Oaks Designer Resource Guide 6.0

Incorporating Guards, Fences and Barriers

Wall: Proterra™ Smooth, Natural

Whenever a guard, fence or barrier is placed at or near the top of a retaining wall, there is a potential for overturning at the post location. People lean against guards. A car can strike the barrier. Snow could be pushed up against the fence. Wind can exert pressure on solid (glass panel or board) fences. For these reasons, minimum setback requirements from 0.3m (11.8”) to 1.0m (39.4”) are usually applied between the back of the wall and the centerline of the guard, fence or barrier. The greater the setback, the lower the impact on the wall facing. Because property owners prefer not to have large spaces between the fence and the back of the wall (wasted space that is difficult to maintain), Oaks has developed creative ways to incorporate guards, fences and barriers into SRWs.

MECHANICS OF WALL OVERTURNING People or objects pushing against a guard or fence can cause over­ turning around the bottom of the guard/fence post. If the guard/fence post is buried behind the wall, a surcharge at the back of the wall can occur. To avoid this and prevent the whole system from moving, the weight of the wall and soil in front of guard/fence and the resistance of the geogrid, need to be sufficient. When designing pedestrian guards you need to analyse the following: 1. T he horizontal load applied inward or outward on any point at the top of the guard (e.g. 200 lbs at each post). 2. An evenly distributed vertical load applied at the top of the guard (e.g. 50 lbs/linear foot of wall). The load that creates the most critical condition applies. For wind loads consider: 1. T he percent of area obstructed by the fence – this can range from 3% for chain link to 100% for solid wood. 2. Wind pressure – available in Canada in the National Building Code, Appendix C. Typically 1/30 hourly is used.

Privacy fence or noise barrier (designed by others)

PEDESTRIAN OR WIND LOAD

SURCHARGE ON BACK OF WALL

Sonotube (installed during wall construction)

WEIGHT OF WALL AND SOIL

RESISTANCE OF GEOGRID

ROTATIONAL MOMENT

Geosynthetic Reinforcement

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APPLICATIONS AND SOLUTIONS

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