토함산 석굴에 대한 건축사적 해석 (Seokguram: An Architectural Enigma from the Past)

서지정보

· 발행기관 : 한국불교미술사학회
· 수록지 정보 : 강좌미술사 / 46호 / 33 ~ 60페이지
· 저자명 : 이강근

초록

경주 토함산 석굴이 한국예술사에서 차지하는 높은 위상에 대해서는 누구도 부인하지 않는다. 석굴 내부에 모셔져 있는 불상의 완벽한 아름다움과 조화로운 구성, 그것을 둘러싼 내부공간의 장엄한 분위기 등은 많은 이들로 하여금 그 비밀의 해석에 열중하도록 만들었다. 그리하여 그 위치설정이 동해 대왕암(문무왕의 수중릉)과 유관하다는 점, 석굴의 평면과 입면이 본존불의 크기를 기준단위로 하여 조화로운 비례를 이루도록 설계되었다는 점 등이 역설되었다. 여기에 더하여 한국건축사상 의의는 전무후무한 새로운 구조 즉 도움(Dome)으로 설계되었다는 사실이다. 원형 평면과 이를 둘러싼 원형 벽체에 원형 도움 천정을 얹음으로써 완성된 새로운 건축은 완벽한 불세계를 지향하던 당시 불교계에 이상적인 석굴사원으로 제시되었다.
당시에는 석조건축의 천정을 해결하기 위해서 주로 말각조정식(모서리내쌓기) 축조법을 사용하였다. 돌방무덤은 물론 서역의 축조식 석굴사원에서도 크게 이 천정이 널리 유행하였다. 따라서 석굴암처럼 원형 평면에 입체적인 반구형 천정을 쌓아올린 도움 구조는 실험적인 시도의 결과였다. 그러나 천정의 정점부에 덮개돌을 얹는 순간 붕괴 사고가 일어났고, 이 문제를 해결하기 위하여 특별히 고안된 방법이 쐐깃돌을 천정의 여러 곳과 덮개돌 둘레에 설치하는 것이었다. 못처럼 생긴 쐐깃돌을 고안하여 못 머리 부분은 천정 아래로 향한 채 천정돌을 받치게 하고, 못 뿌리 부분은 천정 속에서 큰 돌에 눌린 채 천정 돌을 치켜 올리는 역할을 하도록 고안함으로써 거대한 석조 도움 지붕을 성공적으로 쌓아올릴 수 있었던 것이다.
그런데 이 도움 구조는 신라건축은 물론 고구려 건축, 백제 건축에서도 과거에 사용된 적이 없기 때문에, 학계에서는 외국인 건축가나 외국 건축기술의 결과로 설명하려는 경향이 있어 왔다. 그러나 건축기술 특히 구조기술은 사전 준비 없이 단기간에 유입되거나 적용할 수 있는 게 아니다. 석굴암은 원형 벽체, 벽체 상부 받침돌 위에 틀어 올린 도움 구조물과 도움 천정 정상부의 거대한 덮개돌 등이 구조적으로 문제없이 축조되었기 때문에 붕괴되지 않고 버틸 수 있었던 것이다. 구조물 아래로부터 각 축조 단계에 적합한 축조 기술이 적용되었을 것이고, 이 기술은 신라건축기술의 발전과정에서 이미 개발되고 적용되어 온 일반기술이지 석굴암에만 적용된 특수기술은 아니었을 것이다.
8세기 후반에 석굴암을 굴착식 석굴이 아니라 조적식 건축으로 축조할 수 있었던 데는, 신라 석조건축의 사적 전개 과정에서 발전된 다양한 건축술이 성공적으로 적용되었기 때문이다. 아울러 건축의 아름다움을 실현하는 데 바탕이 되었던 비례이론이 나정 유적 평면, 망덕사지 목탑 평면의 구성을 거치면서 더욱 발전된 형태로 석굴암의 평면 구성과 입면 구성에 조화롭게 적용될 수 있었다. 또 고구려 석실분의 천정 축조 과정에서 보이는 기술의 발전이 마침내 천왕지신총에 이르러 목조와 석조건축을 결합한 ‘3단 도움’ 형식으로 개화되었던 사실에 주목할 필요가 있다.
신라의 석조건축술은 삼국통일을 계기로 백제와 고구려의 석조건축술과 결합하여 한 단계 높은 건축술로 도약할 수 있었을 것이다. 그리하여 신라 동궁과 월지의 조성, 감은사 석탑 건립, 월정교 축조를 계기로 다져진 석조건축술이 8세기 후반에 석굴암과 불국사 건설에 훌륭한 밑거름이 되었던 것이다. 즉, 석굴암은 외래 건축가와 건축기술의 도입으로 단 한 번만 이룰 수 있었던 신비로운 건축이 아니라, 신라 건축술의 창의적인 디자인이 가능케 했던 새로운 석조건축인 것이다.

영어초록

Architectural history has evolved with the progress of construction technology. Modern architecture in the West, in particular, has been developed on the basis of technological development that resulted from the Industrial Revolution. Developing an architectural structure of a new style can be successfully conducted only after obtaining complete technological knowledge via experiences.
The birth of new architecture takes place only after a matrix has formed via experimentation with new technologies. However, no one can say that experimental effort always results in success. Good fortune may bring success in one’s first attempt, but that does not guarantee that it will bring the same results in actual works. That is why we sometimes witness an unexpected catastrophe in construction projects. Even today, it is not uncommon for Korean architects to invite experts from overseas to prevent such misfortune when they attempt new construction works.
The status of Seokguram in Korean architecture is unique, and many art historians argue that it is one of the finest architectural achievements in the world; the perfect Buddha image enshrined at the center of the hall, the layout of the stone deities surrounding the Buddha, and the structural grandiosity that creates a solemn religious atmosphere are among the elements the building is praised for. Some add that the perfect location, particularly in connection with Daewangam (“Rock of a Great King”) which is known as the “underwater tomb” of King Munmu, and the proportion and balance between the principal Buddha image and the spatial dimension of the hall are also worthy of praise.
One might argue that the most striking feature of this man-made grotto is the vaulted roof of its main hall, since Korea had no precedent of such construction until then. Art historians believe that the new architectural structure consisting of a circular plane with its matching dome was suggested to the Silla people as an ideal grotto temple for representing the world of Buddha. If that was the case, what difficulty did they have in the course of materializing their vision of the perfect Buddhist temple? Was the construction of the temple actually completed in just one attempt thanks to one architectural genius as it was recorded and as an ancient history book outlines? The History of the Three Kingdoms (Samguk Yusa) had this to say about Seokguram: “[He] built Bulguksa (“Temple of Buddhist Land”) for the parents of this world, and Seokbulsa (“Temple of Stone Buddha”) for the parents of the other world “When he was carving a large stone canopy to enshrine a stone Buddha, the stone suddenly split into three parts. Dae-seong Kim was vexed at this and then fell into a deep sleep. At that time a heavenly deity descended and completed it before returning.” Seokbulsa in this record means today’s Seokguram at Tohamsan Mountain. Then, we can surmise that the builders of the grotto incurred a major accident in constructing the vaulted roof (the canopy in the record). What is interesting here is that the dome was completed in a single night, not by Dae-seong Kim who was in charge of the construction, but by a deity sent from the Buddhist paradise. The ceiling of today’s grotto has its lotus-shaped capstone divided into three parts. This tells us that the record is not very far from the truth, although one can plausibly argue that the mention of the heavenly being was fabricated for religious purposes. What is certain here is that the builders had a difficult time in the construction of the dome.
The typical ceiling of stone structures during the Three Kingdoms period was the corbelled vaulted ceiling, a style that had widely spread from the grotto temples in the Near East to the stone-chamber tombs of Goguryeo. However, building a hemispheric ceiling with stones over a circular floor plane was surely a new venture at the time. We can then infer from the record that the accident, in which a large stone fell from a 9m height and split into three parts, took place at the very moment when the builders were attempting to top the vaulted ceiling with a single capstone.
Then, how were they able to complete the building after the accident? The size of the capstone (2.47m in diameter at the lower part, 3m in diameter at the upper part, and 1m in thickness) tells us that it must have weighed about 20 tons. That it still retains the three-part split reveals that they must have used the same stone they had dropped in the earlier effort. Topping the ceiling with a split capstone should have been a far more difficult task than using a new, unimpaired stone. But they succeeded in using the old stone. How did they accomplish this? The builders under the leadership of Dae-seong Kim thought that a solution may lie in using wedge-shaped stones. Hence, they put a number of “wedge stones” all over the ceiling including at both ends of the capstone. Carved in the shape of a nail, these stones were designed to support the capstone by being squeezed between other stones forming the ceiling. The result was so incredible that they thought it was achieved not by their concepts and efforts, but by the intervention of some heavenly deity.
Gradually, their success became legendary to later generations who believed by the time the history book was written that it was a work of a heavenly being rather than human beings. For today‘s art historians, the builders who invented a new principle of structural dynamics are the ones that should be praised. It was a triumph achieved through the unyielding spirit of great architects.

참고자료

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