Papers by Author: Yoshinori Iwasaki

Abstract: In this paper, we purpose to assess the crack and deterioration level of composed stones in Angkor Monument, Cambodia, by an elastic wave test. The degree of deterioration and crack is generally examined by supersonic wave test, electromagnetic wave test and hardness test. However, the above general methods are difficult to be applied to the stones in Angkor Monument, because there are some problems such as damages on the surface relief and an accuracy of the test results which highly depend on the surface deterioration level. Therefore, in this paper, we suggest the method of an elastic wave test by slightly knocking on the stones. Then, we analyze the elastic wave’s profile, such as velocity, amplitude ratio and frequency etc. From the results, we examine about the relationship between the elastic wave profile and existence of crack or deterioration level of stone. The above examinations are applied to assess the structural safety of composed stones in Angkor Monument.

Abstract: Based on the past monitoring data of crack movements and various weather conditions by JASA (Japanese Government Team of Safeguarding Angkor), we quantitatively examine about the effects of each weather conditions to each crack movements at Bayon main tower. Then, we applied the time series analysis using a state-space representation in the examination. In the model of the state-space representation, the factors of crack movement are assumed as temperature, wind velocity and rainfall. Those quantitative examinations of crack movements will be necessary for the planning of reinforcement and restoration at Bayon main tower.

Abstract: This paper presents a case study of foundation of an inclined independent masonry tower in Angkor. One of the Prasat Sour Prat towers had been dismantled before reconstruction for conservation. The foundation was inclined as the same as the upper structure of the tower and spreading outwards. The inclination was considered caused by foundation failure with some differential settlements of the ground. During dismantling, the soil layers exposed on the trenched section were found rather horizontal than the inclined state that had been expected. Laterite blocks of step slope stones was found to have slid down along the soil mound of the foundation. The mechanism might have been caused by weakening of soil strength by wetting ground. Without dismantling, the real mechanism of the inclination was never known as well as the corresponding counter measures.