Performance of Soil-bearing Spread Footings Supporting Highway Structures

Soil-bearing spread footings (SBSF) are emerging as an increasingly attractive option for supporting highway structures. SBSF offers numerous benefits compared to deep foundations, including cost-effectiveness, accelerated construction, straightforward design, environmentally friendly characteristics, and reduced maintenance requirements.

The primary objective of this study is to assess the performance of highway structures that SBSF supports at four specific locations in Ohio. The findings from this assessment will serve as valuable recommendations for the future application of spread footings while identifying potential usage constraints.

The project team conducted a comprehensive review of documented performance data, assessed the effectiveness of existing footings, and compared these assessments against established structural performance criteria. Additionally, the team analyzed calculated settlements, provided an estimate of acceptable structural settlement, compared measured settlements with predicted values, and examined the relationship between performance and soil conditions.

The data gathered, and field assessments conducted at all four sites encompassed in this investigation affirm that SBSF structures function as designed, displaying no signs of settlements or cracks associated with rideability. Both measured and calculated settlements fall within acceptable tolerances. While all structures exhibited acceptable levels of differential settlement, one encountered a differential settlement of approximately 54 mm between substructures, attributed to cohesive soil (A-6) in deeper layers.

SBSF structures were constructed by the manuals and guidelines established by the Ohio Department of Transportation (ODOT) and exhibited satisfactory performance. This paper also offers recommendations for settlement monitoring methods and plan notes that should be incorporated into the Ohio Department of Transportation's practices.