This paper presents the results of two-way cyclic lateral load tests carried out on model pile groups embedded in soft marine clay. The tests are conducted on 1 × 2, 2 × 2 and 3 × 3 pile groups having length to diameter ratio (L/D) of 15, 30 and 40 with the spacing to diameter ratio (S/D) of 3, 5, 7 and 9. The experimental results are presented in the form of load-deflection curves and bending moment profiles. Cyclic group efficiency, critical spacing, critical cyclic load level and cyclic p-multipliers are evaluated. It is found that the lateral capacity of the 3 × 3 group reduces by about 42% after 50 cycles of loading. The cyclic p-multipliers of 3 × 3 pile group are found to be 0.41, 0.25 and 0.29 for leading, intermediate and rear rows respectively. The test results are compared with the numerical analysis carried out by p-y method using GROUP program. The analysis carried out with experimentally evaluated p-multipliers predicts load-deflection and bending profiles of pile groups reasonably well, but underestimates the depth to maximum bending moment by about 15%. © 2010 Springer Science+Business Media B.V.

Adimoolam Boominathan

Department Of Civil Engineering

Goudappa R. Dodagoudar

CYCLIC EFFICIENCY

CYCLIC P-MULTIPLIERS

Lateral loads

P-y curves

Pile group

Soft clays

Bending (deformation)

Bending moments

Cyclic loads

Geologic models

Numerical analysis

Piles

Harmonic analysis

Cyclic loading

experimental study

LOADING TEST

numerical method

Pile response

Soft clay

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Geotechnical and Geological Engineering

The effects of pile spacing, number of piles, and configuration on displacement and bending response of pile groups in clay under dynamic lateral loading were investigated. The displacement response of pile group in clay is strongly nonlinear. Pile-soil-pile interaction is predominant for the groups with closer spacing and with greater number of piles. Group interaction causes reduction in the group stiffness and increase in damping of the pile group. Strong group interaction leads to significant differences in bending profiles of different row piles of the groups. Dynamic lateral loading increases the maximum bending moment and active pile length. Copyright © A. S. Elnashai and N. N. Ambraseys.

Journal of Earthquake Engineering

Dynamic response of laterally loaded pile groups in clay

Experimental investigation is carried out to study the lateral load–deflection and bending behaviour of model flexible pile groups embedded in soft clay. The effects of embedment length of pile, magnitude of applied lateral load, size of group, row and column wise position of piles in the group, cyclic loading and presence of vertical loading on lateral response of pile group are evaluated. Results from the tests reveal that flexible piles subjected to lateral load greater than about 60 % of ultimate lateral load cannot be considered as flexible. Maximum bending moment of front row pile of 3 × 3 group is about 16 % higher than that of middle row pile. Within the same row piles, corner pile has about 10 % higher bending moment than that of middle pile. Maximum bending moment in pile subjected to 15 cycles of loading is about 80 % higher than that for static loading. The lateral capacity of the 3 × 3 pile group with 60 % of ultimate vertical load is about 18 % less than that of the pile group with no vertical load. © 2015, Indian Geotechnical Society.

Indian Geotechnical Journal

Factors Influencing the Behaviour of Flexible Pile Groups Under Lateral Loading in Soft Clay

This paper presents the results of static lateral load tests carried out on 1×2, 2×2, 1×4, and 3×3 model pile groups embedded in soft clay. Tests were carried out on piles with length to diameter ratios of 15, 30, and 40 and three to nine pile diameter spacing. The effects of pile spacing, number of piles, embedment length, and configuration on pile-group interaction were investigated. Group efficiency, critical spacing, and p multipliers were evaluated from the experimental study. The experimental results have been compared with those obtained from the program GROUP. It has been found that the lateral capacity of piles in 3×3 group at three diameter spacing is about 40% less than that of the single pile. Group interaction causes 20% increase in the maximum bending moment in piles of the groups with three diameter spacing in comparison to the single pile. Results indicate substantial difference in p multipliers of the corresponding rows of the linear and square pile groups. The predicted field group behavior is in good agreement with the actual field test results reported in the literature. © 2010 ASCE.

Journal of Geotechnical and Geoenvironmental Engineering

Group interaction effects on laterally loaded piles in clay

Static and dynamic lateral load tests were carried out on model aluminium single piles embedded in soft clay to study its bending behaviour. Model aluminium piles with length to diameter ratios of 10, 20, 30 and 40 were used. Static lateral load tests were conducted on piles by rope and pulley arrangement upto failure and load-deflection curves were obtained. Dynamic lateral load tests were carried out for different magnitudes of load ranging from 7 to 30 N at wide range of frequencies from 2 to 50 Hz. The load transferred to the pile, pile head displacement and the strain variation along the pile length were measured using a Data Acquisition System. Safe static lateral load capacity for all piles is interpreted from load-deflection curves. Dynamic characteristics of the soil-pile system were arrived from the acquired experimental data. The soil-pile system behaves predominantly in nonlinear fashion even at low frequency under dynamic load. The displacement amplitude under dynamic load is magnified by 4.5-6.5 times the static deflection for all piles embedded in soft clay. But, the peak magnification factor reduces with an increase in the magnitude of lateral load mainly because of increase of hysteretic damping at very soft consistency. The maximum BM occurs at the fundamental frequency of the soil-pile system. Even the lower part of the pile affects the pile head response to the inertial load applied at the pile head. The maximum dynamic BM is magnified by about 1.5 times the maximum static BM for model piles in tested consistency of clay. The maximum dynamic BM occurs at a depth of about 1.5 times the depth of maximum static BM for model piles, which indicates an increase of active pile length under dynamic load. © Springer Science+Business Media, Inc. 2006.

An experimental study on static and dynamic bending behaviour of piles in soft clay

The analysis of laterally loaded piles in soft clay is carried out idealising the pile as beam elements and the soil by nonlinear inelastic spring elements modeled with elasto-plastic sub-elements. The nonlinear hyperbolic model for static load condition is developed based on the undrained shear strength and modulus of subgrade reaction. An iterative procedure is adopted to perform a nonlinear finite element analysis and the effect of static lateral load on deflection is studied. Based on the lateral deflection at the end of first cycle (static load), the degradation factor is assumed and the p-y curve is modified. The cyclic load analysis is carried out using the static analysis program idealising the soil by modified p-y curve, which considers the effect of number of cycles and magnitude of cyclic lateral load. The results of the proposed analytical model compare well with the published experimental results, on piles subjected to one-way cyclic loading for different magnitude of cyclic lateral load and number of cycles. Copyright © 1996 Elsevier Science Ltd.

Computers and Geotechnics

Degradation Model for One-way Cyclic Lateral Load on Piles in Soft Clay

In the field of ocean engineering, pile foundations are extensively used in supporting several structures. In many cases, piles are subjected to significant lateral loads. The environment prevalent in the ocean necessitates the piles to be designed for cyclic wave loading. In this investigation, the behaviour of rigid piles under cyclic lateral loading has been studied through an experimental programme carried out on model piles embedded in a soft marine clay. Static tests were also conducted on piles embedded in a clay bed prepared at different consistencies suitable to field situations. Cyclic load was applied by using a specially designed pneumatic controlled loading system. Tests were conducted on model piles made of mild steel (MS), aluminium and PVC with wide variation in pile soil relative stiffness. For cyclic load levels less than 50% of static lateral capacity, the deflections are observed to increase with number of cycles and cyclic load level and stabilise after a certain number of cycles. For cyclic load levels greater than 50% of static lateral capacity, the deflections are observed to increase enormously with number of cycles. The results of post-cyclic load tests indicate that the behaviour under static load can improve for cyclic load levels less than 40% of the static lateral capacity. The variations in the load capacity due to cyclic loading are explained in terms of the changes in strength behaviour of soil. © 1993.

Ocean Engineering

Behaviour of rigid piles in marine clays under lateral cyclic loading

Earthquake Engineering & Structural Dynamics

Cyclic behavior of laterally loaded concrete piles embedded into cohesive soil

Experimental investigations on the behaviour of pile groups in clay under lateral cyclic loading

Journal	Geotechnical and Geological Engineering
ISSN	09603182
Open Access	No