2305 100TH ST SE 2018-01-02 MF Import

I W-4940-01 Aun: Mr.Tony Vivolo, P.G. � Junc 1G, 198R c�a "0 Page 4 � �a c r. i y � N H .t r� f1 O C� O � N H o r�. � At-re�t oanh pressures due to the soil c-� both side: of the ringw all are shown on Figure 10. If I the soil along the outside of the wall uill not be remova�during the life of the swcturc, such � � ns for maintenan�e o(pipes,the ai mst pressure along the c,utsidc of the wall can be used to � M , teduce the pressures un the inside of tne wall. � H � Two values for:.he at-rest earth pressure ccefficient,Ko,are given on Figure 10. I(the y � rin�+�all is conswcted such tnat its faas are poured against a very dense venical, undisturtxd, � o y glacial ull surface, a Ko value of Q4 can be used to calculate the lateral pressures on the wall. � � � If the ringwall is forraed on both sides and then bacldilled with compacted smicmral fill, a Ko � value of 0.5 shnald Ix uscd. N The passive nressure illustrated along the outside of the u all on Figure 10 is not to be used in thc hoop tension design of the µa1L The passive pressure shown should be used to resist horizonwl forces during seismic or wind loading. The passive tanh pressure ccxificient, Kp= 3.6, gi�'en o�i Figure ]0, is based on the assumption that the outside of the wall µ�ill be bacY.t-illed w�th swctural fill or drainage materia] (see folloµ�ing secrion). ' I�in�nr an�1 f3ackfill� .e I Ground wster seepage was observecl in the test pit explorarions m�de at the sitt on April I 1, 198R. This watcr appeared to by perched aior the very dense glacial till. We recommend that a � �� a dt emoveathis u ier.�aTha groundhaz u d the re�ervoir sholuld tx:sloped�go promotelsurface� � „ drainage away (rom ihe tank. � �� Backfill on both sides of ihe ringwall, including the drainage sand and gravel,should bc a�� Strucwr:� Fill,compacted to at least 95 perceN of its 1�1odified Procror maximum dry densit�•. Native soil th�t is essentially free of roots and organic material could be used as Svuctural Fill provided that its moisture content at the time of compactian is ncar the optimum. Soil generally� '� encountered below a depth of about 2 feet in the iest pits could be used as Swctural Fill; ��I hoµ�e��cr,dn�ing woul� oe necessary to :ower i�s moisrore content(appmximately 12 to 29 percent in TP-1 through lP•a)to nearer optimum for compacuon. H'e estimate the optimum moismre conient of these native soils�o be between R and 12 percent. Grain size distribuuon� � and compaction tat results for the native soils cncoumere�f in the test pits below a depth of= �,� feet are shoµn in Figures 7, 8 and 9. lf sufficient native matenal is not a��ailable for use as Stn:cwral Pill, u'ell-graded sand and , � gravel should be imponed. The imported sand and gra��el should ha��e a maximum paniclr size �� of 3 inchea, should be free of orFanics, and its moisture content should not be above the optimurn for compaction. Fer fill placed in non-structural areas, such as for landscaping, the compacuon requiremen[ iI��) may be re�±uced to 42 percent. � ]f backfilling is auempted during wet, rainy weaihcr,the native soil w�ll not be usable as Strucr�ral Fill, and die fines contem (percentage of minus 3/4-inch material passing the No. SHANNUN 6 V`'ILSON INC