1997-07-28_GENERAL DOCUMENTS - M1973021 (9)

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Atterberg Limits tests were run to test the variability of the red clay gouge encountered at different intervals in the various borings and as another, indirect measurement of likely strength properties of the material. The results indicate variability of the material from a nonplastic silt (ML) to a relatively high plasticity lean clay (CL). One of the five samples was nonplastic, one was a low plasticity silt(ML), and three were lean clays (CL) with liquid limits ranging from 35 to 47 percent and plasticity indices all at about 21 percent. Based on ' standard correlations, these results indicate a drained value for(D of approximately 30 degrees. 5. Inclinometer A temporary inclinometer consisting of 54.7 ft of 1-1/4 in. PVC pipe ' inserted in inclined Boring B104 was used to measure possible subsurface movement prior to constructing the repair of the slide. The casing had a 2 ft stickup and was, therefore installed to 52.7 ft, ' approximately 10 ft below the deepest clay seam encountered in the core for this boring. ' Boring B 104 was completed on 12 March 1996 and the casing installed within the next several days. Approximately one month after the installation, probing the casing with a weighted tape revealed tight (distorted) spots at approximate depths of 25 ft, 38 ft, and 45 ft, roughly coinciding with the depths of the three clay shears encountered during drilling confirming continued movement along ' these features. Several weeks later, the casing was blocked at the deeper spot and the inclinometer was destroyed by repair activities soon thereafter. ' 6. Survey Twenty pre-repair surface survey monitor points (1001 through 1020) ' were installed as shown on the figure in Appendix D to monitor slope movements and help analyze the failure mechanism/geometry. Displacement versus time plots for these points included in Appendix ' D illustrate from zero to approximately 1.6 ft of total displacement of the points from their installation in late January 1996 through their destruction during repair activities in late March/early April 1996. The displacements measured include active points within the slide mass as well as points outside the obvious slide area to confirm stability behind the visible scarps that developed. As important as the displacement amounts are the displacement vectors, shown in the figure at the back of Appendix D. These data, ' combined with the mapping and drilling data, confirm west-southwest movement of the slide mass along the slide plane. ' 13 G:\PROJECTS\20200\002\96ANNRPr.WPD 'o