Anchoring rock masses is a commonly applied measure to prevent rockburst, whereas many deep tunnels still encountered rockburst after anchoring with rockbolts. Currently, the absence of suitable evaluation methods impedes the timely grasp and improvement of the rockburst prevention effect. This paper first investigates the alterations of rockburst pit depths before and after anchoring in three deep tunnels. The results indicate that the potential rockburst pit (PRP) depth exhibits two mitigation trends, i.e., “From small to none” and “From large to small”. Subsequently, the analysis model of PRP depth after anchoring and the quantitative evaluation method of prevention effect are presented. In this method, the evaluation of prevention effect is based on the decrease rate of PRP depth after anchoring, which is calculated after obtaining parameters associated with rock mass properties, geostress, excavation damage and rockbolts. Furthermore, the variation of PRP depth after anchoring and the rockburst prevention effect under different excavation damage and rockbolt parameters are quantitatively analyzed. It is found that the prevention effect is negatively correlated with excavation damage. Specifically, when the damage is minor, a smaller PRP depth is observed, and the rock mass strength is significantly enhanced after anchoring, leading to a noticeable shallowing or even disappearance of PRPs. In such cases, relying solely on anchor support can achieve good prevention effects. Conversely, when excavation damage is severe, the reduction in PRP depth after anchoring is quite limited, necessitating the implementation of more measures. In addition, the application of large-diameter and densely spaced rockbolts contributes to diminishing the PRP depth and improving the prevention effect.

中文翻译：

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深埋隧道周围锚固岩体防岩爆效果定量评价方法


锚固岩体是防止岩爆的常用措施，而许多深隧道在用锚杆锚固后仍然遇到岩爆。目前，缺乏合适的评价方法，阻碍了对岩爆防治效果的及时把握和提高。本文首先研究了 3 条深隧道锚固前后岩爆坑深度的变化。结果表明：潜在岩爆坑 （PRP） 深度呈现“从小到无”和“从大到小”两种缓解趋势。随后，提出了锚定后 PRP 深度分析模型和预防效果的定量评价方法。该方法以锚固后 PRP 深度的下降率为依据，在获得岩体特性、地质应力、开挖损伤和锚杆相关参数后计算出防治效果。此外，定量分析了锚固后 PRP 深度的变化以及不同开挖损伤和锚杆参数下的防岩爆效果。研究发现，预防效果与开挖损伤呈负相关。具体而言，当损伤较小时，观察到较小的 PRP 深度，锚固后岩体强度显著增强，导致 PRP 明显变浅甚至消失。在这种情况下，单靠锚支撑可以达到良好的预防效果。相反，当开挖损伤严重时，锚固后 PRP 深度的减少非常有限，需要采取更多措施。 此外，大直径和密集间距的锚杆的应用有助于减少 PRP 深度并提高预防效果。