1. A 10.75 in diameter steel pipe is driven 70 ft into stiff insensitive clay. The clay has an un-drained shear strength of 1250 lbf/ft^2. The clay's specific weight is 120 lbf/ft^3. Water table at ground surface. Entire pile length is effective.
a) Find the end bearing capacity.
b) Find the friction capacity.
c) Find the allowable bearing capacity.
2. Test show that a single pile by itself would have an uplift capacity of 140 tons. And a compressive capacity of 600 tons. 36 piles are installed on a grid with a spacing of 3.5 ft. The pile group is capped and connected at the top by a thick steel-reinforced concrete slab adding it's own axial load of 600 tons. What is the maximum moment that the pile group can take in the x and y directions assuming axial load is applied to permit the moment.
3. A 25 ft deep, 35 ft square excavation in sand is being designed. The sand is dewatered before excavation. The angle of internal friction is 40° and the specific weight of the sand is 120 lbf/ft^3. Bracing is horizontal lagging, supported by 8 in soldier piles separated horizontally by 7 ft.
a) What is the shape of the pressure diagram on the lagging?
b) What is the bending moment on the lagging?
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