Resistance of Caisson Tip with Internal Bevels for Suction Caissons Penetrating into Clay

Acknowledgments

Notation

A_i

cross section of the soil plug;

D, D_m, D_i

outer, mean, and inner diameters of the suction caisson;

F_o, F_i, F_tip, F_tot

outside, inside, caisson tip, and total resistances of the caisson wall;

f_s

safety factor for the large soil plug heave, f_s = p_cri/p_re;

h

penetration depth;

m

thickness of the flat section of the caisson tip;

N_q, N_c, N_γ

bearing capacity factors;

p

mean stress;

p_re, p_cri

required and critical suction;

S_t

sensitivity of clay;

s_u

in situ undrained shear strength;

s_u1

average shear strength over the penetration depth of the caisson wall;

t

thickness of the caisson wall;

V′

effective caisson weight;

z

depth below the mud-line;

α, β

angles between the α and β slip lines with the z-axis, respectively;

α_i, α_o, α_b

adhesion factors along the inside and outside and at the base of the caisson tip, respectively;

γ′

effective unit weight of clay;

δ

inclination angle of the internal bevel from the horizontal;

ɛ

angle between the direction of the normal stress and the z-axis on a boundary Γ;

η_b, η_i, η_o

boundary inclinations of wedge and passive shear zones inside and outside the caisson;

θ

angle between the direction of the major principal stress and the z-axis;

μ

angle between the slip line and the direction of the major principal stress;

σ₁, σ₃

major and minor principal stresses;

σ_h, σ_tip

horizontal stress and equivalent bearing capacity at the caisson tip;

σ_i, σ_o

equivalent overburdens at the caisson tip level inside and outside the caisson;

σ_n, τ_n

normal and shear stresses on a boundary Γ; and

τ_i, τ_o, τ_b

shear stresses on the inside and outside of the caisson wall and at the base of the caisson tip, respectively.

References