基于Hoek-Brown准则的板岩强度特征研究

 建立在岩体各向同性基础上的Hoek-Brown经验强度准则被广泛地应用于地下和边坡工程的设计与安全评估。但Hoek-Brown准则不能直接用来处理层(片)状岩体如板岩或页岩以及含有1或2组优势结构面岩体的强度问题，因为这类岩体往往沿层(片)理或优势结构面破坏，必须对准则加以改进。基于对Hoek-Brown经验破坏准则的深入研究，通过对层状岩体完整岩石试件定义的改进，提出用Hoek-Brown准则的一个很重要的参数，即完整岩石试件的单轴抗压强度 来表征层状岩体强度随层面倾角的变化规律以及应用Hoek-Brown准则来分析层状岩体强度的方法。按照该方法对南水北调西线工程场区不同层面倾角板岩岩石试件进行单轴、三轴压缩试验。根据对试验结果的统计分析，确定不同层面倾角板岩岩体的Hoek-Brown经验破坏准则的相关参数，建立不同层面倾角板岩岩体的Hoek-Brown强度准则。此外，还获得完整岩石试件的单轴抗压强度 随层面倾角的变化规律，建立南水北调西线工程场区板岩岩体的Hoek-Brown经验破坏准则的统一表达式，并预测围压为10，15，20和25 MPa下南水北调西线工程场区板岩岩体的三轴强度随层面倾角的变化规律。本文的工作可以为类似工程提供借鉴。

STUDY ON STRENGTH CHARACTERISTICS OF SLATES BASED ON HOEK-BROWN CRITERION

The Hoek-Brown empirical strength criterion is based upon the assumption that the rock mass is isotropic and has widely been used for design and safety assessment of underground and slope engineering. A common problem will be encounted in rock mechanics involving the determination of the strength of schistose or layered rock masses such as slates,shales or rock masses containing dominant discontinuities. Because the failure of these anisotropic rock masses is controlled by one or two discontinuities,the Hoek-Brown criterion can not be directly applied to analysis of such issues. So the criterion must be evolved for this purpose. On the basis of detailed study on Hoek-Brown criterion,the definition of intact rock pieces for layered rock mass is evolved and an important parameter in Hoek-Brown criterion,the uniaxial compressive strength of intact rock pieces' is proposed to be used for characterizing the variation of slates strength with schistosity orientation. A method of utilization of Hoek-Brown criterion to assess the strength of layered rock is then introduced. According to the proposed method,uniaxial and triaxial compression tests of slates in the West Route of South-to-North Water Transfer Project are conducted. Based on the experimental results,the related parameters and Hoek-Brown criterion for different layer directions of slates are determined. The variation of uniaxial compressive strength of slates with layer directions is also studied and the general Hoek-Brown criterion for the layered slates is then established. In addition,the triaxial compressive strength of slates under confining pressure of 10,15,20 and 25 MPa are predicted. The study results in this paper can provide references for similar projects.