C.R. Nelson

Intelligent Soil Compaction Technology: Results and a Roadmap Toward Widespread Use

Intelligent compaction (IC) is a new technique in the U.S. construction market that uses an instrumented compactor to control soil or asphalt compaction in real time. This technology provides one of the first opportunities to apply process control to civil construction. IC is based on the measurement of the mechanical characteristics of the compacted soil, commonly soil stiffness, but other properties are used also. Initiatives in both the United States and Europe started more than 10 years ago and have demonstrated the technical viability of measuring in situ soil stiffness. The measured soil stiffness is used to estimate or compute in situ soil modulus on the basis of assumptions about soil behavior and the interaction between the compaction machine and the soils. IC offers immense potential benefits in embankment, buried structure, and dam and pavement construction. These benefits—including improved quality, reduced compaction cost, reduced life-cycle cost, and integration of design with construction a...

Recommended Design Specifications for Live Load Distribution to Buried Structures

This report provides recommendations to revise the AASHTO LRFD Bridge Design Specifications relating to the distribution of live load to buried structures. The report details the development of simplified design equations (SDEs) for structural response based on three-dimensional (3D) analysis of 830 buried culverts. In addition, the report provides guidelines for conducting 2D and 3D modeling for design situations with conditions not covered by the SDEs. The material in this report will be of immediate interest to roadway and bridge designers.

DESIGN AND CONSTRUCTION OF A WIDE TUNNEL UNDER SHALLOW COVER - THE LAFAYETTE BLUFF TUNNEL SOUTH PORTAL

Abstract The south portal of the Lafayette Bluff tunnel is an interesting case history of wide, shallow tunnel construction. The paper focuses on the site investigation, design, construction-time investigation and construction of the south portal. It illustrates how the nature and quality of the available rock information changed during design and construction, and how the design techniques were adapted accordingly.