jo beth folger fac cf breakout - [email protected] april 8, 2005 1 site...
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Jo Beth Folger
FAC CF Breakout - Geotechnical [email protected]
April 8, 20051
Site Conditions and Geotechnical DataPresentation Outline
Site Overview
Historical Data
LCLS Investigation
Future Work
Jo Beth Folger
FAC CF Breakout - Geotechnical [email protected]
April 8, 20052
SLAC Site Geologic Overview
Miocene Ladera Sandstone, overlain by Santa Clara Formation and native fill
Very soft, very weakly cemented (by clay) sandstone, with strongly cemented (by calcium carbonate) thin interbedding locally
Nearest major fault is the Peninsula Segment of the San Andreas Fault, 5 miles SW
Groundwater is not expected at LCLS depths
Jo Beth Folger
FAC CF Breakout - Geotechnical [email protected]
April 8, 20053
Historical Geologic Data
Numerous geologic studies at the site since the late 1950’s
2 mile long Linac – 1959
Positron Electron Project (PEP) tunnel – 1975
Stanford Linear Collider - 1981
SPEAR – 1982
Almost 200 boreholes drilled by 1994
At least 32 geologic reports written by 1994
Jo Beth Folger
FAC CF Breakout - Geotechnical [email protected]
April 8, 20054
Geologic Map with LCLS Boring Locations
Jo Beth Folger
FAC CF Breakout - Geotechnical [email protected]
April 8, 20055
Groundwater Elevation Contours
240’ contour
180’ contour
LCLSElev. 247.25’
Jo Beth Folger
FAC CF Breakout - Geotechnical [email protected]
April 8, 20056
LCLS Geotechnical InvestigationTwo Phases
Summer 2003 and Summer 2004Rutherford & Chekene12 soil boringsSample Analyses
Dry DensityMoisture ContentUnconfined CompressionConsolidated Undrained TriaxialPetrographic AnalysisSlake DurabilityParticle sizeShrink/swell expansion pressureCerchar abrasionCreepR-valueCorrosion potential
In-Situ TestingBackground vibration measurement Shear wave velocity ~1,800 feet/sec Compression wave velocity ~4,100 feet/secPressure meter testing/ insitu deformation modulus - Deformation parameter varied from 1,000 bars to 12,500 bars, indicating interbedded layers of soft and hard rock
Seismic Analysis
Jo Beth Folger
FAC CF Breakout - Geotechnical [email protected]
April 8, 20057
LCLS Boring Locations
1 2
A B
3a,b
C
4
D E 5
6
Jo Beth Folger
FAC CF Breakout - Geotechnical [email protected]
April 8, 20059
Analytical Results cont.
Jo Beth Folger
FAC CF Breakout - Geotechnical [email protected]
April 8, 200510
Tunneling Memorandum Summary
Tunneling will occur entirely in Ladera Sandstone Formation
Tunneling condition categorized as “fair to poor soft rock”
Suggested construction method – roadheader excavation, followed by shotcreting
Horseshoe tunnel cross section
Stand open time and advance rate discussed
Jo Beth Folger
FAC CF Breakout - Geotechnical [email protected]
April 8, 200511
Future Work
Support structural engineering effort – ongoing
Produce Geotechnical Baseline Report – bids received, award planned 4/8/05