Grouting condition inside the model pipe is checked by scanning type shock echo method.

Based on these investigations and stresswave propagation theory, the impact echo scanning technology was used to study onthe testing and recognition of defects in the concrete structure, estimating the damagedegree of concrete, multi-layer structures, and the technology was used to estimatethe thickness of tunnel concrete lining.

Pulse-coded impact sources based on swept impact seismic technique can effectively increase the signal-to-noise ratio and resolution of seismic prospecting compared with the conventional single-pulse method.

An introduction was given to the principle,scope of application,and characteristics of the vacuum grouting method and impact-echo method.

The basic principle of impact-echo method is introduced for checking concrete quality.

Based on the shortcomings of conventional detecting methods, the impact-echo method is put forward and its principles and superiority are discussed.

The overall condition of the concrete structure is firstly evaluated with ground penetrating radar(GPR),and the abnormal area detected by radar are located with the impact-echo(IE)scanning technique, then the style and position of the potential defects are diagnosed effectively.

The applications of impact-echo method on nondestructive testing for concrete structures are researched in this paper.

Several methods for measuring Raman gain coefficient in optical fibers,such as on-off method, pulse-scan technique and single light source measurement method,are presented in detail in the aspects of operation principle and experiment equipment.