1018 14TH ST 2023-02-09 - Laserfiche WebLink

Port of Everett SHANNON 6WILSON,INC. Attn: Mr. Erik Gerking April 16,2013 Page 2 of 5 GROUND SETTLEMENT Using IBC ground motion design criteria,we estimated the ground settlement that could occur due to liquefaction at the site. The settlement was estimated using empirical methods and laboratory index test results from the borings performed for the project. The results of our analyses indicated that 2 to 8 inches of ground settlement could occur during the IBC design ground motion. This settlement will result in downward forces on the sheet pile bulkhead, structure foundations, and utilities. Depending on the bearing depth of foundations, this could also result in settlement of the bulkhead and structures. The settlement would not be uniform and could cause damage to utilities located behind the bulkhead. LATERAL SPREADING Lateral spreading occurs when a sloped site or a site near a free-face (such as the bulkhead) moves toward the free face as underlying soils liquefy. This phenomenon has been experienced at numerous waterfront facilities during a seismic event. We used a published paper based on empirical methods to evaluate the potential lateral displacement that could occur(Youd et al., 2002) during the IBC design ground motion. Youd et al. (2002) uses multiple empirical case histories and developed a relationship for lateral movement as related to the earthquake characteristics, thickness of liquefied soil, composition of liquefied soil, and configuration of the sloping ground. Using the procedure presented in the Youd et al. (2002), for the conditions at the project site, we estimate lateral displacements of about 2 to 3 inches at approximately 100 feet from the wall face during the IBC design ground motion. Although this method is not recommended to evaluate locations closer to the wall, lateral displacements will progressively increase at locations closer to the wall (potentially as large as 2 to 3 feet at the wall face). Two other published methods (Gazetas et al., 1990 and McCullough and Dickenson, 1998) present lateral spreading estimates for anchored sheet pile walls. However,these methods assume that the anchor system provides resistance during a seismic event. For the East Marina site, the deadman anchors are founded within the soil layers that are anticipated to liquefy during the design IBC ground motion,thereby resulting in a significant loss of resistance. Therefore the methods outlined in Gazetas et al. and McCullough and Dickenson would likely underestimate the lateral ground displacement. These methods are summarized as follows: