Integral bridges - Computational Analysis and Design of Bridge Structures - page 503

Table 16.1 Parameters for soil springs

Case

Parameter Clay Sand

lateral springs
P u 9 c u B 3 γ Bk p x

k h 67 c u n h x

Vertical springs
f max (H - piles), (klf )

The least of
2( d + b f ) c u
2( d + 2 b f ) c a
2( dc u + b f c a )

0 . 02 N [2( d + 2 b f )]

f max (others), (klf ) The lesser of:

l g c a
l g c u

0 . 04 Nl g

k v f z c

10 max 10 max q z c

Point spring
q max (ksf)

9 c u 8 N corr

k q 10 max q z c 10 max q z c

B = pile width;
b f = lange width of H - pile (ft);
c a = adhesion between soil and pile = α c u (psf);
c u = undrained cohesion of the clay soil = 97.0 N + 114.0 (psf);
d = section depth of H - pile or diameter of pipe pile (ft);
J = 200 for loose sand, 600 for medium sand, 1500 for dense sand;
l g = gross perimeter of the pile (ft);

ϕ

2

k p = tan 45

;

° + 2

N = average standard penetration blow count;
N corr = corrected standard penetration test (SPT) blow count at the depth of pile tip
= N (uncorrected) if N ≤ 15;
= 15 + 0.5 ( N − 15) if N > 15;
n h = constant of subgrade reaction = J γ/ 1 . 35;
x = depth from the soil surface;
z c = relative displacement required to develop f max or q max
= 0.4 ″ (0.033 ′ ) for sand;
= 0.2 ″ (0.021 ′ ) for clay;
α = shear strength reduction factor;
γ = effective unit soil weight;
φ = angle of internal friction.