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A shallow foundation is a type of foundation which transfers building loads to the earth very near the surface, rather than to a subsurface layer or a range of depths as does a deep foundation. Shallow foundations include spread footing foundations, mat-slab foundations, slab-on-grade foundations, pad foundations, rubble trench foundations and earthbag foundations. ==Spread footing foundation== A spread footing foundation, which is typical in residential building, has a wider bottom portion than the load-bearing foundation walls it supports. This wider part "spreads" the weight of the structure over more area for greater stability. The design and layout of spread footings is controlled by several factors, foremost of which is the weight (load) of the structure it will support as well as penetration of soft near-surface layers, and penetration through near-surface layers likely to change volume due to frost heave or shrink-swell. These foundations are common in residential construction that includes a basement, and in many commercial structures. But for high rise buildings they are not sufficient. A spread footing which changes elevation in several places in a series of vertical "steps" in order to follow the contours of a sloping site or accommodate changes in soil strata, is termed a stepped footing. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Shallow foundation」の詳細全文を読む スポンサード リンク
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