Integrity assessment of rock mass behind the shotcreted slope using thermography

This paper presents the results of a field study of using thermography to identify the existence of eroded caves behind shotcrete-protected slopes. The temperature variation calculated from the highest and lowest temperatures measured at each point on the shotcrete surface is utilized to evaluate the integrity of the rock mass behind the concrete. In addition, ground penetration radar (GPR) is performed at three selected locations near the toe of the slope of concern; while the necked eye observation and knocking tests are conducted at two of the selected areas. The soils taken out from the rock mass and the abnormal echo, as well as strong GPR reflection patterns, confirm the existence of eroded caves behind the shotcrete surface. The agreement of the locations that show both strong GPR reflection and large temperature variation verifies the applicability of thermography in evaluating the integrity of rock mass behind the shotcrete surface.