Abstract: In the treatment of the urban karstic rock cavities, grouting is often used to fill and to reinforce the karstic rock cavities. However, it is difficult to obtain the volume information of the cave and the grouting quantity is difficult to control. Therefore, the key to fill the rock cavities is to obtain the volume information of the karstic rock cavities. Based on the experimental principle of the ideal gas state equation, a method of the volume measurement for a closed dry cave is proposed by using the method of the gas injection pressure excitation. That is, the volume of the cave is estimated by measuring the change of the air pressure and the temperature before and after the gas exchange between the model of cave and auxiliary measuring device. The simplified test principle is verified by the CFD software FLUENT. The experimental equipment is designed for the indoor test. The test results verify the feasibility of the simplified principle and the operability of the test device. This method is simple in both principle and application and has the application potential of the cavity connectivity judgment, size estimation and the cave volume estimation.

Key words: Equation of State for Ideal Gas, Pressure Stimulation Method, Karst Rock Caves, Volume Measurement, Numerical Simulations