Effects of earthquake on damage evolution and failure mechanism of key rock pillars in underground engineering

地震荷载对地下关键岩柱损伤演化与失效机理的影响

Rock pillar is the key supporting component in underground engineering.During an earthquake,the key rock pillar must bear both the seismic load and the load transferred from other damaged pillars.This paper attempts to reveal the influence of the mainshock on damage evolution and failure characteristic of the key rock pillar during aftershocks by cyclic loading test of marble.Four levels of pre-damage stress(i.e.,10,30,50 and 70 MPa)in the first cycle were used to simulate the mainshock damage,and then cyclic stress with the same amplitude(namely 10 MPa)was conducted in the subsequent cycles to simulate the aftershock until rock failure.The results indicate that the presence of pre-damage has an obvious weakening effect on the bearing capacity and deformation resistance of rock materials during the aftershock process.Besides,the increase of pre-damage significantly changes the final failure pattern of the key rock pillar,and leads to an increase in the proportion of small-scale rock fragments.This study may contribute to understanding the seismic capacity of the unreinforced rock pillar during mainshock-aftershock seismic sequences and to optimizing the design of the key rock pillar in underground engineering.

岩柱是地下工程中关键性支护构件。地震发生时,地下关键岩柱势必遭受主余震序列荷载和其他受损岩柱迁移载荷的动力扰动。通过大理岩循环加载试验,本文研究了主震损伤对关键岩柱在余震阶段的损伤演化与破坏特征的影响。试验首先采用4级不同预应力(10、30、50和70 MPa)模拟主震不同损伤程度,随后施加相同幅值循环应力(10 MPa)模拟余震过程,直至岩石试件破坏。研究结果表明:主震损伤会明显弱化地下岩柱在余震阶段的承载强度和变形抵抗性能。同时,主震损伤会明显影响关键岩柱的最终破坏模式,导致小尺度岩屑的比例显著增加。本研究有助于了解地下未加固岩柱的抗震性能和优化地下岩柱工程设计。