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NSLS – II CFAC Review. Conventional Facilities Geotechnical Conditions Tom Joos Civil/Structural Engineer BNL Plant Engineering Division October 18, 2006. Geotechnical Conditions. Subsurface exploration program conducted July & August 2006.
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NSLS – II CFAC Review Conventional Facilities Geotechnical Conditions Tom Joos Civil/Structural Engineer BNL Plant Engineering Division October 18, 2006
Geotechnical Conditions • Subsurface exploration program conducted July & August 2006. • Survey of proposed site conducted June 2006. • Additional soil boring data from adjacent project sites: • Center for Functional Nanomaterials (CFN) - 2003 • National Synchrotron Light Source (NSLS) - 1977
Geotechnical Conditions (cont’d) • 2006 Subsurface Exploration Program • Test borings taken at four locations • Standard Penetration Tests continuous for first 10’ of depth. • SPT at 5’ depth intervals thereafter. • Borings to depths between 32 and 62 feet. • Soil samples collected from SPT tests. • Particle size (sieve) analysis performed on soil samples. • Cone Penetrometer Soundings taken at 12 locations • Shear wave velocity measurements at 4 CPT locations. • CPT to depths between 53 and 100 feet.
Geotechnical Conditions (cont’d) • Subsurface Exploration Results • Site consists of 3 to 6 feet of fill overlying a naturally deposited (glacial) sand exceeding 100 foot depth. • Groundwater encountered from 38 to 37 feet below existing ground surface. • SPT N-Values • Fill layer – 8 to 15 blows per foot (bpf) - loose to medium dense. • Sand Layer – 15 to >50 bpf - medium dense to very dense • N-Values calculated from CPT results averaged above 20 bpf. • Shear wave velocity measurements ranges 860 to 1,180 fps. • Velocity was uniform to slightly increasing with depth. • Average of 34 measurements is 975 fps.
Geotechnical Conditions (cont’d) • Recommendations for design: • Foundations • Maximum allowable bearing pressure 2.5 tons per square foot (tsf). • Minimum footing width of 3 feet. • Estimated total settlement for column footings of 1 inch/differential settlements <0.75 inch. • Will be much less for slabs on grade • Expect 90% of settlement before end of construction. • These are typical values for this type of soil on BNL Site – not problematic • Floors • Slabs on grade placed on minimum 6” thick layer of compacted structural fill. • All structures are above groundwater levels encountered. • Foundation soils are Site Class D, “very dense soil/soft rock” (BCNYS/IBC 2000). • Existing fill layer to be removed below foundations. • Proposed floor elevation 73. • Existing site grade varies from Elevations 83’ to 70’.
Geotechnical Conditions (cont’d) • Conclusions/path forward • Proposed site appears to be excellent for NSLS-2 siting. • Soil conditions fairly uniform throughout proposed site. • No evidence of clay or poorly consolidated (soft) sands beyond topmost fill layer. • Recommended bearing capacity is favorable to proposed foundation design (individual spread footings). • Further investigation (Title I/Title II) • Additional borings to further quantify thickness of fill layer ($$$). • Test Pits • Further define obstructions in warehouse area • Obtain samples for laboratory density tests • Geotechnical risks are mitigated by having site preparation performed well in advance of general construction
