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掌子面岩墙预留厚度是高风险岩溶隧道采用释能降压法施工时的一项重要技术参数。本文基于弹性厚板理论,分析了岩溶隧道掌子面突水机制,推导了边界条件分别为固支和简支两种模式的岩溶隧道掌子面岩墙安全防突厚度及临界水压计算公式。上述计算公式的参数化分析表明,两种模式下掌子面岩墙安全防突厚度随前方岩溶水压力、岩体泊松比的增大而增大;掌子面岩体质量越差,防突厚度愈大。临界水压力随掌子面岩墙厚度增加而增加,掌子面岩体质量越差,临界水压力愈小。掌子面岩墙安全防突厚度的理论分析及算例结果表明,固支边界条件下的计算结果与施工中普遍采用的预留厚度值较为一致,该结论可为类似工程提供参考和借鉴。
The reserve thickness of face rock wall is an important technical parameter in the construction of high-risk karst tunnel by using energy-saving and pressure-relief method. Based on the theory of elastic thick slab, the mechanism of water inrush on the face of karst tunnel is analyzed and the formula for calculating the inrush prevention thickness and critical hydraulic pressure of face rock face of karst tunnel with two different modes . The parametric analysis of the above formulas shows that the safety dip thickness of the facet rock face increases with the increase of the karst water pressure and the Poisson’s ratio of the rock mass in the two modes. Sudden thickness greater. The critical water pressure increases with the increase of the thickness of the dug rock face, and the poorer the quality of the rock mass is, the smaller the critical water pressure is. The theoretical analysis of the outburst-prevention thickness of the face rock face and the example results show that the calculated results under the condition of the fixed-support boundary are in good agreement with the pre-set thickness values commonly used in construction. This conclusion can provide reference and reference for similar projects.