10200 25TH AVE SE Geotech Report 2018-01-02 MF Import

(. . � Propased Modernization and Addifions to Subsurface Explormion, Geologic Hazardr, Eisenhower Middle School and Geotechnica!Engineering Reporr E�<�reu, IYashinRton Design Recommendations otlierwise suspect. The need for addition�i load testing beyond the 2-pi;e minimum would be determined by tiie geotechnical engineer or engineering geologist at the time of construction. Pipe piles subjected to loa� testing shoulcl be loaded to 200 percent of the allowable pile capacity. Testing should begin with a set load equal to 10 percent of the m��ximum test load. The piles should then be loaded from the set load to the maximum test load in iacrements of 25 percent, with each load held for 2.5 minutes. Afrer holding the maximum load f'or 20 minutes, Ihe load should be reduced ro the initial set load, held for 2.5 minutes, and the permanent deflection recorded. The recommended acceptance crirerion for the test is a permanent deflection of 0.25 inch or less with no significan[ creep at the maximum load. 10.3 Alternate Foundation Support Usine GeopiersT" As an alternative ro removing and replacing the existing fili beneath the new buildings where existing fill is more than a few feet thick, short aggregate piers (GeopiersT") or rock-filled trenches could be used for foundation support. GeopiersT" are a patented soil reinforcement system delivered through a turnkey design-build process. The GeopierT"' system consists of a drilled cavity filled with well-graded or open- graded stone in lifrs which are rammed using a beveled tamper. The beveled .tamper and ramming action forces the stone la[erally into shaft sidewalls reinforcing and increusing the lateral pressure in the matrix soil around the pier ;.nd increasing the GeopierT" stiffness. GeopiersT" are a proprietary system and are designed by the contractor who installs them. The contractor will determine the depth and diameter of the GeopierT" holes, and the appropriate spacing. Conventional shallow foundations are then constructed above the subgrade after GeopiersT" hc,ve been installed. The advantage of the GeopierT" system is that conventional foundations can be constructed above the GeopiersT" without the grade beams or pile caps associated with conventional deep foundation systems. �1s discussed under Site Preparatron, where GeopiersT" are used, the building pad should be eecavared into the existing fill soils to provide a surface at least 2 feet lower than the building pad subgrade elevation. This will allow placement of a 2-foot-thick compacted fill blanket on which to support the building slab. The building pad excavation should be proof-rolled with a loaded dump truck or otlier suitable equipment. Any soft or yieiding areas should be excavated to expose imyielding soils and the everexcavations backfilled with structural fill. GeopiersT" can then be installed. When GeopierT" installation is compiete, the building pad can be cleared of drill cuttings and brought to grade with structural fill. If work wiil proceed during the winter, the structural fill placed to finish the building pad should consist of select till [hat contains less than 5 percent passine the No. 200 sieve based on tha[ fraction passing the No. �3 sieve and at least 25 percent retained on the No. 4 sieve. Spread footings may then be used for building support when placed and centered over properly constructed GeopiersT" that bear on suitable till. Footines wfiich bear on approved GeopiersT" may be desi;ned for an Jmuurrv 23. ZOOd ASSOCI.ITED F.IhTH SCIENCES, lNC. � .t?dd-REO.i7J3aJ-Pru�rrrsCGli7JyiXE�tYP-117K PaP�,e 16 ' �