The purpose of this study is to analyze the overall condition of the foundation for the three storied stone pagoda of Bulguksa temple in GyeongJu. As a research method, exploration of the electrical resistivity, refraction seismic, surface wave exploration, GPR exploration, Reputation loading test. The results of the investigation, the range of the foundation was formed in foundation stone outskirts of 1.5 ∼ 2.0m. It was confirmed to be about 2.0m depth. The depth of the foundation becomes shallower from the base portion to the outside. And the bearing capacity of foundation was sufficient conditions to weight. It can sufficiently support the weight of pagoda. And, the result of this investigation becomes basis data for repair work.

선본사의 두 석조문화재 관봉 석조여래좌상과 삼층석탑의 석재들은 암석기재적으로 거의 동일한 특징을 보인다. 즉, 회백색의 조립질로서 반상조직을 보이는 화강암이며, 주 구성광물은 사장석, 알칼리장석, 석영, 흑운모, 각섬석, 녹니석 등으로 이루어져 있다. 이런 기재적 특징들은 선본사가 위치한 팔공산 화강암체 서남부의 화강암 노두에서 확인되는 것과도 유사다. 모드조성에서는 석조여래좌상의 경우 몬조화강암에 속하나 삼층석탑 및 인근 화강암 노두의 암석은 섬장화강암과 몬조화강암의 양쪽 조성을 나타낸다. 전암대자율 측정값을 보면 관봉석조여래좌상, 삼층석탑, 선본사 인근화강암 노두에서 각각 10-14, 10-15, 9-16(×10-3 SI)의 범위를 보여 거의 동일하며, 자철석계열의 팔공산 화강암을 나타낸다. 감마스펙트로미터 측정값에서도 세 암석에서 K, eU, eTh의 함량들이 거의 유사한 범위에 속한다. 결론적으로 선본사의 관봉 석조여래좌상과 삼층석탑은 팔공산 화강암으로 만들어졌으며, 주변 지역의 화강암체가 그 원산지라고 추정된다.

The purpose of this study is to analyze the cause of damage to the three storied stone pagoda of Bulguksa temple in GyeongJu. This report is attempted to making reinforcement and conservation plan through investigating and analyzing the cause of damage to that. The damage is caused by occurring of stress, degrading of stone strength, changing of underground soil structure, natural disasters and so on. Compressive stress, shear stress, bending stress and lateral pressure affected to the pagoda since built up. Ultrasonic examination data tells the strength of the stone. According to this result, strength of the stereobate stone materials is enough to support the weight of the upper ones. But we could found many other factors of the damage could consider, for example the problems occurred on building the pagoda construction and the weakness of the stone material(soft rock). And many environmental factors being changed in soil structure(subsidence of soil and degradation of bearing power of soil and freezing and melting of soil) can be seen as the cause of the damage. Natural disasters like earthquake, lightning and heavy rain were also thought to give direct impact to the damage. At last Concentration of compressive stress caused the crack and exfoliation on the stone materials and shear stress, bending stress and lateral pressure were main causes of the stereobate stone materials shearing.

Three-story Stone pagodas in Gameunsa Temple site, one of the early staged stone pagodas, has been known as a standard of Silla stone pagodas. A stone pagoda is not only a stone art work and but also a stone architecture. In understanding the stone pagoda it is very important to be approached with technological side in which we can investigate the stone pagoda deeply and as well as to have been approached with art historical view. Also it needs that we should see the stone pagoda in view of structural safety. We can get many high technique from our ancestors who made Gameunsajiseoktap. 1. To reduce any deformation such as relaxation and sinking of members which is caused by a heavy load the members such as the lower tier of the base is made up of the foundation stone and side stone in each, comprising one stone. 2. A special construction method for connection between wall stone and column stone in stereobates was invented. It is to make column stone projected partially and wall stone be caved in that two members should be jointed well. This unique method is not used any longer after the three-story Stone pagodas in Gameunsa Temple Site. 3. In each side upper and lower member are not engaged as the size of roof stones and support stones of roof stones are different. It can be done for a distribution of perpendicular load and a prevention for relaxation of members. 4. It makes sure that to make upper ends of support stones 10mm lower was to be avoid upper loads to it judging from survey in disassemblying east pagoda. It proves that ancestors who made this stone pagoda had a technique to understand the structural matters to make small members as big as possible, not to engage in joint, to avoid in ends of members from upper load.