ML20094J291
| ML20094J291 | |
| Person / Time | |
|---|---|
| Site: | Midland |
| Issue date: | 01/11/1983 |
| From: | Kane J NRC |
| To: | |
| Shared Package | |
| ML19258A087 | List:
|
| References | |
| CON-BX16-038A, CON-BX16-38A, FOIA-84-96 NUDOCS 8408140280 | |
| Download: ML20094J291 (5) | |
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v RECORD OF TELEPHONE CONVERSATION DATE: January 11, 1983 0 2:0] PM PROJECT: Midland RECORDED BY: Joseph D. Kane TALKED WITH:
CPC Bechtel bEI NRC J. Mooney M. DasGupta S. Poulos R. Landsman J. Schaub
.W. Paris J. Kane T. Thiruvengadam R. Wheeler K. Razdan G. Murray R. Ramanujam B. Culk1 J. Darby B. Adler M. Lewis B. Crouse ROUTE T0:
J. Knight H. Singh, COE G. Lear S. Paulos, GEI L. Heller R. Landsman, Region III D. Hood J. Kane MAIN SUBJECT OF CALL: To discuss background settlement read.ngs -
Auxiliary Building Underpinning ITEMS DISCUSSED:
This call had been arranged at the request of NRC to discuss the background (underpinning had not yet started) settlement records provided to NRC for the period from 8/23/82 to 10/14/82. The records provided were for DSB-AN1, DSB-lE, DSB-2E, DSB-AS4 and DMD-3E and the ambient air temperatures for the same time frame. Region III had requested that HGEB review the background data and provide comments on the apparent upward movement of the EPA which is indicated by the settlement monitoring program.
1.
CPC was asked to briefly describe the procedure that was followed to establish the uncorrected and corrected settlement curves which were provided for the deep-seated benchmarks (DSB). The uncorrected curves are based on the recorded LVDT readings. The occasional small triangles plotted on the curves are points estabhsbed from the back-up dial gages.
The corrected curves adjust the uncorrected curves for temperature changes measured at the deep-seated benchmarks (DSB) since the time of initial hjg2eo84071g RECE84-96 png
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installation. Temperature changes are reasured at each DSB location at depths.of 3 ft,15 ft and 50 ft through thermocouples.which were placed during installation.1 Minimal changes in. temperature are being observed below the upper themocouple. CPC is to provide the temperature readings with depth to support their position that temperature corrections at c DS8-AN1, DS8-AN2 DSB-lE and DSB-lW are not required in the future. The plot of. ambient air temperatures which was provided was not used in correcting for. temperature variations.
2., During this call the following information was provided by CPC on - Ai
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values (See Drawing C-l_493(Q) and prior reports for definition of differential settlement, A ).
j Building Mdnitoring' Location Uncorrected Settlement Corrected Settlement (in mils as of 1/11/83).
(in mils as of 1/11/83)'
DSB-ANI.(NorthMainAuxil.')
68
-118 DSB-AS4 (South Main Auxil.)
46 63 DSB-2E(EastEPA) 35 43 DSB-3E (Control Tower) 22-44 DSB-2W(WesEEPA)'
27 39 Computed values of A that were given include:
j DSB-2E:
aj = -18 mils DSB-3E:
a) = -17 mils DSB-2W:
a = 415 mils j
DSB-3W:
Aj = -10 mils -
These values are based on uncorrected readings for DSB-AN1 and corrected readings for the other loctions. The minus signs reflects a magnitude of settlement at the EFA and Control Towers less than the Main Auxiliary Building.
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- 3.
Additional infonnation provided by CPC included:
Building Monitoring Actual Settlement (corrected)
-Location (in mils as of 1/3/83)
DSB-2W' 29 DSB-3W 38 DSB-3E 39 DSB-2E 30 Estimated bearing pressures: EPA = 4.5 ksf, Control. Tower = 5.2 ksf and Auxil. Bldg. = 9.5 ksf 4.
Possible explanations for the lahger amount of settlement occurring at the north end of the Main Auxiliary Building were discussed and included:
a.
The heavier loaded Auxiliary Building which rests on glacial till' may be picking up additional load from the EPA and Control Tower through cantilever actim because the more compressible till beneath the EPA and Control Tower is providing little foundation support.
b.
The EPA is affected moie by changes in temperature than the other structures which causes an upward expansion of the EPA. This is reflected as less settlement than the other structures.
c.
The dewatering for underpinning is causing an uneven immediate settlement over a relatively large area in the thick glacial till layer.
5.
The NRC Staff.and -its consultant made the following recommendations for 1
plotting of the settlement data in order to sort out the many variables affecting the settlement readings.
a.
Plot the uncorrected and corrected readings for each monitor location along one line (North Auxil. Bldg. through to Control Tower) at the noon time interval.
(On 1/12/83 this was later agreed to be at themidnightinterval). Two settlement history plots on standard 11" by 17" graph papr should be developed for each monitoring location.
One plotrwould have both horizontal and vertical (suggested 1 inch =
20 or 40 mils) arithmetic scales and the other plot would graph time in days (1,10,100,1000) on semi-log paper. The temperatures used to correct the data should be plotted on the same graph at the same time interval (Temperdure plot needed only on settlement graph plotted toarithmeticscales).
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6.
CPC. indicated the requeted settlement plots would be furnished to NRC in about one week's time. This was noted to be acceptable and will permit staff review prior'to any site visit for reviewing underpinning progress (now planned for time when pier load test of Wil is being-conducted).
7.
The staff and 'its consultant believe the relatively small settlement values and the trends of that data which have been recorded to date are a result of temperature changes.
It is felt that if sufficient. background data were available, where comparable temperature and seasonal conditions were repeated, that the effects of sustained temperature changes would be clearer. It is also felt that the apparent upward movement of the EPA with respect to the other structures will be quickly reversed as underpinning operations progress beneath its foundation slab. The present trend indicated by'the settlement readings is favorable with respect to the settlement acceptance criteria which has been established to control underpinning operations.
8.
At the request of R. Ramanujam, CPC, several other items were discussed and included:
a.
CPC plans to explore for buried utilities in advance of drilling the SWPS dewatering wells and soldier piles by using a' jet-wash type-boring (3-1/2" diameter water pipe) which would be inspected by the Resident Geotechnical Engineer.
R. Landsman and J. Kane, NRC, agreed that this type of boring would be acceptable.for. attempting to locate utilities when performed in foundattn soils which would eventually-be removed either in underpinning operations or in replacement of service water piping.
There is a concern when using this type of drilling that-the jetting and washing action, if not properly controlled, could cause development of voids and loosenin f cohesionless foundation soils.
The NRC staff expressed' preference for other types of exploratory drilling-(e.g., augering) in areas where future foundation stability was required.
W. Paris of CPC indic4ted th4t this position does give them problems. At the ' staff's'requesti,"CPC is to identify the specific location of proposed borings which will be located in permanent foundation soils required to remain stable. This information will be' used to guide the staff in a future response on the use of the jet-wash type boring.
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b.
R. Landsman indicated that his review of underpinning procedures developed by CPC.has :fdentified a problem. The procedures presently indicate that backpacking behind pit excavation lagging is not required when " neat cut" of the pit excavation is made. CPC indicated that the lagging would be essentially in direct contact with the foundation soils when neat cutting was performed. After considerable discussion the major difference became centered on the interpretation of essential and whether the entire length of lagging is required to be in contct or if short, narrow intermittent voids 3
were acceptable behind lagging. All parties did agree that backpacking should be required, even if neat cutting procedures were used, if sufficient voids behind lagging did exist.
It was acknowledgedt that reasonable judgements will have to be made curing construction when faced with widelz differing conditions of voids that may run from several inches tapeveral feet in length behind the lagging.
-It is hoped that the early planned site visit will permit the typical void conditions to be viewed where a consensus of agreement can be reached.
9.
An additional call from J. Kane-to R. Landsman and X. Razdan on 1/12/83 requested that settlement be plotted vertically downward in the conventional engineering manner on the settlement history plots which CPC has agreed to provide. In addition CPC agreed to provide the background readings for the extensometers and strah monitoring 2 devices.
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