Multi-sensing Investigation of Crack Problems for Concrete Dams based on Detection and Monitoring Data: A Case Study

Abstract Cracks, a major issue in concrete structures, will reduce structural integrity, stability and impermeability. In this paper, a comprehensive site crack status monitoring system was constructed in a roller compacted concrete (RCC) gravity dam during the construction period, by combining acoustic emission (AE), micro-seismic (MS), cross-hole acoustic wave detection (CAWD), crack gauge and strain gauge techniques; this system was used to investigate crack development problems that may occur under varying construction conditions. Through knocking location tests, the acoustic wave transmission rate of RCC was determined by the AE and MS system, to monitor the real-time status of micro-cracks. Moreover, the crack tip displacement, adjacent concrete strain and concrete ultrasonic velocity were captured, to monitor the propagation of macroscopic cracks. By combining the information obtained at both the micro- and macro- levels, the development trend of a crack was analyzed. Results show that micro-crack signals were captured, but the sensitivity of the AE approach was relatively smaller than that of MS method, and the crack status was in the structural internal stress adjustment stage. On the macro-level, the macroscopic expansion phenomenon of the original crack was not captured by the crack gauge, strain gauge and acoustic penetration. Based on the size, the concentration of micro-cracks and the development trend of the macro-cracks monitored by the multi-sensing system, the crack behavior can be evaluated in huge concrete infrastructures.