This report contains proposed specifications for the design and construction of soil-nailed retaining structures. Despite their advantages in cut applications, these structures are not available to some state DOTs, due to the lack of guidance for their use in AASHTO's standard specifications based on load and resistance factor design (LRFD).

Model Uncertainties in Foundation Design is unique in the compilation of the largest and the most diverse load test databases to date, covering many foundation types (shallow foundations, spudcans, driven piles, drilled shafts, rock sockets and helical piles) and a wide range of ground conditions (soil to soft rock). All databases with names prefixed by NUS are available upon request. This book presents a comprehensive evaluation of the model factor mean (bias) and coefficient of variation (COV) for ultimate and serviceability limit state based on these databases. These statistics can be used directly for AASHTO LRFD calibration. Besides load test databases, performance databases for other geo-structures and their model factor statistics are provided. Based on this extensive literature survey, a practical three-tier scheme for classifying the model uncertainty of geo-structures according to the model factor mean and COV is proposed. This empirically grounded scheme can underpin the calibration of resistance factors as a function of the degree of understanding – a concept already adopted in the Canadian Highway Bridge Design Code and being considered for the new draft for Eurocode 7 Part 1 (EN 1997-1:202x). The helical pile research in Chapter 7 was recognised by the 2020 ASCE Norman Medal.

Uncertainty, Modeling, and Decision Making in Geotechnics shows how uncertainty quantification and numerical modeling can complement each other to enhance decision-making in geotechnical practice, filling a critical gap in guiding practitioners to address uncertainties directly. The book helps practitioners acquire a working knowledge of geotechnical risk and reliability methods and guides them to use these methods wisely in conjunction with data and numerical modeling. In particular, it provides guidance on the selection of realistic statistics and a cost-effective, accessible method to address different design objectives, and for different problem settings, and illustrates the value of this to decision-making using realistic examples. Bringing together statistical characterization, reliability analysis, reliability-based design, probabilistic inverse analysis, and physical insights drawn from case studies, this reference guide from an international team of experts offers an excellent resource for state-of-the-practice uncertainty-informed geotechnical design for specialist practitioners and the research community.

Soil nailing is an in situ soil reinforcement technique that can be used to enhance the stability of slopes, retaining walls, embankments, and excavations. It involves installation of closely spaced, relatively slender unstressed tension-carrying structural elements into the ground to stabilize the soil mass. These elements, which are called soil nails, comprise steel or other engineering materials such as fiber reinforced polymer. Soil nailing did not gain popularity until the 1970s when engineers started to realize that the technique could offer an effective, robust, and economical reinforcing system for a variety of ground conditions. More importantly, the track record has been excellent in that no major collapses have been reported in properly designed and well-constructed soil nailed structures so far. Considerable experience and knowledge of the technique have been gained in the past few decades through systematic technical development work comprising laboratory tests, numerical modeling, physical modeling, site trials and field monitoring covering design, and construction practices. Soil Nailing: A Practical Guide consolidates the experience and advances made in the development and use of the soil nailing technique and encourages a wider adoption of the technique by practitioners. The book is intended for use by postgraduate students, researchers, and practicing civil and geotechnical engineers, who wish to have a more in-depth and fundamental understanding of the theory and practice behind the technique. It presents the basic principles of the technique as well as state-of-the-art knowledge and recommended standard of good practice in respect of design, construction, monitoring, and maintenance of soil nailed structures.

This report explores analytical and design methods for the seismic design of retaining walls, buried structures, slopes, and embankments. The Final Report is organized into two volumes. NCHRP Report 611 is Volume 1 of this study. Volume 2, which is only available online, presents the proposed specifications, commentaries, and example problems for the retaining walls, slopes and embankments, and buried structures.