INITIAL CHARACTERIZATION OF SUBGRADE SOILS AND GRANULAR BASE MATERIALS AT THE MINNESOTA ROAD RESEARCH PROJECT

Abstract

This research was conducted on the behavior of materials at the Minnesota Road Research Project (Mn/ROAD),
\nthe construction of which was completed in 1994. Falling-Weight Deflectometer (FWD) tests were conducted on
\nthe test sections at all stages of pavement construction (pre-base, post-base, and post pavement). Deflection
\nvalues were highly variable due to variability in surface condition, soil moisture content, density, and stressdependent
\neffects.
\nIn general, backcalculated subgrade moduli tended to increase with increasing FWD sensor offset (decreasing
\nstress). Post-base and post-pavement testing also indicated an apparent increase in subgrade modulus relative to
\npre-base values. Moduli values were also determined for granular base results.
\nThese results were compared to Dynamic Cone Penetrometer (DCP) penetration index values as well as to
\nresilient moduli values from tests conducted on subgrade and granular base materials in the lab. The
\nbackcalculated subgrade soil modulus values compared well with the laboratory resilient modulus values, but no
\ncorrelation was seen between backcalculated moduli and penetration index values.
\nThe results of this testing will provide a baseline for future analysis of the test sections at Mn/ROAD.