Vibration Method For Measuring Compression Wave Velocity Of Rock Mass

Rock mass wave velocity testing can obtain the compression wave velocity or shear wave velocity by analyzing the propagation time and distance of elastic wave inside or on the surface of rock mass,it can provide the dynamic mechanical parameters for engineering investigation of hydropower,roads and bridges,tunnels.In the current code,the testing methods of compression wave velocity of rock mass are mainly divided into seismic exploration technology and ultrasonic testing technology.The seismic exploration technology is restricted by the drilling conditions of the site,and the ultrasonic signal is obviously affected by the high-frequency filtering,so the above two methods are not suitable for the test of broken or relatively broken rock mass.In this paper,the vibration method is used to measure the engineering practice,the corresponding test methods have been compiled,and the test data has been processed and analyzed,including the following contents:(1)The concept of vibration method which is suitable for testing broken or relatively broken rock mass is proposed.The vibration is excited in the shallow borehole,and the vibration signals are received by many low-frequency sensors arranged on the surface of rock mass,thus the compression wave velocities are measured.This method need not deep drilling and has little disturbance to the rock mass.The seismic wave is generated by hammering excitation,which can increase the testing distance.The compression wave velocities are measured section by section by using multiple sensors to receive signals.(2)The test scheme of compression wave velocity by using vibration method is presented,the field measurement and data processing analysis are carried out.Based on the wavelet transform,the high-frequency signals are filtered and recombined to realize the noise reduction,and the MATALB program is compiled to calculate the compression wave velocity data through the cross-correlation principle.The relative error between the vibration method and ultrasonic method is-2.10%,and that of numerical simulation is-6.87%.(3)The integrity of engineering rock is quantitatively evaluated by vibration method,the sectional evaluation results of the integrity coefficient K_v of rock mass are achieved by combining the wave velocity test data in the laboratory.The qualitative evaluation results of rock mass are obtained after the engineering investigation,the comparison shows that the results of the two evaluation methods are consistent,which verifies the accuracy of the method.