For Problem 19.1, determine the factor of safety against bottom heave. Use Eq. (19.20) suggested by Chang (2000), assuming a smooth base for the excavation. There is no stiff stratum or bedrock in the vicinity of the bottom of the excavation, which is very long.

Eq. (19.20)

Problem 19.1

A 5 m wide braced excavation is made in a saturated clay, as shown in Figure P19.1, with the following properties: c = 20 kN/m², ϕ = 0, and γ = 18.5 kN/m³. The struts are spaced at 5 m center to center in plan.

a. Determine the strut forces.

b. Determine the section modulus of the sheet pile required, assuming σ_all = 170 MN/m².

c. Determine the maximum moment for the wales at levels B and C.

Figure P19.1

0.2B" cH 5.14c 1 + L B' FS yH + q ||