Posted in Academic Issues

The Raising of the Maine, Cellular Cofferdams, Why Puerto Rico is Part of the U.S., and Why Puerto Ricans are Americans

On this day in 1898 the USS Maine was sunk in Havana harbour, which precipitated (after a great deal of “yellow journalism” on the part of the American press) the Spanish-American War.  This topic is of interest, not only because of its place in American history, but also in the history of geotechnical engineering, as it was an early large-scale application of sheet piling and an early use of cellular cofferdams.

The cause of the Maine’s explosion is still a matter of debate, although the weight of the evidence leans toward some kind of coal explosion.  The Maine used the same type of Scotch marine boilers that Vulcan preferred for its offshore hammers in the 1960’s and onward; coal was the usual fuel at the time.  It was necessary, sooner or later, to get the wreckage off of the bottom of Havana harbour, and that involved a celluar cofferdam.  The following description of the job comes from H.S. Jacoby and R.P. Davis, Foundations of Bridges and Buildings, New York, NY: McGraw-Hill Book Company, 1914:

The cofferdam for raising the “Maine” represents a special type of steel cofferdam, very large and strong.  *”The problem was to surround the wreck of the vessel, lying in about 29 to 37 feet of water, with a cofferdam, which when unwatered would be tight enough to prevent leakage, strong enough to resist outside water and mud pressures, and a protection that would assure safety during the work.  The cofferdam should be self-sustaining, if possible.  Bracing by struts across its interior to resist the water and mud pressures might be difficult to install and would interfere with the operation of removal.  The borings indicated bad conditions for foundations.  The building of a cofferdam without internal bracing, which would withstand pressures from a head of 37 feet of water and practically 21 to 23 feet of mud, was an unprecedented task.

“The cofferdam should be not only self-sustaining and safe against the pressures to which it  was to be exposed, but it should also be capable of complete removal after it had served its purpose.  It should be able to support more or less superimposed loads, for working platforms had to be built upon it.  The work of unwatering the area enclosed had to be carried on from the top of the cofferdam; and afterward, men and materials had to be transferred from there to the interior, for work upon the wreck…The cofferdam decided upon consisted of 20 equal cylinders, 50 feet in diameter, and composed of steel piling 75 feet long…”  A plan is shown in Fig. 71e.

Raising the Maine, views of the cofferdam, from Jacoby and Davis, Foundations of Buildings and Bridges.

“The length of the major axis of the cofferdam was practically 399 feet, and of the minor axis 219 feet, leaving a 20-foot clearance at the submerged bow of the ship and a 14-foot clearance at the stern, with 45 feet at the side cylinders.  Such clearance was necessary to avoid portions of the wreck which had been blown beyond the position occupied by the hull.

“The units of the cofferdam were made cylindrical for the reason that the extremely high pressures, which would be exerted by the mud filling, would act radially and uniformly on each pile, straining each joint to the same amount at equal depths, and in the entire cofferdam cylinders would deform least from play in the piling interlocks.”*

The cylinders were driven tangent to one another and to insure their stability and prevent leakage of water through them when the cofferdam was pumped out they were filled to the top with clayey material that was dredged from the bottom of the harbor.  A curved diaphragm of steel-piling, as shown in Fig. 71f, was driven to connect the adjacent cylinders, and the space between this arc and the outer surfaces of the large cylinders was likewise filled with dredged material.

The piling used was the Lackawanna section, weighing 35 pounds per linear foot, and had a web 1/2 inch thick.  The piles were driven so that their tops were 2 to 3 feet above normal water level (Fig. 71g) and the 75-foot length of piling, which penetrated the harbor bottom to a distance of approximately 35 feet, was made of two lengths spliced together with channels.

*Bulletin No. 102, Lackawanna Steel Co., Buffalo, N.Y.

Cellular cofferdams have gone on to become an important type of retaining wall structure.  Probably the most significant change from this project is that cellular cofferdams are always built with permeable materials such as gravel and not clays such as were dredged from Havana harbour.  More information on this project and related topics are here:

The wreckage of the Maine wasn’t the only result of the Spanish-American war.  The United States virtually ended the Spanish empire, which had once covered much of the Western Hemisphere.  Cuba became independent.  The Philippines became an American possession (except for Japanese rule during World War II) until their independence in 1946.

Puerto Rico also became part of the United States by military invasion and annexation, and (through a long process) Puerto Ricans became full American citizens.  That’s something I remind my students about every time I teach this subject; an American history lesson never hurt anyone.  And the Puerto Ricans I go to church with (and I have in class) are grateful.

Posted in Geotechnical Engineering

Engineering Geology in the Civil Engineering Curriculum

For this post I’m featuring an article by J. David Rogers, Professor and Karl F. Hasselmann Chair in Geological Engineering, Department of Geosciences and Geological and Petroleum Engineering, Missouri University of Science and Technology, which he entitled  Disappearing Practice Opportunities: Why Are Owners And Engineers Taking Increased Risks? What Can Be Done To Counter This Threat?  It’s been around a while but bears repeating, especially for one thing: why we need to restore engineering geology to the civil engineering curriculum.

Posted in Soil Mechanics

Van der Merwe’s Method, Adapted for SI Units

Van der Merwe’s method, which was first introduced in the 1960’s, is a simple method for estimating the vertical movement of expansive soils.  The method at its most basic is described in publications such as Foundations in Expansive Soils, and basically looks like this:

Van der Merwe Method

The problem with this presentation is that it is entirely in “Imperial” units, which were the standard in the South Africa of van der Merwe’s day.  We need to convert this to make it usable in SI units as well.  First we present the potential expansion chart, from Soil Mechanics:

Volume Change Potential Classification for Clay Soils

Then we reconstruct van der Merwe’s equation to make it applicable for SI units as well as US (or Imperial) units:

Van der Merwe's Method SI and US Units

Note that the swell potential is now in the denominator.  That’s a convenience to make the PE values of a reasonable order of magnitude.  But now it’s dimensionless. Also note that the depth reduction factor has a different exponent for SI units than it does for US units.

Posted in Academic Issues

The Problem with "Going Dark" in the Technical Literature

When starting out on a major research project in science or engineering, the first thing to do is to go through “the literature” (which usually means the peer-reviewed body of articles and published books, although internet stuff is becoming increasingly important) and try to figure out the current “state of the science” (we used to say “state of the art” but people are less inclined to use that expression than they used to be).  From here we proceed to do new things which will hopefully advance the state of whatever field of endeavour we are operating in.  As I stated in my master’s thesis:

In any investigation such as this the ideal goal is to come up with something truly novel, and many of such works emphasize their novelty to the denigration of those who have gone on before. While in some fields of endeavour this might be appropriate, in this case such sweeping novelty cannot be claimed. This work fits the mould as outlined by Pascal above: it takes the work that has been done before, advances it a step while realizing that there are many more steps before “perfection” is achieved.

But stepping back to those who have “gone before”, the scientific and engineering literature isn’t as transparent as one would like.  In recent years fraud and misrepresentation of results has required any researcher to be careful as to what he or she believes.  There are also situations where stuff that looks really good at one point in time get abandoned later for various reasons; we have to make sure our research takes a long sweep in time as well as topic.  We also have the problem of “non-novel” papers, which are really rehashes of stuff figured out a long time ago but put back into the literature to give glory to someone else.  These don’t do much for the originality reputation of their writers but, sometimes, can be useful, putting back into currency things which have “gotten lost in the shuffle” over the years.

But one serious problem that deserves some attention–and one that doesn’t get a lot of press–is the matter of “going dark” in the literature.  An overview of the pattern of scientific and engineering advance is in order.

Generally speaking, in any given field there are “seminal papers” (usually more than one), which is where the field was kicked off.  From there we have what comes after, which usually refers back to the seminal paper.  In my field of pile dynamics, we have one paper that gets cited in just about everything written on the subject.  From here the science and technology are developed and things advance.  And then, without much fanfare, the literature “goes dark”.

That doesn’t mean that people stop publishing anything on a given topic.  Far from it; however, it’s like a line from Hogan’s Heroes, when Gestapo Col. Hochtstetter tells Klink that he can make Hogan talk.  Klink’s reply was, “You can make him talk.  He just doesn’t say anything”.  A lot of the literature is little better than fluff or promotion of a new idea without substantive detail on how these “new” improvements really work.  The obvious question is why.

One reason is that the material is classified for military or national security purposes.  Generally speaking, however, that literature doesn’t go dark as much as it’s dark to start with and it’s only later when things come to light.

Another reason is that the field has become inactive, usually temporarily.  There are a number of reasons this happens.  In my field, wave propagation in driven piles was discovered in the early 1930’s in Australia, and the English carried out some research later in the decade.  (The Americans got into a food fight on the subject).  But things went dark for a very big reason: World War II, which focused the participants on other matters, such as rational soil classifications and nuclear weapons.  After that conflagration, things resumed and progressed to the current state.

In my experience, however, the biggest reason the technical literature goes dark is because of commercialisation.  In the early stages, the research is the “property” of academic institutions, individuals and the government (especially since World War II) which funds it.  In these conditions there is a relatively free exchange of ideas and expression of these ideas in articles and books.  However, when technologies are commercialised (especially when it’s done by a relatively small number of organisations) things start getting proprietary, and then things start getting secret.  Although it’s possible to have patents and copyrights to protect oneself in some cases, it’s not possible to copyright an idea; it’s easier to simply use trade secrets, even if those trade secrets are derivative from research from more “open” sources.

The fact that a technology can be commercialised is a good thing in that it shows that it works and is useful.  Over time, however, it happens that organisations use institutional inertia and human habit–to say nothing of our tort system, which stifles innovation by punishing experimentation which can go wrong–to make their proprietary method a “standard” and keep its true nature under wraps to discourage its replacement or even improvement.  In time this slows the advance of science and technology in ways that are not obvious to most people.

Researchers who set out to try to advance methods in areas which have “gone dark”–assuming they can get funding for their work in the first place–face a number of obstacles.  First they must realise that beyond the dark literature are doubtless some improvements the nature of which are obscure.  They may find themselves “reinventing the wheel” in an unavoidable way.  If they get past that, they find that they lack the benefit of the learning curve which those who actually use the existing method.  The road to advancement can be a perilous one under these circumstances.

But advancement is what science and engineering is supposed to be about, isn’t it?

Posted in Academic Issues

Mirroring Our Creator

Not too long ago, while grading homework for a course I was teaching, I saw a “better than usual” performance from one of my students.  I noted that, if she would consistently concentrate on what she was doing, she was capable of very good work.   The response I got to this was as follows:

I just stumbled across the feedback you gave me…Thank you for that. It’s nice to hear those things once in a while, and especially from a professor of your calibre.

My response to this was as follows:

At the beginning of his poem Paradiso, Dante wrote the following:

The glory of Him who moves all things rays forth
through all the universe, and is reflected
from each thing in proportion to its worth.

Our first task in life is to point the mirror in the right direction.

I’m sure that it’s the rare professor in the College of Engineering and Computer Science that would quote Dante in a communication with a student, but doing so brings up some things that need to be said.

Today the concept of “equality” is endlessly paraded before us.  In practice, however, equality is a tricky concept.  It’s one thing to pass some legislation and give each other the high-five that we’ve moved towards a more just society. It’s another to achieve real equality.  To do that would require either that we accept that everyone have the same outcome (which was a goal of Communism) or abolish any kind of reward for performance, and frankly we’re not near either one.

No where is that more evident than in education.  In spite of the levelling efforts of the last fifty years, we still don’t have real equality, not only among the students and faculty but among differing institutions.  There are many reasons for this but the most important one is that people are not the same; thus, inequality is built into the system from the start.

A teacher is presented with a varied lot each time class assembles.  In addition to differing levels of intelligence, there are other things that vary.  Students learn differently one from another.  Some take too many courses in one semester.  Some work full-time jobs and/or have a family.  Some do both, which can be a real disaster.  Some experience personal tragedy, either going into their studies or during them.

It’s tempting for an academic to focus on their “best” students.  Having worked in industry first, I am aware that there is more to life than academic performance, and I’ve seen in class that the “smart” students aren’t always the ones who come up with the best solutions, especially on projects.  That tells me that, as one of my own professors observed, testing may not be the best was to gauge performance, but it’s the best we’ve got.  We need to understand its limitations, along with those of the whole academic system.

Getting back to Dante, he lived in a world where inequality was accepted as a fact of life.  But he also lived in a Christian world where each and every human being had worth to his or her Creator.  Each of those creatures should reflect whatever glory their creator put in them; if they did so, they fulfilled their purpose, and found their value in doing so.

Today our obsession with “equality” leads us to try to do all and be all.  But our God doesn’t expect that, and neither do I.  As a professor, what I want to see from my students is their best, to bring out that which their God and their creator has endowed them with.  If I get that, I’ve succeeded and they’ve succeeded.

That is what I meant by my comment: our first task is to direct ourselves in such a way as to reflect the glory of our Creator best, and that first is towards Him.  But that leads to another point of the Paradiso: we get to the point where we realise we cannot achieve our true goal without God’s help and presence in our lives.  To fully reflect the glory of our Creator and to fulfil his purpose for us requires that step, and for that the provision is his, not ours.

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