基于横观各向同性模型的片岩隧洞稳定性研究

Research on stability of schist tunnel based on transversely isotropic model

以四川大渡河丹巴水电站引水隧洞为研究对象,结合三轴试验和自主研发的空间多角度片理抗拉强度测试技术,对不同片理夹角下石英云母片岩的力学参数进行测定,得出石英云母片岩的弹性模量、c和φ与围压之间的关系,并分别给出干燥和饱和条件下各力学参数围压敏感性排序。通过表征各向异性的参数k1、k2,对不同片理夹角下石英云母片岩的各向异性与围压的关系进行评价,并进一步指出不同高度岩样抗拉强度随片理角度的变化规律。采用横观各向同性本构模型,通过设定材料主轴空间方位,可模拟片理空间任意角度展布的岩体。针对大区域模型存在的不足,提出一种主应力构造精细应力场的新方法,避免了大模型的应力边界效应,可方便快捷对局部区域进行精细应力构造。根据片理走向及不同倾角选定15个不同片理空间展布模型进行计算分析,分别得出应力、位移、塑性区随片理角度的变化规律,并指出不同片理展布条件下的最不利工况。

Taking the diversion tunnel of Danba Hydropower Station of Dadu River in Sichuan Province as the research object,we developed the space multi-angle tensile strength test technology and combined with the triaxial test.The mechanical parameters of quartz mica schist under different angles were measured.The relationships between elastic modulus,c,φand confining pressure of quartz mica schist were obtained,and the order of confining pressure sensitivity rankings of the mechanical parameters under dry and saturated conditions were calculated.By analyzing the anisotropic parameters k1、k2,the relationship between the anisotropy of quartz mica schist and the confining pressure under different angles was evaluated,and the change law of the tensile strength of different heights along with the angle of schistosity was further obtained.Using a transversely isotropic constitutive model and setting the spatial orientation of the material’s principal axis,it is possible to simulate the rock mass distributed at any angle in the schistosity space.In view of the deficiencies of the large-area model,this paper proposes a new method for constructing the fine stress field with principal stress,avoiding the stress boundary effect of the large model,and making it possible to perform fine stress construction on the local area quickly and easily.According to the trend of the schistosity and different dip angles,fifteen different schistosity spatial distribution models were selected for calculation and analysis.The changes of the stress,displacement,and plasticity regions with the angles of the schistosity were respectively given,and the worst working conditions under different schistosity distribution were pointed out.