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• Testing). The USCS classification of the material that constituted the body of the failure in the <br />hillside and is evident in the face of the head-scarp is CL (low plasticity clay with some sand). <br />The black materia[ at the tce was also CL (low plasticity clay with some sand). <br />• <br />The soil samples were tested for USCS classification, Atterberg Limits, grain size <br />distribution, specific gravity, and triaxial sheaz strength. Two samples were also tested for <br />delivered moisture content. The results of all the soil testing are included in Attachment 2. Since <br />the properties of the CL material in the hillside is different than the black clay material at the base <br />of the slide both materials were subjected to triaxial testing to determine the soil strengths (see <br />Table 1 & 2). As shown on the Tables 1 and 2, effective strength parameters for the hillside clay <br />material are intemal friction angle (~') of 34.6° with cohesion of 57.6 psf. The total strength <br />parameters of the hillside clay are ~ of 12.0° and cohesion of 187.2 psf. The value of wet unit <br />weight selected for the existing condition of the hillside clay was chosen to approximate the <br />properties measured in the field and is 114.2 pcf. The black shale clay encountered at the toe of <br />the slide has an effective intemal angle of friction ~' of 26.4° and a total ~ of 15.3°. The effective <br />cohesion and total cohesion were 115.2 and 144 psf, respectively. These values were utilized to <br />model the stability of the hillside. <br />.~s~ ~ ~-EI~EC'I'Iy~ Tt~ItFll')~ _OF'' ILS` -;ri ~ _', <br />- <br />w . <br /> <br />~ w <br />RI~A4 <br />ALE ~F <br /> <br />COHE$~LTN .. <br /> <br />~ x ~~~ ~ ; J <br /> <br />''USCS <br />' ~ fx z= <br /> <br />S~A'~A ' <br />f <br />~' SA117PL6 ~ <br />' <br />i ' ~' . i <br />~ <br />q ~_, =I <br />1~,7 <br />YOI <br />i "r _ <br />;,-T S <br />- ~ta~silreap~ 1'To Ing <br /> <br />... ~.. .. .. <br />.. n .. <br />_ <br />:...-. <br />.' ~ .._ .._ ~~.- <br />.. _ . <br />Hillside Clay 34.G° 57.6 psf 33 - 17 CL 73 <br />Shale Clay (a[ Toe) 26.4° 115.2 psf 49-32 CL 99 <br />;, TABS)?, ~ - <br />t T[y7'AI,;tTR6N~'1•HP86FFtRTI):S.QFSOCtS';- <br />,. ~ .L~~F~~ l~ ,~ ..<~ s .- y <br />' ~'' <br />~. PA~tTICLE <br />" <br />SALYB?Lf ~ AN~L'E OF COHfrSION F'RBERG <br />" ''AT'4 <br />ITS _ USC$- <br />° SIZE DATA>> <br /> FRI~'L'IQN <br />( <br />u <br />Pn - Class~Gcatiou (4fo P~Br: <br /> tr <br />- .: <br /> C „e No, 200): <br />Hillside Clay 12.0° 187.2 psf 33 - 17 CL 73 <br />Shale Clay (a[ Toe) 15.3° 144 psF 49-32 CL 99 <br />3. Slope Stability Analysis <br />The slope stability for the Pond l2 Slide was analyzed with the two-dimensional slope <br />stability program SLOPFJW ®(Version 2.41). The SLOPFJW model utilizes the Morgenstern <br />and Price Method to determine the factor of safety (FOS) for a circular failure surface that is <br />found during a seazch routine (or defined) for the critical surface. To confirm the soil properties <br />retrieved form the laboratory testing the pre-slide slope conditions were modeled to confirm that <br />the slope would have failed given the pre-slide topography. To analyze the lower portion of the <br />• slope, which experienced the slide, total stress analyses were performed. The total stress analysis <br />