Assessment of variability in soil properties from various field and laboratory tests

ABSTRACT

Subsurface investigations are planned and executed to evaluate soil and rock conditions at project sites and to obtain relevant properties needed for analysis and design of structures. There are various field and laboratory tests used to characterise subsurface soil conditions. All tests have their own advantages and limitations. An extensive subsurface exploration programme was implemented for sections of two existing roadways experiencing continuing settlements which, as a result, require periodic pavement patching and resurfacing. The subsurface investigations involved drilling and soil sampling; field testing including SPT tests and CPT soundings; and various laboratory testing to assess conditions at the two roadway sections. The results show that CPT estimated N₆₀ values on average agree well with the SPT measured N₆₀ when all soil types are considered, but there is a significant scatter in the data. CPT estimated N₆₀ values for sandy soils were higher than the SPT measured N₆₀ values in nearly all cases, while CPT estimated N₆₀ values were lower than the SPT estimated N₆₀ values in the majority of cases for cohesive soils. The results also show that there is a good correlation between the average CPT-N₆₀/SPT-N₆₀ ratios with respect to CPT soil behaviour type, SBT.

KEYWORDS:

• Subsurface investigations
• site characterisation
• field testing
• laboratory testing
• soil properties

Acknowledgments

The work presented here was part of a project funded by the Ohio Department of Transportation (ODOT) and the Federal Highway Administration (FHWA). The CPT tests were performed by ODOT and the help provided by Chris Merklin of ODOT is greatly appreciated.

Disclosure statement

No potential conflict of interest was reported by the authors.