循环载荷作用下煤的力学性质及声发射特征演化规律

Mechanical Properties and Acoustic Emission Evolution Characteristics under Cyclic Loading

声发射是煤等脆性材料破坏过程中经常伴随的现象,可以通过研究煤的声发射规律掌握其损伤和裂隙的演化规律。借助三轴液电伺服加载系统和声发射测试系统,针对原煤试样,进行了循环加载实验,揭示了循环载荷作用下的煤力学性质和声发射演化特征。研究结果表明:多级加载疲劳试验中,循环载荷幅度相同的条件下,随着加载频率的减小,弹性模量降低30%～40%、不可逆塑性变形增加,说明煤样损伤及裂纹发展有时间效应;循环加卸载频率对于煤样内部原有的或新生的微裂纹扩展规律具有较大的影响;验证了声发射试验中的Kaiser效应和Felicity效应,发现煤的应力记忆特征、应变记忆特征具有Felicity效应,而且相对于应变记忆特征,应力记忆特征变化更加明显,说明煤的物性参数(应变)记忆能力相对好于状态参数(应力),更能准确地描述损伤。

Acoustic emission is often accompanied by the phenomenon of brittle materials such as coal rock mass destruction process, the damage and fracture evolution can be gained through the study of coal - rock acoustic emission law. Based on three - axis the elec- trohydraulie servo loading system and acoustic emission test system, cyclic loading experiments reveal the evolution of the characteristics of coal - rock mechanical properties and acoustic emission under cyclic loading. The results show that ： the multistage load fatigue test, the same magnitude of cyclic loading conditions, with decreasing load frequency, the elastic modulus decreased from 30% to 40% , the irreversible increase in plastic deformation described coal sample damage and crack development time effect;cyclic loading frequency of existing or new micro - crack propagation law within the coal sample has a larger impact; verify Kaiser effect and Felicity effect of the a- coustic emission test, found that coal stress memory characteristics, strain memory feature exist Felicity effect, and with respect the strain memory characteristics, the stress memory characteristics change more obvious, physical parameters of coal （strain） memory capacity is relatively good state parameters （stress）, a more accurate description of the damage.