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• Iiudditstozi -Bn -Berry <br />Driven Steel Piles <br />For driven piles, it is anticipated that most of the axial pile capacity will be <br />developed in end bearing in the dense gravel soils. Therefore, concrete filled pipe piles <br />or H -piles are recommended. <br />Based upon the anticipated working loads and pile driving conditions, pipe piles <br />should be a minimum of 10% inch diameter. H -piles should be minimum HP 10X57. <br />The piles should penetrate the fill materials and soft clay soils and bear into the dense <br />gravel soils. The actual penetration of individual piles will be dependent upon driving <br />conditions and size of pile used; however, it is anticipated that the piles will reach refusal <br />within 2 to 10 feet of the top of the gravel layer. As indicated in the boring logs, the <br />gravel soils were encountered at a depth of 22.0 feet below the existing ground surface. <br />Therefore, pile lengths of up to approximately 32 feet may be possible. However, a <br />minimum pile length of 10.0 feet is recommended. <br />For ION -inch diameter, concrete filled pipe piles or HP IOX57 piles driven to <br />refusal, MET recommends an allowable geotechnical capacity of 40 tons. However, <br />higher capacities may be possible depending upon the results of pile load testing. In <br />general, a minimum 3/8 -inch wall thickness is recommended for pipe piles. However, '/- <br />inch wall thickness may be utilized provided the structural engineer and /or contractor can <br />demonstrate that the driving stresses will not damage the thinner walled piles. <br />The refusal criterion for driven piles is dependent upon the type and size of the <br />hammer. However, the refusal criteria should be established as the number of blows <br />required for the last few inches of penetration. For a hammer delivering 20,000 foot - <br />pounds of energy to a 10 inch pipe pile or HP 10X57 pile, we would expect refusal to <br />be at approximately 5 to 8 blows per inch to reach a capacity of 40 tons. However, the <br />contractor should coordinate with HBET to develop specific pile refusal criteria based <br />upon the specific pile /hammer combination. Due to the nature of the gravel soils, to <br />reduce the possibility of excessive tip deflection and tip damage, pile tip reinforcement is <br />recommended. <br />To eliminate reductions in capacity from group effects, the minimum center -to- <br />center spacing of piles should be 3 pile diameters. Group effects should be considered <br />for piles grouped less than 3 diameters apart. <br />With regard to the pile cap, the bottom of pile cap elevation should be a minimum <br />of 36- inches below the finished grade for frost protection. In addition, it is recommended <br />that a minimum of 1 foot of soil cover be maintained above the tops of the pile caps. <br />Screw PileslRelical Piers <br />Screw piles and helical piers consist of circular or square steel shafts with load <br />carrying helices attached to them. Some of these types of piles /piers are proprietary. In <br />• general, the precise type, size, and quantity of piles /piers should be established by the <br />contractor in conjunction with the structural engineer. However, HBET provides the <br />following design comments. <br />WA2008 ALL PRO)ECTSti00756 - lk4tr City Consultants W..0756 -0007 New EW200 - Geo'.00456 -OW4 R082410 doe. 8 <br />