毛羽山特长公路软岩隧道初始地应力反演分析

针对毛羽山公路隧道工程区地质构造的复杂性,为探明毛羽山公路隧道轴线方向的初始地应力场状态,文章基于现场水压致裂法获得隧道初始地应力实测数据,利用ANSYS软件建立毛羽山隧道工程区三维计算模型,计算得到水压致裂法各测点位置的地应力量值,运用多元回归方法对毛羽山公路隧道全长范围内轴线方向上的初始应力分布规律开展反演分析。实测地应力数据表明毛羽山隧道工程区构造应力在地应力分布中占主导地位,最大水平主应力以西北—东南向挤压为主。基于数值模拟展开的多元线性回归分析,获得的初始地应力回归计算值与实测值较为接近,误差基本控制在20%以内,验证了反演回归计算结果的合理性。通过毛羽山地应力反演回归计算表明,毛羽山隧道工程区作用应力从大到小依次为最大水平主应力 $ \sigma_{H} $、垂直应力 $ \sigma_{v} $、最小水平主应力 $ \sigma_{h} $,且最大水平主应力与最小水平主应力的量值差距较大,隧道平面内存在较大的剪应力,易导致围岩产生过大变形或破坏。该研究成果对毛羽山公路隧道支护结构的设计、围岩稳定性的评判及施工加固方案的选择具有重要的指导意义和应用价值。

In view of the complex geological structure in the Maoyushan highway tunnel project area, it is necessary to ascertain the initial ground stress field state along the axis direction of the Maoyushan highway tunnel. In this paper, the in situ hydraulic fracturing method is adopted to obtain the measured data of initial ground stress in the tunnel project area, and then the ANSYS software is used to establish the three-dimensional calculation model of the Maoyushan tunnel project area, the ground stress values at each measuring point of the hydraulic fracturing method are calculated, and finally the multiple regression method is used to carry out the inverse analysis of the initial stress distribution law in the axial direction within the full length of the Maoyushan highway tunnel. The measured ground stress data show that the tectonic stress in the Maoyushan tunnel project area is dominant in the distribution of ground stress, and the maximum horizontal principal stress is dominated by northwest-southeast compression. The multiple linear regression analysis is carried out by numerical simulation. The initial ground stress regression calculation value obtained is relatively close to the measured value, and the error is basically controlled within 20%, which verifies the rationality of the inverse regression calculation result. The inverse regression calculation shows that the stresses acting over the Maoyushan tunnel project area in descending order are: the maximum horizontal principal stress $ \sigma_{H} $, vertical stress $ \sigma_{v} $, and minimum horizontal principal stress $ \sigma_{h} $, and the magnitude difference between the maximum horizontal principal stress and the minimum horizontal principal stress is large. There is a large shear stress in the tunnel plane, which is likely to cause excessive deformation or damage to the surrounding rock. The research results have important guiding significance and application value for the design of supporting structure, evaluation of surrounding rock stability and selection of construction reinforcement scheme of Maoyushan highway tunnel.