Some Lessons from “Savinov and Luskin”

One of the mysteries of geotechnical engineering relative to driven piles is why the Soviets, with their mathematical prowess, never applied wave mechanics to predict the performance of pile driving systems using the wave equation. In a sense this book, which is a classic in the geotechnical literature, answers that, but not in a direct way.

Let’s start by considering the development of the wave equation itself. It took place at the Raymond Concrete Pile Company under the direction of their chief mechanical engineer, E.A.L. Smith. From the years immediately following World War II until Smith’s own classic 1960 ASCE paper, the effort was funded and carried out by what was then the greatest pile driving organisation in the world. It was a significant effort that did not have a sure outcome, but in the end it revolutionised the installation of driven piles and other types of deep foundations.

If we look at things from an equipment standpoint, things weren’t so revolutionary. Raymond’s arsenal of pile driving equipment was for the most part a development from Vulcan’s own air/steam hammers, and many Raymond rigs had steam to power them long after other contractors had switched to air. Raymond had made some significant and generally helpful improvements to the Vulcan design, some of which (such as the capblock follower/shield and cable-tied hammers) Vulcan itself adopted. But the equipment which Smith used in his wave equation program was basically the same configuration as the Warrington brothers had designed for the single-acting hammers and Campbell Adams had done for the differential ones.

In the case of the Soviets, they started with a completely new concept for installing (or “immersing” as they liked to say) piles, from the sheet piles at the Gorky project to large pipes and concrete piles, cylinder and square (or “prismatic” to use their term.) To to this required some theoretical development, which was helpful but sadly is not where it should be to this day. They had to develop a new type of pile driving equipment from scratch and they had to either adapt existing lifting equipment to handle it or develop new equipment. In doing this they had to pull together theoretical specialists, equipment designers and even job superintendents to make the whole thing work. It was truly an amazing effort which involved a large number of organisations in different parts in the largest country on the planet.

The benefits of their effort are evident to anyone who has watched the installation of sheet piling or large caissons for drilled shafts. It’s true that more improvements came after the technology emerged in the West. Some of these improvements came in the performance but others (such as the use of high-pressure hydraulics to drive the eccentrics) were simply more in line with the way contractors operated and, in the case of high-pressure hydraulics, the result of better development technology. (One of Raymond’s own innovations, the 65CH and 80CH (at right) hydraulic hammers, was hampered by the state of high pressure mobile hydraulics in the early 1960’s; the Soviets were wise to use electrics at the time.)

The follow-up in both cases is equally interesting. The publication of Smith’s paper got the attention of the U.S. government, both military and civilian, and they poured a significant amount of resources into the development of the wave equation. This resulted in programs such as the TTI program and the WEAP family of programs, the latter including CAPWAP, which enabled the use of the wave equation as an “inverse” problem. By the time the method achieved acceptance in the complex and high-inertia system of U.S. construction, the motivation for improvement wasn’t what it should have been and, with other changes in the whole U.S. research situation, we are not as far ahead of where we were a half century ago as we would like to think.

With the Soviets, although advances certainly took place, after the onset of the Brezhnev years stagnation was the order of the day, and what Vulcan representatives saw in 1988 wasn’t much advanced from what was depicted in this book. The impact-vibration hammers were summarily dumped in the early 1970’s in favour of the diesel hammers, and the translational-rotational drivers never quite got past prototype, only to be “rediscovered” (yes, that term is accurate) in the last few years.

Both the wave equation analysis and vibratory drivers were the product of major efforts by large organisations (or groups of organisations.) Today we’re content to do research piecemeal; the risk of failure for a large project is deemed too high. But there are those in the world who in fact are applying large-scale efforts to advance technology, and the effort described in “Savinov and Luskin” is a testament to what can happen when such an effort is properly conceived and executed.