earthworks module #7 prepared by dr. randy r. rapp july 2005
TRANSCRIPT
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EarthworksModule #7
Prepared by
Dr. Randy R. RappJuly 2005
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2005, Randy R. Rapp 2
Soil Classification
• Texture, consistency, mineralogy, and structure
• Unified Soil Classification System (USCS)
• American Assn. of State Highway and Transportation Officials (AASHTO)
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2005, Randy R. Rapp 3
USCS
• Coarse-grained vs. fine-grained• Coarse:
– Gravels– Sands– Sieve analysis size distribution: well and poorly
graded• Fine:
– Silts– Clays: kaolinite, illite, montmorillonite or smectite– Mineralogy and geological history matters: Atterberg
liquid and plastic limits (LL or wl; PL or wp)• Chart, pp. 152-53
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2005, Randy R. Rapp 4
Compaction
• Standard or Modified Proctor test: optimum moisture content (OMC) to achieve γdry,max (lb/ft3, pcf) for compactive effort
• Specifications usually % range of γdry,max and ± 1.5 to 2% of OMC
• Proctor suffices for most soils, but relative density might be applied for coarse soils
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2005, Randy R. Rapp 5
Compaction Molds and Hammers
• Standard Proctor– Mold, 4-in I.D.
• 0.333-ft3 or• 944-cm3
– Hammer blow• 5.5-lb• dropped 12-in
• Modified Proctor– Mold, 6-in I.D.
• 0.0752-ft3
• 2,130-cm3
– Hammer blow• 10-lb• dropped 18-in
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2005, Randy R. Rapp 6
Field Compaction
• Roller types
• Behavior of rollers during multiple passes
• Relating Proctor to field density: test strips
• Field density testing:– Random, at least every few thousand yd3
– Nuclear density gauge (or meter)– Sand cone density test to check the nuke
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2005, Randy R. Rapp 7
Inspection Control
• Observation of passes• Borrow pit concerns (p. 163)• Embankment (pp. 163-64)• Determining average depth of lift• Payment
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2005, Randy R. Rapp 8
Stabilizing Additives
• Additives– Portland cement– Lime (hydrated and quick)– Bituminous materials
• Curing requirements are critical
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2005, Randy R. Rapp 9
OSHA
• Competent person– Knowledge– Authority
• Expedient soil classification (pp. 167-69; 174-76)• Rock and Soil Types, for trench shoring
– A, ¾:1– B, 1:1– C, 1-½ : 1