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Subsr�rfacc Exp(orario��, Geologic Ha<nrd, and <br /> Everetr Schoo!Drstrict Mnintermnce Facifity Preliminary GeorecG�iica!Erigineering Repon <br /> Everert, Wasl�in,�rai DesiRn Recommendarinac <br /> l <br /> The latcral pressures presented above are based on the conditions of' a uniform, horizontal <br /> backfill consisting of imported sand and gravel compacted to 90 percent of ASTM:D 1557 <br /> within 3 feet horizontally of the wall. A higher degree of compaction is not recommended this <br /> close to the wall, as this will increase the pressure acting on the wall. Lower compaction <br /> amounts may result in setdement of structures above the walis. Beyond 3 fect from the back of <br /> the wall, the structural fill should be compacted to 95 percent of AS1'i�i:D 1557. The <br /> compaction Icvels are critical and should be tested during placement. Surchargcs from <br /> adjacent footings, heavy construction equipment, or sloping ground mu;t be addcd to the above <br /> valucs. Footing drains should be provided for all retaining walis as discussed mider the section <br /> on Drai�tnge Consideratio�is. <br /> [t is imperative th�t proper drainage be provided so [hat hydrostatic prrssures do not dcvelop <br /> against the wall. 'Chis would involve installation of a minimum 1-fout-wide imponcd, washed <br /> gravel blankct drain, a blira-Drnin 6000 drainage mat, or equivalent ti�r the full wall height <br /> (excluding thc upper I fooq. <br /> 11.1 Passive Resistance and Friction Factore <br /> Retaining wall footings cast direcUy against new struca�r�; fill or un�isturhed glaciolacustrine <br /> soils in a trench may he designed for passive resistance against lateral translation using an <br /> � equivalent Iluid cyual to 2i0 pcf. The passive equivalent tluid pressure diagram begins at the <br /> top o( thc louting; ho�vever, total lateral resistance should be summeJ only over die depth of <br /> the actual key (truncatcd triangular diagram). If footings are placeJ on grade and then <br /> backfilled, the top uF the cumpacted backfill must be horizontal and ex[enJ outward from the <br /> footing Cor a minimum lateral distance equal ro three times the height of thc backfill, before <br /> tapering do�vn to grn�e. With backfill placed as discussed, footings may also be designed tbr <br /> passive resistance against lateral translation using an equivalent fluid equal to 250 pcf and the <br /> truncated pressurc �iagram discussed above. The passive resistance valuc includes a factor of <br /> safety equal to 3 in order to reduce Q�e amount of movement necessary to generate passive <br /> resistance. The friction coefficient for footings cast direcdy on these soils may be taken as <br /> 0.3. This value includes a safery factor of at least 1.5. <br /> 12.0 FLOOR SUPPOR'1' <br /> Slab-on-grade tloors m.�y be constructed on the glaciolacustrine deposit or on an overexcavated <br /> 3-Coot minimum tl�ickness of structural fill with setdements similar to those mentioned in <br /> Sectio�e 10./ above. In order to limit moisture intrusion throagh floor slabs, the slabs should be <br /> constructed atop a capillary break material and a vapor barrier. 1'he capillary break material <br /> should consist of a minimum thickness of 4 inches of washed rock, pea eravel, or other low <br /> fines content Qess than 5 percent passing the No. 200 sieve) coarse aggregare, with a 6-mil or <br /> � <br /> h�� `� ��� dSSOClATED F.IRTI/SCIENCES, lNC. <br /> JDC/Qo-AEOIOSIAI-D b�y1JmJ�0/-{V:� Page 12 <br /> ly <br />