Abstract— Grout method is used for the purpose of reinforcement or cutoff by injecting thickener into the ground or structure. Recently, it's also used to prevent the leakage by filling the cracks during tunnel excavation. The deeper the tunnel the less the cracks in the rock for excavation and the leakage would possibly occur through microcrack. A plane parallel plate injection device that simulates the microcrack was fabricated to test the clogging. Less clogging was occurred in microcrack with polymeric injection material even in case of higher viscosity, resulting in relatively stable injection because of less variation in injection volume. When using cement as injection material, adjusting the viscosity and minimizing the cohesiveness of cement particles are more than important and thus mechanical and chemical process to prevent the cement from being cohered is considered essential in grouting process. This study is intended to identify the clogging depending on change to viscosity with regard to micro cement and polymeric injection material which have been used for repairing and reinforcing the microcrack. 