Richland College Review Checklists and Technical Guidelines Paper Checklist and guidelines for review of geotechnical reports and preliminary plans and spe
Richland College Review Checklists and Technical Guidelines Paper Checklist and guidelines for review of geotechnical reports and preliminary plans and specificationsLiving with unstable soils Publication No. FHWA ED-88-053
August 1988
Revised February 2003
CHECKLIST AND GUIDELINES
FOR REVIEW OF GEOTECHNICAL
REPORTS AND PRELIMINARY PLANS
AND SPECIFICATIONS
PREFACE
A set of review checklists and technical guidelines has been developed to aid engineers in
their review of projects containing major and unusual geotechnical features. These
features may involve any earthwork or foundation related activities such as construction
of cuts, fills, or retaining structures, which due to their size, scope, complexity or cost,
deserve special attention. A more specific definition of both unusual and major features
is presented in Table 1. Table 1 also provides a description of a voluntary program by
which FHWA generalists engineers determine what type and size projects may warrant a
review by a FHWA geotechnical specialist. The review checklists and technical
guidelines are provided to assist generalist highway engineers in:
Reviewing both geotechnical reports and plan, specification, and estimate
(PS&E)* packages;
Recognizing cost-saving opportunities
Identifying deficiencies or potential claim problems due to inadequate
geotechnical investigation, analysis or design;
Recognizing when to request additional technical assistance from a geotechnical
specialist.
At first glance, the enclosed review checklists will seem to be inordinately lengthy,
however, this should not cause great concern. First, approximately 50 percent of the
review checklists deal with structural foundation topics, normally the primary
responsibility of a bridge engineer; the remaining 50 percent deal with roadway design
topics. Second, the general portion of the PS&E checklist is only one page in length.
The remaining portions of the PS&E checklist apply to specific geotechnical features
such as pile foundations, embankments, landslide corrections, etc., and would only be
completed when those specific features exist on the project. Third, the largest portion of
the checklists deals with the review of geotechnical reports, with a separate checklist for
each of eight geotechnical features. The checklist for each geotechnical feature is only
one to two pages in length. Therefore, on most projects, reviewers will find that only a
small portion of the total enclosed checklist needs to be completed.
* For purposes of this document, PS&E refers to a plan and specification review at any
time during a projects development. Hence, the review may be at a preliminary or
partial stage of plan development.
i
TABLE OF CONTENTS
TITLE
PAGE NO.
PREFACE …………………………………………………………………………………………………. i
TABLE OF CONTENTS ……………………………………………………………………………… ii
Introduction ………………………………………………………………………………………………… 1
What is a Geotechnical Report? …………………………………………………………………….. 3
Use of Review Checklists and Technical Guidelines ……………………………………….. 4
Geotechnical Report Review Checklists:
Section A Site Investigation …………………………………………………………….. 12
Section B Centerline Cuts and Embankments ……………………………………. 14
Section C Embankments Over Soft Ground ………………………………………. 16
Section D Landslide Corrections ……………………………………………………… 18
Section E Retaining Walls ………………………………………………………………. 20
Section F Structural Foundations Spread Footings …………………………… 21
Section G Structural Foundations Driven Piles ……………………………….. 22
Section H Structural Foundations Drilled Shafts ……………………………… 25
Section I Ground Improvement Techniques ………………………………………. 27
Section J Material Sites …………………………………………………………………… 28
PS&E Review Checklists
Section A General ………………………………………………………………………….. 31
Section B Centerline Cuts and Embankments ……………………………………. 32
Section C Embankments Over Soft Ground ………………………………………. 32
Section D Landslide Corrections ……………………………………………………… 33
Section E Retaining Walls ………………………………………………………………. 33
Section F Structural Foundations – Spread Footings …………………………… 35
Section G Structural Foundations – Driven Piles…………………………………. 35
Section H Structural Foundations – Drilled Shaft ………………………………… 36
Section I Ground Improvement Techniques ………………………………………. 37
Section J Material Sites …………………………………………………………………… 38
LIST OF TABLES
TITLE
PAGE NO.
Table 1 Project Review Guidelines ……………………………………………………………… 2
Table 2 Guideline Minimum Boring, Sampling and Testing Criteria ………………. 6
Table 3 Geotechnical Engineering Analysis Required for Embankments,
Cut Slopes, Structure Foundations, and Retaining Walls ………………….. 8
Table 4 Correction of Soil and Rock Related Instabilities ……………………………… 10
ii
GEOTECHNICAL REVIEW CHECKLISTS AND TECHNCIAL GUIDLINES
Introduction
The following review checklists and technical guidelines have been developed to aid
engineers with review of geotechnical reports, plans and special provisions on projects
containing major and unusual geotechnical features. These may involve any earthwork
or foundation related activities such as construction of cuts, fills, or retaining structures,
which due to their size, scope, complexity or cost, deserve special attention. A more
specific definition of both major and unusual features is presented in Table 1. The
checklists and review guidelines are intended to serve four primary purposes.
First, for projects that are submitted to a FHWA geotechnical specialist, the checklists
and technical guidelines are provided to aid FHWA generalist engineers in making a
quick review of the geotechnical report and accompanying support data provided by the
State, to insure that the information provided by the State is complete enough to allow
adequate technical review by the FHWA geotechnical specialist.
Second, for projects which will not be submitted to a FHWA geotechnical specialist for
formal review (which will be the majority of projects handled by the FHWA division
office) the checklists and technical guidelines are provided to assist generalist engineers
in (1) reviewing geotechnical reports and preliminary plan and specification packages;
(2) recognizing cost-saving opportunities; (3) spotting deficiencies or potential claim
problems due to inadequate geotechnical investigations, analysis, or design; (4)
recognizing when to request technical assistance for a FHWA geotechnical specialist.
Third, it should be noted that the checklists and technical guidelines also include
coverage of structure foundations. These review checklists and technical guidelines have
been developed to fill an existing need in this area.
Fourth, this document sets forth minimum geotechnical standards or criteria to show
transportation agencies and consultants the basic geotechnical information which FHWA
recommends be provided in geotechnical reports and PS&E packages.
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TABLE 1
PROJECT REVIEW GUIDELINES
The following project review guidelines are given to assist FHWA generalist engineers in determining what
type and size projects may warrant review by a FHWA geotechnical specialist.
A FHWA geotechnical specialist should review Geotechnical reports and supporting data for major or
unusual geotechnical features, described below. The FHWA division office should also request FHWA
geotechnical specialist review for any project that is considered to involve geotechnical risk or excessive
expense in its design or construction. Supporting data for these reviews include preliminary plans,
specifications, and cost estimates (if available at the time of geotechnical report submittal). Emphasis will
be placed on review of these projects in the preliminary stage in order to optimize cost savings through
early identification of potential problems or more innovative designs. To be of maximum benefit
geotechnical reports and supporting data should be forwarded for review as soon as available, and at least
60 days prior to the scheduled project advertisement date. The review by the FHWA geotechnical
specialist should be completed within 10 working days.
A. Major Geotechnical Features
Geotechnical reports and supporting data for major geotechnical project features should be
submitted to the FHWA geotechnical specialist for review if the following project cost and
complexity criteria exist:
Cost Criteria
1. Earthwork soil or rock cuts or fills
Greater than $1,000,000
where (a) the maximum height of cut or
fill exceeds 15 m (50 ft), or (b) the cuts or fills
are fills are located in topography and/or
geological units with known stability problems.
2.
Soil and Rock Instability Corrections cut,
fill, or natural slopes which are presently
or potentially unstable.
Greater than $ 500,000
3.
Retaining Walls (geotechnical aspects) maximum height at any point along the
length exceeds 9 m (30 ft). Consideration of
bidding cost-effective alternatives and
geotechnical aspects (bearing capacity,
settlement, overturning, sliding, etc.) are
of prime concern. Structural design of
and footings is beyond the scope of these
reviews.
Greater than $ 250,000
B. Unusual Geotechnical Features
Geotechnical reports and supporting data for all projects containing unusual geotechnical features
should be submitted to the FHWA geotechnical specialist for review.
An unusual geotechnical project feature is any geotechnical feature involving: (1) difficult or
unusual problems, e.g. embankment construction on a weak and compressible foundation material
(difficult) or fills constructed using degradable shale (unusual); (2) new or complex designs, e.g.
geotextile soil reinforcement, permanent ground anchors, wick drains, ground improvement
technologies; and (3) questionable design methods, e.g. experimental retaining wall systems, pile
foundations where dense soils exists.
2
What is a Geotechnical Report?
The geotechnical report is the tool used to communicate the site conditions and design
and construction recommendations to the roadway design, bridge design, and
construction personnel. Site investigations for transportation projects have the objective
of providing specific information on subsurface soil, rock, and water conditions.
Interpretation of the site investigation information, by a geotechnical engineer, results in
design and construction recommendations that should be presented in a project
geotechnical report. The importance of preparing an adequate geotechnical report cannot
be overstressed. The information contained in this report is referred to often during the
design period, construction period, and frequently after completion of the project
(resolving claims). Therefore, the report should be as clear, concise, and accurate. Both
an adequate site investigation and a comprehensive geotechnical report are necessary to
construct a safe, cost-effective project. Engineers need these reports to conduct an
adequate review of geotechnical related features, e.g., earthwork and foundations.
The State or their consultant should prepare Preliminary geotechnical reports for
submittal to the design team whenever this information will benefit the design process.
Early submittal of geotechnical information and recommendations or engineering
evaluation of preliminary data may be necessary to establish basic design concepts or
design criteria. This is commonly the case on large projects or projects containing
complex or difficult geotechnical problems where alignment and/or grade changes may
be appropriate based on geotechnical recommendations. The development of a Final
geotechnical report will not normally be completed until design has progressed to the
point where specific recommendations can be made for all of the geotechnical aspects of
the work. Final alignment, grade, and geometry will usually have been selected prior to
issuance of the final geotechnical report.
While the geotechnical report content and format will vary by project size and highway
agency, all geotechnical reports should contain certain basic essential information,
including:
Summary of all subsurface exploration data, including subsurface soil profile,
exploration logs, laboratory or in situ test results, and ground water information;
Interpretation and analysis of the subsurface data;
Specific engineering recommendations for design;
Discussion of conditions for solution of anticipated problems; and
Recommended geotechnical special provisions.
It is suggested that the State routinely include this minimum information in the
geotechnical report for Federal-Aid highway projects and that a copy of this report be
supplied to the FHWA division office at the time when the report is internally distributed
in the State.
For brevity in this document, the term geotechnical report will be used as a general term
to cover all types of geotechnical reports, e.g., foundation report, centerline soils report,
landslide study report, etc.
3
Use of Review Checklists and Technical Guidelines
Review checklists have been prepared for review of geotechnical reports and review of
the geotechnical aspects of preliminary plans, specification and estimate (PS&E)*
packages. To simplify their use, the checklists are set up in a question and answer
format. The geotechnical report checklists (pages 11 through 27) cover the important
information that should be presented in project geotechnical reports. The PS&E review
checklists (pages 28 through 33) cover the geotechnical aspects, ranging from assuring
continuity between the project geotechnical report and contract documents to avoiding
common claim pitfalls. Items that are identified with an asterisk (*) are considered to be
of major importance. A response other than (yes) or (N/A) for any of these checklist
questions is cause to contact the appropriate geotechnical engineer for a clarification
and/or to discuss the project.
Groups of related questions and, in some cases, individual questions have been cross
referenced to the Soils and Foundations Workshop Manual** so as to provide the
generalist engineer user a reference on basic geotechnical items. Technical guidelines are
presented in Tables 1 through 4. Since it is not possible to establish strict criteria for all
geotechnical information that should be obtained or geotechnical analysis that should be
performed for a particular project, only general or minimum guidelines can be
established. Table 1 provides definitions of both major and unusual features and
guidelines as to which projects may be appropriate for review by the FHWA geotechnical
specialist. Table 2 presents guideline minimum boring, sampling, and testing criteria for
subsurface investigations that should be conducted for major or unusual geotechnical
features. Table 3 presents general guidelines on the major types of geotechnical
engineering analyses that are normally required for embankments and cut slopes,
structure foundations, and retaining structures. Guidance is given for all major soil types.
Table 4 presents a list of technical support data that should be provided for correction of
soil and rock instabilities (landslides). Due to the unique situation that landslides present
in terms of a major expenditure of funds for rehabilitation, a concise and specific list of
necessary support information is warranted.
The enclosed review checklists and technical guidelines cover the following geotechnical
features:
Centerline Cuts and Embankments
Embankments Over Soft Ground
Landslide Corrections
Retaining Structures
Structure Foundations (spread footings, piles, drilled shafts)
Ground Improvement Techniques
Material Sites
*For the purposes of this document, PS&E refers to a plan and specification review at
anytime during a projects development. Hence, the review may occur at a preliminary or
partial stage of plan development.
** Soils and Foundations Workshop Manual, Publication # FHWA NHI-00-045
4
Reviews made during the preliminary stage of project development will commonly
consist of reviewing the geotechnical report only, since detailed plans and specifications
may not yet be prepared.
When reviewing the PS&E, the plans, special provisions, and final geotechnical report
should be examined together. A major aspect of the PS&E review of project
geotechnical features is to verify that the major design and construction recommendations
given in the geotechnical report have been properly incorporated into the plans and
specifications. The practice of most highway agencies is to prepare a single geotechnical
report that includes subsurface information, interpretations, and design and construction
recommendations. However, some agencies prepare two separate reports; one report that
only presents the factual subsurface data (made available to bidders), and a separate
report or design memorandum (not made available to bidders) which contains the
interpretation of subsurface conditions and the design and construction recommendations.
These reports not only form the basis of technical reviews but should also be the agencys
basis for design and construction of earthwork and foundation features.
The review checklists should be used as the working document while the guidelines in
Tables 1 through 4, and the indicated sections of the Soils and Foundations Workshop
Manual should be used as references. The checklist questions should be completed by
referring to the geotechnical report and contract documents, the appropriate sections of
the tables, and by use of engineering judgement. For each question, the reviewer should
indicate a yes, no, or unknown or non-application response. Upon completion of the
checklists, the reviewer should summarize the negative responses and discuss these with
the appropriate geotechnical engineers to determine if additional follow-up is appropriate.
Seismic design of geotechnical features has not been considered in this document. For
guidance the reader is referred to Geotechnical Engineering Circular No. 3, Design
Guidance: Geotechnical Earthquake Engineering for Highways, Volume I Design
Principles, FHWA SA-97-076. Seismic loads represent an extreme loading condition
therefore relatively low factors of safety are generally considered acceptable in a pseudostatic analysis. Factors of safety on the order of 1.1 to 1.15 are typically used in practice
for both bearing capacity and sliding resistance. The choice of the factor of safety and of
the seismic coefficient are intimately linked. For instance, of a seismic coefficient equal
to the PGA (divided by g) has been used in the pseudo-static analysis because the
foundation cannot tolerate large movements, a factor of safety of 1.0 may be used.
Alternatively, if the seismic coefficient is one-half the PGA and the soil is susceptible to
a post-peak strength decrease, a factor of safety of 1.1 to 1.15 should be used.
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TABLE 2
GUIDELINE MINIMUM BORING, SAMPLING, AND TESTING CRITERIA
The most important step in geotechnical design is to…
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