PE-20-Mat-Foundations

PE-20-Mat-Foundations - 20 - Mat Foundations 01: The...

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20 - Mat Foundations 01: The ultimate bearing capacity of a mat in a pure clay soil. 02: The ultimate bearing capacity of a mat in a granular soil. 03: Find the depth D f for a fully compensated mat. 04: Find the consolidation settlement of mat foundation. 05: Find the immediate settlement of a mat foundation. 06: Mat foundation for a large transfer girder. 07: Design a mat foundation for a small office building. 440
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*Mat Foundations–01: Ultimate bearing capacity in a pure cohesive soil. (Revision: Sept-08) Determine the ultimate bearing capacity of a mat foundation measuring 45 feet long by 30 feet wide placed 6.5 feet below the surface and resting upon a saturated clay stratum with c u = 1,950 lb/ft 2 and φ = 0º. Solution: Mat foundations in purely cohesive soils have the following ultimate bearing capacity: () ult(net) ult(net) 0.4 0.195 = 5.14 (1+ )(1+ ) 0.195 30 0.40 6.5 = 5.14(1.95 ) [1+ ] [1 + ] = 45 12 30 f u D B qc LB ft ft qk s f ft ft ksf 450
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*Mat Foundations–02: Ultimate bearing capacity in a granular soil. (Revision: Sept-08) What will be the net allowable bearing capacity of a mat foundation 15 m long by 10 m wide, embedded 2 m into a dry sand stratum with a corrected SPT to 55% efficiency N 55 = 10? It is desired that the allowable settlement is H all = 30 mm. Solution: The allowable bearing capacity of a mat foundation in granular soils was proposed by Meyerhof (with a Factor of Safety of 3) to be based on the SPT corrected to a 55% efficiency as, ( ) () 2 55 55 2 55 55 0.33 0.33 2 30 = 12.5 [1 + ] [ ] = 12.5 [1 + ] [ ] = 25.4 10 25.4 An alternate formula is, 30 = 15.9 [ ] = 15.9 [ ] = 188 / 25.4 25.4 Si 151 / = 1 nce 51 f all all all all all D ft H mm qN N Bm m f tm m H mm N k N m mm mm kN m qk 2 is the smaller of the two, choose this one for the an r / swe . Nm 451
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*Mat Foundations–03: Find the depth D f for a fully compensated mat. (Revision: Sept-08) The mat shown below is 30 m wide by 40 m long. The live and dead load on the mat is 200 MN . Find the depth D f for a fully compensated foundation placed upon a soft clay with a unit weight γ = 18.75 kN/m 3 .
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This note was uploaded on 09/07/2011 for the course CEG 4012 taught by Professor Staff during the Spring '10 term at FIU.

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PE-20-Mat-Foundations - 20 - Mat Foundations 01: The...

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