Study On Acoustic Parameters And Random Acoustic Field Of Drilling Shaft Lining And Grouting In Deep Alluvium

Backfilled grouting is an important process of shaft drilling construction, and the stabilityand the waterproof of the shaft structure is largely decided by the grouting quality. In deepalluvium, the widely used multi-rebar reinforced concrete and steel-concrete structure in the deepunderground engineering have limited the application of ground penetrating radar (GPR), whilethe typical ultrasonic detection is limited by the Signal to Noise Ratio (SNR) and its detectingdepth cannot meet requirements of the detection on the shaft structure.So it was prompted to improve the SNR and the detecting depth by Ultrasonic PhasedArray(UPA). In the paper, the stochastic media model of the shaft structure are built at first. Then,the ultrasonic field numerical simulation of different shaft structure (reinforced concrete shaftwall, inner steel plate shaft wall and dual steel plate shaft wall), different stimulating model(point source, Multi-point synchronous source, and phased concentration source), and differentfrequencies (10kHz,20kHz and50kHz) are carried out and the snapshot of the ultrasonic fieldare obtained. It is proved by the numerical simulations that the SNR would be enhancedobviously by the Multi-point synchronous, and phased concentration stimulating and the10kHz-20kHz is selected as the suit frequency of the backfilled detecting UPA. Thirdly, the UPAwas custom-made. The low frequency (5MHz) phased probe are used in the1:100modelexperimental test, and the Effective Imaging Depth(EID) of the probe is6.8mm; one canestimate that the EID of the50kHz would be0.68m, which cannot get the effective focusedsignal from the backfilled grouting area. So lower frequency probe should be developed in thefuture.From the comprehensive study of the numerical simulations and the preliminary modelexperiment,10kHz-20kHz is adopted as the suit frequency of the ultrasonic probe. In this paper,the ultrasonic field of the stochastic media is introduce into the NDT equipment development ofgeotechnical engineering, and Some beneficial attempt on model experimental are also beimplemented, which could be of reference value to the NDT of underground engineering.