ML19256A708
| ML19256A708 | |
| Person / Time | |
|---|---|
| Site: | Palo Verde  |
| Issue date: | 01/04/1979 |
| From: | Van Brunt E, Vanbrunt E ARIZONA PUBLIC SERVICE CO. (FORMERLY ARIZONA NUCLEAR |
| To: | Boyd R Office of Nuclear Reactor Regulation |
| References | |
| PVNGS200JMAWFQ, NUDOCS 7901090241 | |
| Download: ML19256A708 (16) | |
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P. C. B O X 21666 PH CE N I X, A R12 C N A 8503G January 4,1979 PVNGS-200-JMA/WFQ Director of Nuclear Reactor Regulation U.S. iluclear Regulatory Commission Washington, D.C.
20555 Attn:
Mr. Roger S. Boyd, Director Division of Project Management Re:
Palo Verde Nuclear Generating Station Units 4 & 5 Docket Nos. STN-50-592/593
Dear Mr. Boyri:
Per request of your staff, submitted herewith are six (6) copies of an example calculation for the mean blowcounts as well as the mean normalized blowcount values to clarify the procedure identified in the PVNGS 4 & 5 PSAR Section 2T.3.2.1.
Sincerely,
(-
M hh E. E. Van Brunt, Jr.
APS Vice President, Nuclear Project.
ANPP Project Director EEVBJr/WFQ/dic On its own behalf and as Agent for all other joint applicants.
STATE OF ARIZONA
)
) ss.
County of Maricopa )
Subscribed and sworn to me this' 8 day of January,1979.
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V. ww
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Notary PJblic My Ccmmission Expires:
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if es,
7901090 5/
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DRAFT RESPO!!SE TO t1RC BLOWCOUt1T Atl ALYS IS QUESTIOt1 PALO VERDE tlUCLEAR GEllERATItJG STATIOtJ Project tJ o. 77-222-25 December 12, 1978
r1HC n!.0WCour1T At1 AI.Y'il: ; OUl::;T10!1 Sone additional explanation of the procedure identified in Section 2T.3.2.1 is required.
Provide an example calculation for the mean blowcounts as well as the mean normalized blowcount values.
em 6 wg *
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2 I tJTRODUC T 10tl The methodology used in the PVilGS Units 4 and 5 blowcount analyses allows blaucounts taken from a large vertical range to be co ns id e r ed as pa r t of a specific layer of smaller vertical extent for the purpose of increasing the blowcount analysis data base.
The combinat ion of blowcounts taken from discontinuous layers into idealized cont inuous layers requires b lowc ou n t extrapolation.
A variety of methods can be used to extrapolate blowcounts to different depths; the particular method u t ili zed depends u po n the specific case in question.
This report contains blowcount analyses of a s i ng le site using three methods of extrapolation.
The first method is the av e r ag e fl/D ratio method used in the PVNGS Units 4 and 5 PSAR.
The second method, termed the discrete blowcount method, treats each blowcount individually, utilizing the relation between confinement and blowcount at constant relative density for the e x t r apca l a t i o n.
This procedure was developed by Gibbs and 1101 t 2 and used by Se ed, et al (1977) for determination of the blowcount that would exist under an ove rburrien 0 2 one ton per square foot.
The third method also utilizes this relative density extrapolation method.
Ilo w e v e r, the extrapolation
- i. of mean measured blowcounts for each layer rather than ext rapo la t ion of individual blowcounts.
BLONCOUtJT AN ALYS IS M ET110DO LOG I E S As the first step in the preparation of examples of the varion:, appr oaches to the blowcount analysis, it is necessary to present the soil profile analyzed.
As a typical case of
3 a multi-layered protile, the site at the PVNGS Unit 4 Turbine Building has been selected.
Figure 1 shtws a portion of the simplified profile presented in Figure 2T.3.1 of the PSAR for PVNGS Units 4 and 5, along with the idealization of this profile as used in the blowcount analyses.
It must be noted that both profiles are simplified:
small pockets of differ-ing soil type falling within a layer have been omitted; however, the blowcounts taken in such pockets have not been omitted.
Each blowcount was examined as to material type; blowcounts were then combined by material type and depth zone into the id eal ized layers (Figure 2).
Blowcount Analysis Based on Average N/D Ratios The following steps we re followed in performing the N/D analysis.
1.
After segregation of blowcounts by material type and depth into idealized layers, the ratio of blowcount to depth (N/D) for each blowcount was determined.
The N/D ratios were summed and the average N/D ratio wa s calculated for each idealized layer.
These values are shown in Table 1.
2.
The layers were then divided into sublayers, where approptlate, and depth to the midpoint of each sub-layer was calculated.
The blowcount for that selected depth was then determined by multiplying the selected depth by the average N/D ratio.
Th is pr ovided an ap-proximation to the average blowcount that would exist at that depth.
4 3.
The ef f ect ive overburden pressure at the selected depth was calculated, Cg (adjustment factor for con-fining pressure) determined, and N1 (the blowcount expected to exist at an effective overburden of 1 ton per square food) and the liquef act ion streng th ratio, T/c ', were calculated in the same manner y
an discussed in Section 2T.3.2 of the PSAR.
4.
The total overburden stress and the induced stress at that depth were then calculated using the Seed-Idriss method.
The above values, together with the resulting calculated factors of safety, have been tabulated in. Table 1.
Discrete Blowcount Analysis Method An alternative approach to calculation of factors of safety against earthquake-induced liquefaction is to treat each blow-count separately.
This procedure involved the following steps.
1.
Blowcounts were normalized to a pressure of 1 tsf, N1, by multiplying the blowcount by Cg.
2.
The N1 values were averaged from which the average liquefaction strength ratio, T/c ', was determined.
y 3.
The induced and resisting stresses were calculated for the depth of interest.
4.
An ave r ag e factor of safety for each idealized layer or sublayer was calculated.
5 Each step in this development has been tabulated in Tables 2a and 2b.
Table 2a contains the data used in calculation of the ave r ag e N 1, and Table 2b shows the calculation of factors of safety based on these average values.
flean Blowcount tiethod The following steps were used in the mean blowcount method.
1.
The mean blowcounts and the average depth at which the blowcounts were taken were calculated.
2.
The stress conditions at that depth were used for subseqlent calculation of the liquefaction strength ratio, T/ cy'.
3.
Resisting and induced stresses and factcrs of safety were then calculated at the depth of interest.
All ca lcul a t io ns employing this procedure, including the resulting f ac to rs of safety, have been tabulated in Table 3.
DISCUSSION The ba s ic problem in performing a blowcount analysis of a dis'ontinuous, non-horizontal profile such as occurs at P VN G S Units 4 and 5, is the establishment of a large enough blow-count data base to ensure valid results.
Fo r this reason, blowcounts taken in similar materials isolated from the region identified as constituting the bulk of each idealized layer were combined.
6 A d i f f icul ty encounter ed in coribination o f blowcounts is that the blowcount analysis must be performed at depths different from t ho s e at which the blowcounts were taken.
For the case in which there are only small differences between the depth at which the blowcount was taken and the depth at which the factor of safety is calculated, the method of blowcount extrapolation is not critical.
Fo r such cases ext rapola tion is usually not even necessary, and if it is necessary, the approach presented by Seed relating effective overburden pressure and blowcount for specific relative densities is usually used.
This approach was followed in the discrete blowcount method.
A limitation of this method is that confinement and relative density are the only factors cons id e r ed as influencing blowcount.
Because confinement and relative density are not the only factors af fect ing blowcounts, the use of the N/D ratio approach is designed to provide a more comprchensive basis for extrapo-lation of blowcounts from the average depth at which they were measured to the depth at which the factor of safety is calcu-lated.
Of course the use of the linear M/D relation between blowcount and depth would result in errors if used for extrapo-la tion over large depth intervals where the assumed linearity would no l ong e r model the actual behavior.
For the sites at PVNGS Units 4 and 5, this condition did not occur, and thus it is felt that use of the N/D ratio provides a valid method for blowcount extrapolation.
7 CONCLUSIONS In Table 4 is presented a summary of factors of safety mal-culated for the susceptible layers by the three methods.
It is seen that the factors of safety calculated by the average N/D ratio method agree well, within a few percent, with the values calculated by the discrete blowcount method.
The method using the mean blowcount produces results also within a few percent of the other methods.
Thus it can be seen that any of the methods used to conipile blowcounts into average layers produce results that ag r ee to a degree of precision within the inherent sensitivity of the blowcount method.
8 Ill:FElli:NCES Seed, 11.
B.,
- Mori, K.,
and Chan, C.
K.,
(1977), "In fl uence of Seismic Ilinto ry on Liquef act ion of Sands," Jour _nal Of Ile_Geotechnical Engi_neering Division, ASCE, Vol. 103, l
IJo. GT4, April, pp. 257-270.
ILIVAllON (feet) 950 -
BL0hCOUNT fl0 DEL utn20 ut 033 x
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PROFILE x
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LAYER 2 920 -
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LAYER 7
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INDIC ATES LAYER INTO WHICH BLOWCOUNTS PERE C0!JPILED 8 10 --
NOTE: BL0hCOUNTS TAKEN FRCH ALL UNIT 4 TURBINE EulLDING B0 RINGS WERE USED: U4 B20, 17, 33, 21, 19. 38, 4.
S0ll PROFILE AND IDEAllZED LAYERING 860 -
UNIT 4 TURBINE BUILDING Figure 1
BLORCOUNT - N 0
13 2'
33 43 50 CO 70 89 90 i;3 10 20 I
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- Life 4 4 BLCnCCUNIS A LATER E ELCn:CLNTS 8J NOTES:
1.
ANALYSIS BASED ON SEED BLOWCOUNT METHOD 2.
BLOWCOUNTS FROM BORINGS U4 B20, 17, 33, 21, 19, 38. 4.
3.
BLOWCCUNTS UTILIZED INCLUDE THOSE TAKEN IN SANDS, SILTY SANDS, AND CLAYEY SANDS CNLY.
BLOWCOUNT PROFILE AND AVERAGE N/0 RATIOS FOR UNIT 4 TURBINE BUILDING figure 2
TABLE 1 N/D BLOWCoutli METHOD DATA v i '.l a f ! #
(Fif;ftst 70 fat LIC;[f t:fl0 I t! 'CE D Fa 70s cr C'
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tafle avisa;( = 0 p p g,,
i s t!'. t a T ! 3 g p g p;g, g,g gs.14 USNT4 UBW laF W
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).^4 o.31 1,31 0,42 3,1 1 21 n.c t 32
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r TABLE 2a DISCRETE BLOWCOUNT METHOD DATA EFFECTIVE TOTAL C
N LAYER BLOVl COUNT DEPTH OVERBURDEN OVERBURDEN N
I TSF (FT)
C ' (KSF)
U,(KSF) y 3
47 29 3.19 3.19 0.82 39 3
43 31 3.44 3.44 0.80 34 3
49 39 3.95 4.44 0.75 37 3
58 33 3.56 3.68 0.78 45 3
41 35 3.68 3.93 0.77 32 3
49 27 2.96 2.96 0.85 42 3
20 29 3.19 3.19 0.82 17 3
53 37 3.82 4.19 0.76 40 3
53 39 3.95 4.44 0.75 40 1
T A3LE 2a (con't)
DISCRETE BLOAC0VNI METHOD DATA EffECilVE TOTAL N
LAYER BLOACQUNI DEPTH OVEREURDEN OVERBUPDEN G
I TSF (fi)
O~,' ( K ST )
0, (KSF) 4 45 33 3.56 3.68 0.78 35 4
55 35 3.68 3.93 0.77 42 4
41 41 4.03 4.70 0.74 30 4
41 43 4.21 4.96 0.73 30 4
30 45 4.34 5.21 0.72 22 4
30 47 4.46 5.45 0.71 21 4
64 37 3.82 4.19 0.76 49 4
69 42 4.15 4.83 0.73 50 4
38 45 4.34 5.21 0.72 27 4
42 31 3.44 3.44 0.80 34 4
71 33 3.56 3.68 0.78 55 4
54 35 3.68 3.93 0.77 42 4
38 41 4.08 4.70 0.74 28 i
4 26 43 4.21 4.96 0.73 19 4
68 29 3.19 3.19 0.82 56 4
37 31 3.44 3.44 0.80 30 4
39 33 3.56 3.68 0.75 29 4
46 35 3.68 3.93 0.77 35 4
45 41 4.08 4.70 0.74 33
\\
4 31 4'
4.21 4.96 0.73 23 4
41 2'
2.85 2.85 0.87 37
1 T APLE 2a (con't)
OlSCRETE BLOWCOUNT METHOD DATA EFFECTIVE TOTAL C
N LAYER BL0nCCUNT DEPTH DVERBURCEN OVERauRDEN N
j 73p (fi)
U,' ( F,S F )
U,(KSi) 4 65 31 3.44 3.44 0.80 52 4
72 34 3.62 3.80 0.78 56 6
65 47 4.46 5.45 0.71 46 6
73 52 4.78 6.08 0.69 50 6
l ot, -
55 4.96 6.45 0.67 67 6
43 70 5.89 8.31 0.62 27 6
36 39 3.95 4.44 0.75 27 6
50 45 4.34 5.21 0.72 36 TABLE 2b DISCRETE BLOWCOUNT METHOD DATA vi:tarta Err [ttist teint tic' tr a:!6:s Cf'C'"4 ImNtga ra:tta CF
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LitlR t[p:d C i t 8!'J1:!%
CV!P'J [g T C,-
$;pgg;t, STAT!!
l4fEff t
s
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T, 7,, 7 0, a p!r i 7,
F i 3
36 31 33' 3.43 0.41 1.?5 0.91 0.41 3.3 Ji 3 t>
37 3.17
- 4. 32 0 al 1.53 0. l 0.43 3.,
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- 22 9.7' J.57 3.9 4
TABLE 3 MEAN BLOWCOUNT METH00 y__
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utse sefss:(
uittsite Lit;t r a;t:t=
in:.:tc ra;t;B CF
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- t P ri-ifate;f" fe m 3f"3:
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iff>
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9 74 M
0.40 31.0 1
0.91 0.42 3.2 43 47 17 0.:(
F 0. 4 ')
37.0 1.55 0.33 0.43 3.2 4b 47 il
". 7r 36 0.49 42.0 1.67 0.93 0.53 3.2 6
(1 51
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- 0. H 11.5 2.2?
0.76 C.57 3.9 TABLE 4 SUYYARY OF FACTORS OF SAFETY BY OlFFERENT METHODS FACTOR OF SAFETY LAYER N Ah DISCRETE AVERACE N D BLC COUN,.
3 3.3 3.1 3.1 4a 3.2 3.3 3.2 4b 3.2 3.5 3.2 6
3.9 3.4 3.9