Laserfiche WebLink
LA <br />C� <br />C� <br />TECHNICAL MEMORANDUM <br />Page 7 <br />June 3, 1992 <br />SAC31583.AC.ZZ <br />encountered in Boring BH -2 at an approximate depth of 19 feet. This layer <br />was not encountered in other borings and is believed to be discontinuous. <br />A 5- to 10 -foot layer of very stiff yellowish -brown lean clay. This material is <br />moist, with moisture contents between the plastic and liquid limit. A <br />consolidation- test indicates that this material is consolidated to approximately <br />three times the effective overburden stress (OCR of 3). The overconsolidation <br />ratio (OCR) is the ratio of the maximum effective stress the soil has•been <br />subjected to in the past (preconsolidation.;pressure) to the existing effective <br />stress in the soil. A UU_ triaxial compression test at an approximate depth of <br />34 feet in Boring BH -1 indicated a -shear strength .of•26psf. <br />A 30- to 36 -foot layer of very dense° dy aterial • 'IhisixmaterW,,ra aged:xff4= <br />silty and clayey sand to poorly graded and well graded sand. Within this layer, <br />zones of very stiff lean clay (ULT •,shear. st ng1h ,,of...3,3102 _,psf) were encountered <br />in Borings BH -1 and BH -2 at approximate depths of 50 feet and 64 feet. This <br />material has an approximate OCRof 1.4. <br />A 30 -foot layer of material consisting of 'Very stiff tO d. silt d...1 ,clay. <br />This material is moist to wet, with moisture contents between the plastic and <br />liquid limit. This material has an apprro)dmate OCR ..of_L7 (BorinBH-1, <br />approximate depth 78 feet). <br />® Very dense poorly graded sand was observed near the bottom of Boring BH -l. <br />starting approximately at a depth ,of 4110 feet. Sand: was also observed in <br />Emcon's Boring No. 17 to the maximum depth drilled of 178 feet (EMCON, <br />1972). <br />Soil type and properties, of the matenals.,rmcoauntered in theReotechnical explorations <br />performed by EMCON and Insitu-Tech were generally consistent with the conditions <br />described above. In EMCON's subsurface,explora=tion,.,a.-M.odified-California Sampler (with <br />a 140 -pound hammer with a 30 -inch drop) was used to collect samples. Blow -counts <br />recorded with the Modified California Sampler -typically -ranged from 20 to 60 blows .per <br />foot. Unconfined compression strength tests performed on silty clay samples between depths <br />of 3 to 10 feet ranged from 1,310 psf to 5,100 psf (3,000 psf average shear strength) <br />(EMCON, 1972). The shear strength is defined as one half of the deviator stress at failure. <br />Shear strength based on Insitu-Tech's CPT data (performed to a maximum depth of 50 feet) <br />