Example 13: Main modulus of subgrade reaction *k*_{sm}
Description of the problem
It is known that the modulus of subgrade reaction *
ks
*is not a soil constant but is a
function of the contact pressure and settlement. It depends on foundation
loads, foundation size and stratification of the subsoil. The main modulus of subgrade
reaction *ksm
*for a rectangular foundation on layered subsoil can be obtained from dividing
the average contact pressure *qo
*over the settlement *
so
*under the characteristic point on the
foundation, which had been defined by *Graßhoff *
(1955). Clearly, this procedure is valid
only for rectangular foundations on a layered subsoil model. Determining the main modulus of
subgrade reaction *ksm
*for irregular foundation on an irregular subsoil model using another
analysis is also possible by *
ELPLA*.
In this example, settlement calculations at the
characteristic point on the raft, using *
Steinbrener's *formula
(1934) for determining the settlement under the corner of a rectangular loaded area with the principle of superposition, are used to
verify *ELPLA *
analysis for determining the main modulus of subgrade reaction *
ksm*. Consider the square raft in Figure 17, which has area of
*Af
*= 8 *12 [m ] and thickness of
*d *
= 0.6 [m]. |