American Society of Civil Engineers.

Transactions of the American Society of Civil Engineers (Volume 81) online

. (page 80 of 167)
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more confined the soil under compression, the less its yielding
under load, and hence the higher its safe bearing value;
furthermore, the greater the area under compression, the
greater the proportion of the stressed soil which is confined
against "flow".

3. — In general, the foundation soil of the east bank at the dam
site has a higher bearing value than that of the middle of
the valley, or of the west bank.

Loading of the Foundation Soil. — Calculations as to the loading
of the foundation soil were based on the assumption that where the
cut-off, whether in its original state or underpinned, is of relatively
great depth, and especially where it extends down to bed-rock, the
cut-off wall forms a relatively rigid, unyielding support for the dam;
whereas the foundation soil down stream from the cut-off forms a
yielding support. For practical purposes, therefore, it has been
assumed that, when under load, the dam pivots about the top of
the original concrete cut-off wall, the cut-off and the foundation soil
down stream therefrom each carrying its due proportion of the total
vertical load. The axis about which the dam is assumed to pivot is
approximately in the plane of the base of the original footings.
Following this assumption further, it is evident that the deflection in
the foundation soil would vary approximately uniformly from zero
at about the center of the cut-off wall to a maximum at the down-
stream edge of the toe of the dam.

There is, of course, a certain amount of flexibility in the concrete
footings; that is, the true deflection (and hence stress) diagram of
the soil underlying the structure would not be a straight line. How-
ever, the effect of such flexibility in the footings is indeterminate,
and the straight-line assumption was adopted in computations.



980



EECONSTRUCTION OF THE STONY RIVER DAM



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Online LibraryAmerican Society of Civil EngineersTransactions of the American Society of Civil Engineers (Volume 81) → online text (page 80 of 167)