随着城市空间的不断扩展,城市道路山体隧道洞口穿越顺层边坡情况不可避免。川东地区山体滑坡等地质灾害频发,为了安全合理地解决穿越顺层边坡的洞口边仰坡方案设计问题,对某隧道洞口附近道路路堑边坡滑移案例进行补充勘察与现场踏勘,首先分析边坡滑移产生的机制,然后采用传递系数法与强度折减法分别进行反演计算,并与验证滑动面土体抗剪强度参数,并采用三维有限元数值模拟方法对洞口仰坡的稳定性进行评价。结果表明: 1)传递系数法反演与强度折减法得到的安全系数接近,说明滑坡参数反演成果适用于附近隧道洞口边仰坡三维数值模型计算; 2)隧道洞口顺层边仰坡处受力复杂,数值模拟稳定性计算时未考虑隧道结构与支护对边仰坡的作用,对稳定性计算结果影响有限; 3)后续施工的地面变形监测结果与三维数值模拟计算结果接近,说明采用滑坡反演参数能够合理模拟顺层边仰坡稳定性计算,验证了洞口边仰坡设计方法的合理性、准确性和可靠性。
Geological disasters such
as landslides occur frequently in eastern Sichuan, and with the continuous
expansion of urban space, it is inevitable for urban road mountain tunnel
openings to cross bedding slopes. To find a safe and rational design method for
the side slope of the tunnel opening through bedding slope, a supplementary
investigation and site survey are conducted on the side slop sliding of a road
near a tunnel opening, the mechanism of slope sliding is analyzed. Then, the
transfer coefficient method and strength reduction method are used to invert
and verify the shear strength parameters of the sliding surface soil. Finally,
a three-dimensional finite element
numerical simulation of the tunnel entrance slope is established to carry out
the stability evaluation of the tunnel entrance slope. The results show the
following: (1) The safety coefficient obtained by the transfer coefficient
inversion method is close to that obtained by the strength reduction method,
indicating that the inversion results of landslide parameters can be applied to
the three-dimensional numerical model calculation of
the side slope of the tunnel entrance. (2) The forces at the side elevation
slope of the tunnel entrance are complicated, and the effect of tunnel
structure and support on the side elevation slope is not considered in the
numerical simulation stability calculation, which has limited impact on the
stability calculation results but can enhance the safety measures at the
entrance. (3) The ground deformation monitoring results of subsequent
construction are close to the calculated data of the three-dimensional numerical model, indicating that the landslide inversion
parameters can reasonably simulate the stability calculation of the real side
slope along the bed, and verify the rationality, accuracy, and reliability of
the design and construction of the side slope of the tunnel entrance and the
finite element simulation method.