10.1. SR 01-22-2013 - Laserfiche WebLink

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AMERICAN ENGINEERING TESTING,INC. AET Project No. 25-00538 The free draining subbase layer assists in reducing periods of saturation, and greatly reduces the detrimental effects of frost heaving and subsequent thawing. Some of the onsite fill soils encountered in our borings may meet the MnDOT Specification for Select granular Barrow (MnDDT 3149.2B2) based on the sieve analysis performed on materials collected in our borings. The results of these sieve analysis tests are shown on the respective boring logs in Appendix A. Please note these test results should not be relied upon for bidding purpose and that contractors are encouraged to perform their own testing to determine quantities of materials for reuse. Placement of the 12-inch thick sand subbase layer will require excavation of the existing subgrade throughout the project. Before placement of new fill,the existing subgrade soils should be scarified and recompacted to the levels recommended later in this report. New fill should be like materials and consist of sands (SP), sands with silts (SP-SM) or silty sands (SM). Clays and silts should not be used as fill. The recommended 12-inch thick sand subbase should be provided with a means of subsurface drainage to prevent buildup of water within the sand. This can be accomplished by placing short segments of properly engineered drainage lines which are connected to the catch basins in low elevation areas (referred to as "finger drains"), or to other gravity outfail areas. Where the street is relatively level, and if finger drains are not frequent, you should consider placing a longer parallel drainage line through the level area to better remove infiltrating water. Where the thickness of the sand subbase varies longitudinally, we recommend a 24:1 (H:V)taper to minimize differential frost heaving. Where organic sails are found to be present, we recommend removing these soils where present within or below the critical subgrade zone. Where buried rubble or pavements are exposed in excavations, we recommend removing these soils where present within the critical subgrade zone. Page 5 of 9