中文摘要：

针对土体的非均质和各向异性，以土质浅埋隧道为例，采用极限分析上限法和可靠度方法研究隧道支护力的大小．结果表明，土体非均质和各向异性对支护力的影响程度取决于隧道的埋深．当埋深小于15m时，围岩的自稳能力较差，土体非均质和各向异性的影响不能明显地体现出来，支护力主要随埋深的增大而增大；当埋深大于20m时，围岩的自稳能力较强，支护力随土体非均质和各向异性的增大发生明显变化，埋深越大，土体非均质和各向异性对支护力的影响越强．可靠度研究表明，非均质和各向异性参数的分布及变异系数的大小对支护力的影响较大，对数正态分布时影响更为明显．建议在土质浅埋隧道设计时，务必考虑土体的非均质和各向异性，防止保守支护增加工程成本或支护力不足引起隧道坍塌．

英文摘要：

The upper bound theorem and reliability method were utilized to investigate the stability of shallow tunnels excavated in nonhomogeneous and anisotropic soils.The result shows that the effect degree of soil nonhomogeneity and anisotropy is governed by the buried depth of tunnel.When the buried depth is less than 15 re,the self-stabilization capacity of the surrounding rock is poor.As a result, the influence of nonhomogeneity and anisotropy is not obvious, and the supporting pressure tends to increase with the in- crease of buried depth.However,when the tunnel is deeply buried,greater than 20 m, the self-stabilization capacity of the surround rock is strong.In this circumstance, the supporting pressure varies greatly as the parameters of nonhomogeneity and anisotropy increase.It is also found that the distribution of nonhomoge- neity and anisotropy parameters and the variable coefficient have a great effect on the supporting pressure through reliability research, especially when the parameters obey the logarithmic normal distribution. It is suggested that more attention should be paid to the nonhomogeneity and anisotropy of soil mass in the design of shallow tunnel, which would prevent either the increase of construction costs or the collapse of tunnel.