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Experimental and numerical evaluation on debonding of fully grouted rockbolt under pull-out loading
International Journal of Coal Science & Technology Pub Date : 2022-02-23 , DOI: 10.1007/s40789-022-00482-4
Shuisheng Yu 1, 2 , Wancheng Zhu 1 , Leilei Niu 1
Affiliation  

The axial loading in rockbolts changes due to stress redistribution and rheology in the country rock mass. Such a change may lead to debonding at rockbolt to grout interface or rupture of the rockbolt. In this study, based on laboratory experiments, ultrasonic guided wave propagation in fully grouted rockbolt under different pull-out loads was investigated in order to examine the resultant debonding of rockbolt. The signals obtained from the ultrasonic monitoring during the pull-out test were processed using wavelet multi-scale analysis and frequency spectrum analysis, the signal amplitude and the amplitude ratio (Q) of low frequency to high frequency were defined to quantify the debonding of rockbolt. In addition to the laboratory test, numerical simulation on the effect of the embedment lengths on ultrasonic guided wave propagation in rockbolt was conducted by using a damage-based model, and the debonding between rockbolt and cement mortar was numerically examined. It was confirmed that the ultrasonic guided wave propagation in rockbolt was very sensitive to the debonding because of pull-out load, therefore, the critical bond length could be calculated based on the propagation of guided wave in the grouted rockbolt. In time domain, the signal amplitude in rockbolt increased with pull-out load from 0 to 100 kN until the completely debonding, thus quantifying the debonding under the different pull-out loads. In the frequency domain, as the Q value increased, the debonding length of rockbolt decreased exponentially. The numerical results confirmed that the guided wave propagation in the fully grouted rockbolt was effective in detecting and quantifying the debonding of rockbolt under pull-out load.



中文翻译:

全灌浆锚杆在拉拔荷载作用下脱粘试验与数值评价

由于围岩体中的应力重新分布和流变性,锚杆中的轴向载荷会发生变化。这种变化可能导致锚杆与灌浆界面脱粘或锚杆破裂。在这项研究中,基于实验室实验,研究了不同拉拔载荷下全灌浆锚杆中的超声波导波传播,以检查锚杆的脱粘。采用小波多尺度分析和频谱分析对拉拔试验过程中超声监测得到的信号进行处理,得到信号幅值和幅值比(Q) 从低频到高频被定义为量化锚杆的脱粘。除室内试验外,还利用基于损伤的模型对嵌入长度对超声导波在锚杆中传播的影响进行了数值模拟,并对锚杆与水泥砂浆的脱粘进行了数值研究。证实了超声导波在锚杆中的传播由于拉拔载荷对脱粘非常敏感,因此可以根据导波在注浆锚杆中的传播来计算临界键长。在时域中,锚杆中的信号幅度随着拉拔载荷从 0 增加到 100 kN 直到完全脱粘,从而量化了不同拉拔载荷下的脱粘。在频域中,作为Q值增大,锚杆的脱粘长度呈指数下降。数值结果证实,在全灌浆锚杆中的导波传播可以有效地检测和量化锚杆在拔出载荷下的脱粘。

更新日期:2022-02-23
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