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<br />01REP019 (12/08) AMERICAN ENGINEERING TESTING, INC. <br /> <br />DEFINITIONS RELATING TO PAVEMENT CONSTRUCTION <br /> <br />TOP OF SUBGRADE <br />Grade which contacts the bottom of the aggregate base layer. <br /> <br />SAND SUBBASE <br />Uniform thickness sand layer placed as the top of subgrade which is intended to improve the frost and drainage <br />characteristics of the pavement system by better draining excess water in the base/subbase, by reducing and <br />“bridging” frost heaving and by reducing spring thaw weakening effects. <br /> <br />CRITICAL SUBGRADE ZONE <br />The subgrade portion beneath and within three vertical feet of the top of subgrade. A sand subbase, if placed, would <br />be considered the upper portion of the critical subgrade zone. <br /> <br />GRANULAR BORROW <br />Soils meeting Mn/DOT Specification 3149.2B1. This refers to granular soils which, of the portion passing the 1" <br />sieve, contain less than 20% by weight passing the #200 sieve. <br /> <br />SELECT GRANULAR BORROW <br />Soils meeting Mn/DOT Specification 3149.2B2. This refers to granular soils which, of the portion passing the 1" <br />sieve, contain less than 12% by weight passing the #200 sieve. <br /> <br />MODIFIED SELECT GRANULAR BORROW <br />Clean, medium grained sands which, of the portion passing the 1" sieve, contain less than 5% by weight passing the <br />#200 sieve and less than 40% by weight passing the #40 sieve. <br /> <br />GEOTEXTILE STABILIZATION FABRIC <br />Geotextile meeting Type V requirements defined in Mn/DOT Specification 3733. When using fabric, installation <br />should also meet the requirements outlined in Mn/DOT Specification 3733. <br /> <br />COMPACTION SUBCUT <br />Construction of a uniform thickness subcut below a designated grade to provide uniformity and compaction within <br />the subcut zone. Replacement fill can be the materials subcut, although the reused soils should be blended to a <br />uniform soil condition and recompacted per the Specified Density Method (Mn/DOT Specification 2105.3F1). <br /> <br />TEST ROLL <br />A means of evaluating the near-surface stability of subgrade soils (usually non-granular). Suitability is determined <br />by the depth of rutting or deflection caused by passage of heavy rubber-tired construction equipment, such as a <br />loaded dump truck, over the test area. Yielding of less than 1" is normally considered acceptable, although <br />engineering judgment may be applied depending on equipment used, soil conditions present, and/or pavement <br />performance expectations. <br /> <br />UNSTABLE SOILS <br />Subgrade soils which do not pass a test roll. Unstable soils typically have water content exceeding the “standard <br />optimum water content” defined in ASTM: D698 (Standard Proctor test). <br /> <br />ORGANIC SOILS <br />Soils which have sufficient organic content such that engineering properties/stability are affected. These soils are <br />usually black to dark brown in color.