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壁基礎の安定性チェック

Retaining Wall Footing Stability Checks

Retaining Wall or Wall Footings

Retaining wall or wall footings are vertical or close to vertical structures aimed to retain soil on one side, preventing the retained material from collapsing, slipping, and eroding. Wall footings provide support to the soil arranged in a way that its repose internal friction angle is exceeded, and therefore would collapse if not stabilized with a structure. Wall footings are normally used for creating usable flat land out of steep terrain to construct another structure such as a highway or a building. They can be considered as independent structures or as part of wider construction systems.

Retaining wall footing structures are basically composed of a concrete wall stem and a concrete footing base. There are three different soil zones that are considered in the stability analysis: パッシブ土壌, 活性土壌, and Substructure soil. The passive soil helps the retaining wall footing and active soil self-weight to withstand the action of the retained soil pressure and the pressure associated with the external surcharge when applied. The substructure soil is in charge of bearing the wall footing system overall weight.Skyciv Concrete Retaining Wall Footing Components with Names, wall footings

Stability Requirements

A wall footing may fail in any of the following ways, in terms of stability:

  • It may overturn about its toe
  • It may slide along its base
  • It may fail due to the loss of 支持力 of the soil supporting the base

Skyciv Concrete Retaining Wall Footing showing Stability Requirements

チェックを覆す

For calculating the Factor of Safety against 転覆 about the toe (the most bottom-left corner of the base), the sum of resisting moments is divided by the sum of overturning moments. Each of the components for the retaining wall footing overturning factor of safety calculation, is listed below:

  • Resisting moments: From all the downwards forces located to the right and all the rightwards forces above the left-most corner of the base multiplied by its lever to the centroid of the load resultant.
    • Stem wall weight
    • Base footing weight
    • Active soil weight
    • Passive soil weight (含まれている場合)
    • 転倒モーメント計算例
    • The vertical component of the active soil pressure (裏込めが傾斜している場合)
    • 追加料金合力圧力の垂直成分 (裏込めが傾斜している場合)
    • パッシブ土壌圧力 (含まれている場合)
  • 転覆の瞬間: From all the leftwards forces above the left-most corner of the base multiplied by its lever to the centroid of the load resultant.
    • The horizontal component of the active soil pressure
    • The horizontal component of the surcharge resultant pressure

A calculation example of the overturning moment can be found ここに, and the overturning check can be performed using the Free SkyCiv Wall Footing Calculator

スライディングチェック

For calculating the Factor of Safety against sliding, the sum of the horizontal resisting loads (pointing to the right) is divided by the sum of the loads pointing to the left.

  • 転倒モーメント計算例:
    • Horizontal force due to friction between the footing base and the substructure soil
    • パッシブ土壌圧力 (含まれている場合)
  • Sliding loads:
    • The horizontal component of the active soil pressure
    • The horizontal component of the surcharge resultant pressure

A calculation example of the sliding can be found ここに, and the sliding check can be performed using the Free SkyCiv Wall Footing Calculator

Bearing capacity check

For calculating the Factor of Safety against bearing capacity failure, the maximum allowable pressure of the substructure soil is divided by the maximum pressure exerted by the total vertical load accounting for the trapezoidal distribution of the subsoil reaction on the retaining wall footing base.

SkyCiv Wall Footing Calculator

Using the SkyCiv Retaining Wall Calculator you can easily perform stability checks both for cantilever and gravity walls, with the possibility to use tapered stem or parapet, use an inclined backfill, and include or neglect passive soil pressure contribution.

OscarSanchez製品開発者
オスカーサンチェス
製品開発者
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