Soils

In this study, researchers devised a scheme for calibration of earth pressure cells to observe their response to various loading configurations and to recommend a procedure for field installation. As a result of calibration tests, a field installation procedure was developed. Preliminary field data indicate that soil calibration and placement procedure provide reasonably accurate measurements.

The use of salt as a deicer is common in Minnesota because of its low cost and efficiency, but it causes many problems for highway maintenance staff because of its impact on the adjacent vegetation. Salty soils are not conducive to healthy vegetation growth, and the absence of healthy vegetation along the road may lead to weed control problems, increased erosion, and resulting damage to the pavement structure. The report outlines salt effects on soil, as well as methods to avoid vegetation damage by salt and ice before it occurs and to repair damage. It also contains a list of salt-tolerant grasses and woody plants for use in Minnesota. Preventive methods include selection of appropriate vegetation for conditions; use of salt-tolerant grasses and sods; use of native grasses and wildflowers; effective turf establishment practices; protection of existing vegetation; optimization of salt use; and use of products that are friendly to vegetation. Maintenance methods include irrigation to flush salt from soil; soil treatments; vacuuming and sweeping; rejuvenation (reseeding or aeration) of damaged areas; and design and construction strategies.

This report presents the results of a two-year field study on the performance of erosion control products under natural and artificial rainfall conditions. Vegetation, runoff, and erosion data were collected at a newly constructed roadway. Runoff and erosion data were gathered using natural rainfall events and using a rainulator to spray water onto the surface. Treatments included a wood fiber blanket, a straw/coconut blanket, a straw blanket, a bonded fiber matrix, and disk-anchored straw mulch for natural rainfall events. For the rainulator events, a bare soil treatment also was used. Biomass, percent cover, and species composition also were measured at the research site. Five runoff events from natural rainfall were measured and revealed very little difference in sediment production between the straw, straw/coconut, and the wood fiber blankets. These blankets had approximately one-tenth the erosion that was observed for the straw-mulch plots. The impact of the erosion control treatment was substantial for early season artificial events. The sediment loading rates from the blankets and bonded fiber matrix plots were roughly one hundred times smaller than the bare soil plots and 10 times smaller than the straw mulch plots. For late season events, the erosion from these products were approximately one-half of that from straw mulch treatments.