Ultrasonic Properties of a Stone Architectural Heritage and Weathering Evaluations Based on Provenance Site

Abstract

In this study, we performed customized ultrasonic measurements of the stone block foundation of the Sungnyemun Gate, which is representative of the stone architectural heritage in the Republic of Korea. Furthermore, the weathering evaluation standards, which are extensively used in stone heritage, were improved considering the type of rock and its provenance site. In particular, the absolute weathering grade used the ultrasonic velocity (P-wave) of a universal hard rock, whereas the relative weathering grade used the differences between the ultrasonic velocities of the materials in the stone block foundation of the Sungnyemun Gate (weathered stone) and the fresh rocks in the provenance. Among these, the absolute weathering grade was observed to be constant regardless of the type of rock; however, the relative weathering grade varied depending on the type dof rock. Because the average ultrasonic velocity of the original blocks of the stone block foundation of the Sungnyemun Gate was 2665 m/s, it was estimated that their ultrasonic velocity reduced by approximately 2.1 m/s per year as compared to that observed in case of fresh rocks (average 3932 m/s) in the provenance site. Furthermore, the weathering evaluation exhibited that there were approximately two stages of difference between the original blocks and the new blocks. As compared to the relative weathering grade, the absolute weathering grade was observed to underestimate the overall ultrasonic velocity of the stone block foundation of the Sungnyemun Gate. This study presents a customized method for performing ultrasonic measurements and for evaluating weathering. It is assumed that the results of this study will be extensively used in diagnosing and monitoring the stone architectural heritage.