Advertisement

Geotechnical and Geological Engineering

, Volume 25, Issue 3, pp 339–347 | Cite as

Uplift capacity of pile group anchors

  • L. Vanitha
  • N. R. Patra
  • S. Chandra
Original paper

Abstract

Experimental investigations on model single pile anchor and pile group anchors of configuration 2 × 2 subjected to uplift loads were conducted on dry Ennore sand, obtained from Madras, India. The embedment length to shaft width ratios, L/d = 20 and L/d = 30, and enlarged base width to shaft width ratios, B/d = 1,2,3, center to center spacing of pile anchors in the groups, 3d, 4d, 6d and 8d were used. The load displacement response, ultimate resistance and variation of group efficiency with L/d, B/d and spacing have been studied quantitatively and qualitatively. For short pile group anchors (L/d = 20), the isolation spacing appears to be at a spacing of about 4d to 6d and 8d for B/d = 1 and B/d = 2 and 3, respectively. For long pile group anchors (L/d = 30), the isolation spacing appears to be at a spacing of about 4d, 6d and 8d for B/d = 1, 2 and 3, respectively. The analytical model of limit equilibrium method has been proposed to predict the net uplift capacity of pile group anchors. The predicted results compare reasonably well with the experimental results.

Keywords

Pile group anchors Axial uplift loads Ultimate uplift capacity Foundations Sandy soil 

List of symbols

B

Width of anchor

c

Unit cohesion of soil

C

Cohesion

Cf

Cohesive force

F

Friction force

d

Width or diameter of pile

Pp1

Total passive earth pressure at embedment depth L 1

Pp2

Total passive earth pressure at embedment depth L 2

σ

Effective normal stress on failure surface

Kp

Coefficient of passive earth pressure (calculated from Columb’s equation)

L

Embedment depth

L1 = L

Embedment depth

L2

Embedment depth below overlapping zone

n

Number of pile anchors in a group

n1

Number of rows in a pile group anchors

n2

Number of columns in a pile group anchors

Pp

Total passive earth pressure inclined at average angle δ

Qu

Ultimate uplift load

Qug

Gross ultimate uplift load

Qnu

Net uplift capacity of single pile anchor

Qgnu

Net uplift capacity of pile group anchor

W

Weight of soil and pile within failure zone

Wso

Weight of soil in the overlapping zone

wp

Weight of pile

wa

Weight of anchor

η

Uplift capacity efficiency

α, β

Average inclination with vertical of forces C f and F respectively

ϕ

Angle of internal friction of soil

γ

Unit weight of soil

δ

Angle of wall friction between pile and soil

References

  1. Das BM, Seeley GR, Smith (1976) Uplift capacity of group piles in sand. J Geotech Eng Div, ASCE, 112(3):282–286Google Scholar
  2. Downs I, Chieurazzi R (1966) Transmission tower foundations. J Power Div, ASCE, 92(PO2), Proc Paper 4750:91–114Google Scholar
  3. Hanna H, Robert S, Mehmet Y (1972) Anchor behavior in sand. J Soil Mechan Found Div, ASCE, 98 (SM11):1187–1207Google Scholar
  4. Mayerhof GG, Adams JI (1968) The ultimate uplift capacity of foundations. Can Geotech J Ottawa 5(4):225–244CrossRefGoogle Scholar
  5. Morray EJ, Geddes JD (1987) Uplift of anchor plates in sand. J Geotech Eng, ASCE 113(3):202–215CrossRefGoogle Scholar
  6. Patra NR, Pise PJ (2001) Ultimate lateral resistance of pile groups in sand. J Geotech Geoenviron Eng, ASCE 127(6):481–487CrossRefGoogle Scholar
  7. Patra NR, Pise PJ (2003) Uplift capacity of pile groups in sand, Electronic Journal of Geotechnical Engineering, EJGE, 8 (bundle B). web link: http://www.ejge.com/2003/JourTOC8B.htmGoogle Scholar
  8. Prakash C (1980) Uplift resistance of under reamed piles in silty sand. Indian Geotech J 10(1):539–542Google Scholar
  9. Sharma BVR, Pise PJ (1994) Uplift capacity of anchor piles in sand under axial pulling loads. Indian Geotech J 24(3):181–203Google Scholar
  10. Sharma D, Jain MP, Chandra Prakash C (1978) Handbook on under-reamed and bored compaction piles. CBRI, Roorkee, IndiaGoogle Scholar
  11. Turner EA (1962) Uplift resistance of transmission tower foundation. J Power Div, ASCE 88:17–33Google Scholar

Copyright information

© Springer Science+Business Media, Inc. 2006

Authors and Affiliations

  1. 1.Department of Civil EngineeringIndian Institute of Technology KanpurKanpurIndia

Personalised recommendations