爆破作用下层状围岩隧道突变失稳判据研究

Study on catastrophe instability criterion of layered surrounding rock in tunnel under blasting

为判断爆破振动与损伤作用下层状岩体隧道的围岩稳定性,根据层状围岩失稳特征建立隧道力学模型,考虑爆破损伤和振动效应,构建层状围岩隧道系统总势能方程和突变失稳判据,分析爆破作用下层状围岩稳定性演化规律;并以沪昆高铁湖南段姚家隧道为工程背景,分析层状围岩隧道稳定性。结果表明:层状围岩隧道发生突变失稳的充要条件是满足分岔集方程,即当突变特征值Δ≤0时系统可能发生突变失稳;爆破累积效应造成围岩刚度不断降低,爆破药量增加提高爆破振动效应,这些均导致层状围岩失稳概率增加;实际隧道失稳评价结果与施工现场情况、监测结果一致,验证了失稳判据的有效性。

In order to judge the stability of the surrounding rock in a tunnel under the blasting vibration and damage,the mechanics model was established according to the instability characteristics of the layered surrounding rock.Considering the blasting damage and vibration effect,the total potential energy equation and catastrophe instability criterion were established,and the stability evolution law of tunnel under blasting was analyzed.Taking Yaojia tunnel in Hunan of Shanghai-Kunming high-speed railway as an engineering background,the stability of the layered surrounding rock in the tunnel was analyzed.The results show that the necessary and sufficient condition for the catastrophe instability of layered surrounding rock in the tunnel satisfies the bifurcation equation,that is,when the mutation eigenvalue Δ≤0,the system may suffer catastrophe instability.The cumulative effect of blasting results in the continuous reduction of surrounding rock stiffness,and the increase of blasting charge aggravates the blasting vibration effect,both of which increase instability probability for stratified surrounding rock.The actual instability evaluation results are consistent with the construction site situation and monitoring results,which verifies the effectiveness of the instability criterion.