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2_CEG 4012 Notes Fall 2011 CEG 4012 Notes Fall 2011

# 2_CEG 4012 Notes Fall 2011 CEG 4012 Notes Fall 2011 - ;~...

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Geostatic Stresses These self-weight stresses (ay, a'y, ah' a'h) are called geostatic stresses For a level surface there are no shear forces induced by the geostatic stresses, and therefore they are also principal stresses: a, =ay and a3 = ah Karl Terzaghi's principle of effective stress (a' or 0) governs most soil behavior (probably the most important point in this class). Examples: Pressure on a retaining wall depends on stress due to soil weight Shear strength, t. of soli depends on cohesion and O'n due to soil weight T = C + an tan 0:. failure surface Geostatic Stress Example 1 Determine the total horizontal stress at point P:
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Unformatted text preview: (,';~ ll:'~ '" Sand v." 100 Del. K .. 0.4 6' ~* ~~ Sand y. .. " 118 pet. K .. 0.4 4' Clay Yw" 126 pet. K .. 0.6 6' Clay 1..... 120 pet, K =0.5 t 4' 8'-i--:-p • U = • 0" = v • I = O'h • O'h = = LYjZj = 6' (100 pet) + 4' (118 pet) + 6' (126 pet) + 4' (120 pet) = 600 pst + 472 pst + 756 pst + 480 pst = 2308 pst 14' (62.4 pet) = 874 pst (a y-U) = 2308 pst· 874 pst = 1434 pst K a'y = 0.5 (1434 pst) = 717 pst (a' h + u) = 717 pst + 874 psf = 1591 psf 1591 pst x (0.04788 kN/m z 11 pst) = 76.18 kN/m z...
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