Three-Dimensional Coupled Stress and Fluid Flow Analysis and Design Provisions for Lake Mead Intake No. 3 Low Level Pumping Station in Fractured Rock Mass

The stability evaluation of the Low Lake Level Pumping Station (L3PS) at Lake Mead is presented in this study. The subsurface structure consists of a riser shaft, an access shaft, 34 well shafts, a 107-m-long forebay with a height of 11 m and width of 10 m, a stub connector tunnel, and a future forebay extension. The site geology contains several joint sets, faults, and shear zones intersecting the excavation. The behavior of the entire subsurface structure and the interaction of various components in the vicinity of fault/shear zones were evaluated using a coupled hydromechanical finite element method (FEM) approach. The response of the rock mass was also evaluated using a hybrid finite difference-discrete element method (FDM-DEM) by accounting for major and minor discontinuities within the rock mass. The areas exhibiting significant plastic yielding were identified for a prompt installation of rock support to stabilize the heading.