基于层状围岩变形特征的高地应力陡倾板岩隧道合理洞型研究

即将开工建设的川藏铁路雅安至昌都段，隧道穿越地层多以陡倾（立）变质层状板岩为主，埋深大都在千米左右，地应力高或极高，其建设面临着很严重的大变形问题，给设计阶段初期带来极大挑战。针对以上工程背景，基于层状围岩的变形特征，对高地应力陡倾板岩隧道的合理洞型选择展开研究。首先通过解析计算分析圆形洞室层状围岩的变形特征，并进一步采用离散元数值模拟计算分析马蹄形洞室的变形特征，经相互对比验证数值计算的可行性和合理性，在此基础上，对比研究高地应力陡倾板岩地层单洞双线隧道、双洞单线隧道选择对控制变形的优越性，最后在选定的双洞单线隧道洞型基础上进行优化选择。研究结果表明：与岩层倾角垂直处围岩以结构变形为主，结构面张开变形与薄层结构的弯曲变形为变形的主要来源，且垂直结构面方向围岩变形程度与影响范围均大于其他方向；从控制隧道变形及开挖影响范围考虑，在高地应力陡倾（立）板岩地层采用双洞单线隧道更为合理；在高地应力陡倾（立）板岩地层中，单线隧道高跨比为1.02~1.06时，变形控制最好，而圆形隧道由于开挖面积的增大并非为最优断面。

Study on Reasonable Tunnel Types of Steeply Dipping Slate Tunnels with High Geostress Based on Deformation Characteristics of Layered Surrounding Rock

In the early stages of the construction of the Sichuan-Tibet Railway from Ya'an to Changdu,the tunnels were buried 1 km deep and were mostly stratified by steeply inclined (vertical) metamorphic layered slates under high or extremely high ground stress, which led to large deformations that became a tremendous challenge facing the early design stage. Considering the above engineering background, this study conducted an in-depth research on the selection of high-situ stress and steeply inclined slate tunnels based on the deformation characteristics of the layered surrounding rock. In this study, the deformation characteristics of the layered surrounding rock of the circular tunnel were initially analyzed via analytical calculation,and the deformation characteristics of the horseshoe tunnel were further calculated and simulated using the discrete element method. The comparison between number calculations showed that the proposed method is practical and its results are correct. Consequently, the single-hole double-line and double-hole single-line tunnels were compared to study their effectiveness in controlling high deformation and steep sloped slate strata. Finally, the optimized selection was made based on the selected double-hole single-line tunnel and the results made three indications. First, the surrounding rock perpendicular to the dip angle of the rock layer is mainly a structural deformation, the opening deformation of the structural surface and bending deformation of the thin layer structure are the main sources of deformation, and the degree of deformation and influence range of the surrounding rock in the direction of the vertical structural plane are both larger than other directions. Secondly, considering the scope of tunnel deformation and excavation, it is more practical to use double-hole single-line tunnels in high-situ stress steep slopes (stand). Finally, in slate strata, deformation control is best when the single-track tunnel has an aspect ratio of 1.02 to 1.06, and circular tunnels are not optimal sections owing to the increased excavation area.