+))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))),
*DATA REQUIRED:
*
*
*
*
from the proposed foundation level to a depth of 2B, or to boundary of *
an incompressible layer, whichever occurs first. Value of soil modulus*
*
*
E+s, is established using the following relationships.
*
*
*
*
E+s,/N
*
Soil Type
*
*
*
*
Silts, sands silts, slightly cohesive
*
*
silt-sand mixtures
4
*
*
*
*
Clean, fine to med, sands & slightly
*
*
silty sands
7
*
*
*
*
Coarse sands & sands with little gravel
10
*
*
*
*
Sandy gravels and gravel
12
*
*
*2. Least width of foundation = B, depth of embedment = D, and
*
*
*
proposedaverage contact pressure = P.
*
*
*3.
*
Approximate unit weights of surcharge soils, and position of water
*
*
table if within D.
*
*
*4. If the static cone bearing value q+c, measured compute E+s, based on
*
*
E+s, = 2 q+c,.
*
*
*
*ANALYSIS PROCEDURE:
*
*
*
*Refer to table in example problem for column numbers referred to by
*
*parenthesis:
*
*
*
*1. Divide the subsurface soil profile into a convenient number of layers *
*
of any thickness, each with constant N over the depth interval 0 to 2B *
*
*
below the foundation.
*
*
*2. Prepare a table as illustrated in the example problem, using the
*
*
*
indicated column headings. Fill in columns 1, 2, 3 and 4 with the
*
*
layering assigned in Step 1.
*
*
*3. Multiply N values in column 3 by the appropriate factor E+s,/N (col. 4)*
*
to obtain values of E+s,; place values in column 5.
*
*
*
*4. Draw an assumed 2B-0.6 triangular distribution for the strain influence*
*
factor I+z,, along a scaled depth of 0 to 2B below the foundation.
*
*
*
Locate the depth of the mid-height of each of the layers assumed in
*
Step 2, and place in column 6. From this construction, determine the *
*
I+z, value at the mid-height of each layer, and place in column 7.
*
.)))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))-
FIGURE 7
Settlement of Footings Over Granular Soils: Example Computation
Using Schmertmann's Method
7.1-220
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