The main goal of the grouting is to seal the fractures in the rock mass,improve the strength properties of the rock mass and decrease deformability. However,the overuse of the grouting should be avoided due mainly to economic reasons,optimizing the project time and sometimes severe environmental issues.Insufficient grout spread can cause worse sealing results and decreasedurability. To control the process of grouting and predict the penetrationlength an analytical solution called Real Time Grouting Control theory (RTGC) hasbeen developed. This thesis aimed to evaluate RTGC theory on the equipmentrepresenting a one-dimensional model of a fracture called Varying Aperture LongSlot - VALS. The evaluation was based on a comparison between the calculated(predicted) penetration length according to RTGC theory and the realpenetration obtained in the experiments. Results of the tests show that the RTGCtheory is a good tool to predict the penetration length of the grout at thejoints with apertures close to the hydraulic apertures. At the apertures,significantly less than the hydraulic aperture, the results of the test andRTGC theory differ a lot.