EAG346-Sem II 2014/2015 Lesson 2

Problem You will be given a cross sectional profile where a slope will be cut, a retaining wall will be constructed, and on an adjoining plot of land a fill will be laid. The Site Investigation (SI) data for points along the cross sectional profile will be provided. You will design the: 1. Slope 2. Retaining Wall 3. Foundation 4. Fill 5. Protection against erosion - Sedimentation control - General mitigation

SI1 a cross sectional profile with SI points – FROM A PREVIOUS YEAR SI points Soil SI2 Bed Rock SI3 Clay Sand Bed Rock

a slope will be cut, a retaining wall will be constructed, and a fill will be laid – SI positions as indicated Batter Face Platform Berm Soil Retaining Wall Platform Fill Bed Rock Clay Geometry Sand Bed Rock

Slope Geometry

Slope Design Batter face Berm Toe Crest Steepest acceptable by JKR for unsupported face < 9 m: 1:1 (next 1:1.5) Steepest acceptable by JKR for unsupported face > 9 m: 1:1.5 (next 1:2) Height (vertical berm to berm) 5 m or 6 m only Berm 2 m or wider Berm drain Toe Toe Drain Crest Factor of Safety (Local and Global) 1.5 in civil engineering or 1.25 in mining engineering Batter Face Crest Berm Toe

1 1.5

Aspects of a Retaining Wall Stem and Base proportioning Toe and Heel Backfill Height of backfill Flat or incline backfill Foundation (shallow or pile) Drainage (weep holes and drain)

Retaining wall resting on shallow (sub grade) foundation Active, Passive, or at Rest

Retaining wall resting on pile foundation Active, Passive, or at Rest

Retaining wall resting on pile foundation Batter Face Platform Berm Soil Retaining Wall Platform Fill Bed Rock Clay Sand Bed Rock

Batter Face Retaining wall resting on pile foundation Berm Platform Soil Retaining Wall Fill Bed Rock Clay Sand Bed Rock

Retaining Wall Analyses (and normally acceptable FOS) Stability against sliding Least FOS=2 Stability against toppling Stability against bearing failure Shallow foundation (FOS=3) Deep foundation (piles)(FOS>2)

Retaining Wall Design Active, Passive, or at Rest (Normally assumed active) Dimensions and Reinforcement Shallow Foundation enough? Or Deep Foundation (piles) required? If piles, how long, how many, how big, and what type – driven or bored (micropile)?

Dimensioning Top of stem should be at least 0.3m to provide for concrete placement Depth to the bottom of base slab should be at least 0.6m Bottom of base slab should be below frost line Width of base slab should be 0.5-0.7H For cantilever retaining wall, the thickness of stem and base slab should be at least 0.1H For counterfort retaining wall, the counterfort slabs should be about 0.3m thick and spaced at 0.3-0.7H For gravity retaining wall the toe should be 0.1-0.2H wide and the heel should be 0.1-0.2H thick For cantilever retaining wall, the toe should be 0.1H wide and the heel should be 0.1H thick