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� � <br /> �° � � �� �� � �� Stork Twin City Testing Corporation <br /> Materials Technology <br /> PRECAUTIONS FOR EXCAVATING AND REFILLING DURING COLD WEATHER <br /> The winter season in this area presents specific problems for foundation construction. <br /> Soils that are allowed to freeze undergo a moisture volume expansion, resulting in loss of <br /> density. These frost-expanded soils will consolidate upon thawing, causing settlement of <br /> any structure supported on them. To prevent this settlement, frost should not be allowed <br /> to penetrate into the soils below any proposed structure. <br /> Ideally, winter excavation should be limited to areas small enough to be refilled to grade <br /> higher than footing grade on the same day. Typicaliy, these areas should be filled to floor <br /> grade. Trenching back down to unfrozen soils for foundation construction can then be <br /> performed just prior to footing placement. The excavated trenches should be protected <br /> from freezing by means of insulating or heating during foundation construction. Backfilling <br /> of the foundation trenches should be performed immediately after the below-grade <br /> foundation construction is finished. In addition, any interior footings or footings designed <br /> without frost protection should be extended below frost depth, unless adequate <br /> precautions are taken to prevent frost intrusion until the building can be enclosed and <br /> heated. <br /> In many cases, final grade cannot be attained in one day's time, even though small areas <br /> are worked. In the event final grade cannot be attained in one day's time, frost can be <br /> expected to develop overnight. Leaving a layer of loose soil on top of the compacted <br /> material overnight can minimize the depth of frost penetration. However, any frost that <br /> forms in this loose layer, or snow that accumulates, should be completely removed from <br /> the fill area prior to compaction and additional soil placement. Frozen soils or soils <br /> containing frozen material or snow should never be used as fill material. <br /> After the structure has been enclosed, all floor slab areas should be subjected to ample <br /> periods of heating to allow thawing of the soil system. Alternatively, the frozen soil can be <br /> completely removed and be replaced with an engineered fill. The floor slab areas should <br /> be checked at random and representative locations for remnant areas of frost and density <br /> tests should be performed to document fill compaction to slab placement. <br /> Due to the potential problems associated with fill placement during cold weather, a full- <br /> time, on-site soils technician should monitor any filling operations. Full-time monitoring <br /> aids in detecting areas of frozen material, or potential problems with frozen material within <br /> the fill, so the appropriate measures can be taken. The choice of fill material is particularly <br /> important during cold weather, since clean granular fill material can be placed and <br /> compacted more efficiently than silty and clayey soils. In addition, greater magnitudes of <br /> heaving can be expected with freezing of the more frost susceptible silts and clays. <br /> If more specific frost information or cold weather data concerning other construction <br /> materials is required, please contact us. <br /> Stork Twin City Testing Corporation is an operating united of Stork Materials Technology B.V., <br /> ewu,c�ev eest�nq Amsterdam,The Netherlands,which is a member of the Stork group <br /> ����b� <br />