Page 18 - Geotechnical Engineering Soil and Foundation Principles and Practice

Introduction
Introduction 13

including self-boring ‘‘pressuremeters’’ in France and in England, and more
recently the ‘‘K o Stepped Blade’’ in the U.S. As demonstrated by Terzaghi with
his consolidometer, new instrumentation can lead to new discoveries.

The problem of sample disturbance was addressed by John Schmertmann in
connection with settlement preditions, and by C. C. Ladd in connection with shear
strength testing. An approach that is gaining favor is to test the soil in situ, with
a variety of electronically instrumented cone-tipped penetration devices such as
the ‘‘piezocone,’’ which also monitors pore water pressure. The spade-shaped
‘‘Dilatometer’’ developed in Italy by Marchetti is used to measure modulus and
predict settlement. The ‘‘Borehole Shear Test’’ developed in the U.S. measures
drained or effective stress shear strength in situ, thereby avoiding disturbances
from sampling.

Two important textbook references that emphasize a scientific approach to geo-
technical engineering include Soil Mechanics by T. W. Lambe and R. V. Whitman,
and Fundamentals of Soil Behavior by J. K. Mitchell.

1.18 SOIL DYNAMICS AND COMPUTER MODELING

Certain behaviors of soils in earthquakes, such as the development of quicksand
or sand ‘‘liquefaction,’’ contribute much of the damage to buildings. Studies of
soil dynamics in relation to earthquake damage were pioneered by H. Bolton Seed
and his associates at the University of California, Berkeley, and later by
T. L. Youd. Influences of machine vibrations were studied by D. D. Barkan in
Russia, and more recently by F. E. Richart at the University of Michigan.
Pile driving also involves soil dynamics, and procedures have been developed
based on computer modeling of soil reactions during pile driving, a concept
introduced in 1957 by a practicing foundation engineer, E. A. L. Smith.
The computer revolution also led to computer modeling of complex
soil mechanics problems by finite element analysis. This requires mathematical
modeling of soil strength and volume change behavior, which is difficult as these
tend to be discontinuous functions. Emphasis has been directed toward refined
laboratory testing to define idealized ‘‘constitutive equations’’ to describe
soil behavior under widely varying stress environments, a problem that may be
open-ended without some guiding theory.
As pile driving has gone out of favor in populated areas, alternatives have been
introduced including drilled-and-filled concrete shafts. Major advances in design
were made by Lyman Reece and Michael O’Neill in Texas, who developed design
procedures based on full-scale load tests. A more recent and rapidly growing
method involves replacing the concrete with aggregate that is rammed in place

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