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method is defined in the OVER-EXCAVATION AND STRUCTURAL BACKFILL section of this <br /> report. <br /> Foundation support soil exposed at excavation bottoms must be protected against detrimental <br /> changes that reduce shear strength and relative density of this soil. These changes can result <br /> from construction activity disturbing this soil, freezing, excessive drying, or soaking due to rain, <br /> groundwater seepage or other sources of water. Surface water run-off must be directed away from <br /> open excavations, to prevent water from wetting, accumulating or standing in open excavations. If <br /> this protection is not provided, exposed support soil in excavations can soften and loosen, thereby <br /> weakening this soil and making it unreliable to support foundations. All foundations must be <br /> properly steel-reinforced to minimize differential foundation settlement over localized areas of the <br /> foundation sub-grade with non-uniform material.characteristics. 4 <br /> _ FOUNDATION EMBEDMENT PROTECTION <br /> MINIMUM EMBEDMENT DEPTHS Bearing grades of all foundations subjected to freezing <br /> temperatures must be embedded beneath ground surfaces for frost penetration protection. <br /> Minimum embedment depths are specified in State of Minnesota building codes or local building <br /> codes. The greatest embedment depth of these codes should be used for protection. ' In general <br /> accordance with these codes, TABLE F lists recommended embedment depths for frost protection. <br /> FOUNDATION AND SUB-GRADE PROTECTION All built foundations subjected to freezing <br /> temperatures must be embedded according to TABLE F. This includes foundations in heated <br /> areas subjected to freezing temperatures before heating. Foundation support soil must be kept dry <br /> continuously and frost-free before embedment protection is provided. Accumulating or standing <br /> water must be prevented from wetting support soil before embedment 'protection is provided. <br /> Embedment protection must be provided to built foundations without delay. <br /> FROST HEAVING AND ADFREEZING PROTECTION All foundations subjected to freezing must <br /> be designed against detrimental effects from frost penetration. These include perimeter wall <br /> foundations in heated buildings and foundations in unheated buildings and structures. Frost <br /> penetration can cause frost heave and adfreezing. Frost penetration can occur if three conditions <br /> exist: freezing temperatures, frost-susceptible soil, capillary water "wicking" to the freezing zone. <br /> Frost-penetrated soil increases in volume and can heave the ground surface upward. Adfreezing <br /> occurs when soil freezes on foundation surfaces. Frost heaving induces upward acting shear <br /> _ stress along vertical foundation surfaces. This stress can potentially drag foundation surfaces <br /> upward. When this shear stress becomes greater than building loads, upward foundation heaving <br /> can potentially occur. If foundations are not properly designed to resist frost heaving and <br /> adfreezing forces, seasonal ground freezing can potentially distress buildings. Three methods <br /> described below may be considered in designing foundations to resist frost penetration. An <br /> — alternative method is using bond breakers to prevent soil from adfreezing to foundation surfaces. <br /> Allied Project 04049 g July 27, 2004 <br />