闽南小净距隧道中夹岩力学特性与加固措施

为研究山区浅埋偏压小净距隧道开挖对中夹岩力学特性的影响，以福建三明莆炎高速公路布盂隧道为工程背景，采用Midas GTS有限元软件建立三维数值模型，分析了浅埋偏压小净距隧道中隔壁法施工条件下中夹岩柱的力学特性，并提出了采用中空注浆锚杆的中夹岩注浆加固技术。结果表明，隧道浅埋偏压条件下采用中隔壁法施工，围岩与初支变形相对较小，但拱腰位置中夹岩变形应加强监控；小净距隧道开挖施工，中夹岩柱会产生水平位移，拱腰位置左右线隧道平均水平位移为 4.25 mm；采用小导管注浆加固的中夹岩柱正应变和塑性区显著减小，左右线隧道拱腰位置中夹岩应变分别减小77%和81%，拱脚位置应变分别减小85%和80%；结合数值模拟分析结果和现场设计，采用 5 m长中空锚杆对小净距段中夹岩进行注浆加固，提高了中夹岩柱的整体稳定性，保证了隧道施工安全，为后期类似工程提供了较好的借鉴意义。

Mechanical Characteristics and Reinforcement Measures of Middle Rock Column of Shallow Bias Small Spacing Tunnel in Southern Fujian

In order to study the influence of the excavation of shallow bias small spacing tunnel on the mechanical properties of middle rock column in mountainous area, taking the Buyu Tunnel of the Puyan Expressway in Sanming, Fujian Province as the engineering background, a three-dimensional numerical model was established by using Midas GTS finite element software. The mechanical characteristics of the middle rock column under the construction conditions of the center cross diaphragm (CRD) method of the shallow buried and biased small spacing tunnel were analyzed, and the grouting reinforcement technology for the middle rock column using hollow grouting bolts was proposed. The results show that the deformation of the surrounding rock and the initial support is relatively small when the center cross diaphragm (CRD) method is used under the condition of shallow buried bias, but the monitoring of middle rock column deformation of the arch waist should be strengthened. During the excavation of the small spacing tunnel, the middle rock column will have horizontal displacement, and the average horizontal displacement of the left and right tunnels at the arch waist position is 4.25 mm. The normal strain and plastic zone of the middle rock column strengthened by small pipe grouting are significantly reduced. The strain of the middle rock at the waist of the left and right tunnels is reduced by 77% and 81%, and the strain at the arch foot is reduced by 85% and 80% respectively. Combining the results of numerical simulation analysis and on-site design, a 5 m long hollow anchor bar is used for grouting reinforcement of the middle rock column in the small spacing section, which improves the overall stability of the middle rock column, ensures the safety of tunnel construction, and provides a good reference for later similar projects.