Study on strength characteristics and fracture mechanism of filling body under different stress rates

Filling body is a key factor to maintain the safety and stability of stope, which is composed of heterogeneous materials mixed with many kinds of materials.The mechanical properties are complex and the change of loading condition have a significant effect on the mechanical properties and damage mechanism.The uniaxial compressive strength test of the filling under different stress rates is carried out, and the evolution process of the specimen is monitored by the non-contact full strain measurement system.The result shows:With the increase of the stress rate, the peak intensity of the filling body is increasing, and the strength of the low concentration and low gray sand is more obvious than that of the sample.Under low stress rate, a large number of macroscopic cracks appear on the surface of the specimen and tensile failure occurs.The single cant shear failure occurs under the high stress rate.The microfractures and pores in the specimen under low stress rate are fully developed to form a through surface, which weakens the strength of the filling.The microfracture and pore development of the specimen under high stress rate are limited, and the effect of the overall bearing structure on the strength of the specimen is dominant.Under stress loading, the specimen is destroyed at the moment of peak intensity, and the accumulation of energy concentrated instantaneous release, rupture phenomenon violent.