基于锚杆受力分析的软岩隧道变形规律及柔模支护技术

研究支护状态下围岩变形范围及其位移量将为合理确定软岩隧道开挖的预留变形量及其支护方案提供重要的理论依据。通过将隧道围岩简化为理想弹塑性介质，在围岩中布设全长锚固锚杆。基于锚杆与围岩的协调变形原理，建立杆体与其周围岩体相互作用的力学模型，分析锚杆表面摩阻力及轴力的分布规律，并根据杆体的静力平衡条件，推导出杆体与岩体相对位移为0的中性点位置及其最大轴力值，讨论初期支护条件下隧道围岩的塑性区及破裂区的厚度计算公式及其影响因素；综合考虑隧道表面围岩变形过程中的塑性位移和破裂区岩体的碎胀变形位移，提出隧道表面围岩的位移公式及预留间隙柔模支护技术，进而定量分析榴桐寨软岩隧道的围岩位移及其预留变形量。结果表明：通过锚杆轴力可以反演分析隧道围岩的变形范围，确定围岩稳定后的最终位移量；柔模支护结构能够大量吸收大变形软岩的变形能，且具有适当的刚度抵抗围岩的有害变形，研究成果可为合理设计软岩隧道的开挖及支护方案提供新的思路。

Deformation Law and Flexible Formwork Support Technology of Soft Rock Tunnel Based on Force Analysis of Rock Bolt

Information on the range of deformation and the displacement of surrounding rock under support conditions provides an important theoretical basis for a reasonable determination of the reserved deformation size and its support scheme for a soft rock tunnel excavation. The surrounding rock mass of the tunnel is simplified as an ideal elastic and plastic medium, in which some full-column rock bolts are fixed. Based on the principle of coordinated deformation, this paper establishes a mechanics model of the interaction between the rod body and surrounding rock mass. In addition, the distribution law of surface friction and the axial force of an anchor bolt are analyzed, and the neutral point position where the relative displacement between the bolt body and the rock mass is zero, and the maximum axial force of the bolt body according to the static equilibrium condition of the bolt body, are derived. Plastic zone and loose zone formulas, along with the influencing factors of surrounding rock with a support structure, are discussed. A displacement formula and a rigid-gap-flexible formwork supporting technology of the surrounding rock are also proposed, based upon which, the displacement and reserved excavation deformation size of surrounding rock are calculated; in addition, the surrounding rock is supported using a flexible formwork. The results show that the deformation range of tunnel-surrounding rock can be analyzed inversely according to the axial force of the anchor body. Moreover, the flexible formwork support structure can absorb a great deal of deformation energy of a largely deformed soft rock, the appropriate stiffness of which can resist the harmful deformation of the surrounding rock, and new research approach is put forward for a reasonable design of the excavation and support scheme of a soft rock tunnel.