithmic, and the law of gas flow can be exactly judged on based of deformation coefficient of coal containing gas.