In this chapter, deformation and displacement in roof, floor and sidewalls of a powerhouse are estimated using the empirical, numerical, artificial intelligence and statistical methods. First, empirical equations are presented to determine horizontal and vertical displacements around a power station cavern. Then, key point location, boundaries of the key zone, key point displacement, maximum depth of plastic zone and horizontal and vertical displacements around a powerhouse cavern are estimated using the numerical modeling. In the following, displacements and plastic zones at different points around the powerhouse cavern including key point and middle points of the floor, roof and right and left sidewalls are determined using the fuzzy logic, neural networks, gene expression programming and statistical models. The above models are constructed and evaluated based on the input data including surrounding rock mass properties and powerhouse geometry. Accordingly, new predictive equations are developed to determine the plastic zone and displacement around a powerhouse i.e., at the key point. Finally, using warning levels of tunnel stability loss proposed by Sakurai, a new classification scheme is proposed for key point surrounding the powerhouse based on the critical displacement.
