Document Type : Research Paper
Authors
Civil Engineering Dept., University of Technology-Iraq, Alsina’a street, 10066 Baghdad, Iraq.
Abstract
A 3D numerical model generated using PLAXIS-3D software was used in the present research to predict the behavior of under-reamed piles under pullout loading conditions with presumed soil Mohr-Coulomb failure. The under-reamed pile was embedded in homogeneous, layered clay soil, with stiff clay overlain by soft clay and soft clay overlain by stiff clay. The piles were chosen per the Indian Code (IS 2911) specification, and two variables were studied: bulb provision and soil layering. Inhomogeneous clay with varying cohesion values (20, 40, and 80 kPa) and under the same conditions, the pullout capacity was improved compared to a straight shaft (SP). The pullout capacity of the single bulb (SURP) increased once, while that of the double bulb (DURP) increased twice. The results revealed that anchoring the pile in a stronger stratum at a greater depth is advantageous when designing under-reamed pile foundations. In the case of stiff clay on top of soft clay, additional resistance against pullout is achieved, reducing the risk of pullout failure compared to soft clay in the upper layer.
Graphical Abstract
 "Enhancing Pullout Load Performance of Under-Reamed Piles in Homogeneous Layered Clay: A Numerical Comparative Study")
Highlights
- Increased soil cohesiveness improves the load-deformation behaviour of the under-reamed pile under pullout loads.
- The bearing pullout load rises as the number of bulbs increases.
- The maximum ultimate pullout capacity is obtained in the case of the stiff clay resting on the soft clay.
- The failure patterns of soil movement around the projections were larger than those around the shaft.
Keywords
Main Subjects
- Majumder, D. Chakraborty, Bearing and uplift capacities of under-reamed piles in soft clay underlaid by stiff clay using lower-bound finite element limit analysis, Front. Struct. Civ. Eng., 15 (2021) 537-551. https://doi.org/10.1007/s11709-021-0708-x
- Honda, Y. Hirai, E.Sato, Uplift capacity of belled and multi-belled piles in dense sand, Soils Found., 51 (2011) 483-496. https://doi.org/10.3208/sandf.51.483
- E George, G. Hari, Numerical investigations of under-reamed piles, Proc. Indian Geotech. Conf., 2016.
- N. Khatri, A. Kumar, S.K. Gupta, R.K. Dutta, T. Gnananandarao, Numerical study on the uplift capacity of under-reamed piles in clay with linearly increasing cohesion, Int. J. Geotech. Eng., 16 (2022) 438-449. https://doi.org/10.1080/19386362.2019.1660527
- E. Martin, R.A. DeStephen, Large diameter double under reamed drilled shafts, J. Geotech. Eng., 109 (1983) 1082-1098. https://doi.org/10.1061/(ASCE)0733-9410(1983)109:8(1082)
- Vali, E.M. Khotbehsara, M. Saberian, J. Li, M. Mehrinejad, S. Jahandari, A three-dimensional numerical comparison of bearing capacity and settlement of tapered and under-reamed piles, Int. J. Geotech. Eng., 13 (2019) 236-248. https://doi.org/10.1080/19386362.2017.1336586
- M.J. Alhassani, Analysis of Under-reamed Piles Subjected to Different Types of Loads in Clayey Soil, Int. J. Eng., 34 (2021) 1940-1948. 1 https://doi.org/0.5829/IJE.2021.34.08B.15
- A. Al-Neami, F.H. Raheel, An Experimental and Theoretical Studies Wings Piles at Different Sandy Soil Densities, Eng. Technol. J., 40 (2022) 1-10. https://doi.org/10.30684/etj.2022.132336.1104
- Bhattacharya, J. Kumar, Uplift capacity of strip and circular anchors in soft clay with an overlay of sand layer, Geotech. Geol. Eng., 33 (2015) 1475-1488. https://doi.org/10.1007/s10706-015-9913-5
- S. Farokhi, H. Alielahi, Z. Mardani, Optimizing the performance of under-reamed piles in clay using numerical method, Electron. J. Geotech. Eng., 19 (2014) 1507-1520.
- H. Rahil, M.A. Al-Neami, K.A.N. Al-Zaho,Effect of relative density on behavior of single pile and piles groups embedded with different lengths in sand, Eng. Technol. J., 34 (2016)1206-1220. https://doi.org/10.30684/etj.34.6A.15
- S. Al-Tememy, M.A. Al-Neami, M.F. Asswad, A Numerical Analysis on Pullout Capacity of Batter Pile Groups in Sandy Soil, Eng. Technol. J., 40 (2022) 1-6. https://doi.org/10.30684/etj.2021.131818.1062
- Kumar, V.N. Khatri, S.K. Gupta, Effect of linearly increasing cohesion on the compression and uplift capacity of the under-reamed pile in clay, SN Appl. Sci., 2 (2020) 1-17. https://doi.org/10.1007/s42452-020-2111-y
- I S :2911 (Part IV), Design and Construction of Pile Foundation Code of Practice, Load Test on Piles New Delhi, India, Bureau of Indian Standard, 2013.
- IS: 2911 (Part III), Indian Standard Code of Practice for Design and Construction of Pile Foundations, Underreamed Piles (First Revision), 1980.
- Waterman, Dennis, Structural elements and excavations, Presentation in CG1 Chile, 2006.
- Budhu, M. Soil mechanics and foundations, John Wiley & Sons, Inc, 2020 .
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