The subgrade reaction
modulus method is used to model the deformability of the ground.
This method usually assumes linearly increasing subgrade reaction
modulus and cannot account for the influence of sloping ground.
(3) The section (BC) in the disturbance: the pipe-roof is affected not only by the rock mass pressure of q(x) but also by the subgrade reaction
According to the literature , it is assumed that the stiffness of normal springs can be equivalent to the coefficient of a subgrade reaction
of the backfill and that the stiffness of the tangential springs is a function of the stiffness of normal springs.
In Winkler or subgrade reaction
approach the pile is considered as supported by an array of uncoupled springs.
where [eta] and k are factors for shape of pile (i.e., for circular cross-section = 1) and initial modulus of subgrade reaction
, respectively; D is pile diameter and z is the depth; A is a coefficient based on loading conditions (static or cyclic); and [P.sub.u] is determined based on wedge type and flow failure which takes from the smaller from the following equations:
Consequently, runway design requirements and pavement evaluation are largely affected by potential deflection, which primarily relates to California bearing ratio (CBR) or modulus of subgrade reaction
of soil subgrade of the runway (Ashford, Wright 1992; Horonjeff, McKelvey 1994).
where k is the spring constant, also called the modulus of horizontal subgrade reaction
(it has a unit of force/[length.sup.3]).
A relationship between deflection and soil pressure known as modulus of subgrade reaction
is extensively used in the structural analysis of foundation.
where [sigma]--tensile stresses in bending, kN/[m.sup.2]; P= Q/2--wheel load (half of a single axle load Q, kN); E--modulus of elasticity of cement concrete slab, kN/[m.sup.2]; v--Poisson's ratio of cement concrete slab; h--thickness of concrete slab, m; k--modulus of subgrade reaction
, kN/[m.sup.3]; b = [square root of 1.6[a.sup.2] + [h.sup.2]] -0.675h, m, for a < 1.724h, b = a, for a > 1.724h, a--radius of contact area between tire and pavement, m.
The design procedure established by the American Association of State Highway and Transportation Officials (AASHTO) is only moderately sensitive to subgrade support values (in terms of "k" or modulus of subgrade reaction