ML19209C522

Responds to NRC 781227 Request for Assistance in Evaluating Rock Fill Characteristics for Main Dam.Review of Test Fill Rept & Site Visit Indicates That well-graded Rock Fill Can Be Achieved Utilizing Proposed Placement Procedure

ML19209C522
Person / Time
Site:	Harris
Issue date:	09/05/1979
From:	Mccormick W ARMY, DEPT. OF, CORPS OF ENGINEERS
To:	Knight J Office of Nuclear Reactor Regulation
References
NUDOCS 7910160062
Download: ML19209C522 (2)

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T DEPARTMENT OF THE ARMY

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[7d, South Atlante- Division. Corps.ol Enginetas 510 Title Building, 30 Pryor :treet. S.W.

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Atlanta, Georgia 30303

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SkDEN-F 5 September 1979 i i 4

5&. James P. Knight Assistant Director for Engineering Division of Systems Safety l Office of Nuclear Reactor Regulation

. U. S. Nuclear Regulatory Commission Washington, D. C. 20555 L

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Dear Mr. Knight:

l Reference is made to the request in the Nuclear Regulatory Commission I letter dated 27 December 1978 and subsequent telephone request by Mr.

Owen O. Thompson of the Geosciences Branch, NRC, for assistance in evaluating the rock fill characteristics for the main dam of the Shearon Harris Nuclear Power Plant. -

We have reviewed the " Report on Rock Fill Test Sections" for the main dam and our Str. Gregory R. Baer has participated in an on-site visit to the test fills and quarry with representatives of NRC, EBASCO, and CP S L on 13 August 1979. The following comments are offered concern-ing the quality and characteristics of the rock fill with respect to

, gradation, strength and permeability. The comments were discussed by l

telephone with Mr. Thompson and other representatives of NRC, EBASCO, and CP S L on 17 August 1979.

of 3-inches presented on Figure ThegradationcurvewiththeminimumD9 12 of the " Report on Rock Fill Test Se8 ion"representstheminimum acceptable gradation for the rock fill. Our review of the test fill report and site visit indicates that a well graded rock fill free of segregation, and meeting the minimum gradation, as well as density, can be achieved utilizing the proposed placement and compaction procedures. The requirement, however, of specifying the maximum stone si:e for the rock fill based on the average of the 3-dimensions for each stone is not entirely understood. It is anticipated that such a require-ment will be difficult to control during construction. The accepted I

practice within this agency is to specify the intermediate dimension as the maximum particle size which is directly related to the gradation.

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79101600(2-

SADEN-F 5 September 1979 Mr. James P. Knight

-2 I Results of the field permeability tests indicate a permeability of 10 cm/sec

! in the test fills. A permeability of this order of magnitude is normally considered free draining. Assuming the fines are uniformally distributed throughout the fill, as was the case in the test fi14s, and the fines are

non-plastic, as sta ed by representatives of EBASCO at the site visit, a permeability of 10 }cm/see appears to be representative'.of the rock fill.

Caution should, however, be exercis*ed during construction to insure uniform

! distribution of fines in the fill and to avoid the use of weathered rock

! containing plastic fines. Mr. Thompson has recommended that the first 3 lifts of rock fill in the downstream section of the dam (in the valley) be limited to a maximum of 5 percent fines. Mr. Thompson also has recom-mended that field permeability tests be conducted as part of the normal,3 quality assurance testing program and that a minimum pemeability of 10 cm/see be required for all rock fill. Implementation of these recommenda-I tions should insure adequate drainage of the rock fill.

A 15-inch triaxial test, R, was conducted on the rock fill with a gradation representative of the lower gradation which will ge ellowed. The results l

of the test show an effective strength and no cohesion. In design, an effective strength 9' of 40,p' ofno and 40.5 cohesion was assumed for the rock fill. It is noted in the " Report on Rock Fill Test Sections" that, as the excavation progresses, fresher granite of coarser gradation j

will be encountered. Based on this fact and the fact that the gradation of the material tested was the lower limit of gradation to be used, it is believed that the test results are representative of the strength of the rock fill. It is recommended, however, that a minimum of two additional triaxial tests be conducted on representative sampics of the rock fill during the early stage of construction to substantiate the design values.

It has been a pleasure for the South Atlantic Division, Corps of Engineers, l to be of assistance to the Nuclear Regulatory Commission. If we can be of any further assistance or offer any further clarification on the above comments, please contact Mr. Gregory R. Baer at FIS 242-4696.

Sincerely, b& Yh&/

WILLIAM N. McCORMICK, JR.

j Chief, Engineering Division l

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