Project relevance: During construction, when large loads are applied to rock, it may undergo deformations which undermine the overall stability of rock mass. To estimate the behavior of rock mass, it is important to know the level of stress acting on rock at a certain depth. This chapter will explain how to calculate the vertical stress and discuss the major failure criteria that engineers use to assess the rock strength. As part of the project work, the laboratory data obtained for the sandstone and mudstone will be analyzed to determine the strength characteristic of these rocks.