ML19329E156

App 2F of AR Nuclear 1 PSAR, Dardanelle Dam. Prepared for Util.Includes Revisions 1-18

ML19329E156
Person / Time
Site:	Arkansas Nuclear
Issue date:	11/24/1967
From:	ARKANSAS POWER & LIGHT CO., BECHTEL GROUP, INC.
To:
References
NUDOCS 8005300759
Download: ML19329E156 (12)

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APPENDIX 2F DARDANELIE DAM 1 PURPOSE AND SCOFE 2 IOCATION AIO DESCRIPTION 3 STABILITY ANAIXSES 31 NON-0VERFIOW SECTION 32 GENERATOR SECTION 33 OVERFIUd SECTION 34 IOCK GATES AND TAIITIER GATES 3.4.1 UPPER IOCK GATE 3.4.2 In4ER IOCK GATE 3.4 3 TAIITIER GATES 35 IOCK walls 3.6 EARTHFILL SECTION 4 CONCLUSI01E 5 REFERENCES  !

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SAFETY INVESTIGATION REPORT DARDANELLE LOCK AND DAM ARKANSAS RIVER, ARKANSAS FOR ARKANSAS POWER & LIGHT COMPANY BY BECHTEL CORPORATION, SAN FRANCISCO

1. Purpose and Scope. This report presents the results of an investigation performed to evaluate the effect of a hypothetical seismic loading condition on Dardanelle Lock and Dam. The hypothetical seismic load results from a 0.2g ground surface acceleration which has been adopted by Bechtel as the " maximum earthquake" for this area.

This investigation was performed in connection with the design of the Arkansas Power & Light Russellville Nuclear Unit. It would draw its cooling water from the reservoir formed by Dardanelle Lock and Dam. It is of critical importance that this nuclear unit have an adequate supply of cooling water at all times. The specific purpose of this investigation was to determine if the " maximum earthquake" would fall the dam, thereby causing reservoir drawdown and a loss of cooling water for the nuclear unit.

2. Location and Description. Dardenelle Lock and Dam is situated on the Arkansas River near Russellville, Arkansas.

For Plan, elevation and typical sections of Dardanelle Dam,. refer to Plate 2 of U. S. Army Corps of Engineers' Design Memorandum No. 11-1, dated April 1958. A plan view and typical sections of the lock walls are shown on Drawings 6600-3 and 6600-4 of this, report.

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l 3 Stability Anal fses. Each of the major dam structures was aaalyzed for a loading condition induced by a 0.29 ground surface acceleration acting in the most critical direction. The following is a discussion of the stabilite iraiyses re:ults for each major dam section.

3.1 Non-Ovarflow Section. The stability analysis of this section is summarized on Drawing 6600-2. In this analysis the seismic force was assumed to act in the upstream direction because the adjacent earthfill would prevent its failure in the downstream direction. On the basis of this analysis, this structure has an ample degree of safety for the 0.2g seismic loading condition.

3.2 Generator Section. The stability analysis of this section is summarized on Drawing 6600-1. This summary indicates that the Generator Bays meet all of the - - 'f Engineers' Design Criteria for the

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0.29 seismic loading conditio they are therefore considered to have an adequate degree of safety.

33 Overflow Section. The stability analysis of the overflow section is summarized on Drawing 6600-2. The Shear-Friction Factor of Safety of 11.3 indicates this structure has an adequate degree of safety against sliding.

The overturning analysis indicates a maximum compressive stress of 12.5 kips per square foot (KSF) would be induced. This is well below the design strength c.r this concrete and the allowable stress for the foundation rock. However, this calculation was based on the assumption that the bond between the concrete dam and the rock foundation is broken and therefore no tensile stresses are induced. This is an important consideration in this particular stability analysis because, if the bond '

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w were actually broken it is possible the hydrostatic uplift pressure beneath the dam could increase during the hypothetical earthquake.

Therefore, an additional analysis was performed to determine the tensile stress which would be required to prevent the bond from breaking during the application of the assumed loading condition. This analysis indicated that if the bond renained unbroken the maximum induced tensile stress would be 2.78 KSF. Based on a study of the geologic characteristics of the foundation rock and the test results provided in Design Memorandum No. 11-2 It was concluded ' hat the tenslie stress caused by a transient load condition would not be sufficient to break the bond between the dam and the foundation rock. It was therefore concluded that this structure has an adequate degree of safety.

3.4 Lock Gates and Tainter Gates.

3.4.1 Upper Lock Gate. It was not considered necessary tc perform a detailed analysis of this gate because it was determined that one of the loading conditions assumed in the design of the gate was more severe than the load imposed by the 0.29 seismic loading condition. The specific design load resulted from the gate being overtopped by 6 feet of water. This proved to be more severe than the normal hydrostatic load plus the hydrodynamic and inertia loads induced by the 0.29 seismic loading condition.

3.4.2 Lower Lock Gate. It was also considered unnecessary to analyze the Lower Lock Gate in detail. In designing this gate it was assumed that the horizontal structural members would each resist a vertical increment of the hydros tatic load imposed by the water l

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Inside the lock. In the present analysis it was determined that the hydrodynamic load would be about 28% greater than the hydrostatic load on each horizontal gate member. A corresponding 28% increase in " normal" working stresses would provide an adequate degree of safety for 0.2g seismic load condition.

3.4.3 Tainter Gates. The individual members of these gates were analyzed in detail and it was determined that they have an adequate degree of safety for the assumed loading condition.

35 Lock Walls. The stability analysis of each major type of lock wall is summarized on Drawings 6600-3 and 6600-4. In these analyses the seismic force was assumed to act perpendicular to the axis of walls.

In general the stability of the Lock Walls is similar to the i

stability of the Overflow Section. Each type of wall has an adequate i margin of safety against sliding but a lesser degree of safety against overturning and overstressing. If it is assumed that these structures are not bonded to the foundation rock, the area of base compression is extremely small during the application of the 0.2g sels.r.ic loading condition.

However, in no case is the maximum allowable compressive stress of either the concrete or the foundation rock exceeded.

if the bond between these structures and the foundation rock remains unbroken it was calculated that the 0.2g seismic load condition would induce maximum tnesile stresses of 6.2 KSF to 9.5 KSF. In the geologic evaluation of this site it was concluded that these transiently applied stresses would not break the bond. It was therefore concluded that the Lock Walls have an adequate degree of safety for the assumed

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loading condition.

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s it should also be ncted that the Upper Cate Lock Walls (Sections I and 2 on Drawing 6600-3) have an additional undetermined degree of safety because of adjacent structures. There is an Upper Gate Sill Block between these two walls which would ra.sist overturning of the Land Wall. The River Wall is adjacent to the Overflow Section of the dam which would aid in resisting overturning.

3.6 Earthfill Section. The stability analyses of the earthfill section are summarized on Drawings 6600-4 and 6600-5. These analyses were performed by a computerized circular arc method of slices.

The stability summary shown on Drawing 6600-4 Indicates that this section of the dam would be failed by the 0.29 seismic load condition.

Af ter this analysis was comnieced. we were informed verbally by the Corps of Engineers that they intend to construct a berm downstream of the.

present earthfill dam. This berm is scheduled to be completed in the Fall of 1969 Based on that verbal advice, it will have a surface elevation of 348 and an approximate width of 125 feet at this station. It is obvious from inspection that no failure surface caused by the 0.2g seismic load would breach the dam and berm at this station.

The stability summary shewn on Drawing 6600-5 Indicates that this section of the dam would also be failed by the 0.2g seismic load condition.

However, in studying this section, the downstream berm was included in the analysis and as this summary indicates, the 0.29 seismic load would not breach both the dam and the dcwnstream berm.

The stability analyses of these two sections of the earthfill dam indicate that the 0.2g seismic load would cause a large section of the upstream face of this dam to slide out. This sil'e' d e uld probably include 03.L1 M

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the core of the dam and result in a slide scarp, which would be very susceptible to erosion by wave action, and a substantial increase in the flow of seepage water through the downstream berms. This would require renedial work shortly after the occurrence of the earthquake to prevent additional serious damage to the dam, it was concluded, however, that erosion following the earthquake would not breach the dam because:

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The berms extend several hundred feet downstream of the dam. It would therefore require a large period of time for erosion to breach then.

b. There will be operators on duty at the dam full time.

These personnel would be able to summon assistance and begin remedial work immediately to prevent excessive erosion.

4. Conclusions. On the basis of this investigation, it is concluded that Dardanelle Lock and Dam could withstand the " Maximum Earthquake" of 0.2g without losing its functional integrity. It is probable that some damage would be sustained, especially in the earthfill section on the left abutment of the dam, but the dam would retain the reservoir at the normal pool level.

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5. References. The following references for this study were obtained from the Little Rock District of the U. S. Army Corps of Engineers:

1. Dardanelle Lock and Dam, Power Plant, Analysis of Design, Volume 1.

Prepared for the U. S. Army Corps of Engineers by Svedrup & Parcel and Associates, Inc., March 1963.

2. Dardanelle Lock and Dam, Design Memorandum No. 11-2, Dam -

Overflow Section, U. S. Army Corps of Engineers, Little Rock, Arkansas, May 1959.

3 Dardanelle Lock and Dam, Design Memorandum No. 11-1, Dam -

Embankment Section. U. S. Army Corps of Engineers, Little Rock, Arkansas, April 1958.

4. Dardanelle Lock and Dam, Supplement to Design Memorandum No. 11-2, Dam - Overflow Section, U. S. Army Corps of Engineers, Little Rock, Arkansas, January 1960.

5. Dardanelle Lock and Dam, Design Memorandum No. 10, Navigation Lock, U. S. Army Corps of Engineers, Little Rock, Arkansas, March 1958, revised July 1959.

6. Dardanelle. Lock and Dam, Design Memorandum No. 10-3, Navigation Lock Completion, U. S. Army Corps of Engineers, Little Rock, Arkansas, June 1962.

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