Deformation and Failure Characteristics of Strong-Weak Coupling Structures with Different Height Ratios Under Cyclic Loading and Unloading.

Strong-weak coupling outburst prevention technology can reduce the hazard of coal and gas outburst in mines based on hydraulic punching and grouting reinforcement. In this study, the mechanism of outburst hazards in the strong-weak coupling structure under mining disturbance was explored, and then cyclic loading and unloading experiments were performed on samples with different strong-weak height ratios (HRs) using the noncontact full-field strain testing (DIC) system and the acoustic emission (AE) system. The results show that the failure strength of the sample gradually increases with the increase in HR. The residual strain of the strong and weak structures undergoes three stages, i.e., the decelerated deformation, the constant-velocity deformation, and the accelerated deformation. Deformation mainly occurs in the weak structure and starts at the strong-weak interface. The AE signals present strong regional distribution characteristics and the Felicity effect, and the damage is concentrated near 70% of each stage in the cyclic loading process. As the HR rises, the weak structure transitions from brittle damage to ductile damage and from shear damage to tensile damage. In addition, due to the difference in Poisson effects of strong and weak structures, the strong structure transitions from a unidirectional stress state to a triaxial tensile-compressive stress state. When the HR increases to 85:15, the strong structure undergoes tensile damage.