Characterizing the Strength Layering of Freezing Ground

A test section was constructed for vehicle testing on frozen soils having overall dimensions of 6 m (20 ft) wide by 32 m (105 ft) long. The section had three test cells. Each test cell was approximately 7.6 m (35 ft) long by 6 m (20 ft) wide, and contained one of three different soils: clay (CL), silt (ML) and silty sand (SM). The test soils were constructed and compacted in four 0.15-m (6-in.) lifts to a total depth of 0.6 m (24 in.). Each lift was compacted with a roller to a target density of approximately 90 to 95 percent of optimum compaction (CE12) to simulate a trafficked un-surfaced road or trail. Various soil characterization tests were conducted during trafficking for monitoring the condition and homogeneity within each test soil. To characterize the test section, frost depth, soil strength, soil density, and soil moisture were measured and examined with several instruments or monitoring tools that worked well on frozen soils. This paper focuses on frost depth and soil strength measurements using various tools and relates the California Bearing Ratio (CBR) to the soil modulus (E or Mr) value using several existing correlations developed for various soil conditions.