Message from the Society President in 2021
With the Covid-19 pandemic growing worse all the time and health services in some larger cities coming close to breakdown point, we now find ourselves confronted in Sapporo, where the Olympic marathon is due to be held, with summer temperatures higher than any recorded in the past hundred years. This 2021 Annual General Meeting of the GEOASIA Research Society has also been switched to online mode again, but I trust that all of our members are still as active in their research as ever.
In June, I received a request from the Chubu Geological Surveys Association to create a brief review guide that would be of value to engineers currently working in geological surveys and soil experiments. Being vanity-prone, I readily accepted this task, but when I actually got down to writing it, I came to see – not for the first time – how my faculties have gone down with age. As regards the guide, I was saved by the requirement that it should be “brief.” But this also serves as a timely reminder to me of some of my own repeated appeals in this column up until three years ago about the need for a “GEOASIA textbook.”．
The theory of plasticity in geomechanics was originally adopted from the plasticity of metals. Geomechanics could never have existed without the von Mises criterion, The plasticity of metals had its own ample field for development in plastic processing, but in soil mechanics, much hard thought was needed before the two soil properties of compaction and induced anisotropy, neither of which exists in metals, could be worked into a theory of elastoplastic geomechanics. This may sound like an ordinary enough field designation, the kind of name found everywhere, but in fact, even for me, this is my first ever use of this term “elastoplastic geomechanics.”
Except under conditions of heat change, there are no other building materials – no metals, for example – that undergo compaction under the kinds of forces met with in civil engineering. Water is no exception. The behavior of soil compaction is the result of soil being a mixed body, combined out of earth, water and air. The property of “consistency” often attributed to clay soils similarly depends on it being viewed as a mixture, a mixture of earth and water. Sand, too – it hardly needs saying – will compact quite densely when dry with nothing but a few light taps. Moving on to induced anisotropy, this is another mode of behavior, like compaction, that is unknown in other materials. Why should this be? It is obvious that a clay soil should display anisotropic behavior, but visualizing the way sand is made up of discrete granules, clarification comes in a flash. Compared to the kinematic hardening in metals, which is much more of an ad hoc adjustment to circumstances, induced anisotropy in soils has its origin in their grain structure and can just as convincingly indicate and account for the phenomenon of re-liquefaction.
All of this hangs on the concept of the soil skeleton. The discovery of this notion, which made it possible to overcome the early limitations of the Cam clay model of elastoplastic mechanics for remolded clay, was of vital significance in this field. But even before that breakthrough, if one stops to think, it was already plain that metals and soils were essentially different.
Once I get going on this topic, there is no end to it. As a more practical indication of what might be wanted in a six-part GEOASIA coursebook, let me offer a few ideas, offered from the aging head of Asaoka rather than proposed from a platform.
A 6-part GEOASIA Learning Course
- .Elastoplastic Geomechanics 1
The mechanism of soil compaction, Beyond e – log p‘
- Elastoplastic Geomechanics 2
The one truth of soil is anisotropy!
The anisotropy of clay, Liquefaction (and re-liquefaction) of sand
- Elastoplastic Geomechanics 3
Unsaturated soils, Ultimate states of soil mixtures
- Computational Geotechnology 1
Equations of motion in a continuum, Finite variable analysis, Calculations of interaction in a mixed body
- Computational Geotechnology 2
Where solids and fluids meet, State-of-the-art computational geotechnology
- GEOASIA in Geotechnology
No need for computation in geotechnology?
Using the GEOASIA program, Analysis guidance using latest case examples
Speaking from my experience as a not-so-young retiree, who still managed to put together an easy-to-digest outline for Part 1 in under ten days, an active team member assigned with a task of this size ought to be able to finish in five or six weekends, I would think, without the load interfering too badly with research and administrative routine. I hope at any rate that this sketch of a plan may help to restore a little momentum again to this stalled project.
Let me leave you with a light-hearted Chinese-style verse message in 4 x 7 measure:
To tell the truth, I’ve since turned twenty-four – fifty years back, of course.
Senior research advisor, the Association for the Development of Earthquake Protection (reg. foundation)
Emeritus professor, Nagoya University