3A Public Hearing 2006 1204 - Laserfiche WebLink

Home

GEOTECNIA Project Number: 060805 2888 Darius Way, San Leandro October 27, 2006 Page C-l APPENDIX C Field Exoloration Our field exploration consisted of a geologic reconnaissance and a subsurface exploration program by means of drilling eight borings on October 12,2006. The borings were drilled and sampled at the approximate locations shown on Plate 2 using a track-mounted drill rig. The logs of the borings are displayed on Plates 3-10. Representative disturbed and relatively undisturbed samples of the earth materials were obtained at selected depth intervals with a 3- inch-diameter (outside diameter), modified California sampler; and a 2-inch-diameter, split- barrel, Standard Penetration Test (8PT) sampler. Penetration resistance blow counts were obtained by dropping a I40-pound hammer through a 30-inch free falL The sampler was driven 18 inches and the number of blows was recorded for each 6 inches of penetration or fraction thereof. These blow counts were then correlated to SPT blow counts. The blows per foot recorded on the Boring Logs represent the accumulated number of blows (correlated to SPT blow counts) that were required to drive the sampler the last 12 inches or fraction thereof. A correction factor of 0.66 was applied to the field blow counts for the modified California sampler. The shear strength of some of the cohesive soils was estimated in the field using a pocket penetrometer. The soil and bedrock classifications are shown on the Boring Logs and referenced on Plates 11 and 12. Laboratorv Testinl! Three Atterberg limits tests were performed on selected samples of the cohesive soils from some of the borings. The results of these tests are presented on the appropriate Boring Logs, and also on Plate 13. The two R-value tests performed yielded values of 52 and 49 for bulk samples R-I and R-2, respectively.