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浅埋隧道由于具有埋深浅、开挖面大的特点,在开挖过程中遇到的土质分层情况往往比较复杂。隧道掌子面的稳定性会对隧道施工的安全产生重要影响。保证掌子面稳定性的关键在于如何确定合适的极限支护压力。因此对水平分层土质条件下掌子面的极限支护压力进行研究。首先,根据村山公式的对数螺旋线假设,建立了具有共同旋转中心的分层超前核心土旋转破坏模式。其次,依据覆盖层楔形破坏模式和前人模型试验结果,简化隧道覆盖层土体对掌子面的影响模型;同时,根据极限分析理论计算了土体的外部荷载功率和内能耗散功率。然后,建立引入支护压力的极限方程,推导出了保证浅埋隧道掌子面稳定的极限支护压力的计算公式。最后,为验证理论计算的准确性,将理论分析结果和Flac3D数值模拟结果进行了对比分析。以上理论为研究水平分层土质条件下浅埋隧道掌子面的支护稳定性提供了一定的理论指导。
Shallow tunnels have the characteristics of shallow buried depth and large excavation face. The stratification of soil encountered in the excavation process is often complicated. The stability of tunnel face can have a significant impact on the safety of tunnel construction. The key to ensure the stability of the face is how to determine the appropriate limit support pressure. Therefore, the research on the limit support pressure of the face of the soil under the condition of horizontal layered soil is carried out. First, based on the logarithmic spiral assumption of Murayama formula, a rotational failure mode of layered advanced core soil with a common rotation center is established. Secondly, based on the wedge failure mode and the results of the predecessor model test, the influence model of tunnel cover soil on the face is simplified. At the same time, the external load power and internal energy dissipation power of soil are calculated according to the limit analysis theory. Then, the limit equation of supporting pressure was established, and the formula of the ultimate supporting pressure to ensure the stability of the shallow surface of shallow tunnel was deduced. Finally, in order to verify the accuracy of the theoretical calculation, the theoretical analysis and the results of Flac3D numerical simulation are compared. The above theories provide some theoretical guidance for studying the stability of the support surface of the shallow tunnel under horizontal layered soil conditions.