임진강유역 고구려 성곽의 발굴조사 성과와 축성법

Abstract

Since Archaeologists found 20 Goguryeo fortifications around Achasan Mountain in 1994, 10 more Goguryeo fortifications have been excavated in Yangju area, along with 10 on Imjin River basin. It is estimated that there are 40 or more Goguryeo fortifications in South Korea, and archaeological excavation projects were launched on 22 sites. Based on the findings from the excavations in South Korea, Goguryeo fortifications are divided into two types: wooden fence fortress and stone fortress. Goguryeo wooden fence fortresses were uncovered at Horogoru Embankment, Jeongokritseong Earthen Fortress, Dogidongsanseong Fortress in Anseong and Namseonggolsanseong Fortress in Cheongwon. Those fortresses typically have a double-row wooden fence, which is different from the single-row one erected by Baekje. Naturally, the method to build a fence is different from Baekje's. In addition, Goguryeo's stone fortress construction style is also different from Baekje's and Silla's. Baekje mostly built earthen fortresses. Its stone fortresses constructed during Sabi Period, such as Seokseongsanseong Fortress in Buyeo and Marosanseong Fortress in Gwangyang, have a double wall erected by using crushed stones for inner and outer walls and Gaegeo-style (開居式) fortress gates. Silla piled up stones to build a facade of its fortresses, and the reinforced fortress wall and Heyonmun-style (懸門式) fortress gate are major features of Silla fortifications. On the other hand, Goguryeo founded the base inside the wall by banking earth and surrounded it with stones to build a fortress, called Toshimseokchuk (土芯石築) method. As Goguryeo developed this unique method by combining construction techniques of earthen fortress and stone fortress, it enabled Goguryeo to better build a fortress and promote its defense capability. Furthermore, it could overcome weaknesses of the fortress site and secure plenty of room for use. The major feature of this method is wooden pillars, which supported thin stone wall for reinforcement. In building a fortress, Goguryeo's engineers first founded the base, cut grooves along the edge of it and slope, and set logs, about 25cm in diameter, into the grooves. Then they fixed these logs, called Yeongjeongju(永定柱), vertically and crosswise with wooden bars, inserted planks, and rammed clay. After this process, they removed the planks, built an outer wall by laying stone blocks, and put more clay on the bottom of the fortress wall to reinforce. Although the circumference is about 200 meters, which is quite small, Goguryeo fortifications have 7 guard towers projected from the fortress wall, as known as Chi(雉), to enhance defense capability and minimize the structural weaknesses of the fortress wall. The major feature of the stone-built section is cavity wall. Since a cavity wall is required to reinforce the stone-built section of a flatland fortress, logs were fixed into the ground in rows like Yeongjeongju used for the earthen section, stones were piled up to set up the inner wall, and wall stones were laid to reinforce the fortress wall. Also, the bottom of the reinforced fortress wall was tamped with clay. A stone fortress was born through this process. The process left marks of the grooves. The middle wall of Daeseongsanseong Fortress and Horogoru Embankment and the groove marks at Dangposeong Fortress exhibit the features of Goguryeo's fortress construction technology. Even though it is not a thick stone wall, the cavity wall must have been one of the fortress construction techniques Goguryeo's engineers preferred, as the wall is very noticeable in uncovered Goguryeo fortresses, such as Hongryeonbong-il-boru Bastion and Wolpyeongsanseong Fortress. In reinforcing the stone wall, Goguryeo used wet construction method by piling stone blocks up and filling the gaps with clay to prevent segregation of clay from stone blocks. Goguryeo's fortress construction method described above has been found in Goguryeo fortresses in South Korea, China and North Korea, such as Guknaeseong Palace, Paewangjosanseong Fortress and Daeseongsanseong Fortress. This suggests that the central government took charge of fortress construction technology management.