07 BRAE 433 Ch 8 Retaining wall design-2

07 BRAE 433 Ch 8 Retaining wall design-2 - Retaining Wall...

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1 Retaining Wall Retaining Wall Design Chapter 8 Walls provide lateral support for earth fill, Walls provide for earth fill, embankment, can also support vertical loads, i.e. bridges. Main purpose -- retain the backfill. Examples of Retaining Walls ± 8-1a. Gravity Wall- plain concrete up to 10 feet high ± 8-1b. Cantilever wall – 10 to 25 feet high, most common, so named because the toe, heel and stem act as cantilever beam Toe Heel Gravity or Semigravity Wall (a) Stem Toe Heel Footing Cantilever Wall (b) ± 8-1c. Counterfort wall – higher than 25 feet, requires “counterforts” to act as tension members Stem Footing Counterfort Wall (c) Counterfort
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2 Examples of Retaining Walls ± 8-1d Buttress wall – same as 8 1d. Buttress wall same as previous, but with “buttresses” as compression members ± 8-1e. Basement or foundation wall – Stem Footing Buttress Wall (d) Buttress Wall Floor Slab First Floor cantilever except 1st floor provides additional horizontal reaction Footing Basement or Foundation Wall (e) Examples of Retaining Walls ± 8 1f Bridge abutment – similar to 8-1f. Bridge abutment – similar to basement wall – bridge induces horizontal loads 8 1B i l l tt i l Footing Stem Backwall Bridge Abutment (f) Steel Beam ± 8-1g. Bearing wall – supports vertical load as well as own weight. Footing Bearing Plate Bearing wall Bearing Wall (g) Slab
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3 Long Crested Weirs
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5 Cross Regulators
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8 Retaining Walls
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11 8-2: Lateral Forces on Retaining Walls ± Earth pressures – backfill, drainage, water table, slope added loads soil compaction wall slope, added loads, soil compaction, wall movement ± Largest problem is the lateral earth pressures ± Behavior is indeterminate - compaction, movement ± Big problem with saturation - most walls not designed for saturation Three Categories 1. Active state – if wall deflects, moves away from backfill - lowest earth pressure 2. At rest – if wall absolutely rigid - medium pressure 3. Passive state - if wall moves toward backfill - highest earth pressure ² Usual design – active earth pressure, horizontal pressure against wall called “equivalent fluid pressure” ² Assume it is linear ² Will be economical and safe??
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12 3 Situations for Retaining Walls ± Level Backfill: Total Active Earth Pressure h w h H p H a y h w 3 (Ha) = ½ K a w e h w 2 K p w e h K a w e h w Unit pressure (Passive State) Unit Pressure (Active State) Figure 8-2 Analysis of forces acting on walls: level backfill Total Passive Earth Pressure (Hp) = ½ K p w e h' 2 Ka and Kp are coefficients 3 Situations for Retaining Walls ± Sloping Backfill: Θ Total Active Earth Pressure (Hs) H v H H H s Θ h b h w Assume equal to backfill angle = ½ K a w e h b 2 h b 3 K a is a coefficient Figure 8-3: Analysis of forces acting on walls: Sloping backfill
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13 3 Situations for Retaining Walls ± Level backfill with Surcharge w s = Equivalent height H a h w surcharge (psf) h w 2 H w of earth h w h w 3 K a w e h w K a w e h w H a = ½K a w e h w 2 (due to level backfill) H su = k a w e h su h w (due to surcharge)
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This note was uploaded on 01/13/2011 for the course BRAE 433 taught by Professor Styles during the Fall '10 term at Cal Poly.

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07 BRAE 433 Ch 8 Retaining wall design-2 - Retaining Wall...

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