Experimental and Analytical Investigation of the Bearing Capacity of Bulbs for Squeezed Branch Piles
Publication: International Journal of Geomechanics
Volume 23, Issue 5
Abstract
Reasonable estimation of the bearing capacity of bulbs is essential for the design of squeezed branch pile (SBP) foundations, and existing analytical methods cannot be applied to SBPs. This study investigated the bearing capacity of bulbs by model tests, field tests, and theoretical and numerical analysis. From the laboratory model loading test and transparent soil model test assisted by particle image velocimetry technology, the bearing features of SBPs and the displacement field around a bulb under failure state were investigated, respectively. It was found from the tests that the bulb’s bearing ratio is up to approximately 50% out of the total applied load to the pile at failure. Furthermore, by referring to Meyerhof’s theory of bearing capacity for deep foundations, an analytical method was proposed to calculate the bearing capacity of a bulb for an SBP considering its unique geometry. Finally, field tests with a real-size SBP and numerical study were conducted to verify the proposed method. The ultimate bearing capacity (UBC) of the bulb estimated by the proposed method has an acceptable difference of 4.21% from the model test and 17.6% from the numerical field cases. The proposed solution can be used as an effective explicit solution to evaluate the UBC of the single bulb of SBPs considering the pile’s dimensions and soil parameters.
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Acknowledgments
Financial support for this investigation was provided by the National Natural Science Foundation of China (Grant Nos. 51908235 and 42177126). This support is gratefully acknowledged.
Notation
The following symbols are used in this paper:
- A
- is the vertical projected area of the bulb;
- b
- is the width of bulb annular;
- c
- is the cohesive of soil;
- cu
- is the undrained shear strength of soil;
- Db
- is the bulb’s diameter;
- Dp
- is the pile shaft diameter;
- E
- is the compression modulus of soil;
- Gs
- is the specific gravity of soil;
- H
- is the buried depth of bulb;
- h
- is the height of bulb;
- Nc
- is the general bearing capacity factor corresponding to cohesion c;
- Nq
- is the general bearing capacity factor corresponding to p0;
- Nγ
- is the general bearing capacity factor corresponding to b;
- p0
- is the normal stress on the EF surface;
- p1
- is the normal stress on the AD surface;
- p2
- is the stress on the DE surface;
- p3
- is the stress on the CD surface;
- pp
- is the normal stress on the AC surface;
- Q
- is the total load on pile top;
- Qb
- is the load borne by bulb;
- Qs
- is the load borne by shaft;
- qu
- is the ultimate soil-bearing capacity;
- qub
- is the ultimate bearing capacity of bulb;
- r0
- is the initial radii of radial shear zone;
- r1
- is the end radii of radial shear zone;
- S
- is the settlement of pile top;
- s1
- is the shear stress on the AD surface;
- sp
- is the shear stress on the AC surface;
- T
- is the thickness of the bulb;
- γ
- is the gravity of the soil;
- θ
- is the angle between r0 and any radii, r;
- ρ
- is the density of the soil; and
- φ
- is the inner-friction angle of the soil.
References
Amenuvor, A. C., G. Li, J. Wu, Y. Hou, and W. Chen. 2020. “An image-based method for quick measurement of the soil shrinkage characteristics curve of soil slurry.” Geoderma 363: 114165. https://doi.org/10.1016/j.geoderma.2019.114165.
API (American Petroleum Institute). 2008. Recommended practice for planning, designing and constructing fixed offshore platforms. 21th edn. Washington, DC: API. working stress design.
Bolton, M. D. 1991. Geotechnical stress analysis for bridge abutment design. Contractor Report 270. Crowthorne, UK: Transport and Road Research Laboratory.
Borana, L., J. H. Yin, D. N. Singh, S. K. Shukla, and H. F. Pei. 2017. “Influences of initial water content and roughness on skin friction of piles using FBG technique.” Int. J. Geomech. 17 (4): 04016097. https://doi.org/10.1061/(ASCE)GM.1943-5622.0000794.
BSI (British Standards Institution). 1986. Code of practice for foundations. BS 8006. London: BSI.
Cai, Y., B. Xu, Z. Cao, X. Geng, and Z. Yuan. 2020. “Solution of the ultimate bearing capacity at the tip of a pile in inclined rocks based on the Hoek-Brown criterion.” Int. J. Rock Mech. Min. Sci. 125: 104140. https://doi.org/10.1016/j.ijrmms.2019.104140.
Cheng, F., K. X. Wu, and S. He. 2013. “Field tests on load transfer performances of SBPs.” [In Chinese.] Chin. J. Geotech. Eng. 35: 990–993.
Collins, L. E. 1954. “A preliminary theory for the design of under-reamed piles.” Civ. Eng. 1954 (5): 149–157.
Fan, M. H. 2011. “Bearing capacity and critical plate spacing of piles with expanded branches and plates based on the minimum resistance.” [In Chinese.] Chin. J. Geotech. Eng. 33 (S2): 295–298.
Honda, T., Y. Hirai, and E. Sato. 2011. “Uplift capacity of belled and multi-belled piles in dense sand.” Soils Found. 51 (3): 483–496. https://doi.org/10.3208/sandf.51.483.
Hou, Y.-Z., G.-W. Li, J.-T. Wu, and W. Chen. 2019. “Quick identification of expansive soil in the field based on PIV technique.” Jpn. Geotech. Soc. Spec. Publ. 7 (2): 185–193. https://doi.org/10.3208/jgssp.v07.028.
Kong, G. Q., X. J. Sun, Y. Xiao, and H. H. Zhao. 2016. “Comparative experiments on compressive deformation properties of transparent soil and standard sand.” [In Chinese.] Chin. J. Geotech. Eng. 38: 1895–1903.
Li, C., X. Ma, S. Xue, H. Chen, P. Qin, and G. Li. 2021. “Compressive capacity of vortex-compression nodular piles.” Adv. Civ. Eng. 2021: 6674239.
Li, F., H. B. Song, and Y. D. Zhou. 2010. “Study of the bearing property of squeezed branch pile.” [In Chinese.] J. Hohai Univ. 38: 202–205.
Li, L. X., X. J. Li, and X. Y. Cheng. 2018. “Load transfer method for squeezed and branch piles considering cavity expansion theory.” [In Chinese.] Chin. J. Highway Transp. 31(8), 20–29.
Liu, J. T., and G. Y. Su. 2011. “Application of squeezed branch pile in a plant foundation.” [In Chinese.] Drill. Eng. 38: 42–44.
Lu, C. Y., S. S. Wang, and F. L. Meng. 2007. “Model tests on piles with branches and plates in unsaturated silt under cyclic loads.” [In Chinese.] Chin. J. Geotech. Eng. 29: 603–607.
Lu, Q. K. 1997a. “Application and evaluation of multi branch pile.” [In Chinese.] Soil Eng. Found. 2: 51–53.
Lu, Q. K. 1997b. “Choice of pile types in swelling soils.” [In Chinese.] Soil Eng. Found. 4: 30–32+35.
Mao, W., H. Hamaguchi, and J. Koseki. 2020. “Discrimination of particle breakage below pile tip after model pile penetration in sand using image analysis.” Int. J. Geomech. 20 (1): 04019142. https://doi.org/10.1061/(ASCE)GM.1943-5622.0001535.
Meyerhof, G. G. 1951. “The ultimate bearing capacity of foundations.” Géotechnique 2: 301–332. https://doi.org/10.1680/geot.1951.2.4.301.
Meyerhof, G. G. 1983. “Scale effects of ultimate pile capacity.” J. Geotech. Eng. 109: 797–806. https://doi.org/10.1061/(ASCE)0733-9410(1983)109:6(797).
Mohan, D. 1969. “Design and construction of multi-under-reamed piles.” In Vol. 2 of Proc., 7th Int. Conf. Soil Mechanics and Foundation Engineering, 183–186. Mexico City: Sociedad Mexicana de Mecanica.
MTC (Ministry of Transport of China). 2020. Technical specification for foundation piles testing of highway engineering. [In Chinese.] JTG/T 3512-2020. Beijing: MTC.
Ni, Q., C. C. Hird, and I. Guymer. 2010. “Physical modelling of pile penetration in clay using transparent soil and particle image velocimetry.” Géotechnique 60: 121–132. https://doi.org/10.1680/geot.8.P.052.
Ports and Harbours Bureau, MLIT (Ministry of Land, Infrastructure, Transport and Tourism). 2009. Technical standards and commentaries for port and harbour facilities in Japan (English version). Chiyoda, Japan: The Overseas Coastal Area Development Institute of Japan.
Prandtl, L. 1921. “Über die Eindringungsfähigkeit Plastischer Baustoffe und die Festigkeit von Schneiden.” Z. Angw. Math. Mech. 1 (1): 15–20. https://doi.org/10.1002/zamm.19210010102.
Qian, Y. M., X. W. Xie, and R. Z. Wang. 2013. “Research on the ultimate bearing capacity of soil about push-extend multi-under-reamed pile at the compression.” Adv. Mater. Res. 718–720: 1867–1871.
Serrano, A., and C. Olalla. 2002. “Ultimate bearing capacity at the tip of a pile in rock—part 1: Theory.” Int. J. Rock Mech. Min. Sci. 39: 833–846. https://doi.org/10.1016/S1365-1609(02)00052-7.
SS (Singapore Standard). 2003. Code of practice for foundations. SS CP4. Singapore: Spring.
Terzaghi, K. T. 1943. Theoretical soil mechanics. Chichester, UK: Wiley.
Thielicke, W., and R. Sonntag. 2021. “Particle image velocimetry for MATLAB: Accuracy and enhanced algorithmsin PIVlab.” J. Open Res. Softw. 9: 12. https://doi.org/10.5334/jors.334.
Tian, W. 2014. “Research of damage mode and UBC of the expansion concrete piles in bridge foundation.” [In Chinese] Ph.D. thesis, School of Transportation, Jilin Univ.
Wang, H. X., and X. Z. Shi. 2011. “Construction technology of squeezed multi-branch pile for library of nantong university.” [In Chinese.] J. Nantong Univ. 10: 91–94.
Wu, X. L., K. Q. Sun, and Z. H. Ling. 2020. “Application of squeezed branch pile in soft soil foundation treatment of expressway bridge head.” [In Chinese.] Guangdong Highway Commun. 46: 57–60+66.
Xia, T. H., and G. F. He. 2010. “Analysis of results and static loading test of squeezed branch pile and boring pile with constant section in soft soil ground.” [In Chinese.] Geotech. Invest. Surv. 38: 11–15.
Yuan, B., M. Sun, Y. Wang, L. Zhai, Q. Luo, and X. Zhang. 2019. “Full 3D displacement measuring system for 3D displacement field of soil around a laterally loaded pile in transparent soil.” Int. J. Geomech. 19 (5): 04019028. https://doi.org/10.1061/(ASCE)GM.1943-5622.0001409.
Yuan, B., K. Xu, Y. Wang, R. Chen, and Q. Luo. 2017. “Investigation of deflection of a laterally loaded pile and soil deformation using the PIV technique.” Int. J. Geomech. 17 (6): 04016138. https://doi.org/10.1061/(ASCE)GM.1943-5622.0000842.
Zhang, L. P., and X. M. Wang. 2016. “Comparison on load-bearing characteristics among equal diameter pile, belled pile and branch pile.” [In Chinese.] J. Chang’an Univ. 36: 37–44.
Zhang, M., P. Xu, W. Cui, and Y. Gao. 2018. “Bearing behavior and failure mechanism of squeezed branch piles.” J. Rock Mech. Geotech. Eng. 10: 935–946. https://doi.org/10.1016/j.jrmge.2017.12.010.
Zhou, J. B., and B. Xie. 2010. “Application of squeezed branch pile in bridge construction of Ningbo Ring Expressway.” [In Chinese.] New Technol. New Prod. China 4: 61. https://doi.org/10.13612/j.cnki.cntp.2010.04.067.
Zhou, J.-j., K.-h. Wang, X.-n. Gong, and R.-h. Zhang. 2013. “Bearing capacity and load transfer mechanism of a static drill rooted nodular pile in soft soil areas.” J. Zhejiang Univ. 14 (10): 705–719. https://doi.org/10.1631/jzus.A1300139.
Zhou, J.-j., X.-n. Gong, K.-h. Wang, R.-h. Zhang, and J.-j. Yan. 2017. “Testing and modeling the behavior of pre-bored grouting planted piles under compression and tension.” Acta Geotechnica 12 (5): 1061–1075. https://doi.org/10.1007/s11440-017-0540-6.
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Published In
International Journal of Geomechanics
Volume 23 • Issue 5 • May 2023
Copyright
© 2023 American Society of Civil Engineers.
History
Received: Aug 10, 2022
Accepted: Dec 3, 2022
Published online: Mar 7, 2023
Published in print: May 1, 2023
Discussion open until: Aug 7, 2023
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