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通过引入圆锥椭圆截交线计算公式,改进浅埋隧道掌子面三维被动破坏多椭圆锥体几何参数的计算方法。基于非线性破坏准则和极限分析上限法,推导浅埋隧道掌子面三维被动支护力的上限表达式,并进一步采用非线性规划程序优化计算获得了极限支护力最优上限解。通过对比分析,验证本文方法的可靠性;同时分析非线性抗剪强度参数对被动破坏极限支护力和破坏模式的影响,并绘制相应的破坏模式图。研究表明:被动破坏极限支护力与地面超载σ_s及地层容重γ大致呈线性变化,而与非线性参数m、量纲一化的参数c_0/σ_t及超负荷比C/D呈非线性变化;非线性参数m、量纲一化的参数c_0/σ_t和超负荷比C/D对破坏模式影响显著,而地面超载σ_s对破坏模式影响则较小。研究成果为隧道掌子面稳定性分析提供一种新思路,进一步完善了隧道掌子面稳定性评价体系。
By introducing the formula of conic elliptical cutoff line, the calculation method of geometrical parameters of three - dimensional passive failure multi - elliptical cone in shallow tunnel surface is improved. Based on the non-linear failure criterion and the upper bound limit analysis method, the upper bound of the three-dimensional passive support force of shallow tunnel surface is derived and the optimal upper bound solution of ultimate support force is obtained by nonlinear programming procedure. Through comparative analysis, the reliability of the method in this paper is validated. At the same time, the influence of nonlinear shear strength parameters on the ultimate support force and failure modes of passive failure is analyzed, and the corresponding failure modes are plotted. The results show that the ultimate supporting force of passive failure has a linear change with the ground overburden σ_s and the bulk density γ, but nonlinearly with the nonlinear parameter m, the parameterized c_0 / σ_t and the overload ratio C / D. The nonlinear parameter m, the dimensionless parameter c_0 / σ_t and the overload ratio C / D have a significant influence on the failure mode, but the effect of the ground overload σ_s on the failure mode is small. The research results provide a new idea for the analysis of the stability of the tunnel face and further improve the stability evaluation system of the tunnel face.