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• <br /> <br />requ've careful backfilling in order to develop [he required lateral capacities, considering the <br />steep site slopes. These criteria can be considered fmal for the downhill conveyor, but should <br />be finalized for other conveyors. <br />Building_Foundations: Most of the buildings will be steel-flame and metal skin buildings typical <br />of mining projects. They will be situated on pads formed by cut and fill gtading, and may be <br />on non-homogeneous foundation materials. Typically, these structures can utilize shallow <br />foundations with good performance. Spread footings, pads or trenched grade beams designed <br />for a preliminarily allowable bearing pressure of 4,000 psf can be considered. Where potential <br />heave or settlement is critical, or where wet processes in or near the stntcture could potentially <br />wet the subgtade, deep foundations (drilled piers) can be utilized with good performance <br />possibilities. Deep piers (L/D > 10) in native very stiff to hard clays can be preliminarily <br />designed for allowable end bearing pressures of 15,000 psf, with 10 percent allowable side shear <br />below a depth of 3 pier diameters. <br />General Drilled Pier Criteria: The design and construction criteria presented below should be <br />observed for a drilled pier foundation system. The consttvction details should be considered <br />when preparing the project documents. <br />(1) Drilled piers should be designed for the allowable end bearing pressure and skin friction <br />for the portion of the pier below a depth of 3 diameters. Uplift due to structural loadings <br />on the piers can be resisted by using 75 % of the allowable skin friction value plus an <br />allowance for pier weight. <br />(2) Drilled piers should also be designed for the highest ptacticable dead load pressure based <br />on the pier bottom end area. <br /> <br />21 <br />