考虑土体强度非均质和各向异性的隧道洞口仰坡地震稳定性上限解

隧道洞口段仰坡稳定性分析是隧道工程设计的关键内容之一。考虑土体强度非均质及各向异性影响,结合极限分析上限理论及土体强度折减理论,推导出的仰坡稳定性极限分析上限解计算公式,对比验证了所提计算方法的合理性,探究了地震力作用下非均质及各向异性系数对隧道洞口仰坡临界坡高、隧道拱顶破坏位置及仰坡安全系数的影响规律。研究表明,地震力作用下,土体强度非均质系数越大、各向异性系数越小,隧道洞口仰坡稳定所需临界坡高越大；非均质及各向异性系数系数越大,仰坡初始滑移面越远离坡肩位置,隧道拱顶破坏范围更广；随着各向异性系数增大,仰坡安全系数呈递增规律,而非均质系数增大将导致仰坡安全系数降低,仰坡整体趋于不安全。研究成果为山区隧道洞口仰坡稳定性设计提供了理论依据。

Upper Bound Solution for Seismic Stability of Slopes at Tunnel Entrance Considering Soil Strength Inhomogeneity and Anisotropy

Stability analysis of slopes at tunnel entrance is one of the key elements in tunnel engineering design. Considering the influence of soil strength inhomogeneity and anisotropy, combined with upper bound method of limit analysis and the strength reduction theory, the stability formula of upper bound solution for limit analysis of slope is derived, and the rationality of the proposed calculation method is verified by comparison. The effects of inhomogeneity and anisotropy coefficients on critical height of slope, failure position of tunnel vault and safety factors of slope under seismic force are investigated. The results show that the larger the coefficient of inhomogeneity and the smaller the coefficient of anisotropy, the higher the critical height required to maintain the stability of the slope at tunnel entrance. The larger the coefficient of inhomogeneity and anisotropy is, the farther the initial sliding surface is from the shoulder of the slope, and the wider the failure range of the tunnel vault is. With the increase of the coefficient of anisotropy, the safety factor of the slope increases. While the increase of the coefficient of inhomogeneity leads to the decrease of the safety factor of the slope, the overall slope tends to be unsafe. The research results provide a theoretical basis for the stability design of tunnel entrance in mountain area.