2721 WETMORE AVE MARQUEE APARTMENTS Geotech Report 2023-06-22

Subsurface Exploration, Geologic Hazard,and 2721 Wetmore Preliminary Geotechnical Engineering Report Everett,Washington Preliminary Design Recommendations tieback easement from the City of Everett. All tiebacks located within 20 feet of the ground surface should be de-stressed subsequent to wall and floor construction. We recommend for this site that each anchor be sized for a design or allowable load of not more than 50 percent of the ultimate load available through the anchor (as indicated by 200-percent verification tests). The test anchors should be capable of holding the ultimate load without excessive yield or creep so that a factor of safety of at least 2.0 is available for production anchors should further stressing occur. The rods or cables should transmit the anchor load to the soldier pile in such a manner to avoid eccentric loading. A series of anchor tests should be performed to verify the design and ultimate skin friction or adhesion of the tieback anchors. Because of the variation in the soil types and their densities, we recommend that AESI monitor the anchor test program. A common anchor testing program would consist of at least two 200-percent verification tests per side of the excavation plus proof-loading every production anchor to 130 percent of the design load. Verification test - anchors are usually loaded in 25-percent increments that are held for 5 minutes up to the final load of 200-percent design load. The 200-percent load is commonly held for an hour and creep measured. The other component of the anchor test program for the project would be proof-loading each of the production anchors to 130 percent of the design load. Each anchor should withstand this load for at least 5 minutes. The anchor should then be locked off at the design load. Subsequent to locking off the tiebacks at the design load, all of the tieback holes should be backfilled to prevent possible collapse of the holes and any related consequences. Typically, sand is used as backfill material; however, most non-cohesive mixtures are suitable (subject to approval by the geotechnical engineer) provided there is no bonding to the tierods. 13.4 Vertical and Horizontal Dynamic Spring Constants Vertical and horizontal spring constants for the very stiff to hard/dense to very dense natural sediments were established using empirical charts. We have used the concept of elastic subgrade modulus as follows: kn =S Where: kn =the spring constant for the selected mode of oscillation Sn =the dynamic subgrade modulus for the mode of oscillation A= the area of wall or foundation under evaluation May 28,2019 ASSOCIATED EARTH SCIENCES,INC. FSM/Id-190168E001-2-Projects\20190168\KOWP Page 19