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为探明蓝家岩超大埋深特长公路隧道轴线方向的初始地应力场状态,依据工程地质勘察报告,利用有限元计算软件ANSYS建立了工程区三维地质模型;以现场水压致裂法测得的初始地应力资料为研究基础,通过地质力学分析确定影响初始地应力场形成的主要因素,并将其表达为数值计算所需的边界和初始条件;在各影响因素单独作用下,计算得到水压致裂法各测点位置的地应力量值;运用多元回归分析获得了蓝家岩隧道轴线方向上的初始地应力场分布规律。根据蓝家岩隧道轴线处地应力场回归方程,计算得到现场应力解除法各测点位置处的地应力,并与实测结果进行比较,从而验证反演回归计算结果的合理性。结果表明:主应力量值随埋深呈现出近似线性增长的关系,垂直主应力等于或略大于单位面积上覆岩层的自重应力;主应力量值呈现出S_H(最大水平主应力)>S_h(最小水平主应力>S_V(垂直主应力)的规律,表明蓝家岩隧道初始地应力场以水平构造应力为主导;主应力量值大部分在20 MPa以上,说明蓝家岩隧道为高地应力场隧道;最大水平主应力与最小水平主应力的量值相差较大,根据摩尔-库仑强度理论可知隧道水平面内存在较大剪应力,易导致围岩产生过大变形或破坏;在断层经过区域,受断层挤压剪切作用,地应力变化剧烈,相对断层前后的地层而言有一定的应力松弛。
In order to find out the state of initial geostress field along the axis direction of Lanjiayan extra-large-depth highway tunnel, the three-dimensional geological model of the project area was established by finite element calculation software ANSYS according to the engineering geological survey report. Of the initial stress data as the basis for the study, through the analysis of geomechanics to determine the main factors that affect the formation of the initial stress field, and expressed as the numerical boundary and the initial conditions required; under the influence of various factors alone, calculated by the water The stress value of each point of the piezoclast method was measured. The distribution of initial geostress field in the direction of the axis of Lanjiayan tunnel was obtained by multivariate regression analysis. According to the regression equation of the stress field at the axis of Lanjiayan tunnel, the in-situ stress at each measuring point of the stress relieving method is calculated and compared with the measured results to verify the rationality of the inversion regression results. The results show that the principal stress value shows an approximately linear relationship with the depth of burial depth, and the vertical principal stress is equal to or slightly greater than the self-weight stress of overlying strata per unit area. The principal stress value shows S_H (maximum horizontal principal stress)> S_h The law of minimum horizontal principal stress> S_V (vertical principal stress) shows that the initial geostress field of the Lanjiayan tunnel is dominated by horizontal tectonic stress, while the principal stress is mostly above 20 MPa, indicating that the Lanjiayan tunnel is a high geostress field Tunnels. The maximum principal stress and the minimum principal stress are quite different. According to the Mohr-Coulomb strength theory, there is a large shear stress in the horizontal surface of the tunnel, which can easily lead to excessive deformation or failure of the surrounding rock. Extruded by shear faults, the in-situ stress changes drastically, and there is some stress relaxation in the strata before and after the fault.