PERMFILE108040

• Permit No: C1981019
• IBM Index Class Name: Permit File
• Doc Date: 12/11/2001
• Doc Name: Sections 10 - 16
• Section_Exhibit Name: Exhibit 12 Experimental Part 3
• Media Type: D
• Archive: No

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~ Doc Date:12/11/2001
S TOTE OF ~pLORADO HiC HAHp n. ~ .ntM Gnvmnm
DEPARTMENT OF NATURAL RESOURC ES
Harris D. Sherman, Executive D~reulo:
KILNED .I,~ND REi:LAIIATION
723 Centennial Building, 1313 Sherman Street
Denver, Colorado 80203 Tel. [phone]
Hamlet J. Barry, III,
D irector
February 6, 1480
TO: Fred Banta f
Dean Massey -~%/~~~t \
FROM: Jim Pendleton '/~ / {
RE: Comment on t S1~~Stab=litg Analusis of Colowyo Coal Company's
Streeter Carn ~FiZL
In response to your request, I have completed a review of C. T- L.
Thomason's consulting report prepared under contract for the Office of
Surface Mining. I have several substantial concerns regarding that
1. The consultant observed that the accuracy of any mathematical
analysis of a fill's slope stability is influenced by the accuracy
of the various aarameters utilized in preparing the analysis. Numerous
experts have investigated the relationship between soil strength. parameters
and *_he variation of calculated factors of 5afetu, Their efforts have
demonstrated that inaccuracy of shear strength parameters may have a
far greater influence on the accuracy of a slopestability analysis than
the method of analysis employed. (Singh, 1970) For this reason it is
considered prudent to investicate the variation in calculated factors
of safety introduced by variation of the strength data.
The consultant's analysis discusses the assumptions made and their
singular inilvence upon the calculated Factor of safety. Each parameter,
inciudinc the angle of internal friction of the spoil material the in-olace
density of the spoil, the slope configuration, the angle of internal
friction of the colluvium underlying the fill, and the level of saturation
of the fi_'1 is analyzed se Para*_ely. The report includes a discussion of
the effect of variations of each input parameter. The teport~neolects,
however, to analyze the cumulative influence of simultaneous variation of
the input factors. ds the report observes, except for the ZeveZ of
fill saturation, the variation due to the separate parameter's variation
is relatively minor. However, comparison of a feco of the factors of
. safety results presented in Table I discerns the following cumulative
var.ance:
(cont'd)