Example

Example: Retaining Wall Stability Analysis

A 5.0 m high cantilever retaining wall retains a horizontal sandy backfill (γ=18 kN/m3,ϕ=30,c=0\gamma = 18 \text{ kN/m}^3, \phi' = 30^\circ, c' = 0). The base of the wall is 3.5 m wide (BB). The total vertical force (V\sum V) acting on the base (including wall weight and soil on the heel) is 420 kN/m420 \text{ kN/m}. The net resisting moment about the toe (MRMO\sum M_R - \sum M_O) is 580 kNcdotm/m580 \text{ kN}\\cdot\text{m/m}. Check the bearing pressure if the allowable bearing capacity is 200 kPa200 \text{ kPa}.

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Example

Example: Overturning Stability Check

A cantilever retaining wall is subjected to a total overturning moment (MO\sum M_O) of 150 kNcdotm/m150 \text{ kN}\\cdot\text{m/m} from lateral earth pressure. The resisting moment (MR\sum M_R) provided by the weight of the wall and the soil resting on the heel is 400 kNcdotm/m400 \text{ kN}\\cdot\text{m/m}. Calculate the Factor of Safety against overturning and determine if it is acceptable.

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Example

Example: Sliding Stability Check

The same retaining wall from the previous example experiences a total horizontal driving force (FD\sum F_D) of 120 kN/m120 \text{ kN/m}. The total vertical force (V\sum V) acting on the base is 300 kN/m300 \text{ kN/m}. The base of the wall rests on a soil with an interface friction angle δ=25\delta = 25^\circ and base adhesion ca=0c_a = 0. Determine the Factor of Safety against sliding.

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Example

Example: Full Bearing Capacity Check

A retaining wall base has width B=4.0 mB = 4.0 \text{ m}. The calculated maximum bearing pressure is qmax=180 kPaq_{max} = 180 \text{ kPa}. The foundation soil is a stiff clay with an undrained cohesion su=c=100 kPas_u = c = 100 \text{ kPa}, friction angle ϕ=0\phi = 0, and unit weight γ=19 kN/m3\gamma = 19 \text{ kN/m}^3. The base is embedded Df=1.0 mD_f = 1.0 \text{ m}. Using Terzaghi's bearing capacity equation (Nc=5.7,Nq=1.0,Nγ=0N_c = 5.7, N_q = 1.0, N_\gamma = 0 for ϕ=0\phi = 0), calculate the Factor of Safety against bearing capacity failure.

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Example

Case Study: Internal Stability Failure of an MSE Wall

A Mechanically Stabilized Earth (MSE) wall was constructed using geogrid reinforcement to support a highway ramp. The design assumed a specific tensile strength for the geogrid and a specific pullout resistance based on the frictional properties of the gravel backfill.

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Example

Case Study: The Importance of the Heel in Cantilever Walls

Two retaining wall designs are proposed for a 4-meter high soil retention project. Option A is an L-shaped wall (no heel, long toe). Option B is an inverted T-shaped wall (long heel, shorter toe).

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