Experimental Study on Characteristics of Fatigue Damage of Coal Specimen under Cyclic Loading

摘要

The characteristics of strength, deformation and fatigue damage of No.3 coal seam from Xinhe Colliery under cyclic loading is studied by MTS servo-controlled rock mechanical test system. The results show that coal is more inclined to fatigue damage than other hard rocks. Under uniaxial cyclic loading, the fatigue failure "threshold value" of No.3 coal seam sample from Xinhe Colliery is less than 78% of its uniaxial compressive strength, and there will also be a certain extent of fatigue damage when cyclic loading and unloading experiment is carried out below the fatigue failure "thresh-old value". Axial deformation of coal specimen can be divided into three stages: Initial deformation, constant speed deformation and accelerating deformation. Under cyclic loading, the evolvement process of compaction, strain hardening, strain softening and breaking of coal can be expressed by the fatigue damage process.