ABSTRACT
Vesic has developed an expression for N*(J based on the ultimate pressure needed to expand a spherical cavity in an infinite soil mass as
(15.27)
where a = 3 a2=(1l2-At)tanAt, a = 1.33sin¢ and N 2(45° At/2) 1 3 _ sin ¢ , 'f' 'f' 3 (l + sin ¢) , ~ =tan + 'f'
According to Vesic
where I 0 °d· 0 d Esr =ngI Ity In ex =-----...;;;..---2(1 + Jl)(c + q~ tan ¢J) G
=-----(c +q~ tan¢J) (15.29)
where I rr
= reduced rigidity index for the soil ~ = average volumetric strain in the plastic zone below the pile point
Es = modulus of elasticity of soil G = shear modulus of soil J.l = Poisson's ratio of soil
Figures 15.11(a) and 15.11(b) give plots of N*(J versus l/J, and~ versus l/Jfor various values of Irr respectively.
