3206 WAVE DR 2016-01-01 MF Import

GeoTest Services,Inc. June 3,2005 Baldv.in Residence,3206 Wave Drive,Everetl,WA Job No. 5233 block failures within ihe area of interest using the modifieG 9ishop's method of slices. Ttie potential effect ��t seismic loading on the global stability of the walls was analyzed assuming a peak horizontal ground acceleration of 0.258g for a seismic event with a probability of exceedance of 10 percent in a 50-year period (USGS 2002). The horizontal forces developed during earthquake shaking were represented by a "pseudo- static" seismic coefficienl, kh. The horizontal acceleration used in seismic stability analysis tor natural soil slopes is typicatly assumed to be one-half of the iree-field acceleration. Accordingly, the seismic cuefficient used in our stability analysis of the walls was 0.129g. The analyses indicated that the global stability meets or exceeds the minimum recommended factors of safety of 1.5 and 1.1 for static and seismic loading, respectively. Allan Block MSE Wall Mechanically Stabilized Earth (MSE) Ailan Block walls have been designed for construction using a block face with sui:abie onsite soils or import gravel backfill that is reinforced with geogrid where the wall exceeds 4 feet in height. The Allan Block units used in this design assume the reuse of the existing blocks already used to construct the previous walls. We understand Yhat they are a 3-degree block wilh typical dimensions of approximately 0.6 teet in height, 1.5 feet in length, 1.0 foot iri depth and a face angle of 3 degrees from verticai. Olher block sizes and shapes are available for use. We have designed the Allan Bloc,k wall for heights not to er.oeed 10 feet of exposed wall face. Walls in excess of 10 feet may not be stable based on the current design. The MSE walls were designed assuming a level backslope and no surcharge loading as described earlier in this report. I( a steeper backslope or a surcharge loading is anticipated, the design may need to be modifieti accordingly. The walls should be founded on a minimum 6 inch thick poured concrete or compacted crushed stone base and the base of the wall should be buried a minimum of one and one half blocks below the surrounding grade. The walis were designed with suKicient block and reinforced soil mass to resist forces and moments acting to slide and overtum the wall. Walis greater ihan four blocks high should be mechanically stabilized with geogrid consisting of Miragric' 5XT or approved equivalent, that is placed as depicted in the design cross- section for a posilive mechanical connection. A stable typical Allan Block MSE wall cross-section is prese�ted in Figure 4 attached with lhis report. The geogrid should extend from the back ot the Allan Block wall facing a distance equal l0 7.5 feet, as indicated in the design cross-section. Construction Recommendations Key elemenls in ihe construction of a stable wall include lhe following: • Bolh wail sections, (upper and lower wails), as described in this report must be founded on a suilably firm and unyielding soils. Based on our site explorations the undisturbed, medium dense to dens= native soil, or a suitably placed and compacied siructural fill placed directly over undisturbed native soil, sho�ld provide adequate bearing capacity for the wall foundations. Page 4 of 7 ��