tatakidoi 敲土居
KEY WORD : architecture / castle
A pounded earth embankment. It was made of layers of earth mixed with water, pounded down and allowed to harden. The wall had a flat top mabumi 馬踏, and widened towards the base. See diagram. The slope koubai 勾配 of the sides varied: according to the Houjou school, Houjouryuu 北条流 the wall should slope upwards at a 45 degree angle. This angle represented a safety standard by which to avoid the earth crumbling when the slopes were being built using form construction. The quality of the soil also made a difference: embankments constructed with black earth without pebbles and sand sometimes collapsed, unlike embankments of red loam that included large quantities of pebbles and sand. The standard measure for tatakidoi is a height of approximately 6m (3 *ken 間), a flat top of width 4m (2 ken) and both sloping sides 6m wide, giving a total base width of about 16m (8 ken).

*doi 土居

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