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1997-07-28_GENERAL DOCUMENTS - M1973021 (9)
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1997-07-28_GENERAL DOCUMENTS - M1973021 (9)
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Last modified
2/28/2021 9:13:20 AM
Creation date
10/14/2011 7:16:00 AM
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Template:
DRMS Permit Index
Permit No
M1973021
IBM Index Class Name
GENERAL DOCUMENTS
Doc Date
7/28/1997
Doc Name
1996 Annual Report- Geotechnical Addendum.
From
CAMAS
To
DMG
Permit Index Doc Type
General Correspondence
Media Type
D
Archive
No
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DRMS Re-OCR
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Signifies Re-OCR Process Performed
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' Of particular note is the fact that the slide area occurred just south of <br /> a swarm of near vertical, ENE-WSW trending mafic dikes that are <br /> 1 believed to have been intruded along preexisting faults. The <br /> significance is that these dikes represent the northern limits of a <br /> faulted zone characterized by numerous such features on a scale from <br /> several inches to several feet. It is speculated that the faulted zone <br /> extends south at least to the southern end of the Central Quarry, and <br /> perhaps through Unnamed Drainage No. 1 which trends roughly <br /> ' parallel to the fault/dike features. The slide, then, occurred at the <br /> margin of a structurally controlled zone of poorer quality rock than <br /> exists farther north in the East Highwall. <br /> The slide surface itself was visible as a two to six inch thick red clay <br /> gouge seam subparallel to foliation jointing in the face of the fourth <br /> highwall. This surface represents an older shear feature developed in <br /> the rock mass along foliation during folding and faulting. The <br /> relatively shallow (20 to 25 degree) dip of the feature allowed it to <br /> ' daylight in the highwall face and the rock mass above it mobilized on <br /> this weak layer. The old shear surface on which the slide occurred <br /> appeared to have a southwesterly dip and steepened and splayed near <br /> ' the head scarp of the slide based on geometric analysis of the <br /> mapping, boring and survey data. It is not certain whether the <br /> geometry represents one nonplanar feature or a compound failure <br /> ' surface formed by the intersection of the two planar shear features, <br /> possibly of different ages. <br /> 3. Rock Core Borings <br /> The five core borings drilled to investigate the slide area, including <br /> ' one boring outside the slide area to investigate rock deeper in the <br /> planned East Highwall, encountered four general rock types: granitic <br /> gneiss, schist, hornfels, and granite porphyry. The granitic gneiss <br /> includes a range of rock types including quartz-diorite gneiss, quartz- <br /> 1 biotite-diorite gneiss, and quartz-mica gneiss. Granitic gneiss was the <br /> major rock type with lesser granite porphyry and hornfels <br /> representing migmatic and mafic intrusive bodies, respectively. <br /> ' Schist was encountered only as a minor rock type in the borings. <br /> Core recovery was excellent and averaged from 97 to 100 percent for <br /> ' each boring. Rock Quality Designation(RQD) varied and, as one <br /> would expect, generally improved with depth. RQD in the borings <br /> ranged from zero to 100 percent by core run, and averaged from <br /> approximately 49 to 78 percent for each boring in aggregate. The <br /> inclined boring (13104) through the slide plane had the poorest RQD <br /> and quality rock and the boring from the quarry floor (13105) had the <br /> ' highest RQD and quality rock as one would expect. Below the 10 to <br /> 20 ft blast halo created by excavating to the quarry floor, rock quality <br /> 11 G:\PROJECTS\20200\002\96ANNRfrr.WPD <br /> •� a <br />
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