Analytical Chem Soil HW Solutions 58

Analytical Chem Soil HW Solutions 58 - immediately(a(b...

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58 water to drain out of or into the soil, which can only occur at a rate governed by the soil permeability. (c) Initially the pore water pressure varies linearly with depth from zero at the excavated surface (z = 0) to γ w .H crit = .d = 200 kPa at the bottom of the sheet piles (z = 10 m). Finally, the variation in pore water pressure is linear between zero at the excavated surface and 100 kPa at depth z = 10 m (hydrostatic). The initial and final distributions of pore water pressure with depth are shown in Figure Q4.6a; subtracting the hydrostatic or steady state component, the corresponding distributions of excess pore water pressure, together with some isochrones in between, are shown in Figure Q4.6b (compare with main text Figure 4.25, and note that the excess pore water pressure in the aquifer at the lower drainage boundary can drop to zero
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Unformatted text preview: immediately). (a) (b) Figure Q4.6: distributions of (a) pore water pressure and (b) excess pore water pressure (with hydrostatic or steady state component subtracted) with depth (d) Consider an element of soil of thickness δ z at a depth z below the excavated surface. The compression of this element is δρ , given by = ( Δσ ' v /E' ). z as by definition E' 0 = ' v / Δε v and v = δρ/δ z Now, E' 0 = (5000 + 4000z) kPa and the eventual increase in vertical effective stress ' v at depth z is equal to the reduction in pore water pressure at the same depth, ' v = 10z (ignoring friction on the sheet piles). Hence the total settlement ρ is given by...
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