单轴压缩荷载下含黏结面花岗岩能量演化研究

Study on energy evolution law of defective granite specimen under uniaxial compressive loading and unloading

为探究能量演化在含黏结面不完整岩石受载过程中的规律,选取带有矿物质黏结斜面的花岗岩进行单轴循环加卸载压缩试验,同时在试验过程中进行声发射检测.得到以下结论:"有效能比"(累积弹性能/输入岩石的总能)可以作为岩石储能水平的表征,也可间接反映岩石内部结构随应力状态的改变;从整个加载过程来看,黏结面部位破坏的声发射释能短促、强烈,峰值强度时声发射持续时间较长,但声发射释能率相比黏结面破坏时较低;应力水平较低时,卸载过程中一般不会有声发射现象或声发射现象基本可以忽略,但当应力水平达到一定值时,即花岗岩积聚的弹性能超过了黏结面部位破坏的耗散能时,花岗岩在卸载时会发生短促、强烈的脆性破坏;由于声发射能量属于耗散能的一部分,定义"声发射检测效率"(声发射累积能量/累积耗散能),对于本次试验对象而言,"声发射检测效率"在压密阶段降低,弹性阶段升高,黏结面局部破坏时达到峰值,之后直至峰值强度该值呈现持续降低趋势;从能量角度分析,卸载破裂所对应的应力水平低于加载强度,但不应低于与峰值强度时耗散能大小相等的弹性能所对应的应力水平.

To investigate the regularity of energy evolution in the process of rock loading with imperfect bounding surface,uniaxial cyclic loading and unloading compressive tests were conducted on granite with mineral bonding slope,during which its acoustic emission was detected. It concludes that： 1） The ＂ Effective energy ratio ＂（ defined as cumulative elastic energy/input rock total energy） can be used as a token of rock energy storage level,which can also indirectly reflect the internal structure of the rock as the stress state changes. 2） The test object＇s acoustic emission energy release rate at the bonding surface of the test object was higher than that at peak intensity during the loading process. Acoustic emission at the site of bond surface release was short and strong,and the duration of acoustic emission at peak intensity was long but the acoustic emission and energy release rate was lower than that at bond surface failure. 3） No acoustic emission phenomenon occurred in the unloading process with low stress level or such phenomenon could be ignored. However,when the stress reached a certain level,where the elastic energy of granite accumulation exceeded the dissipation energy of local damage,short and intense brittle failure occurred during unloading. 4） The ＂ AE detection efficiency＂（ cumulative AE/cumulative dissipation energy） is defined based on the fact that AE energy is part of the dissipative energy. It was found that ＂ AE detection efficiency＂ decreased during the compaction phase and increased in the elastic phase. It reached peak value when the bonding surface was partially destroyed. After that,it tended to decrease until the peak intensity of bonding surface was reached. 5） From the energy point of view,the stress level corresponding to unloading rupture is lower than the loading strength,but it should not be lower than the stress level corresponding to the elastic energy which is equal to the dissipation energy at peak intensity.