水平分层土质条件下浅埋隧道掌子面支护稳定性研究

Supporting Security Research of Shallow Tunnel Face in Horizontal Layered Soil Conditions

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。

Because shallow tunnels have large excavated face and shallow depth,the soil layer is very complicated in the excavation process.The stability of tunnel face has an important impact on the safety of tunnel construction.The key of tunnel face stability is how to determine the appropriate limit support pressure.Therefore,we researched the limit support pressure of shallow tunnel face in horizontal layered soil conditions.Firstly,according to the assumption of logarithmic spiral arcs in Murayama formula,we established the limit rotation destruction mechanism,which has the common center of rotation in nonhomogeneous advanced core soil.Secondly,we simplified the mechanism of the influence of covering soil layers on the tunnel face based on the wedge failure mode and model test results.At the same time,we calculated the external load power and the internal energy dissipation in limit analysis theory.Thirdly,we set up the equilibrium equation,including support pressure,and derived the minimum support pressure formula for tunnel face.Finally,in order to verify the accuracy of the calculation formula,the theoretical analysis results were compared with numerical simulation results of Flac3 D.The above research provides some theoretical guidance for the supporting security of shallow tunnel face in horizontal layered soil conditions.