反复加卸荷作用下两种岩石的变形与声发射特征研究

Study on Deformation and Acoustic Emission Characteristics of Two Rocks Under Repeated Loading and Unloading

【目的】为了研究反复加卸荷作用下不同类型围岩在隧道施工及运营过程中的变形与破坏特征。【方法】选取花岗岩和砂岩试样进行等荷载反复加卸荷试验。【结果】研究结果表明:当应力水平低于裂缝损伤应力时,滞回曲线在循环过程中由疏至密;当应力水平高于裂缝损伤应力时,滞回曲线并不会表现出明显的密集特征;当应力水平低于裂缝损伤应力时,在第一次加卸载过程中损伤已基本形成,花岗岩发生的声发射事件有限,而砂岩声发射事件稀少,并在后续循环累积过程中损伤明显减少;当应力水平超过裂缝损伤应力时,两种岩石在循环加卸荷过程中会逐次产生明显的损伤,且应力水平超过裂缝损伤应力越高,损伤增长速度越快。【结论】循环荷载的增大会促进花岗岩内部裂纹的扩展,导致声发射事件变得活跃,而砂岩只有在应力水平提高至93%时,声发射事件才表现出明显间歇性增长规律。

[Purposes]In order to study the deformation and failure characteristics of different types of sur-rounding rocks during tunnel construction and operation under repeated loading and unloading.[Methods]Granite and sandstone samples were selected for repeated loading and unloading tests.[Findings]The results show that when the stress level is lower than the crack damage stress,the hysteresis curve changes from sparse to dense during the cycle.When the stress level is higher than the crack damage stress,the hysteresis curve does not show obvious dense characteristics.When the stress level is lower than the fracture damage stress,the damage has been basically formed during the first loading and unloading process.The acoustic emission events of granite are limited,while the acoustic emission events of sandstone are rare,and the damage is sig-nificantly reduced during the subsequent cycle accumulation process.When the stress level exceeds the crack damage stress,the two kinds of rocks will produce obvious damage successively in the process of cyclic load-ing and unloading,and the higher the stress level exceeds the crack damage stress,the faster the damage growth rate increase.[Conclusions]The increase of cyclic load will promote the expansion of internal cracks in granite,resulting in active acoustic emission events.However,only when the stress level of sandstone in-creases to 93%,the acoustic emission events show obvious intermittent growth law.