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The erosion under a spillway can be a long-term issue that threatens the structural integrity of a water reservoir. The heavy rainfall associated with storms or typhoons could cause a serious flood if the spillways do not function properly. The spillway under investigation was suspected to be defective after they had been commissioned in 1987. Potholes and subsurface cavities were confirmed in the safety assessment using various NDT techniques including ground penetrating radar and impact echo. The engineering team applied the repair project that aimed to remedy the deteriorating concrete structure. The GPR inspection was able to differentiate the repaired region from the cavities under concrete slabs. The results were verified against other measurement data obtained independently. Hence, the GPR technique is effective for quality check of grouting repair of spillways. Repetitive GPR scans were also carried out after the rehabilitation of spillways. Not only the quality of repair can be evaluated, but the scans were also provided as the baseline record for long-term condition assessment of the spillway-reservoir system in the future.

The temperature field analysis of electromagnetic rail launcher is an important basis for studying the launching stability and life. Aiming at the rail groove erosion phenomenon, the launching initial segment is selected as the research site. The heat generation mechanism of Joule heat and friction heat is analyzed, the heat source model is established, the three-dimensional finite element simulation model is established and the position, velocity and current waveform of the launching initial section are determined according to the circuit simulation, the finite element simulation results show that the heat in the initial stage of launching mainly concentrates on the contact surface between armature and rail. The friction heat is the main factor affecting the temperature rise of the contact surface, and the uneven distribution of the current density will lead to the uneven temperature distribution of the contact surface.