Transcript Site Conditions, Geotechnical Data

Site Conditions and Geotechnical Data
Presentation Outline
Site Overview
Historical Data
LCLS Investigation
Future Work
October 12, 2004
Site Conditions / Geotechnical Data
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Jo Beth Folger
[email protected]
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
October 12, 2004
Site Conditions / Geotechnical Data
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Jo Beth Folger
[email protected]
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
October 12, 2004
Site Conditions / Geotechnical Data
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Jo Beth Folger
[email protected]
Geologic Map with LCLS Boring Locations
October 12, 2004
Site Conditions / Geotechnical Data
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Jo Beth Folger
[email protected]
Groundwater Elevation Contours
LCLS
Elev. 247.25’
240’ contour
180’ contour
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Jo Beth Folger
[email protected]
LCLS Geotechnical Investigation
Phase 1
Summer 2003, Rutherford &
Chekene
5 soil borings
Sample Analyses
Dry Density
Moisture Content
Unconfined Compression
Consolidated Undrained
Triaxial
Petrographic Analysis
Slake Durability
2 Reports Produced
“Geotechnical Data Report”
“Tunneling Memorandum”
October 12, 2004
Site Conditions / Geotechnical Data
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Jo Beth Folger
[email protected]
LCLS Boring Locations
A
1
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B
C
3a,b
7
D
E
5
6
4
Jo Beth Folger
[email protected]
Phase 1 Analytical Results
October 12, 2004
Site Conditions / Geotechnical Data
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Jo Beth Folger
[email protected]
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
October 12, 2004
Site Conditions / Geotechnical Data
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Jo Beth Folger
[email protected]
LCLS Geotechnical Investigation, cont.
Phase 2
Satisfy requirements iterated by Jacobs Engineering
“SLAC Geotechnical Investigation and Report Needs
List”, 2/4/04
Summer 2004, Rutherford & Chekene
7 soil borings in locations chosen to complete
geographical coverage
Additional sample analysis
In-Situ Testing
Geophysical/Shear wave velocity measurement
Pressure meter testing/ insitu deformation modulus
Background vibration measurement
Report due October 2004
October 12, 2004
Site Conditions / Geotechnical Data
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Jo Beth Folger
[email protected]
Phase 2 Summary
Subsurface conditions similar to conditions encountered in
Phase 1
Sample analyses - Same parameters as Phase 1, plus
Particle size analysis with hydrometer
Shrink/swell expansion pressure
Cerchar abrasion
Creep
R-value
Corrosion potential
Shear wave velocity ~1,800 feet/sec Compression wave
velocity ~4,100 feet/sec
Deformation parameter varied from 1,000 bars to 12,500
bars, indicating interbedded layers of soft and hard rock
October 12, 2004
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Jo Beth Folger
[email protected]
Future Work
Develop detailed geologic cross section through
the LCLS alignment – 1/05
Establish site-specific earthquake spectra – 1/05
Perform probabilistic site response analyses – 2/05
Support structural engineering effort – ongoing
Produce Geotechnical Baseline Report – FY05
October 12, 2004
Site Conditions / Geotechnical Data
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Jo Beth Folger
[email protected]