Grounded Amazing Classroom Demonstrations in Soil Mechanics David J. Elton

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Grounded Amazing Classroom Demonstrations in Soil Mechanics David J. Elton


Preface vii
Acknowledgments and Contributors x
Soils Magician Accreditation Procedure xii
Video Demonstrations xiii
Magic Demonstrations
1 Exploding Soils (Extreme Slaking) 1
2 Rice Is Nice (an Exercise in Pile Capacity) 7
3 Break that Block (the Power of Bentonite) 12
4 A Retaining Wall Made of Paper 17
5 Slip Slidin’ away with Effective Stress 25
6 Magic Beaker (Sand Defi es Gravity) 31
7 Effective Potato Chips 35
8 Foam Balls in a Pipe (Soil Arching) 41
9 Geotechnical Rorschach Test (Water Flows around a Drain,
instead of into the Drain) 46
10 Hairy Soil 51
11 Sand Cylinder Hoisting 55
12 Water That Won’t Go through a Sieve (and Water
That Does) 60
13 Dilation in Someone’s Hand (Silty Soil Identifi cation) 65
14 Piping Under a Sheetpile Dam 70
Non-Magic Demonstrations
15 Jar of Rocks (Soil Void Ratio, Porosity, Unit Weight, and
Water Content of Soils) 76
16 Liquefaction by Upward Gradient 82
17 Blow It Out (Critical Hydraulic Gradient)
and Flowlines 90
18 Relative Density of Soil in a Graduated Cylinder 99
19 Soil Filter Demonstration Using Marbles 104
20 Sand in a Jar (Strong as You Are) 111
21 Shear and Compression Waves 115
22 Soil Bridge in a Tube 120
23 Capillarity and Cotton Balls (Bonus: Nonwoven Geotextile
Strength Demonstration) 125
24 Stick-Slip Behavior 132
25 Tilt Me up Scotty (Interface Friction) 136
26 Soils Relaxing (the Angle of Repose) 142
27 Falling Head over Heels for Permeability
(the Permeability of Oobleck) 145
28 Bulking of Soils (AKA: Less Soil for Your Money) 149
29 Geotextile Puncture Test 155
30 Soil Dilation and Compaction Using Ping Pong Balls 160
31 Campus Geology Tour 163
32 Settlement Rates of Soils in Jars 165
33 Bearing Capacity (Bigger Is Better) 169
34 Retaining Wall in a Box 176
35 Rockfall Simulator Lab 181
Bibliography 187
Index 189


Grounded! is a cool collection of engaging science and engineering demonstrations
based on the most common of all civil engineering material:
soil. Public school and undergraduate students, teachers, and service organizations
can do the demonstrations, which illustrate scientifi c principles.
Many have civil engineering applications, the king of all engineering
Most demonstrations require only the simplest materials: soil, water,
paper, some plastic tubing, and other stuff easily found at hardware stores.
The intent is to make the demonstrations accessible to almost everyone.
Layout of the Book
Grounded! consists of two kinds of demonstrations: the fascinating demonstrations
with unexpected results and the not-so-fascinating-but-stillinstructive
demonstrations. These are called Magic Demonstrations and
Non-magic Demonstrations in the Table of Contents. The former are for
public consumption; the latter are more useful to undergraduate university
geotechnical laboratory instructors. The former, which are more fun,
produce unexpected magical results. That said, all the demonstrations
explain the science and engineering behind them. Many of the demonstrations
are followed by engineering applications (e.g., how to build a
retaining wall, how to keep a dam from washing away, how to build fi lters
for walls, and how to strengthen soil for building foundations).
This book includes videos! If a picture is worth a kiloword, a video
is worth a teraword. The videos help illustrate the assembly and procedure
of some of the more complicated demonstrations. The videos are online
at .
Intended Audience
The demonstrations are suitable for elementary, high school, and undergraduate
college students. Most of the demonstrations are captivating. A
few are dull (though instructive), but that ’ s life, eh? Overall, they interest
people in engineering and science, enticing them to pursue careers in
science, technology, engineering, and mathematics.
The book is particularly useful for those tireless souls who conduct
university geotechnical teaching laboratories. Many of the principles and
applications are part of undergraduate geotechnical engineering classes.
The ability to organize and conduct the demonstrations was a high priority,
hence the inexpensive materials for most of them. The more expensive
demonstrations require costly Plexiglas® boxes. Demonstrations using
X-ray tomography, three-dimensional holographic modeling and printing,
hallucinogenic substances, and iPhones were left to future volumes.
An Introduction to Who Are Soil Mechanics and
Geotechnical Engineers
Soil mechanics and geotechnical engineers use soils to do something
useful, such as build dams, roads, building foundations, embankments,
walls, and many other soil structures. Geotechnical engineering is the part
of civil engineering that deals with soils—the world ’ s most popular construction
material. Soils are used in almost every aspect of the built environment:
buildings, walls, slopes, parking lots, subways, zoos, pipelines,
landfi lls, power transmission, transportation, tunnels, power plants, and
more. In fact, few civil engineering projects do not involve soils.
Background of the Book
These demonstrations began in the deep recesses of the author ’ s alter ego
while he was at The Citadel in Charleston, South Carolina. The evolution
from dark, nebulous forms with sinister overtones (such as turning nonperforming
undergraduates into frogs) to humorous demonstrations
took a while. Some demonstrations in Grounded ! come from the literature,
and others were dreamed up when the author should have been
working. The list of demonstrations expanded for more than 30 years,
with a little help from the author ’ s friends. If you have more, please send
them to him so he can put them in another book and become wealthy.
Maybe retire young.
The author, sometimes called the Soils Magician, published another
set of cool geotechnical demonstrations, Soils Magic , in 2001, from this
same publisher. In a sense, Grounded! is a companion volume. Buy both.
They make great Christmas gifts.