One of the most important parameters used in the design of rock structures is the Deformation Module. However, this parameter is taken as a fixed value in almost all designs. Elasticity modulus of the rock material is used in the formulas used during the calculation of Deformation Modulus. Elasticity modulus of the rock material changes with depth, in other words the amount of stress. The variable modulus of elasticity of the rock material requires the deformation modulus of the rock mass to be variable. In this book, it is explained that the use of variable rock mass deformation module in the design of rock structures made by numerical modeling provides more precise results and how this study should be done.