Large open-ended pipe pile has been found to be advantageous for use in transportation projects. The current design method, however, is not adequately developed. To close this practice gap, this paper first summarized different design methods for open-ended pipe piles in sandy soils. A major factor for all the design codes is to properly account for the formation and effects of soil plug. The comparison indicates that there is a large variation in the base capacity evaluation among different methods due to the complex behaviors of soil plug. To close the knowledge gap, discrete element method (DEM) was used to simulate the soil plugging process and provide insight on the plugging mechanism. The simulation results show that the arching effect significantly increases the internal unit shear resistance along pipe piles. The porosity distribution and particle contact force distribution from DEM model indicate a large stress concentration occurs at the bottom of the soil plug. Besides, nearly 90% of the plug resistance is provided by the bottom half portion of the soil column. The soil-pile friction coefficient has a significant effect on the magnitude of plug resistance, with the major transition occurred for friction coefficient between 0.3 and 0.4.
lesser of annulus+ plug resistance or toe resistance
Soil strength is acquired through laboratory or in situ tests
Internal unit friction is equal to external
soil strength
FHWA method
Internal unit friction is 1/2~1/3 of external
soil strength,pile shoe configuration
NGI method
CPT based method
Internal unit friction is three times the external
cone tip resistance, relative density, etc.
FinnRA method
equivalent toe resistance
Plugging coefficient is introduced in the final equation
Fully plugged when Z/D>10 in moraine; Z/D>15 in sand
soil properties, penetration-diameter ratio
Chinese code
Fully plugged when Z/D>5
penetration-diameter ratio
ICP method
CPT based bearing capacity estimation
Piles are classified into plugged and unplugged
cone tip resistance, pile diameter, relative density, driving depth
UWA method
IFR is used to describe the plugging mode during installation
cone tip resistance, pile diameter, IFR
Tab.1
particles friction coeff.
N_Bond1)
S_Bond2)
Kn3) (N/m)
Ks4) (N/m)
pile-soil friction Coeff.
density (g/cm3)
friction angle
E (MPa)
Poisson ratio
0.64
0
0
2.40E+ 6
1.00E+ 6
0.5
1.60
31°
19.63
0.252
Tab.2
Fig.2
Fig.3
Fig.4
Fig.5
Fig.6
Fig.7
Fig.8
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