Settlement Of Pile Groups Research Articles

Pile behaviour — theory and application : Geotechnique V39, N3, Sept 1989, P365–415

This paper discusses the application of theory to the analysis of pile foundation behaviour under axial loading. A classification system is suggested for pile analysis and design procedures, based on the rigour of the underlying theory. It is shown that a number of the analyses in use have a common underlying theoretical basis founded on the boundary element method and that such methods give solutions which are consistent with those from other methods such as the finite element method. The main characteristics of pile behaviour are reviewed for single piles and pile groups subjected to static loading, cyclic loading, and to loading arising from externally-imposed soil movements. Correlations are then summarized for the geotech-nical parameters required for the prediction of axial pile behaviour. Using characteristic values of these parameters, design charts are developed for the load capacity and settlement of piles and pile groups. Finally, three case studies are described which demonstrate the sensitivi...

Pile behaviour—theory and application

This paper discusses the application of theory to the analysis of pile foundation behaviour under axial loading. A classification system is suggested for pile analysis and design procedures, based on the rigour of the underlying theory. It is shown that a number of the analyses in use have a common underlying theoretical basis founded on the boundary element method and that such methods give solutions which are consistent with those from other methods such as the finite element method. The main characteristics of pile behaviour are reviewed for single piles and pile groups subjected to static loading, cyclic loading, and to loading arising from externally-imposed soil movements. Correlations are then summarized for the geotech-nical parameters required for the prediction of axial pile behaviour. Using characteristic values of these parameters, design charts are developed for the load capacity and settlement of piles and pile groups. Finally, three case studies are described which demonstrate the sensitivity of pile performance predictions to the method of analysis, the idealization of the soil profile, and the selection of soil parameters. It is shown that the method of analysis is likely to have less effect on the predicted performance than does the geotechnical characterization of the site. L'article discute L'application de la theorie a l'analyse du comportement des fondations par pieux sous chargement axial. On propose un système de classification basé sur la rigueur de la theorie associée pour l'analyse des pieux et les procédés de construction. On démontre que quelquesunes des analyses employées ont une base théorique commune dérivant de la méthode des éléments limites et que de telles méthodes donnent des solutions qui s'accordent bien avec celles obtenues à partir d'autres méthodes, telles que les éléments finis. Les caractéristiques principales du comportement des pieux sont examinees pour les pieux et les groupes de pieux soumis aux chargements statiques et cycliques aussi bien qu'au chargement résultant des mouvements du sol imposés de L'extérieur. Puis on résume les correlations pour les paramètres géotechniques nécessaires pour la prédiction du comportement axial des pieux. À l'aide de valeurs caractéristiques de ces paramètres on propose des abaques de construction pour la force portante et le tassement des pieux et des groupes de pieux. Trois cas réels sont presentes. Ils illus-trent la facon dont les predictions du comportement des pieux dépendent de la méthode d'analyse, de la schematisation du profil du sol et de la sélection des parametres du sol. On démontre que la performance prevue est probablement moins influencée par la méthode d'analyse que par la détermination des caractéristiques géotechniques du site.

Modified calculation of pile group settlement interaction : Poulos, H G Univ Sydney school of civil and mining engng research reportR582, Nov 1988, 15P

Modified calculation of pile group settlement interaction : Poulos, H G Univ Sydney school of civil and mining engng research reportR582, Nov 1988, 15P

An Elastic Analysis for Piled Raft Foundations in a Homogeneous Soil

ABSTRACT A boundary element analysis based on an elastic theory is performed to analyse the behaviour of piled raft foundations subjected to vertical load. Characteristics of settlement and load transfer for piled raft foundations whose raft rests on a homogeneous isotropic elastic half-space soil are contrasted with free-standing pile groups and single piles. The critical length of pile groups for a vertical loading (the length beyond which settlement shows little further decrease) is longer than that of single piles whose dimensions are the same as the piles in the groups. The reduction of the settlement caused by the presence of the raft is very small, although the raft transmits 20-40% of the applied load direct to the soil. A significant difference of pile load is recognized at the upper part of the shafts between two kinds of pile group with and without raft, and only small difference is found at the remaining part of the shafts. The ratio of long-term settlement to total final settlement of pile groups is greater than that of single piles. The contact earth pressure on the raft is relatively uniform in the inside area surrounded by piles.

Modified calculation of pile-group settlement interaction: technical note : Poulos, H G J Geotech Engng Div ASCEV114, N6, June 1988, P697–706

Modified calculation of pile-group settlement interaction: technical note : Poulos, H G J Geotech Engng Div ASCEV114, N6, June 1988, P697–706

886296 Pile-group settlement using independent shaft and point loads : Polo, J M; Clemente, J L M J Geotech Engng Div ASCE 1/114, N4, April 1988, P469–487

886296 Pile-group settlement using independent shaft and point loads : Polo, J M; Clemente, J L M J Geotech Engng Div ASCE 1/114, N4, April 1988, P469–487

Pile‐Group Settlement Using Independent Shaft and Point Loads

A method of predicting pile-group settlements is presented herein for cases in which the piles are held together by means of a rigid cap. Piles in the group are assumed to be of the same material, length, and diameter. Settlement influence and interaction factors are obtained using a finite element code, modeling the pile as a hollow cylindrical insert in the interior of a homogeneous, linear, elastic, isotropic half-space. These factors are tabulated and can be used with the results of individual, full-scale, pile load tests to provide a very effective means of estimating pile-group settlements. Shaft and point loads are treated independently when applying the method, thus allowing for simulation of implicitly variable shaft and point load ratios during loading. Uniform shaft load distributions are assumed, but other distributions can be considered as well. Few parameters are needed to apply the method, which therefore retains the simplicity of existing elastic methods. A full-scale, pile-group load test reported in the literature is analyzed to show the reliability of the proposed method. Results are presented that indicate excellent agreement between predicted and measured values.

Micro-computer analysis of pile group settlement using independent point and shaft loads

A FORTRAN-77 micro-computer program to predict pile group settlements is presented. The program incorporates concepts described in a recent publication (J. M. Polo and J. L. M. Clemente, J. Geotech. Engng, ASCE, to appear), where the pile cap is considered rigid and point and shaft loads are treated independently. Pile settlements are considered to consist of three components: settlement of pile point due to point load, settlement of pile point due to shaft load and elastic shortening of the pile due to axial load. Each of these components is evaluated taking into account appropriate pile and soil deformation parameters and numerically generated settlement influence factors. Group settlements are evaluated by incorporating settlement interaction factors which are also numerically generated. The program design is such that it can be used with minimum effort. The few input parameters needed can be provided in a user friendly interactive environment. Program use is illustrated with the prediction of the load-settlement behavior of a full scale pile group load test reported in the literature. A typical program output is shown for this example. Results obtained are excellent, indicating the soundness of the previously proposed method when properly used. Results also show the adequacy of the present micro-computer program.

Method for extimating immediate settlement of piles and pile groups : Yamashita, K; Tomono, M; Kakurai, M Soils FoundV27, N1, March 1987, P61–76

Method for extimating immediate settlement of piles and pile groups : Yamashita, K; Tomono, M; Kakurai, M Soils FoundV27, N1, March 1987, P61–76

A Method for Estimating Immediate Settlement of Piles and Pile Groups

In this study we examine a method based on Mindlin’s solution in order to estimate the load-settlement behavior of piles and pile groups for rational design of pile foundations. First, the theoretical aspects of the previous method proposed by Poulos and other investigators are briefly presented. Some modifications are made to the method so as to consider additional factors such as soil non-linearity and multi-layering. Next, in order to evaluate the numerical accuracy, vertical displacements and axial forces of pile groups or single piles embedded in non-homogeneous soil calculated by the previous method and by the modified method are compared with values calculated by more sophisticated methods such as the boundary element method and the finite element method. As a result, we conclude that, from a practical point of view, the modified method based on elasticity is sufficiently accurate in regard to axial force distribution as well as settlement. We also propose tentative input soil constants for immediate settlement using solely the results of SPT. Finally, the values of pile top settlement calculated by the modified method are compared with the results of 26 field vertical load tests on cast-in-place concrete piles. The results show that the calculated values coincide approximately with the measured values, meaning that the proposed modified method of calculation and the proposed input soil constants seem to be adequate for the preliminary estimation of immediate settlement of cast-in-place concrete piles.

Optimisation of pile groups

Abstract The optimisation of pile groups is studied using an optimisation technique in conjunction with a discrete element method for pile group settlement analysis. It is demonstrated that it is possible to optimise the performance of pile groups by minimising the load differentials between piles and/or differential settlements. This could be achieved by apportioning the lengths of the group piles to meet the requirement of their positions in the group. Numerical examples are presented to illustrate this principle.

Discrete element analysis of settlement of pile groups

Two discrete element models are described for the analysis of settlement of vertical pile groups. In both models, the piles are represented by discrete elements with an axial model of deformation, and the soil behaviour for the individual piles is represented by load-transfer curves. The essential difference between the models is the manner in which pile-soil-pile interaction is represented. The first model treats the soil as independent horizontal layers which permit interaction between piles to take place within the same layer only. Thus ignoring the continuity of the soil medium. The second utilizes Mindlin's solution which determines interaction effects in a homogeneous, isotropic elastic half-space, but an approximate procedure is used to account for soil inhomogeneity. Comparisons of both approaches with a rigorous integral equation method for pile groups in a homogeneous, isotropic elastic soil indicate that the second method generally gives good agreement while the first method tends to underestimate interaction, especially for shorter piles. For pile groups in nonhomogeneous soils, where rigorous theoretical solutions are generally not available, parametric studies comparing the two discrete element models solutions are presented. The studies performed using both methods on the nonlinear behaviour of an instrumented pile group compare favourably with the field measurements.

Dynamic Behavior of Pile Groups in Inhomogeneous Soil

An efficient method of analysis has been developed to determine the steady‐state dynamic response of vertically loaded piles and pile groups embedded in a soil stratum in which the stiffness increases linearly with depth. The piles have been represented as compressible columns and the soil as a hysteretic semi‐infinite medium. The results of the analysis have been plotted in nondimensional form to demonstrate the effects of key nondimensional parameters on the vertical response of the pile‐soil system. From the results of analyses of two pile groups, dynamic interaction factors have been calculated. These factors are very different from the interaction factors for homogeneous soils, particularly if the piles are widely spaced. These interaction factors reveal that piles in groups are subject to out‐of‐phase motions, which may result in substantially reduced pile group settlements at certain frequencies. Illustrative results for four and nine pile groups are given, as well as a practical design example.

Pile group settlement prediction by simple theories : Casanovas J.S.; Alonso E.E. Proc 10th International Conference on Soil Mechanics and Foundation Engineering, Stockholm, 15–19 June 1981, V2, P651–658. Publ Rotterdam: A.A. Balkema, 1981

Pile group settlement prediction by simple theories : Casanovas J.S.; Alonso E.E. Proc 10th International Conference on Soil Mechanics and Foundation Engineering, Stockholm, 15–19 June 1981, V2, P651–658. Publ Rotterdam: A.A. Balkema, 1981

Influence of compressible underlying layers on pile group settlement : Poulos, H G University of Sydney School of Civil Engineering research report R337, Dec 1978, 20P

Influence of compressible underlying layers on pile group settlement : Poulos, H G University of Sydney School of Civil Engineering research report R337, Dec 1978, 20P

Estimation of pile group settlements : Poulos, H G Ground Engng, V10, N2, March 1977, P40–50

In this paper attention is concentrated on solutions from elasticity theory and their application to practical problems. The basis of the analysis is described briefly and a number of parametric solutions are presented for the settlement ratio of pile groups. The determination of the soil parameters required to apply these solutions to practice is discussed and brief reference is made to a number of cases in which observed and theoretical pile group settlement behaviour have been compared. An illustrative example is given to demonstrate the use of the parametric solutions and the construction of design charts from the solutions are described with reference to a simple problem. /TRRL/

Estimation of pile group settlements : Poulos, H G Sydney Univ, School of Civil Engineering research report R288, May 1976, 51P

Estimation of pile group settlements : Poulos, H G Sydney Univ, School of Civil Engineering research report R288, May 1976, 51P

Settlement of pile groups bearing on stiffer strata : POULOS, HG UNIV. SYDNEY, AUS MATTENS, NS NSW, ELECT. COMM. SYDNEY, AUS Technical note. 5F, 7R. J. GEOTECH. ENGNG. DIV. V100, GT2, FEB. 1974, P185–190

Settlement of pile groups bearing on stiffer strata : POULOS, HG UNIV. SYDNEY, AUS MATTENS, NS NSW, ELECT. COMM. SYDNEY, AUS Technical note. 5F, 7R. J. GEOTECH. ENGNG. DIV. V100, GT2, FEB. 1974, P185–190

Settlement of Building on Pile Foundation in Sand

Displacement type compacted concrete piles (pressure-injected Franki type) were driven into the upper portion of a medium dense sand stratum for the foundation of a 19-story reinforced concrete building. Results of pile load tests and actual building settlements were recorded over a 2 yr. period. The settlement ranged from 1.6 in (4.0 cm) to 3.3 in. (8.4 cm), the average group settlement being approx. 2.5 in. (6.4 cm). These field measurements are compared with settlement predictions computed using: (1) classical elasticity theory which greatly overestimates the actual settlement of a single pile; (2) recent extensions of elasticity theory which provide reasonable results for both single pile and pile group settlement behavior; and (3) empirical curves which require pile load test data to give average group settlement and compare favorably with the field measured values.

Settlement of Pile Groups Bearing on Stiffer Strata

This paper presents results for the more general case of a pile group bearing on a stiffer stratum which is not necessarily rigid. The stiffness of the bearing stratum can have a marked effect on the settlement and settlement ratio of a pile group; both decrease as the bearing stratum becomes stiffer in relation to the overlying soil. Results are presented demonstrating the influence of the bearing stratum on pile group settlements. Suggestions for application of solutions to field problems are given.