Environmental Engineering Reference
In-Depth Information
engineering procedures. These procedures should reflect the
research published in journals and at research conferences.
In other words, there needs to be a clear connection between
research and engineering practice without
1.7.4 Final Design Protocols
It is suggested that “final design protocols” be based on
the measurement of SWCCs. In other words, representative
soil samples of the material involved in the field should be
tested in the laboratory under the range of soil suctions that
are anticipated to occur during the life of the structure. Only
in situations of extremely low risk it may not be necessary
to perform measurements of the SWCC.
It is the measurement or the estimation of the SWCC
that becomes the primary determining factor separating a
preliminary design protocol from a final design protocol.
Estimation procedures for the determination of unsaturated
soil property functions are later discussed but do not form
the basis for whether a “preliminary design” or a “final
design” is performed.
It is recommended that the most appropriate estimation
techniques be used for the assessment of the SWCC of var-
ious materials when undertaking a preliminary design. The
SWCC results should later be confirmed through laboratory
measurements for the final design. It may also be necessary
to confirm the performance of the design through in situ
monitoring of water content and/or matric suction during
the life of the structure.
turning engi-
neering projects into research-type projects.
A complete engineering protocol needs to address all
aspects of engineering design ranging from the geometric
description of the problem to the assessment of suitable
soil properties and boundary conditions. The protocol
also needs to address the type of analysis that should be
performed when solving a particular problem. Protocols in
this topic are mainly directed toward the determination of
suitable unsaturated soil properties (i.e., SWCC and USPF).
1.7.2 Categorization of Engineering Design Protocols
Engineering design protocols can generally be placed within
one of two primary categories: (i) preliminary design pro-
tocols and (ii) final design protocols, as shown in Fig. 1.30.
It could be reasoned that there might be other intermediate
protocol categories but there is benefit in keeping the cate-
gorization of design protocols as straightforward as possible.
1.7.3 Preliminary Design Protocols
Preliminary engineering design protocols should be as sim-
ple as possible while still taking advantage of the many pro-
cedures that have been proposed, tested, and verified in the
research literature. It is suggested that “preliminary design
protocols” utilize estimation procedures for the assessment
of SWCCs. There are a variety of estimation procedures that
have been proposed and some attributes of each procedure
are later discussed.
1.7.5 Verification or Monitoring Category
There are engineering projects where verification through
field monitoring should be undertaken to ensure that the
engineered structure is performing in accordance with the
design. Verification through field monitoring is left as an
independent confirmation test on design rather than another
design category.
Field monitoring generally requires the measurement of
the same two variables that define the SWCC. In other
words, it will be necessary to measure in situ water content
and soil suction (i.e., matric suction). In measuring these
two variables in the field it is possible to confirm that the
in situ SWCCs are in reasonable agreement with the design
curves.
Implementation of unsaturated soil mechanics
Preliminary design
Final design
Stage of design
1.7.6 Other Factors Affecting Engineering Design
Protocol
The classification of soil type associated with a particular
engineering problem must be known to the engineer. The
saturated soil properties will also need to be measured or
estimated. The detail and reliability sought in assessing soil
properties depend upon a number of factors related to the
engineering project. If the soil classification is known, as
well as the saturated soil properties, it is always possible to
obtain an estimation of the unsaturated soil properties.
All unsaturated soil property functions can be estimated
from saturated soil properties and SWCCs. The SWCC can
also be estimated from the soil classification properties, in
particular, from the grain-size distribution curve. Conse-
quently, there is no reason for an engineer to say that he or
Protocols for preliminary design
Protocols for final design
Estimation of the SWCC from
soil classification properties
Measurement of the SWCC
Estimation of soil property
function USPF from SWCC
and saturated soil properties
Estimation of soil property
function USPF from SWCC
and saturated soil properties
Figure 1.30
Classification of engineering protocols when dealing
with unsaturated soil mechanics problems.
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