环形开挖预留核心土施工对围岩稳定性影响研究

Study on Influence of Reserved Core Soil Construction in Circular Excavation on Stability of Surrounding Rock

摘要:

目的为解决隧道施工中围岩稳定性问题，特别是深埋、破碎围岩及高地应力条件下的施工难题，系统分析环形开挖预留核心土法中核心土长度、高度及顶面宽度等隧道围岩稳定性的影响。 方法以深南铁路某隧道工程为背景，采用有限元数值模拟方法，建立三维隧道开挖模型，分别设置不同核心土长度、高度和顶面宽度的多组工况，系统计算并分析掌子面纵向位移、最大拱腰收敛值、最大拱顶沉降的变化规律，评估围岩稳定性对核心土尺寸的响应特征，并初步分析核心土自身稳定性。结论核心土尺寸参数对围岩变形具有显著影响。增大核心土长度、高度和顶面宽度均能有效减小掌子面位移、拱顶沉降与拱腰收敛，尤其对核心土高度以下区域的位移控制作用更为明显。对于依托的V级围岩条件，在保证核心土自身稳定和施工可行性的前提下，建议核心土高度取隧道断面高度的55%~65%，顶面宽度取底边宽度的55%~65%，并在设备与空间允许条件下尽量增加核心土长度，以实现安全与经济的平衡。

Abstract:

To address the stability issues of surrounding rock during tunnel construction, particularly the challenges under deep burial, fractured rock masses and high geostress conditions, the influence of core soil length, height and top width in the reserved core soil construction in circular excavation on the stability of surrounding rock is systematically analyzed. Taking a tunnel project in the Shenzhen - Nanning Railway as the background, a three-dimensional tunnel excavation model is established using finite element numerical simulation. Multiple sets of working conditions are configured with varying core soil lengths, heights and top widths. The variation laws of the longitudinal displacement of the tunnel face, the convergence value of the maximum arch waist and the settlement of the maximum arch top are systematically calculated and analyzed to assess the response characteristics of surrounding rock stability to core soil dimensions and preliminarily analyze the self-stability of the core soil. The conclusion shows that the dimensional parameters of the core soil significantly influence the deformation of surrounding rock. Increasing the core soil length, height and top width can effectively reduce the tunnel face displacement, arch roof settlement and arch waist convergence. Especially, the displacement control effect in the area below the core soil height is more obvious. Relying on the V-grade surrounding rock conditions, and under the premise of ensuring the stability of the core soil itself and the feasibility of construction, it is recommended that the core soil height be set at 55%~65% of the tunnel cross-section height, and the top width be at 55%~65% of the bottom width, and the core soil length be maximized within equipment and spatial constraints to achieve a balance between safety and economy.