4937 SEA BREEZE WAY 2017-01-13 - Laserfiche WebLink

• Geotechnical Engineering Evaluation Pepe Retaining Wall Everett, WashingYon NGA File No. 916915 April 27, 2015 Page l I We recommend that the wall be analyzed using a triangular earth pressure distribution equivalent to that exerted by a fltiid with a density of 50 pounds per cubic foot (pc� for yielding (active) condition, and 70 pcf for non-yielding (at-rest) condition. These recommended lateral earth pressures are (or a drained granular backfill and are based on the assumption of a horizontal �,ro�md s�u�face behind the wall for � distance of at least the subsurface height ofi the wall, and do not acco�mt for� surcharge loads. Additional lateral earth pressures should be considered for surcharge loads actin�; adjacei�t to the wall and within a distance equal to the subs�irface height of the wall. This would include the effects of surcharges such as traffiic loads, floor slab loads, slopcs, or other surface loads. We could consult with the structural engineer regarding additional loads on retaining walls d�iring final design, if necded. All wall backfill should be well compacted free-draining material as outlined in the Structural Fill subsection of this report. Care should be taken to prevent the buildup of excess (ateral soil pressures due to over-compaction of the wall backfill. This can be accomplished by placing wall backfill in 8-inch loose lifts and compacting the backfill with small, hand-operated compactors within a distance behind the wall equal to at least one-half tl�e height of the wall. The thickness of the loose lifts shouid be reduced to accommodate the lower compactive enerby of the hand-operated equipment. "I'he recominended level of compaction should still be maintained. The recommended lateral loads should be applied across the pile spacing above the excavation line. The lateral pressures co�ild be partially resisted by passive resistance acting on the below-grade portion of the piles. We recommend using 100 pcf p�ssive resistance action on two-pile diair�eter. The upper (ive feet of soil should be neglected. The measurements and conditions of the grouted portions of the wall beams should be evaluated by the structural engineer prior to calculating the passive resistance on the piles, otherwise, all lateral forces should be picked up by the tiebacks. A unifonr� surcharge of 8H should be applied to the wall design to account for seismic loading, where H is the exposed height of the wall. We should be retained to review final plans, monitor installation of the wall repairs, and evaluate tiebacks. Tiebacks General: Grouted tieback anchors are needed for the design for the repair or replacement of the wall. We recommend that one of the anchors be tested to a mini��im of 200 percent of the design loads to confiirm design values. We recoinmenci that meas�n-ements be made by the contractor in the field at the time of NELSON GEOTECHNICAL ASSOC/ATES, INC.