Upheaval Buckling Resistance of Pipelines Buried in Unsaturated Clay Backfills

Acknowledgments

Notation

C

constant parameter;

c

cohesive of unsaturated clay backfills;

c_eq

equivalent cohesion of unsaturated soil;

D

pipe diameter;

d₁₀

effect grain size;

dV

representative elemental volume;

e

void ratio;

H

burial depth from the soil surface to the pipe axis;

h

total height of unsaturated clay backfills;

H_c

height of soil cover;

h_c

height of capillary water;

K₀

coefficient of earth pressure at rest;

L

length of a buried pipeline;

L_c

length of a test chamber;

N_vu

dimensionless load;

P_bot

soil capacity per unit length of a buried pipeline;

S

ultimate shear stress along a failure surface;

S_v

vertical component of the ultimate shear stress along the failure surface;

T_vu

net reaction force;

t

pipe thickness;

u_a

pore-air pressure of unsaturated clay backfills;

u_w

pore-water pressure of unsaturated clay backfills;

W_c

weight of soil cover per unit length of a buried pipeline;

W_p

pipe weight per unit length of a buried pipeline;

w

water content of unsaturated clay backfills;

χ

effective stress parameter;

δ_z

displacement of upward pipe movement;

δ_z-peak

peak value of uplift resistance;

γ

soil unit weight;

γ_w

saturated unit weight;

μ

roughness coefficient of a glass surface;

φ

internal friction angle of unsaturated clay backfills;

φ_d

loading angle;

ϕ_gs

friction angle at the glass–soil interface;

θ

inclination angle of a failure surface;

θ_r

residual volumetric water content of unsaturated clay backfills;

θ_s

saturated volumetric water content of unsaturated clay backfills;

θ_w

volumetric water content of unsaturated clay backfills;

ρ

density of unsaturated clay backfills;

ρ_dry

dry density of unsaturated clay backfills;

σ

total stress;

σ′

effective stress;

σ_eq

equivalent normal stress of unsaturated clay backfills;

σ_y

horizontal stress; and

σ_z

vertical stress.

References