SU0004097 - Laserfiche WebLink

Home Browse Search

KLEINFELDER i f 3 The above is a general summary of the soil and groundwater conditions encountered in the borings drilled at the site. More-detailed descriptions of the soils encountered in the borings are noted on the Logs of Borings, Appendix A, Plates A-4 through A-8. All soils have been classified according to the Unified Soil Classification System (USCS) and Log Key which are described on i Plate A-2 and A-3, respectively, of Appendix A. 3. Laboratory Testing Two unconfined compression tests were performed on large block samples (Photograph 1, Appendix A) obtained at depths between 40 and 50 feet below grade at the adjacent Grarlite Tracy Pit excavation on February 27, 1998. Samples were trimmed as best as possible and capped with hydrocal gypsum. The results of the Unconfined Compressive tests are 2,880 pounds per square foot (pso and 7,200 psf. Previously performed strength tests from remodeled, reclaimed soils I from the nearby Teichert Pit were used for strength values below. Lab tests were performed on selected samples obtained from the borings in order to evaluate the strength characteristics of the soils encountered. The tests performed consisted of Unconfined Compression, Direct Shear tests and Moisture Density Determinations. The results of these tests are noted at the corresponding sample locations, and the Direct Shear test results are presented on Plates A-10 and A-11 of Appendix A. I i 4. Slope Stability Analysis i The existing slopes at the Granite Tracy Pit confirm that the sand and gravel deposits are partially cemented_ Reference is made to photograph 2 on Plate A-12 which shows an approximate 75- foot high, near-vertical (112 :1) slope at the existing Granite Tracy Pit. This slope was approximately 120 feet high in the past, prior to placing reclaimed soils at the base of the slope. This slope has been in place for at least several years and has performed well, even during the past very-wet winters. Very. little erosion was observed, and teeth marks from excavation operations j were still present. These materials have more inherent cohesion than would normally be assumed, 1 considering grain size distribution only. The laboratory tests on block samples from this area justify relatively high shear strength parameters. } i i We have also back calculated strength parameters on the 120-foot high, %z:1 slope described above based on a static Factor of Safety of 1.1. These strength values are still less than the results obtained from our block samples. Using these strength values in our analysis increases the Factors of Safety reported in Table 2 by about 0.2. i i ) As in previous studies for other sand and gravel operations, we have relied on the performance of existing slopes or test excavations and on strength tests performed on relatively undisturbed samples to evaluate input values for our computer analyses. Lab strength tests have not been 20-1108-18/M i 88096 Page 3 of 7 Z) 1998 KleinPelrler Inc