Load Settlement Response of Composite Foundation of Variable Pile Diameters

Data Availability Statement

Acknowledgments

Notation

A_m

cross-sectional area of the model test pile;

A_n

cross-sectional area of the prototype test pile;

A_P

bottom area of the large diameter pile;

$A_P^{\mathrm{\prime }}$

bottom area of the small diameter pile;

a₀

width of the load acting surface;

b₀

length of the load acting surface;

C₁

unit pressure penetration quantity of the cushion for the large diameter pile;

$C_1^{\mathrm{\prime }}$

unit pressure penetration quantity of the cushion for the small diameter pile;

C₂

unit pressure penetration quantity of the underlying soil stratum for the large diameter pile;

$C_2^{\mathrm{\prime }}$

unit pressure penetration quantity of the underlying soil stratum for the small diameter pile;

C_s

similarity coefficient;

$c_a^{\mathrm{\prime }}$

interface cohesion;

E_a

elastic modulus of the cushion;

E_m

elastic modulus of the model test pile;

E_n

elastic modulus of the prototype test pile;

E_r

elastic modulus of the underlying soil stratum;

E_s

elastic modulus of the soil between the piles;

F_m

single-pile bearing capacity characteristic value of the model test pile;

F_n

single-pile bearing capacity characteristic value of the prototype test pile;

G_s

specific gravity of test soil;

H

thickness of the underlying soil stratum;

h_a

thickness of the cushion;

K_S

shear stiffness;

K₀

coefficient of static earth pressure;

l

pile length;

m

replacement rate of large diameter pile area;

N_P

vertical concentrated force on the large diameter pile;

$N_P^{\mathrm{\prime }}$

vertical concentrated force on the small diameter pile;

N_S

vertical concentrated force on the soil between piles reinforced with the large diameter pile;

$N_S^{\mathrm{\prime }}$

vertical concentrated force on the soil between piles reinforced with the small diameter pile;

n

replacement rate of small diameter pile area;

P₀

initial stress;

P_P

large diameter pile top stress;

P_PL

large diameter pile base stress;

$P_P^{\mathrm{\prime }}$

small diameter pile top stress;

$P_{\mathrm{PL}}^{\mathrm{\prime }}$

small diameter pile base stress;

P_S

top stress of the soil between piles reinforced with the large diameter pile;

$P_S^{\mathrm{\prime }}$

top stress of the soil between piles reinforced with the small diameter pile;

P_SL

pile base soil stress of the soil between piles reinforced with the large diameter pile;

$P_{\mathrm{SL}}^{\mathrm{\prime }}$

pile base soil stress of the soil between piles reinforced with the small diameter pile;

P_Z

additional stress;

R

radius of the reinforcement range of the large diameter pile;

R′

radius of the reinforcement range of the small diameter pile;

r

radius of the large diameter pile;

r′

radius of the small diameter pile;

S_p

settlement of Composite foundation monitored by dial gauges;

S_s

settlement of soil monitored by settlement gauges;

s

settlement of CFVPD;

s₁

settlement of the reinforced area of CFVPD;

s₂

settlement of the underlying soil stratum of CFVPD;

U

perimeter of the large diameter pile;

U′

perimeter of the small diameter pile;

V₁

upward penetration of the large diameter pile;

$V_1^{\mathrm{\prime }}$

upward penetration of the small diameter pile;

V₂

downward penetration of the large diameter pile;

$V_2^{\mathrm{\prime }}$

downward penetration of the small diameter pile;

V_a

upward penetration of the pile;

w

natural water content of test soil;

z₀

position of the neutral plane for the large diameter pile;

$z_0^{\mathrm{\prime }}$

position of the neutral plane for the small diameter pile;

z₁

lower boundary point of constant stage of the negative friction zone for the large diameter pile;

$z_1^{\mathrm{\prime }}$

lower boundary point of constant stage of the negative friction zone for the small diameter pile;

z₂

upper boundary point of constant stage of the negative friction zone for the large diameter pile;

$z_2^{\mathrm{\prime }}$

upper boundary point of constant stage of the negative friction zone for the small diameter pile;

${\epsilon }_m$

strain of the model test pile;

${\epsilon }_n$

strain of the prototype test pile;

ξ

settlement influence coefficient;

φ′

interface friction angle;

Δ₁

compression of the soil reinforced with the large diameter pile above the neutral plane;

${\mathrm{\Delta }}_1^{\mathrm{\prime }}$

compression of the soil reinforced with the small diameter pile above the neutral plane;

Δ₂

compression of the soil reinforced with the large diameter pile below the neutral plane;

${\mathrm{\Delta }}_2^{\mathrm{\prime }}$

compression of the soil reinforced with the small diameter pile below the neutral plane;

θ

pressure diffusion angle;

ρ

density of test soil;

σ_p

large diameter pile stress;

${\sigma }_p^{\mathrm{\prime }}$

small diameter pile stress;

σ_s

stress of the soil reinforced with the large diameter pile;

${\sigma }_s^{\mathrm{\prime }}$

stress of the soil reinforced with the small diameter pile;

τ₁

pile shaft positive friction of the large diameter pile;

${\tau }_1^{\mathrm{\prime }}$

pile shaft positive friction of the small diameter pile;

τ₂

pile shaft negative friction of the large diameter pile;

${\tau }_2^{\mathrm{\prime }}$

pile shaft negative friction of the small diameter pile;

τ_u1

pile shaft positive ultimate friction of the large diameter pile;

${\tau }_{u1}^{\mathrm{\prime }}$

pile shaft positive ultimate friction of the small diameter pile;

τ_u2

pile shaft negative ultimate friction of the large diameter pile;

${\tau }_{u2}^{\mathrm{\prime }}$

pile shaft negative ultimate friction of the small diameter pile;

δ₁

pile–soil relative displacement in the negative friction zone of the large diameter pile;

${\delta }_1^{\mathrm{\prime }}$

pile–soil relative displacement in the negative friction zone of the small diameter pile;

δ₂

pile–soil relative displacement in the positive friction zone of the large diameter pile;

${\delta }_2^{\mathrm{\prime }}$

pile–soil relative displacement in the positive friction zone of the small diameter pile;

δ_u1

pile–soil ultimate relative displacement in the negative friction zone of the large diameter pile;

${\delta }_{u1}^{\mathrm{\prime }}$

pile–soil ultimate relative displacement in the negative friction zone of the small diameter pile;

δ_u2

pile–soil ultimate relative displacement in the positive friction zone of the large diameter pile;

${\delta }_{u2}^{\mathrm{\prime }}$

pile–soil ultimate relative displacement in the positive friction zone of the small diameter pile; and

v_r

Poisson’s ratio of the underlying soil stratum.

References