Block analysis for preliminary design of underground excavations.

摘要

Rock mass discontinuities such as joints and faults often intersect to form discrete blocks that are individually stronger than the rock mass as a whole. When encountered during mining or construction, such blocks can cause stability problems. Displacement of the blocks around an excavation, can affect the rock mass in a hydrologic sense and in a mechanical sense. Hydrologic effects of block displacement can include the creation of preferred pathways for fluid flow or the creation of barriers to unsaturated flow of liquids. Mechanical effects occur because unhealed joints cannot support tensile stress, tend to limit the shear stress that the rock mass can carry, and reduce the rock mass stiffness locally as they open. Block theory and related analytical techniques have been developed to address problems of block identification and kinematic stability. These techniques can identify and screen potentially troublesome blocks early in the design process. Although more detailed analyses can be applied in later stages of the design effort to develop block reaction curves or to evaluate the effects of loosening around, the initial process of block identification and screening is the theme of this discussion. 12 refs., 1 fig., 5 tabs.