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### Analytical Interpretation of Pile Installation and Axial Performance

#### Hudson Matlock, Ignatius Lam and Lino Cheang

A program of combined experiment and analytical studies is presently underway with the purpose of extending present understanding of the axial behaviour of pile foundations. The analytical developments are designed for back fitting and correlating the experimental results and for extrapolation to prototype designs. Emphasis therefore is placed on versatile and general-purpose computation tools which will permit examination of a wide variety of soil modelling concepts.

### Comments on One-Dimensional Wave Mechanics

#### Dhanvin Mehta

The classical wave theory, which describes the propagation stress waves in the rods, forms the underlying basis of pile driving theory and pile driving computer programs. In this respect, piles may be considered as rods and the same analogy can be extended to the other parts of the driving system. The purpose of this study is to describe essential differences in the development, modelling as well as basic ideas behind the computer program popularly called 'Weap' (Wave Equation Analysis o f Piles) which was developed for the Federal Highway Department, and the algorithm based on wave equation theory, extended and refined realistically t o include complications due to presence of discontinuities in pile cross section, skin friction as well as internal damping. Only air steam hammers are considered as a part of the latter approach mainly because of the simplified model adopted, and for the ease in the program development. The conflicts associated with any other hammer system during modelling, using wave theory approach are self evident, and needs no further elaboration .

### Dynamic Behaviour of Battered Piles

#### Mohammad Ettouney and Jeffrey Janover

The one-dimensional wave equation is used in many forms. Unfortunately it is not able to take into consideration the lateral effects in battered piles. Battered piles are studied in dynamic situations. It is concluded that the dynamic effects of pile batter exceed those of static effects.

### The Effects of Material Damping on Wave Equation Analysis of Pile-Driving

#### Rick Corder, George Cozart and Jim Field Texas A&M University

A study on the effects of material damping in wave equation analysis of pile driving, with modified factors to properly take this into account.

### Numerical Approximations in Pile-Driving Analysis

#### R.O. Davis and P.J. Phelan International Journal for Numerical and Analytical Methods in Geomechanics, 1978

A finite-difference scheme widely used in analysis of pile driving is examined. The scheme is shown to yield peculiar results in simple symmetric impact problems and to inherently possesses an imprecise definition of energy balance. A modified difference scheme is suggested and comparisons of the two methods are shown.

### An optimisation method for pile driving analysis

#### Jeremy Dolwin and Trevor J. Poskitt Queen Mary College, London

A numerical method has been developed for analysing field data from piles as they are driven. The basis is a "least squares" technique which is used in conjunction with a non-linear optimisation procedure. It enables the measured stress time curve to be fitted by a wave equation analysis by calculating the values of hammer impact velocity, cushion stiffness, coefficient of restitution, soil quake, damping and skin friction such that the difference between the observed and predicted stress-time curves is a minimum. Good estimates of these parameters are of considerable practical value because they enable a comparison to be made between the data assumed at the design stage and that actually observed during installation. The acceleration-time curve produced by the optimised parameters is then compared with the measured acceleration curve. This provides a completely independent check on the validity of the calculated parameters. Since acceleration is a very sensitive variable in the computation, this is the most stringent test of the calculated values which can be devised. Finally, two worked examples are presented.

### Parameters for Friction Piles in Marine Soils

#### F. Baguelin; R. Frank and J.F. Jezequel

The aim of this paper is to show how self-boring pressure meter parameters can be used to predict the load-displacement curves of friction piles, by means of simple numerical analyses : either by load transfer functions analysis (section I) or by finite element analysis assuming a linear elastic behaviour for the soil mass (section II). In section III, the results of such theoretical analyses are compared with the experimental results of full-scale pulling out tests performed on two tubular piles driven in marine soils.

### Pile Driveability is Unpredictable in Sand or Silt Foundation Strata

#### Mari Mes, J. Ray McDermott Petroleum Engineer, October 1976

On a North Sea project, it became evident that the drivability estimates were inadequate to properly predict the depth of penetration of the pile. This paper proposes changes in the modelling scheme to improve the prediction of drivability.

### Sensitivity and accuracy of the pile wave equation

#### G.E. Ramey and A.P Hudgins

The dynamic wave equation provides a means of evaluating pile capacity that is mathematically well-founded and probably provides the most realistic model available for depicting actual behaviour of the hammer-pile-soil system. Numerical integration of this equation, with the aid of a digital computer, appears to be the most rational analytical means of evaluating pile capacity. A computer program solution of the wave equation was utilised in the investigation being reported to adjudge a) the sensitivity of the program-generated P-n curves to the program input soil parameters and b) the accuracy of the program in predicting pile capacity.