On Foundation
On Foundation
(OP)
-In bearing capacity calcualtions of a building foundation, say 4 floors, one has to assume a value for the foundation width (B)(We encountered dense to very dense glacial till at various depth ranging from 2 to 3 m, thus we are going with strip and/or square footings). How B is assumed in the bearing capacity (BC) relation (1 , 1.5 m ,0.9 m..)
- AT the time of drilling the water table is encountered in 2 BHs (out of 10) only at around 2.5 and 3 m. For BC calculations I will assume a water table depth of say 2 m.. ? what do you think.
-When talking about differential settelment. what are the 2 points we refer to commonly?. Is there any recommended relation (soil is dense sandy materials, thus only elastic settelement is expected).
BEST REGARDS AND THANKS IN ADVANCE
- AT the time of drilling the water table is encountered in 2 BHs (out of 10) only at around 2.5 and 3 m. For BC calculations I will assume a water table depth of say 2 m.. ? what do you think.
-When talking about differential settelment. what are the 2 points we refer to commonly?. Is there any recommended relation (soil is dense sandy materials, thus only elastic settelement is expected).
BEST REGARDS AND THANKS IN ADVANCE





RE: On Foundation
Glacial till and dense sand are two distinct soils, which are you using?
RE: On Foundation
Settlement generally controls foundation design.
Elastic settlement analysis applies to granular non-cohesive soils.
Estimate differential settlement as 1/2 total, apply as appropriate,
such as shortest column spacing or wall length.
Check angular distortion vs. building material type (many sources, start w. Terzaghi).
RE: On Foundation
Assume a reasonable bearing capacity, such as 2 tons/sf (100 Pa/m2) (I think) and compute a footing size, adjust to someting that makes sense such as 1m x 1m and compute your capacity. If, based on your results you need a smaller or larger footing, repeat.
Differential settlement is the diffence between 2 adjacent footigs. Although if everyting is uniform 1/2 total is used. However, footings that are heavily loaded or overlyng poor soils may be subject to higher settlements and the effect of these conditions should be investgated.
RE: On Foundation
RE: On Foundation
AS I said Water table was detected in 2 BHs at 3 and 5 m at the time of drilling. I will for conservation consider that the water will, due to seasonal fluctuation will rise 1 m. Thus the design water table is 1 m.
Alos any hint on how conservative will should be when assigning the water table will be appreciated.
I disagree with you guys,as in dense sands or overconsolidated soil (Failure is brittle and the stress-strain curve has a peack)imlying that the bearing capacity failure would happen before the allowed settelment is reached (with a little pit of settelment)
RE: On Foundation
Has any of us "experts" ever seen a brittle, shear failure in dense till? Have we ever seen an excessive settlement situation in same situation?
How do we know which one governs? Many factors here, right?
I'd opt for settlement, using a high GWT. Water can vary over the years.
RE: On Foundation