07-19-21-WS - Laserfiche WebLink

Home Browse Search

Geotechnical Report Arden Oaks Street Improvements Arden Hills, Minnesota WSB Project No. 014297-000 Page 7 Within several years after initial paving, some thermal shrinkage cracks will develop. We recommend routine maintenance be performed to improve pavement performance and increase pavement life. Pavement should be sealed with a liquid bitumen sealer to retard water intrusion into the base course and subgrade. Localized patch failures may also develop where trucks or buses turn on the pavement. When these occur, they should be cut out and patch repaired. 4.6 Optional Frost Free Pavement Design Optionally, the use of a non-frost susceptible sand cushion will help reduce the effects of frost heave. In our opinion, placement of 18 inches of select granular fill below the Class 5 Aggregate Base should generally provide for a non-frost susceptible subgrade. It should be noted that any sand cushion placed below the pavement section will provide positive benefits for reduced potential frost heave. The owner and/or design team should evaluate the costs and benefit of this option to determine if it should be incorporated into the pavement design. Drainage of the sand cushion is recommended. Drainage of the sand cushion may be accomplished by daylighting to adjacent ditches or the use of drain tile. Drain tile wrapped in a sock should be placed at the base of the sand cushion and tied into catch basins. We recommend the sand cushion contain a select granular sand with less than 12% passing the #200 sieve. Alternately, a 3 inch minus rock fill could be placed instead of a select granular sand and drain tile. For transitioning the thickness of the sand subbase along the profile of the roadway, we recommend the thickness have a longitudinal taper of no steeper than 10H:1V. A taper of 4H:1V can be used perpendicular to the centerline for cross street/driveway connections. The placement of the sand subbase should extend slightly beyond the outer edge of the curbs to maintain subgrade uniformity for frost movement. 4.7 Construction Considerations Good surface drainage should be maintained throughout the work. Under no circumstances should fill be placed into standing water. Soil corrections at this site for pavement subgrades may not be continuous in all areas. We recommend tapering the fills back to native soils at a ten to one (10:1) slope. 4.8 Construction Safety All excavations must comply with the requirements of OSHA 29 CFR, Part 1926, Subpart P “Excavations and Trenches”. This document states that excavation safety is the responsibility of the contractor. Reference to this OSHA requirement should be included in the job specifications. The responsibility to provide safe working conditions on this site, for earthwork, building construction, or any associated operations is solely that of the contractor. This responsibility is not borne in any manner by WSB. 4.9 Cold Weather Construction It is our understanding that construction is unlikely to occur during the winter months. However, if the construction does continue into the winter months we recommend the following guidelines. Only unfrozen fill should be used. Placement of fill must not be permitted on frozen soil. 4.10 Field Observation and Testing The soil conditions illustrated on the Logs of Test Borings in Appendix A are indicative of the conditions only at the boring locations. For this reason, we recommend that all excavations at this site be observed by a geotechnical engineer or technician prior to fill or backfill placement or construction of any foundation elements to determine if the soils are capable of supporting the fill backfill and/or foundation loads. These DRAFT REPORT 7-8-2021