Injecting the improvement material into the ground by the chemical solution injection method, the permeability of the ground decreases due to the occurrence of clogging in void of ground. The permeability of the ground greatly affects the penetration range of the chemical solution and the quality of the improved body. In other words, it is very important to prevent the decrease of the permeability of the ground in the chemical injection method. Therefore, in this research, a new chemical grouting method that prevents the decrease of the permeability of the ground is developed by applying ultrasonic vibration when grouting the chemical solution. Consequently, in our previous laboratory and the field verification, it was found that the decrease of the permeability of the ground can be prevented, also the diameter and the quality of the improved body were improved by applying ultrasonic vibration when grouting the chemical solution.
