Example

Example: Apparent Earth Pressure in Sand

A 8.0 m deep (HH) braced excavation is made in a uniform deposit of sand. The sand has a unit weight (γ\gamma) of 17.5 kN/m317.5 \text{ kN/m}^3 and an active earth pressure coefficient (KaK_a) of 0.30. Using Peck's apparent earth pressure envelope for sand, determine the design pressure load on the struts.

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Example

Example: Required Depth of a Cantilever Sheet Pile

A cantilever sheet pile wall is driven into a granular soil to retain a 3.0 m3.0 \text{ m} high excavation (H=3.0 mH = 3.0 \text{ m}). The soil has γ=18 kN/m3\gamma = 18 \text{ kN/m}^3 and ϕ=30\phi' = 30^\circ. The active earth pressure coefficient is Ka=0.333K_a = 0.333 and the passive earth pressure coefficient is Kp=3.0K_p = 3.0. Using the simplified method where the net passive pressure below the dredge line is pnet=γD(KpKa)p_{net} = \gamma D (K_p - K_a), estimate the theoretical depth of penetration (DD) required for moment equilibrium about the bottom of the pile.

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Example

Example: Anchored Sheet Pile Force (Free Earth Support)

An anchored sheet pile wall retains a 6.0 m6.0 \text{ m} deep excavation in sand (γ=18 kN/m3,Ka=0.3,Kp=3.3\gamma = 18 \text{ kN/m}^3, K_a = 0.3, K_p = 3.3). The anchor tie rod is located 1.5 m1.5 \text{ m} below the ground surface. The pile penetrates D=3.0 mD = 3.0 \text{ m} below the dredge line. Assume the passive resistance is fully mobilized at the toe (Free Earth Support assumption). Calculate the required anchor force (FAF_A) per meter run of the wall.

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Example

Example: Bottom Heave in Soft Clay Excavation

A 5.0 m5.0 \text{ m} deep, wide excavation is made in a soft clay layer having an undrained shear strength (sus_u) of 25 kPa25 \text{ kPa} and a unit weight (γ\gamma) of 19 kN/m319 \text{ kN/m}^3. Determine the Factor of Safety against bottom heave using Terzaghi's simplified approach. Assume Nc=5.7N_c = 5.7.

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Example

Case Study: Strut Failure in a Braced Excavation

A deep subway station was being constructed using a braced cut. The excavation was 15 m15 \text{ m} deep in a profile of medium-stiff clay. The support system consisted of steel sheet piles braced by horizontal steel struts at 3 m3 \text{ m} vertical intervals.

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Example

Case Study: Piping Failure in a Cofferdam

A sheet pile cofferdam was driven into a riverbed consisting of fine sand to allow the dry construction of a bridge pier. The water depth was 4 m4 \text{ m}, and the excavation depth below the riverbed was 3 m3 \text{ m}.

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