大理岩单轴循环加卸载破坏声发射先兆信息研究

Precursor information study on acoustic emission characteristics of marble under uniaxial cyclic loading-unloading

  • 摘要: 工程施工中岩体常常处于循环荷载作用下,对循环荷载作用下岩石破坏的预测研究具有重要现实意义。以云南白色大理岩为研究对象,设置了两种不同循环应力路径,研究了大理岩在循环加卸荷下的声发射特征,研究结果表明:大理岩在循环前期阶段卸载过程没有明显声发射产生,声发射出现了间歇期。两种应力路径下,声发射Felicity比值变化趋于一致,均随着循环的进行应力水平的提高而降低,恒定应力下限条件下的Felicity比值较恒定应力上下限差值方案要低,表明恒定应力下限条件加卸载对岩石的损伤更为严重。整个循环过程中大理岩的声发射b值可以为3个阶段,在应力水平较低时,声发射b值随着应力的提高而降低,之后b值在一定范围内波动变化,表明岩石内裂纹稳定发育,在岩石的破坏阶段,b值出现小幅度升高。岩石单个循环声发射b值呈现V形变化趋势,在岩石即将破坏时b值出现大幅度的波动变化。将Felicity比值、整个循环过程b值和单个循环声发射b值结合使用可以提高预测岩石破坏的准确性。

     

    Abstract: In the engineering construction,the rock mass is often under cycle loading-unloading. The prediction of the rock damage under cycle load-unloading has an important practical significance. Two different cyclic stress paths are set to study the acoustic emission characteristics of the Yunnan white marble under cycle loading-unloading. The study shows that:during the unloading phase there is no apparent acoustic emission in the early stage,the acoustic emission appears during the intermission period. The change trend of the Felicity value is relatively consistent under the differ- ent stress paths:the Felicity values gradually reduce with the increase of stress level. The Felicity values of the stress limit constant load-unloading scheme are relatively lower than the stress difference constant load-unloading scheme, which shows that the first scheme causes more serious damage to the rock. The b value can be divided into three parts during the whole cycle loading:the b value decreases with the increase of stress when the rock is under lower stress level,and then the b value fluctuates within certain extent showing that the cracks within the rock goes through a rela- tively stability development period. Before the rock damage,the b value shows a certain degree of increase. In a single cycle unloading the b value presents a V-shaped distribution and the b value has a dramatic change before the destruc- tion of rock. b value and Felicity value have a certain consistency and diversity,the use of the combination of these val- ues can improve the accuracy of rock damage prediction.

     

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