Aaron S. Budge

Monitoring Curing of Emulsion-stabilized Roadways Using the Dynamic Cone Penetrometer

Several counties in Minnesota have used an emulsified asphalt to stabilize unimproved gravel highways in rural areas. This has been done in hopes of reducing dust on such roads, reducing the frequency and extent of maintenance, and improving ride quality. As applications of such a stabilization technique increase, the need to investigate and quantify the benefits of this technique is becoming more important. Several county roads in rural Blue Earth County, in south central Minnesota, were stabilized and monitored during the fall of 2005. Dynamic Cone Penetrometer measurements were taken periodically for several months following the stabilization of two gravel roads using emulsified asphalt. Due to the nature of the emulsion compound, the stabilized material was expected to increase in stiffness with time as curing of the emulsion occurred. The Dynamic Cone Penetrometer results verified that the stiffness did increase with time as expected with this stabilization process.

LRFD Implementation Effects on Geotechnical Investigation and Design

The Minnesota Department of Transportation has successfully implemented the Load and Resistance Factor Design (LRFD) method with respect to structural and geotechnical design of transportation structures. The implementation timeline, strategies, and processes are described, highlighting both the major adoption hurdles and the benefits that have been realized to date. In an effort to derive further benefits from the design method, Mn/DOT has a contract underway to develop regionally specific values for resistance factors used in design for driven pile foundations.

Near-Real-Time Embankment Settlement Monitoring for Construction Control

A proposed multi-span bridge was efficiently reduced to a single span in the design phase of a rural Minnesota project. Geotechnical analysis found it possible and significantly more cost effective to construct and monitor longer approach embankment fills over compressible clays as they deflected 300-450 mm (12-18 in) prior to roadway construction. The revised plan involved: removal of 3 m (10 ft) of compressible surface soils; construction of a reinforced load distribution platform; installation of earth pressure cells, piezometers, and ShapeAccelArray deformation sensors; soil preloading and surcharging; a near-real-time monitoring program to control construction sequencing, and a post-construction waiting period. Five cross sections were instrumented and the performance monitored through the construction period. The monitoring program was successfully able to evaluate increases in load, associated pore water pressure, and resulting deformation responses. High frequency data collection and reporting allowed project engineers to make informed decisions to restrict or accelerate construction. The program, while expensive, was highly cost effective considering reduced bridge construction and long-term maintenance costs.