15-02-2013, 09:38 AM
DESIGN AND DETAILING OF RETAINING WALLS
DESIGN AND DETAILING.ppt (Size: 1.02 MB / Downloads: 561)
Learning Outcomes:
After this class students will be able to do the complete design and detailing of different types of retaining walls.
RETAINING WALL
Retaining walls are usually built to hold back soil mass. However, retaining walls can also be constructed for aesthetic landscaping purposes.
Classification of Retaining walls
Gravity wall-Masonry or Plain concrete
Cantilever retaining wall-RCC
(Inverted T and L)
Counterfort retaining wall-RCC
Buttress wall-RCC
Factors affecting earth pressure
Earth pressure depends on type of backfill, the height of wall and the soil conditions
Soil conditions: The different soil conditions are
Dry leveled back fill
Moist leveled backfill
Submerged leveled backfill
Leveled backfill with uniform surcharge
Backfill with sloping surface
Design of Heel and Toe
Heel slab and toe slab should also be designed as cantilever. For this stability analysis should be performed as explained and determine the maximum bending moments at the junction.
Determine the reinforcement.
Also check for shear at the junction.
Provide enough development length.
Provide the distribution steel
Cantilever RW design
Design a cantilever retaining wall (T type) to retain earth for a height of 4m. The backfill is horizontal. The density of soil is 18kN/m3. Safe bearing capacity of soil is 200 kN/m2. Take the co-efficient of friction between concrete and soil as 0.6. The angle of repose is 30°. Use M20 concrete and Fe415 steel.
Design of Stem
The stem acts as a continuous slab
Soil pressure acts as the load on the slab.
Earth pressure varies linearly over the height
The slab deflects away from the earth face between the counterforts
The bending moment in the stem is maximum at the base and reduces towards top.
But the thickness of the wall is kept constant and only the area of steel is reduced.
Design of Counterforts
The counterforts are subjected to outward reaction from the stem.
This produces tension along the outer sloping face of the counterforts.
The inner face supporting the stem is in compression. Thus counterforts are designed as a T-beam of varying depth.
The main steel provided along the sloping face shall be anchored properly at both ends.
The depth of the counterfort is measured perpendicular to the sloping side.