Study on catastrophe instability criterion of layered surrounding rock in tunnel under blasting
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.
blasting effectlayered surrounding rock tunnelinstability criterioncatastrophe theorystability
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