Part-V-StressesinSoilMass

# Part-V-StressesinSoilMass - 1 Prof M Santagata CE 383 SLIDE...

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Unformatted text preview: 1 Prof. M. Santagata CE 383 SLIDE 1 PART V STRESSES IN A SOIL MASS Â¡ TOTAL STRESS Â¡ PORE PRESSURE Â¡ EFFECTIVE STRESS Â¡ EXAMPLES Â¡ SEEPAGE FORCE Â¡ QUICK CONDITION Â¡ CAPILLARY RISE IN SOILS Â¡ COEFFICIENT OF LATERAL STRESS Prof. M. Santagata CE 383 SLIDE 2 z Generated by the gravitational force acting on the soil mass Â¡ TOTAL STRESS, Ïƒ Note: Â¢ Tensor ( Ïƒ ij ) Â¢ Coordinate system Â¢ Sign convention Ïƒ v : Calculated from unit weights, soil layer thicknesses x z y âˆ« = * z v dz Î³ Ïƒ In general: P z* If Î³ constant for each layer: z i z i v âˆ‘ = * Î³ Ïƒ COMPRESSION = POSITIVE Focus on Vertical Stress Ïƒ v =( Ïƒ zz ) STRESSES IN A SOIL MASS 2 Prof. M. Santagata CE 383 SLIDE 3 H 1 =4 m 1 m 5 m Î³ t1 = Î³ d1 16 kN/m 3 TOTAL STRESS Â¡ EXAMPLES OF CALCULATION OF Ïƒ v z @B: Ïƒ v =16kN/m 3 x5m= =80 kN/m 2 z Î³ t1 = Î³ d1 = 16 =kN/m 3 Î³ t2 = Î³ d2 =18 kN/m 3 B A B A @z: Ïƒ v = Î³ t z = 16z [kN/m 2 ] @B: Ïƒ v = 16kN/m 3 x 4m + 18 kN/m 3 x 1m = = 82 kN/m 2 @z: Ïƒ v = Î³ t1 H 1 + Î³ t2 (z- H 1 ) = = 64 + 18 (z-4) [kN/m 2 ] @A: Ïƒ v = @A: Ïƒ v = Prof. M. Santagata CE 383 SLIDE 4 TOTAL STRESS H 1 =2 m 5 m 5 m @B: Ïƒ v = 16kN/m 3 x1m + 20 kN/m 3 x4m = = 96 kN/m 2 z B A @z: Ïƒ v = Î³ d H 1 + Î³ t (z-H 1 ) = =16 + 20 (z-1) [kN/m 2 ] @A: Ïƒ v = Î³ W H 1 = 9.8 kN/m 3 x 2m = 19.6 kN/m 2 @z: Ïƒ v = Î³ w H 1 + Î³ t z = = 19.6 + 20 z [kN/m 2 ] Î³ t = 20 kN/m 3 Î³ t = Î³ d = 16 kN/m 3 4 m H 1 =1 m z Î³ t = 20 kN/m 3 B A @A: Ïƒ v = @B: Ïƒ v = 9.81 kN/m 3 x 2m + 20kN/m 3 x 5m= = (19.6 + 100) kN/m 2 = 119.6kN/m 2 Î³ w = 9.8 kN/m 3 3 Prof. M. Santagata CE 383 SLIDE 5 Â¡ PORE PRESSURE, u = pressure of water in pores Â¢ acts equally in all direction Â¢ has only a normal component (i.e. NO SHEAR STRESS) CALCULATION Â¢ STATIC WATER: calculated based on distance from water table and unit weight of water Â¢ SEEPAGE: calculated from pressure head (total head â€“ elevation head) and unit weight of water Prof. M. Santagata CE 383 SLIDE 6 5 m 2 m 5 m STATIC CONDITIONS (NO FLOW) z w B A Â¢ CALCULATION OF u @B: u = 9.8kN/m 3 x5m= =49 kN/m 2 @z: u = Î³ w z w = 9.8 z w [kN/m 2 ] @A: u = PORE PRESSURE WITH SEEPAGE z w B A @B: u = 9.8kN/m 3 x 7m= = 68.6 kN/m 2 @z: u = Î³ w h p = 9.8 h p [kN/m 2 ] @A: u = 4 Prof. M. Santagata CE 383 SLIDE 7 Â¡ EFFECTIVE STRESS Note: TENSOR u âˆ’ = Ïƒ Ïƒ ' DEFINITION: Cannot be measured Only calculated IDEA: Total stress is carried in part by water and in part by soil solids at their point of contact The effective stress controls soil behavior (compression and strength) Terzaghi 1936 Â¢ Dry soil: Ïƒ â€™= Ïƒ Â¢ Shear stresses: no contribution from u (...
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Part-V-StressesinSoilMass - 1 Prof M Santagata CE 383 SLIDE...

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