不同保载时间实验的花岗岩声发射特性研究

Study on the Acoustic Emission Characteristics of Granite in Different Holding Time

为了研究冲击地压发生前岩体处于加载或保载阶段,有突出倾向的岩体处于保载蠕变状态的问题,对花岗岩试件以每30 k N为梯度进行单轴不同时间保载实验,保载时间分别为1、3、5、10和15 min,并结合声发射进行实验研究。研究结果表明:(1)不同的保载时间对试件的强度及声发射参数有很大区别。与单轴直接加载相比,保载15 min的试件强度降低了43%;与单轴直接加载试件破坏点相比,保载15 min试件破坏时声发射撞击率提高了47%,保载15 min试件破坏时能量累积提高了53%;(2)不同保载时间,每提高相同加载梯度,保载时间越长试件的声发射撞击率越高;(3)花岗岩试件在实验过程中,保载时试件损坏或保载后刚加载试件便损坏的现象,说明保载阶段对试件的破坏有很大影响;(4)花岗岩在单轴保载压缩条件下,每个阶段产生的声发射具有不同的特征。因此,可以用花岗岩保载实验来研究岩石的微观损伤破坏,也可预测现场工程岩体的宏观断裂过程。

In order to study situation that the rock mass is keeping loading or at loading stage before the rock burst occurs,the rock mass with prominent tendency is often in the state of loading creep. Uniaxial loading experiment of the granite specimens with a gradient of each 30 k N was carried out under different holding time of 1 min,3 min,5 min,10 min and 15 min,combining with experimental studies on acoustic emission.Research results showed that：（ 1） Different holding time on the strength and acoustic emission parameters have a great difference. Compared with uniaxial loading directly,the strength of the test specimen at 15 min is reduced by 43%; Compared with the failure point of uniaxial loading-directly specimen,the acoustic emission hit rate of specimen at holding 15 min is increased by 47%,and the energy accumulation at holding 15 min is increased by 53%;（ 2） In different holding time,and with the same loading gradient increasing,the longer the holding time,the higher the AE hit rate of specimens;（ 3） In the experimental process of granite specimen,there will the phenomenon of specimen damage at loading or just after loading,so it indicates that loading is a great impact on specimen damage;（ 4） Under different uniaxial loading compression conditions,the acoustic emission of granite in each stage has different characteristics. Therefore,the granite loading experiment can be used to study the microscopic damage and failure of rock,and also to predict the macroscopic fracture process of rock mass.