Soil Bearing

In selecting the proper type of foundation, the bearing capacity of the soil is the primary factor. A thorough knowledge of soil properties is necessary to avoid excessive differential settlement and possible failure.

Foundations on sandy soil shall be checked using the weight of water for the tank hydrostatic test since settlement under this condition occurs very rapidly and should be essentially complete after the hydrotest weight (which is the first loading). Foundations on clay soils should be checked using the weight of the commodity (i. e., operation load) because clay settles more evenly and slowly due to consolidation. In some instances, it is advisable to use a water test to consolidate clay layers by slowly filling the tank and wait­ing for settlement to occur.

When considering soil-bearing pressure due to empty plus wind condi­tions, there are two possible cases. In the first case, the foundation has no uplift, so all of the ring beam is subject to compression. If there is no uplift, then maximum soil pressure for empty plus wind will be less than the maxi­mum soil pressure for operating plus wind. Thus, when there is no uplift, soil pressure for empty plus wind does not need to be checked. The e/Do ratio can be used to determine whether uplift is present. If uplift is not pres­ent, then:

qmin = P/A — Mot/ Sxx

or

e/D0 < SxjADa

where

Sxx = п( — D;4)/32D„

A = п( — D;2/4

Thus,

e/Do < 0.125{l + (;/Do)2},

or

e/Do < 0.20 for Di/Do > 0.8,

where

Do = Ring beam outside diameter (m)

Di = Ring beam inside diameter (m) e = Eccentricity (m)

Updated: 28 августа, 2015 — 8:25 пп