In this master thesis, the problem of instability and the rock mass failure mechanisms including planar, wedge, circular, and overturning failure are presented. In order to be able to analyze instabilities, it is necessary to know the types and methods of stabilization, as well as methods of stability analysis, which are used to select adequate stabilization measures. Types of rock slope monitoring, which include remote observations or satellite images, photogrammetric, geodetic and geophysical or physical techniques are presented. Furthermore, possible types of rock slope stabilizing and protection measures are defined. For this purpose, protection measures such as receiving ditches, protective constructions, nets, barriers, galleries, and other methods are presented and explained. After the theoretical part, the project of rock slope protection as a part of entrance section of the Rijeka bypass tunnel, i.e. the southern pipe of the Trsat tunnel. The project assignment was made according to the actual obtained project data and the on site situation. For this purpose, models were created using the computer program Rocscience, Slide2. A total of six computer models were created to analyzed the rock slope stability and in the end, the best solution was presented, according to which the graphic attachments were designed.