Geotech - Shallow

Geotech - Shallow

1. Bearing capacity=????

   • LOW PERMEABILITY, CLAY
     • EFFECTIVE STRESS METHOD
       • sigVO' = effective overburden stress at foundation level
       • Nq, Ny = bearing capacity factors
       • Sc shape factor
       • gamma bulk unit weight
       • pore water pressure at B/2 depth
   • ANY and FREE DRAINING SOIL
     • TOTAL STRESS METHOD
       • qult = Cu*Nc*Sc*dc
         • Nc(bearing capactiy fact) = pi+2
         • Sc(shape fact)=1+0.2(B/L)
         • Cu = undrained cohesion
         • dc=1+0.23(D/B)^0.5
           • D/B<=4, or it is 'deep'
         • NO FORMULA NEEDED!!!!

2. SETTLEMENT

   • immediate (wi) = undraing elastic(yes)/plastic (no)
   • consolidation(wc), water moves out of pores
   • creep(wt) , same load with time
   • TOTAL = wi+wc(wt =0)
     • calculate wi
     • calculate wc
       • wc=mv*h*changeeffstress <<<-known as 1-D method
         • mv, changeeffstress varies with depth
           • INTEGRATE for sc(=wc)
             • OR APPROXIMATE: with multiple layers of mv*effstresschange
         • TABLE: Multiply KqX4!!

3. Types of foundatins

   • Square, B=L
   • Strip, L>>B
     • in eqns disregard L for this
   • Pad, B>L

4. Eccentric loading

   • eccentric w.r. to:
     • L
       • same for B, change b->L, L->B
     • B
       • emax<= B/6
         • qmax=P/BL (1+6e/B)
           • use this for design
         • qmin=P/BL(1-6e/B)
       • e=B/6,
         • qmax=2P/BL
         • qmin=0
       • e<B/6
         • q=4P/3(B-2e)L

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