Development of a numerical method and proposal of design method for structures in discontinuous rock

为了实现安全、经济的岩石结构设计和施工，有必要发展一种能够准确预测开挖过程中岩体性态的分析方法。在本研究中，建立了基于连续介质的细观力学模型。在MBC模型中，节理岩体被等效连续体代替，该连续体的本构方程是由一个代表性体积单元上的平均应力和平均应变的关系得到的。为了得到平均应变，计算了沿节理的位移跳跃。推导出的本构关系直观地反映了主要节理的方位和间距，表现出强烈的诱发各向异性。首先，对Shiobara水电站洞室开挖进行了分析，并将分析结果与实际数据进行了比较。结果表明，该方法较好地反映了大型洞室开挖过程中岩体的复杂性态，而现有数值方法的输入数据必须通过地质调查和现场试验才能确定。提出了一种根据隧道开挖过程中实测收敛来确定MBC模型输入参数的方法，并在此基础上提出了核废物处置深埋隧道的设计方法。结果表明，在给定节理方位和密度的情况下，采用本文提出的设计方法可以合理确定隧道衬砌厚度。

In order to realize safe and economic design and construction of rock structures, it is necessary to develop an analysis method that can accurately predict the behavior of rock mass during excavation. In the present study, MBC (Micromechanics Based Continuum) model is developed. In MBC model jointed rock mass is replaced with an equivalent continuum body whose constitutive equation is obtained from the relationship of the average stress and average strain over a representative volume element. To derive the average strain, the displacement jump along a joint is evaluated. The derived constitutive relationship directly reflects the orientation and spacing of the dominant joints and presents strong induced anisotropy.First, analysis of the cavern excavation for Shiobara power station is carried out and the results of the analysis are compared with real data. It is shown that the developed method captures the complicated behaviors of the rock mass during large-scale cavern excavation.For the present numerical method to be adopted in the design, its input data must be determined from geological survey and in-situ test. A method to determine the input parameters for the MBC model from measured convergence during tunnel excavation is proposed.A design method of deep tunnel for nuclear waste disposal is proposed based on the proposed MBC model. It is demonstrated that the thickness of tunnel lining is determined rationally for given joint orientation and density according to the proposed design method.