小断面膨胀性软岩隧洞一次支护及二次衬砌承载能力分析

Analysis of Bearing Capacity for Primary Support and Secondary Lining in Small-Section Expansive Soft Rock Tunnels

我国在引调水及灌区工程建设过程中,各类软弱围岩隧洞已屡见不鲜。因膨胀性软弱围岩工程性质的特殊性,隧洞施工中经常面对支护结构破坏甚至失稳、大变形等难题。软弱性围岩隧洞以整体变形破坏为主,建立了一次支护数值模型,拟定了不同围岩支护时机及支护措施,通过模拟计算,隧洞围岩收敛变形在规范允许范围内,一次支护措施承载能力满足施工期安全要求,为施工期各类围岩支护时机及支护措施提供了理论依据。建立二次衬砌数值模型,考虑隧洞运行期内水外渗引起的围岩吸水膨胀,剖析不同工况下二次衬砌的力学响应特征,结果表明二次衬砌底板是受力最不利位置,可通过提高底板的厚度或配筋量,提高衬砌整体承载力。本研究可为膨胀性软岩隧洞支护衬砌结构设计提供理论指导,为同类工程设计及施工提供参考。

In the construction process of water diversion and irrigation projects in China,various types of soft rock tunnels have been frequently encountered.Due to the particularity of the engineering properties of expansive soft rock,tunnel construction often faces challenges such as support structure damage,instability,and large deformation.The soft rock tunnels are mainly subject to overall deformation failure.A numerical model for primary support has been established,and different support time and measures for surrounding rock have been proposed.The simulation calculations show that the convergence deformation of the surrounding rock is within the allowable range of the specifications,and the bearing capacity of the primary support measures meets the safety requirements during construction.T his provides a theoretical basis for various rock support time and measures during the construction period.A numerical model for the secondary lining was also established.Considering the absorption and expansion of the surrounding rock due to water seepage during the tunnel operation period,the mechanical response characteristics of the secondary lining under different working conditions were analyzed.The results indicate that the tunnel invert in the secondary lining is the most unfavorable stress position,and the overall bearing capacity can be improved by increasing the thickness of the invert or amount of reinforcement.The study provides theoretical guidance for the design of support and lining structures in expansive soft rock tunnels and offers a reference for the design and construction of similar projects.