Soil Mechanics

Note: UFC 3-220-10N is simply DM 7.01 with a new header. We offer both documents but they are identical in technical content.

Unified Facilites Criteria UFC 3-220-10N
8 June 2005

Replaces NAVFAC DM 7.01 or DM 7.1, 1 September 1986 (click here to download this document)

Considered by many to be the best single reference on soil mechanics.

Checklist and Guidelines for Review of Geotechnical Reports and Preliminary Plans and Specifications

FHWA ED-88-053
August 1988
Revised February 2003

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. 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.

Critical State Soil Mechanics

Andrew Schofield and Peter Wroth
Cambridge University, England

This book is about the mechanical properties of saturated remoulded soil. It is written at the level of understanding of a final-year undergraduate student of civil engineering; it should also be of direct interest to post-graduate students and to practising civil engineers who are concerned with testing soil specimens or designing works that involve soil.

The authors' purpose is to focus attention on the critical state concept and demonstrate what they believe to be its importance in a proper understanding of the mechanical behaviour of soils. They have tried to achieve this by means of various simple mechanical models that represent (with varying degrees of accuracy) the laboratory behaviour of remoulded soils. They have not written a standard text on soil mechanics, and, as a consequence, they have purposely not considered partly saturated, structured, anisotropic, sensitive, or stabilized soil. They have not discussed dynamic, seismic, or damping properties of soils; they have deliberately omitted such topics as the prediction of settlement based on Boussinesq’s functions for elastic stress distributions as they are not directly relevant to the authors' purpose.

Engineering Use of Geotextiles

UFC 3-220-08FA
16 January 2004

Supercedes:
TM 5-818-8, 20 July 1995 (still available)

This manual covers physical properties, functions, design methods, design details and construction procedures for geotextiles as used in pavements, railroad beds, retaining wall earth embankment, rip-rap, concrete revetment, and drain construction. Geotextile functions described include pavements, filtration and drainage, reinforced embankments, railroads, erosion and sediment control, and earth retaining walls. This manual does not cover the use of other geosynthetics such as geogrids, geonets, geomembranes, plastic strip drains, composite products and products made from natural cellulose fibers.

Evaluation of FEM Engineering Parameters from Insitu Tests

F.C. Townsend, J. Brian Anderson, and Landy Rahelison
Florida Department of Transportation RPWO-14
December 2001

The purpose of this study was to take a critical look at insitu test methods (SPT, CPT, DMT, and PMT) as a means for developing finite element constitutive model input parameters. The first part of the research examined insitu test derived parameters with laboratory triaxial tests at three sites: Saunder’s Creek, Archer Landfill, and SW Recreation Center. The triaxial tests on these sands were used to develop baseline input parameters. These parameters were verified by simulating the triaxial tests using two finite element codes. From these comparisons, the following conclusions were drawn:

1. FEM simulations of triaxial test stress-strain curves produced excellent results.
2. The hardening models (PLAXIS – Hardening Soil and PlasFEM – Sandler Dimaggio) simulated the non-linear behavior better than the Mohr-Coulomb or Drucker-Prager models.
3. In general, E50 triaxial test modulus values agreed with those estimated from DMT and PMT unloading tests, and
4. FEM simulations of field PMT curves using triaxial test based parameters were unsuccessful. It was necessary to increase the triaxial E₅₀ values by Ω = 1.3078e^0.0164pl R² = 0.8515, where Ω is the triaxial E₅₀ modulus multiplier and pl is the PENCEL limit pressure.

The second phase of this study was to predict the deformations of a cantilevered sheet pile wall (unloading case), and the deformations of a 2-m diameter shallow footing (loading case). Conventional analyses methods were compared with the FEM using insitu test derived input parameters. Conclusions were:

1. Conventional analyses (CWALSHT) under-predicted wall deformations unconservatively, while wall deflections were accurately predicted by using the Hardening Soil Model with input parameters estimated from SPT correlations and “curved matched” PMT values.
2. Fundamentally, the stress history of a soil profile, i.e., OCR or preconsolidation pressure, must be known for any settlement prediction either using conventional or finite element methods.
3. Of the conventional methods for estimating settlements (CSANDSET), only the SPT based D’Appolonia, and Peck and Bazaraa methods provided reasonable estimates of the observed settlement.
4. The conventional DMT method, which correlates OCR values, slightly overestimated measured settlements.
5. None of the insitu test derived input parameters (SPT, CPT, DMT, and PMT) coupled with FEM Mohr-Coulomb or Hardening Soil models, accurately predicted the shallow footing settlements

Geotextile Reinforcement of Low-Bearing-Capacity Soils:
Comparison of Two Design Methods Applicable to Thawing Soils

Karen S. Henry
USACE CRREL Special Report 99-7
June 1997

Thawing fine-grained soils are often saturated and have extremely low bearing capacity. Geosynthetics are used to reinforce unsurfaced roads on weak, saturated soils and therefore are good candidates for use in stabilization of thawing soils. To stabilize the soil, a geotextile is placed on it, then the geotextile is covered with aggregate. Design involves selection of aggregate thickness and geotextile. There are two commonly used design techniques for geotextile reinforcement of lowvolume roads, and the Army uses one of them. The theory and use of the two design methods for static loading (i.e., up to 100 vehicle passes) are presented and compared in this report. The design method not used by the Army offers the potential to reduce aggregate thickness over the geotextile because it accounts for the fact that the geotextile helps support the traffic load (when in tension) and confines the soil between the wheels and the subgrade. However, this alternative method appears to be unconservative with respect to stresses estimated at the subgrade surface. Thus, the current Army design technique should be used until more research is conducted. In the meantime, straightforward design curves for Army 10- and 20-ton trucks as well as vehicle loading and tire pressure information for a number of other vehicles are included in this report to help make the current design method easy to use. Future work should consider adopting a hybrid design method that provides realistic estimates of stresses at the subgrade and accounts for the tensile properties of geotextiles. In addition, aggregates other than the highquality crushed rock that is inherently assumed by each design method should be accounted for in new design development.

Introduction to Soil Moduli

Jean-Louis Briaud
Texas A&M University

The modulus of a soil is one of the most difficult soil parameters to estimate because it depends on so many factors. Therefore when one says for example:”The modulus of this soil is 10,000 kPa”, one should immediately ask: “What are the conditions associated with this number?” The following is a background on some of the important influencing factors for soil moduli. It is not meant to be a thorough academic discourse but rather a first step in understanding the complex world of soil moduli. In a first part, the modulus is defined. In a second part, the factors influencing the modulus and related to the state of the soil are described. In a third part, the factors related to the loading process are discussed. Fourth, some applications of soil moduli are presented. In a fifth and sixth part, the soil modulus is compared to the soil stiffness and to the soil coefficient of subgrade reaction respectively.

Military Soils Engineering

U.S. Army FM 5-410
23 December 1992
Change 1, 4 June 1997

Construction in the theater of operations is normally limited to roads, airfields, and structures necessary for military operations. This manual emphasizes the soils engineering aspects of road and airfield construction. The references give detailed information on other soils engineering topics that are discussed in general terms. This manual provides a discussion of the formation and characteristics of soil and the system used by the United States (US) Army to classify soils. It also gives an overview of classification systems used by other agencies. It describes the compaction of soils and quality control, settlement and shearing resistance of soils, the movement of water through soils, frost action, and the bearing capacity of soils that serve as foundations, slopes, embankments, dikes, dams, and earth-retaining structures. This manual also describes the geologic factors that affect the properties and occurrences of natural mineral/soil construction materials used to build dams, tunnels, roads, airfields, and bridges. Theater-of-operations construction methods are emphasized throughout the manual.

This manual has an excellent treatment of basic geology as it relates to soil mechnics, a subject not well covered in most soils texts (including many of the documents on this website.) It is also, to our knowledge, unavailable from U.S. government sites that dispense these kinds of documents even though it was released to the public.

Rock Engineering

Click here to download RocLab.

Evert Hoek

A complete treatment on the subject. Topics include the following:

• Development of Rock Engineering
• When is a rock engineering design acceptable
• Rock mass classification
• Shear strength of discontinuities
• Structurally controlled instability in tunnels
• The Rio Grande project--Argentina
• A slope stability problem in Hong Kong
• Factor of safety and probability of failure
• Analysis of rockfall hazards
• In sity and induced stresses
• Rock mass properties
• Tunnels in weak rock
• Large powerhouse caverns in weak rock
• Rockbolts and cables
• Shotcrete support
• Blasting damage in rock
• References

Soil Mechanics

Arnold Verruijt
University of Delft, The Netherlands
2004

What do you think of the soil mechanics textbook you have (or had) has an undergraduate? Good or bad, one thing you didn't like about it -- the price! We are thus pleased to present a really first class textbook by a well known authority in geotechnial engineering. Topics include the following:

You can contact the author by clicking here.

Use of Geogrids in Pavement Construction

U.S. Army ETL 1110-1-188
30 June 2002

Engineers are continually faced with maintaining and developing pavement infrastructure with limited financial resources. Traditional pavement design and construction practices require high-quality materials for fulfillment of construction standards. In many areas of the world, quality materials are unavailable or in short supply. Due to these constraints, engineers are often forced to seek alternative designs using substandard materials, commercial construction aids, and innovative design practices. One category of commercial construction aids is geosynthetics. Geosynthetics include a large variety of products composed of polymers and are designed to enhance geotechnical and transportation projects. Geosynthetics perform at least one of five functions: separation, reinforcement, filtration, drainage, and containment. One category of geosynthetics in particular, geogrids, has gained increasing acceptance in road construction. Extensive research programs have been conducted by the U.S. Army Engineer Research and Development Center (ERDC) and non-military agencies to develop design and construction guidance for the inclusion of geogrids in pavement systems. This document describes the use of geogrids in flexible pavement systems including design charts, product specifications, and construction guidance.