5209 GLENWOOD AVE 2017-04-07 - Laserfiche WebLink

Revised Redi-Rock Retaining Wall Design Western Geotechnical Consultants,Inc, 52XX Glenwood Ave.Property $1 14 91 2 Everett,WA April 17,2015 There is a segment, of wall that will be 9 to 15 blocks high(see topographic site plan, Appendix A.). For this taller segment of wall we designed an MSE wall with a stronger geogrid for the lower portion of the wall. .An MSE wall typical cross-section is included in Appendix A,and we have also included a Redi-R.ock Gravity Wall typical cross-section in Appendix A. Computer generated design wall sections are included in Appendix D to this report along with the backup calculations. For MSE walls, the Redi-Rock blocks have nominal dimensions of 18 inches high by 28 inches deep by 46 inches long, and each unit weighs about 1700 pounds. The Redi-Rock wall is to be founded on a minimum 6" thick poured concrete or crushed stone base. The MSE wall was designed for a maximum exposed height of 23 feet,with a minimum 1-fool burial of the bottom block below the finished ground surface at the base of the wall. The gravel base leveling course should be placed on unweathered glacial till. Redi-rocks are designed with a face batter of 4 • degrees. The design requires that the geogrid properties meet or exceed the strength and durability of Contrac 601) or Huesker, Inc. Fortrac 35 for the MSE wall heights up to 15 feet and Contrac 80()or Fortrac 55 for the lower portion of the wall where the wall exceeds 9 blocks, as indicated on the wall design figures (computer printouts) in Appendix D. Design calculations for the wall are also contained in Appendix D to this report. Note that TenCate Geosynthetics, Miragrid.3XT may be used in place of the Fortrac 35 and Miragrid 5XT may be used in place of Fortrac 55. Note that the bottom geogrid may be reduced to 0.4H,the second geogrid may be reduced to 0.5H and the remaining geogrid=0.611 except the upper geogrids which are longer as specified in Appendix C. The Redi-Rock blocks, together with the MSE,provide sufficient mass to resist forces and moments acting to slide and overturn the wall for the static design loading. However, the analyses using the design earthquake loading (20% of gravity)show a low safety factor for the top block(s) resulting from such a strong earthquake. Consequently, there could be some movement of the top blocks during a very strong earthquake. The length of the uppermost geogrid(s)was increased because of the earthquake loading. In-fill Soil Requirements The wall is designed to retain forces associated with the backfill with soil strength parameters appropriate for specified import fill. Select import is therefore required within the geogrid reinforced infill zone for wall stability. In general,the suitability of a soil for use as compacted structural fill depends on the gradation and moisture content of the soil when it is placed. As the quantity of fines (that portion finer than the No. 200 sieve) increases,the soils become increasingly sensitive to small changes in moisture content and adequate compaction becomes more difficult to achieve. Soils containing more than about 5% fines cannot be consistently compacted to a dense, non-yielding condition when the water content is much greater than optimum. Optimum moisture content is the moisture content