（74）今回ご紹介するのは・・・
（74）This time I would like to introduce...
群馬県藤岡市の伊勢塚古墳
（不正八角墳・石室はドーム状の模様積み）
Isezuka burial mound in Fujioka City, Gunma Prefecture (iniquitous octagonal burial mound, the stone chamber is piled with copper planks)
先日NHKで放映された「飛鳥の八角形古墳」で八角形は
天皇系由来として紹介されていましたが、
群馬県に私が知っている八角形墳が二つあります。
三津屋古墳と伊勢塚古墳です。
There are two octagonal tombs in Gunma Prefecture that I know of. The "Octagonal Tumulus of Asuka" aired on NHK the other day introduced octagons as being of imperial origin.
There are two octagonal tombs that I know of in Gunma Prefecture: the Mitsuya tomb and the Isezuka tomb.
4段築成だが見た目わからない
墳頂から八角の底辺部を望む
今回ご紹介する伊勢塚古墳は当初円墳と考えられていましたが、
発掘調査の結果、最下段のみ不正八角形で
2段目から上は円形である
不正八角墳であることがわかったそうです。
At first, this Isezuka tomb was thought to be a round tomb, but as a result of excavation, it was found to be an illegal octagonal tomb, with only the bottom tier being an illegal octagon and the second tier and above being circular.
墳丘は4段築成で葺石あり、直径27.2ｍ、高さ6ｍ、
The mound was constructed in four stages with thatched stones.
It is 27.2m in diameter and 6m high.
羨道部分
埋葬施設は、南方向開口の横穴式両袖型の石室で、
疑似の楣（まぐさ）も設けられている。
The burial facility is a double-sleeved stone chamber with a south-facing side opening and a pseudo lintel.
奥が玄室で手前玄門の上の出っ張りが楣石・両側の柱石が袖石
羨道と玄室（棺を置く部屋）を仕切る玄門のグレードを図るうえで
次の3点が解説されている場合が多い。
①框(かまち)石・・床面に板状の仕切りを作る
②袖（そで）石・・壁面に縦の柱石で仕切りを作る（両側にあるのが両袖型、片側の身が片袖型）
③楣（まぐさ）石・・天井に仕切りを作る
玄門は上記の3点によって、羨道から玄室（棺を置く部屋）への入口を狭めることで
羨道と玄室の境を強調させるとともに、玄室のスペースを大きく見せる効果を
持っていると言われている。
In many cases, the following three points are explained in order to determine the grade of the gate that divides the envious path and the coffin room (the room where the coffin is placed).
(1) Stile and rail stones: Plate-like partitions are made on the floor.
(2) Sode stone: A vertical pillar stone divides the wall.
(3) Mgusa stone: Making a partition in the ceiling.
It is said that the above three points make the entrance from the envious road to the chamber (where the coffin is placed) narrower, thus emphasizing the boundary between the envious road and the chamber, and also making the chamber appear larger.
石室全長8.9ｍ
玄室（ドーム状）の長さ4.7ｍ・奥壁幅1.84ｍ・中央幅2.41ｍ・前幅1.54ｍ
羨道：長さ4.24ｍ
Total length of the stone chamber: 8.9m
Genshitsu (dome-shaped): length 4.7m, width of the back wall 1.84m, width of the center 2.41m, width of the front 1.54m
Enclosure: 4.24m long
石室の石積みに特徴
Stone masonry in the chamber
玄門
玄門から天井にむけてドーム状に
玄室は流麗な曲線を描く銅張りで、模様積みという独特な石積みによる
ドーム状の構造をもつ。
所々にやや大型の自然石を配し、その周辺に細長い結晶片石を差し込んで
飛白(かすり)模様にしている
The main chamber is a dome-shaped structure with a flowing curved copper plan and a unique stone-piling technique called patterning. The dome-shaped structure is built with a unique masonry technique called "patterning," in which slightly larger natural stones are placed in places and long, thin crystalline stones are inserted around them to create a haze pattern.
銅張りプランとは・・・石室の側壁の胴が張り、さらに湾曲しながら天井へと続く、いわゆる玉子型を呈し、外部からの圧力に耐える形態。
Copper-plated plan: The body of the side walls of the stone chamber is stretched and curved to the ceiling, forming a so-called egg-shaped structure to withstand external pressure.
模様積みとは・・小石材（丸みを帯びた転石と棒状の石）を配して構築できる石室構造の最も頑丈で完成された姿
Patterned masonry is the most sturdy and complete form of stone chamber structure that can be constructed by arranging small stones (rounded boulders and stick-shaped stones).
埴輪は円筒・人物・盾形(たてがた)埴輪が出土
Cylindrical, human and shield-shaped terra-cotta tomb figurines were excavated.
築造は6世紀後半
Constructed in the late 6th century
引用／現地説明版・模様積石室小考（増田逸朗）・藤岡市HP・ウィキペディア
Reference/Explanation of the site, Small Consideration of the Stone Chamber (by Itsuro Masuda), Fujioka City HP, Wikipedia
翻訳／DeepL Pro