jo beth folger fac cf breakout - geotechnicaljbfolger@slac.stanford.edu april 8, 2005 1 site...

Jo Beth Folger

FAC CF Breakout - Geotechnical jbfolger@slac.stanford.edu

April 8, 20051

Site Conditions and Geotechnical DataPresentation Outline

Site Overview

Historical Data

LCLS Investigation

Future Work

Jo Beth Folger

FAC CF Breakout - Geotechnical jbfolger@slac.stanford.edu

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 jbfolger@slac.stanford.edu

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 jbfolger@slac.stanford.edu

April 8, 20054

Geologic Map with LCLS Boring Locations

Jo Beth Folger

FAC CF Breakout - Geotechnical jbfolger@slac.stanford.edu

April 8, 20055

Groundwater Elevation Contours

240’ contour

180’ contour

LCLSElev. 247.25’

Jo Beth Folger

FAC CF Breakout - Geotechnical jbfolger@slac.stanford.edu

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 jbfolger@slac.stanford.edu

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 jbfolger@slac.stanford.edu

April 8, 20058

Analytical Results

Jo Beth Folger

FAC CF Breakout - Geotechnical jbfolger@slac.stanford.edu

April 8, 20059

Analytical Results cont.

Jo Beth Folger

FAC CF Breakout - Geotechnical jbfolger@slac.stanford.edu

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 jbfolger@slac.stanford.edu

April 8, 200511

Future Work

Support structural engineering effort – ongoing

Produce Geotechnical Baseline Report – bids received, award planned 4/8/05