Energy-Based Fatigue-Creep Damage and Failure Pattern of Rock-Backfill Composite Structure Material in Mine Stopes Under High Static Stress: Disturbed Amplitude Effect

It is not uncommon that the rock-backfill composite structure (RBCS) material in underground mine stopes being exposed to alternative fatigue and creep loading condition. Understanding the failure and energy evolution is critical to maintain the backfilled stope stability and ensure safe mining activities. This work aims to investigate the effect of disturbed stress amplitude (DA) on the failure and energy evolution characteristics of RBCS under alternative fatigue and creep loading using a specially designed triaxial-shear fatigue loading apparatus and post-test CT scanning technique. Testing results show that the equivalent lifetime of RBCS is the largest for a specimen with low stress disturbance, and the volumetric strain increases with increasing disturbed stress amplitude. It is found that much more energy is consumed for a sample subjected to high stress disturbance, and the cyclic loading induced damage is much more severe at the whole process. A damage evolution model was established using the dissipated energy to express damage propagation at the respective fatigue loading stage and creep loading stage and the entire process. A series of CT images reveal the cracking pattern, typical tensile failure, and shear failure are found for the surrounding rock and backfill material, respectively. It is suggested that the backfill material plays crucial role in preventing hole spalling and collapse, especially under high stress disturbance. Alternative fatigue and creep loading experiments were conducted on RBCS samples.The equivalent lifetime of RBCS decreases with increasing disturbed amplitude.The accumulative energy consumption at a FLS is larger than at a CLS.Tensile failure and shear failure is found for the surrounding rock and backfill material, respectively.

Automated summary

This study investigates the effect of disturbed stress amplitude on the failure and energy evolution characteristics of the rock-backfill composite structure in underground mine stopes. The results show that specimens with low stress disturbance have the longest lifetime, while volumetric strain increases with increasing disturbed stress amplitude. More energy is consumed and severe cyclic loading induced damage occurs for samples subjected to high stress disturbance. CT images reveal the cracking pattern and failure characteristics of the surrounding rock and backfill material. The backfill material plays a crucial role in preventing spalling and collapse.