This paper presents the effect of lateral cyclic loading on the pullout capacity of model and helical piles in clayey soil. Reduction in pullout capacity mainly depends upon the lateral deflection of the pile during cyclic loading and the embedment ratio of the pile. This reduction in the pullout capacity of model piles is presented in terms of nondimensional parameters. However, in the case of helical piles under similar conditions, it was found that the lateral cyclic loading has very little influence on the pullout capacity. The reasons for the better performance of helical piles over ordinary piles are explained. -from Authors

Srirama Narasimha Rao

Anchors

Clay

Clays

CYCLIC LOADING TESTS

DEGRADATION FACTOR

HELICAL PILE

HELICAL PILES

LATERAL CYCLIC LOADING

Lateral deflection

Pile

Piles

Pullout capacity

Pullout tests

Deflection (structures)

load testing

Mathematical models

Pile foundations

Soil structure interactions

Soils

CLAYEY SOIL

MODEL PILE

ANCHORAGES (FOUNDATIONS)

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

Canadian Geotechnical Journal

The authors refer to the laboratory testing carried out on model caisson embedded in marine clay collected from the Chennai coast in India. The response of lateral load-ground level deflection of caissons under static and cyclic lateral loading is presented and discussed for the varied parameters such as caisson embedment depth ratio (L/D), load eccentricity ratio (e/D), and undrained strength (s u) of clay. The results showed that as the caisson L/D increases, the lateral load required to cause a specified ground level deflection increases. At a given lateral load, the deflection levels are increased as the load eccentricity ratio increases from 0.5 to 2.0. As L/D increases from 2 to 3, the increase in the ultimate lateral capacity is found to be 1.8 to 2.0 times. Similarly, for the change in L/D from 3 to 4, this increase in capacity is found to be 1.6 to 1.8 times at all the undrained strength values and e/D values tested. From the cyclic load test results, it was noticed that the deflections mobilized at the cyclic load ratio (CLR = 0.6) were so small and these are hardly 1% to 2% of the diameter of the caisson. A marked increase in the ground level deflection up to about 900 cycles was observed and thereafter the deflection almost remained the same. © 2012 Copyright Taylor and Francis Group, LLC.

Marine Georesources and Geotechnology

Lateral Load: Deflection Response of an Embedded Caisson in Marine Clay

This paper refers to the laboratory testing carried out on model caissons embedded in marine clay and the results of ultimate lateral loads. Ground level deflection of a caisson was measured for various embedment depth ratios (L/D) of caisson, load eccentricity ratio (e/D), and various undrained strength (s u) of clay. At a given lateral load, the deflection levels are increased as the e/D increases and decreased as L/D, su, and D increases. The ground level deflection (y) and the lateral load (P) data obtained in the testing have been expressed in the rectangular hyperbolic formulation. The agreement ratio obtained by comparing the actual ultimate lateral loads with the ultimate lateral loads of transformed hyperbolic representation showed narrow variation, hardly 214% and the average agreement ratio is 8%. The estimated lateral loads are observed to be slightly greater than the test values. Also the test data of lateral loadground level deflection has been further analyzed using nondimensional plots to arrive at lateral capacity of caissons. The published results of previous researchers based on the tests conducted on field prototype models were compared with the trend of the test data and these are found to be quite satisfactory. © 2011 World Scientific Publishing Company and Japan Society of Civil Engineers.

Coastal Engineering Journal

Lateral load of cylindrical caisson in shore protection: A laboratory study

This investigation refers to an experimental study on earth pressure mobilization in caissons embedded in soft clay. Based on the results, a contiguous wall made up of embedded caissons in soft clay is proposed to serve as a coastal protection wall. Tests were conducted on model caissons embedded in stiff marine clay. Lateral load tests were carried out on models with embedment depth ratios of L/D=2,3 and 4 at load eccentricity ratios of e/D of 0.5, 1.0, 1.5 and 2.0. Earth pressure cells were embedded into the caissons at various depths. Using a pneumatic type of arrangement, controlled lateral loading was applied. The test results show that these caissons can be loaded to produce lateral deflection in the ratios of 30%-35% expressed in terms of diameter. The capacities are estimated corresponding to lateral deflection ratios of 20%. These results suggest that the lateral capacity is a function of undrained strength (su), embedment depth ratio (L/D) and load eccentricity ratio (e/D). There is a good correlation between lateral load and the maximum earth pressure mobilized. At a higher L/D ratio of 4, the lateral earth pressure is found to be unique function of lateral load irrespective of e/D. A unique relation is established between lateral load and deflection in the normalized form. This relation matches very well with the published field lateral load deflection curves. © 2010 Elsevier Ltd.

Applied Ocean Research

Earth pressures on caissons in marine clay under lateral loads - A laboratory study

Anchors are being extensively used in foundations for the structures subjected to both compressive and tensile forces. An attempt has been made to develop screw piles as anchors in clayey soils. The screw piles are made of hollow galvanized iron pipes (dia 25 mm, 44 mm, 60 mm and length 640 mm and 1000 mm) to which helical plates (dia. 75 mm, 100 mm, 150 mm) are welded. Number of plates are varied from 2 to 4 and there are different spacings of these plates adopted. These piles are screwed into soft to medium stiff clay bed prepared in a test tank. Standard type of loading frames have been made for effecting both compressive and tensile forces. In all about 40 Nos. of tests have been conducted in three soils. The behaviour of these piles has been studied through the load deformation curves. Decrease in the moisture contents leads to significant increases in the capacity of the piles. By keeping the ratio of the spacing of the helical plates to diameter of the helical plates between 1.0 and 1.5, optimum capacities of the piles could be obtained. The test results indicate that theoretical predictions for the load carrying capacities can be made by making use of the measured shear strength of the soils.

Fulltext

Soils and Foundations

Behaviour of model screw piles in cohesive soils

Pile Design and Construction Practice

Journal of Geotechnical Engineering

Experimental p‐y Model for Submerged, Stiff Clay

Uplift Capacity of Pipe Piles in Saturated Clay

Offshore Technology Conference

Correlation for Design of Laterally Loaded Piles in Soft Clay

Pullout behaviour of model pile and helical pile anchors subjected to lateral cyclic loading

Journal	Canadian Geotechnical Journal
ISSN	00083674
Open Access	No