Mechanical Characteristics and Failure Prediction of Cement Mortar with a Sandwich Structure

It is necessary to master the mechanical properties and failure prediction of the composite of mortar and rock block in a mined-out area. In this study, uniaxial compression and acoustic emission (AE) synchronous tests of mortar specimens with different sandwich materials and cement–sand ratios were carried out. The results showed that the compressive strength and elastic modulus of mortar specimens increased with an increase in the cement–sand ratio and the stiffness of the sandwich material. The AE counts and energy of mortar specimens with a high-stiffness sandwich material were maximum when they were destroyed. The b value, a number that reflects the extent of fracture propagation, decreased first and then increased with the increase in strain. The inflection point of the b value can be taken as the indication of the imminent failure of the mortar. A method for determining the b value at the turning point was proposed and verified.