07-27-2020-R - Laserfiche WebLink

Home Browse Search

Geotechnical Report 2020 PMP Street Improvements Arden Hills, Minnesota WSB Project No. 014297-000 Page 7 Based on MnDOT’s FlexPave excel design utilizing granular equivalent charts, we recommend the pavement sections indicated below in Table 4. Table 4: Recommended Flexible Pavement Section Section Thickness (inches) Granular Equivalent Bituminous Course, MnDOT 2360 2 4.5 Bituminous Course, MnDOT 2360 1 1/2 3.38 Aggregate Base, MnDOT 3138 (Class 5, 5Q, or 6) 6 6 Subgrade Preparation, MnDOT 2111 Yes - TOTAL 9 ½ 13.88 Within several years after initial paving, some thermal shrinkage cracks will develop. W e 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 Subgrade soils consisting of sand and sand with silt are generally considered negligible to low frost f ree characteristics. However, soils that contain higher percentages of fines (silt/clay particles) such as silty sand and lean clay were encountered in our borings and may be encountered in the pavement subgrades. It is our opinion, that the use of a non-frost susceptible sand cushion will provide a more stable and uniform subgrade which will help reduce the effects of differential frost heave. In our opinion, placement of an additional 20 inches of select granular fill below the Class 5 Aggregate Base s hould 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 should evaluate the costs and benefit of this option. Drainage of the sand cushion will be necessary. The sand may be daylighted to adjacent ditches. If daylighting is not possible, 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. 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.