ML20003H388
| ML20003H388 | |
| Person / Time | |
|---|---|
| Site: | Vallecitos File:GEH Hitachi icon.png |
| Issue date: | 05/01/1981 |
| From: | Pichumani R Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20003H372 | List: |
| References | |
| ISSUANCES-SC, NUDOCS 8105050703 | |
| Download: ML20003H388 (8) | |
Text
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UtilTED STATES OF AMERICA T4UCLEAR REGULATORY COM:11SSIO:1 BEFORE THE AT0!!!C SAFETY A!JD LICEriSIriG BOARD In the flatter of GE:lERAL ELECTRIC C0.
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Docket ilo. 50-70 (Vallecitos liuclear Center -
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(Show Cause)
General Electric Test Reactor,
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Operating License 110. TR-1)
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TESTIM 0!iY OF RAllAll PICHU!!Aill, Ph.D.
Q.1.
Please state your nane and present position with the llRC.
A.I.
My nane is Ranan Pichumani.
I have been enployed since Septen-ber 1980 as a geotechnical engineer, Hydrologic & Geotechnical Engineering Branch, Division of Engineering, U.S. iluclear Regulatory Comission, 11ashington, DC 20555.
I work in the area of foundation engineering as applied to the evaluation of the suitability of nuclear power plant sites.
11y areas of expertise include shallow foundations and deep foundations, and i
soil dynanics as applied to the soil-structure interaction of foundation i
structures.
Q.2.
Please describe your educational background and previous positions neld.
A.2.
I received a B.E. degree in Civil Engineering from the University of iladras, India, and M.S. and Ph.D. degrees in Civil Engineering from Carnegie Institute of Technology (Carnegie-Mellon Univ.), Pittsburgh, PA.
Ily areas of specialization in graduate school were 1) Soil Mechanics and Foundation Engineering and 2) Solid Mechanics and Structural Engineering.
8165050703
.- !s Fron 1977 to 1980 I'was employed as a senior research engineer at the Civil Engineering Research Facility (CERF)~ operated by the University of Weu ilexico for the U.S. Air Force Weapons Laboratory where I was engaged in the analysis of ground notions and dynanic soil-structure interaction data obtained fron large scale field tests of protective ' underground structures loaded by a sinulated nuclear environnent.
Fron 1976 to 1977 I was employed by Bechtel Power Corporation as an engineering specialist and was engaged in the seismic (dynanic) analysis of nuclear power plant facilities.
From 1974 to 1976 I was a senior staff engineer with GAI Consultants, a consulting geotechnical engineering firn, where I was involved with foundation and soil-structure interaction analyses for nuclear power plants and was a staff specialist for deep and shallow foundations.
Fron 1968 to 1974 I was enployed as a research engineer at CERF where I was involved in finite-elenent analyses of layered pavenent systens and was an author or coauthor of several technical reports, and papers published in professional journals and conference proceedings.
Fron 1967 to 1968 I was an Associate Professor of Civil Engineering at West Virginia Institute of Technology.
Fron 1966 to 1967 I worked as an engineer with E. D'Appolonia, Consult-ing Geotechnical Engineers, and was engaged in analyses of earth structures and foundations including piles, cellular cofferdans and sheet pile walls, and performed settlenent calculations and stability analysis.
From 1964-to 1966 I was a teaching and research assistant at Carnegie Institute of Technology.
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.1 Fron 1952 to 1954 I worked in India in various capacities, starting as a Junior Engineer and ending as an Executive Er.gineer (1953-1964) in charge of design and ccnstruction of buildings and airfield pavements.
I an a nenber of the American Society of Civil Engineers and a nenber of the Society of Sigma Xi.
I have servea as a nenber of the Deep Foun-dations Comnittee of the Geotechnical Engineering Division of the ASCE (1975-78).
Q.3.
Please state the nature of the responsibilities that you have had with respect to the review of GE's submittals concerning the effects of an earthquake on the GE Test Reactor.
A.3.
I prepared Appendix B to the January 15, 1981 portion of the Staff's SER entitled " Evaluation of Soil Properties and Pressures and Analysis of the Subgrade Rupture Mechanism at the General Electric Test i
Reactor". fly involvenent with the GETR project essentially began in October 1980. At that time, I was assigned the task of reviewing GE's i
subaittals concerning the soil properties and pressures under the Reactor i
Building due to a combined load case comprised of a ground acceleration vibratory notion and a surface rupture offset.
In these submittals, GE i
furnished a sunmary of the soil properties determined by their consultants based on subsurface investigations and laboratory tests (including grain size analysis and triaxial compression tests). These tests were designed to give numerical values for soil shear strength parameters that would help determine the ultinate bearing capacity of the soil beneath the GETR foundation slab. My evaluation of these paraneters showed that the range
4-4 of the selected strength paraneters reflected the subsoil conditions as revealed, by the field and laboratory test data.
Q.4.
Please describe the results of your evaluation of GE's Con-sultants, Engineering Decision Analysis Company, Inc. (EDAC) analytical nodel that led to the GE's original reconnendation of the " unsupported length" of the GETR foundation slab as a function of ground acceleration.
A.4.
EDAC represented the surface rupture offset analytically as an
" unsupported length" of the reactor foundation slab. They used in their nodel an ultimate bearing capacity of 20 ksf for the foundation soil conditions that was based on the reconnendations made by GE's geotechnical consultants (Shannon & Wilson, and Earth Sciences Associates).
In the EDAC nodel the value of the ultinate bearing capacity of the soil affected the
" unsupported length" of the foundation slab for various cases of seismic loading (i.e., oround acceleration).
While evaluating the EDAC nodel I observed that the ultimate bearing capacity of the soil beneath the GETR building could be more than 20 ksf.
Two factors contributed to this difference, namely (1) the undrained shear strength parameters used by GE's consultant did not cover the entire range of the values determined by tests, and (2) GE's consultant did not account for the effect of the overburden soil (surcharge) that would contribute to the bearing capacity of the foundation soil beneath the reactor. A higher bearing capacity of the soil would likely result in a larger " unsupported length" than that analyzed by GE.
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. 4 Q.5, Please explain why the fiRC staff agrees with GE's conclusion that the previously hypothesized cantilever condition will not develop and that tne thrust fault planes will be deflected away from the base of the reactor slab.
A.5.
GE perforned additional detailed studies of the stability of the GETR building during an assumed thrust faulting in response to questions raised by the ilRC staff. Tnese studies basically exanine the equilibriun of soil wedges forned by thrust fault planes neeting the reactor foundation slab at different locations.
Illustrations to explain the basis of this stability analysis are given in the GE's consultants, Earth Science Associates (ESA) subuittals (figures 1-3) dated December 1980 and subnitted to the ilRC by letter fron D.L. Gilliland to D.G. Eisenhut dated December 3, 1980.
Briefly, GE's stability analysis visualizes that the thrust fault foras a passive Rankine wedge
- that is pushed by a major principal stress as shown in Figure 2 in GE's December 1980 submittal. This nethod of wedge analysis is based on sound soil nechanics principles that have been accepted and applied by foundation engineers in the design of earth retaining structures.
Under the combined action of thrust faulting stresses and heavy downward loads due to the weight of the reactor and the surrounding soil (surcharge),
the fault plane that nay form, with a potential of intersecting the base of the reactor slab, would, in fact, shif t in such a way that the resulting fault plane would bypass the reactor base altogether. The reason for the
- T.W. Lambe, and R.V. Whitman, " Soil llechanics", John Wiley & Sons, New York, 1969.
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O t shifting of the fault plane away from the reactor foundation slab is that a I
lower passive pressure is require.a for the developnent of fault planes away from the reactor base slab than for the development of fault planes inter-secting the foundation slab.
GE perforned an extensive set of paranetric calculations to denonstrate that fault planes not intersecting the foundation slab require the mininun passive pressure.
I checked a fea of these calculations and found then to be correct. ' I'y check revealed,:sowever, that the above conclusion was predicated on the presence of the 21 feet high soil overburden (surcharge) within about 170 feet (horizontal distance) of the reactor building.
If, for any reason, a significant part of this surcharge were renoved, a reevaluation of the stability of the reactor would be necessary.
Q.6.
Describe the additional calculations / independent checks that you perforned to verify that the GE's final conclusions are acceptable.
A.6.
In addition to the check referred to in reply to question 5 I perforced two additional calculations to verify the correctness of GE's final conclusions:
(1) GE's calculations assuned a depth of 70 feet for the passive Rankine wedges developed in the subgrade.
I extended this calculation to cover a wedge depth of 100 feet and found GE's findings to be correct for the existing 21 ft. surcharge load.
(2) An independent check of GE's conclusion was made by performing a similar static stability analysis using a three-dinensional wedge.
In this analysis, instead of considering a single (inclined) failure plane for a 2-dinensional wedge of unit thickness, I considered two additional vertical failure planes, cue on
. o each side of the reactor building. The diffference between the two analyses is the soil shear resistance along the two vertical failure planes that is ignored in the 2-dinensional analysis. The results of ny three dinensional analysis also confirned GE's conclusion that the postulated thrust fault plane will be deflected away from the base of the reactor slab.
Q.7.
Please state if the possibility of deflection of the fault planes under a heavy structure can be verified by any actual field cases known to the 11RC staff.
A.7.
One case of the apparent deflection of a fault plane away from a heavy structure has been observed in the 1972 flanagua earthquake in Nicaragua.
This case relates to the Banco Central Building that is reported to have been inadvertently built across an active trace of an existing fault. The l
foundation soil below this building consists of alternating layers of lightly cemented gravels and uncemented sands. Although the report describing the behavior of the Banco Central Building during this earthquake does not give the detailed properties of the subgrade beneath that building, the descrip-tion of the foundation soil indicates that it is essentially similar to the clayey sandy soils with some gravels that exist beneath the GETR building.
The foundation soil pressures beneath the 15-story Banco Central Building (that also has a basenent housing the bank's storage vaults) appear to be of the sane order of magnitude as those beneath the GETR building.
(Ref:
M.R.
liiccun, L.S. Cluff, F. Chanorro, L. A. Wyllie, Jr., " Banco Central de Nicaragua:
A Case History of a High-rise Building that Survived Surface Fault Rupture",
Proc 6th World Conf. on Earthquake Engineering, New Delhi, India, Jan.1977).
I e
While surface faulting was observed near the Banco Central Building on
-a trace of the fault that passed under the Building, the rupture deviated fron the active trace, and the building foundation and the basenent storage vaults survived the earthquake. The structure above ground level was dauaged during the earthquake, but this danage has been attributed to seismic shaking and not due to the faulting.
It has been reported that model tests perforced by the Bechtel Corp.
have shown that an earthquakt-resistant buried structure built across a fault will cause diversion of the fault, if it is strong enough to resist the earth pressures induced by the faulting.
(
Reference:
J.M. Duncan, & G.
i Lefelvre, " Earth Pressures on Structures Due to Fault Moyenent", Proc.
i ASCE, J. Soil Mech. & Fdns. Division, Vol. 99, tio. SM12, Dec.1973).
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