Field Tests Of The Lateral-Load Behavior Of Pile Groups In Soft Clay

This paper presents the results of three dimensional finite element analysis of laterally loaded pile groups of configuration 1×1, 2×1 and 3×1, embedded in two-layered soil consisting of soft clay at liquid limit overlying dense sand using Plaxis 3D. Effects of variation in pile length (L) and clay layer thickness (h) on lateral capacity and bending moment profile of pile foundations were evaluated by employing different values of pile length to diameter ratio (L/D) and ratio of clay layer thickness to pile length (h/L) in the analysis. Obtained results indicated that the lateral capacity reduces non-linearly with increase in clay layer thickness. Larger decrease was observed in group piles. A non-dimensional parameter Fx ratio was defined to compare lateral capacity in layered soil to that in dense sand, for which a generalized expression was derived in terms of h/L ratio and number of piles in a group. Group effect on lateral resistance and maximum bending moment was observed to become insignificant for clay layer thickness exceeding 40% of pile length. For a fixed value of clay layer thickness, lateral capacity and bending moment in a single pile increased significantly with increase in pile length only up to an optimum embedment depth in sand layer which was found to be equal to three times pile diameter and 0.21 times pile length for pile with L/D 15. Scale effect on lateral capacity has also been studied and discussed. Doi: 10.28991/cej-2021-03091686 Full Text: PDF

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Behaviour of friction piles in soft sensitive clays

Canadian Geotechnical Journal ◽

10.1139/t80-023 ◽

1980 ◽

Vol 17 (2) ◽

pp. 203-224 ◽

Cited By ~ 14

Author(s):

R. Blanchet ◽

F. Tavenas ◽

R. Garneau

Keyword(s):

Precast Concrete ◽

Soft Clay ◽

Load Test ◽

Pile Groups ◽

Test Program ◽

Shear Creep ◽

Soft Clays ◽

The North ◽

Effective Stress Analysis

During the construction of heavy structures, such as bridges and overpasses, on soft clays on the north shore of the St. Lawrence Valley, a detailed load test program on friction piles was performed to establish the characteristics of the most suitable type of pile and to study its long-term behaviour. Three types of piles, timber, steel pipe with closed end, and precast concrete Herkules H-420 piles, were tested. Four timber piles driven in a group and submitted to a 712 kN load served to study the long-term settlement of a small group of piles. Three deep settlement gauges were installed in the centre of this group for measuring settlements in clay at various depths.This test program was completed by the instrumentation of two bridge piers in order to verify the behaviour of larger groups of piles.The paper presents the results of the test piles, the long-term behaviour (4 years) of the bridge pier foundations resting on friction piles in soft clay, and the interpretation of the results.This study shows that the pore pressures induced by pile driving are related to the pre-consolidation of the clay and that they are much larger for tapered piles. It is demonstrated that the effective stress analysis method proposed in 1976 by Meyerhof determines adequately the ultimate pile bearing capacity, but that the effect of the timber pile taper doubles the skin friction.The settlement analysis of pile groups shows that settlements are due to the reconsolidation of the clay and shear creep deformations in the clay close to the pile wall.

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