Geotechnical Investigation and Recommendations for Drayton Bridge

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Geotechnical Investigation and Recommendations
for Drayton Bridge
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Geotechnical Responsibilities

• Settlement/Rate of Settlement
• Slope Stability
• Pile Length Estimations
• Boring Logs
• Instrumentation
• Plan Notes/SPs

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Drilling Operations (2003 to 2008)

• Drilled 13 borings that ranged in depth from 101
  feet to 182 feet. Avg. depth 162 ft
• 2 abutments/36 piers approx. 1boring per 3 pier
  units.
• Average Boring took from 2 to 4 days to complete.
• Goal is to drill 10 feet into 100 bpf material.
• Boring 13 was drilled in the center of the river,
  through the ice, in March 2008.
• Encountered Artesian water flow in almost all of
  our borings.

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Boring Log
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Boring Layout

• Show profile

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Profile with Borings
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Drilling Operations
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Drilling Operations Mud Rotary
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Night Drilling
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Boring 8 - Artesian

• Water being produced at roughly 300 gallons per
  minute.
• Tried numerous times to plug using bentonite
  plugs, inner tubes, neat cement.
• Halliburton finally came in and plugged

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Attempt at Plugging
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Rocks at Bottom of Boring 168 ft.
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Batching Neat Cement19 bag mix
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Halliburton Semenko to the Rescue
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Boring 13 Snow Removal
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Building Ice
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Interstate Drilling Services
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Pile Length Estimations

• Use FHWA Program Driven for Estimations
• Piling Used on this project will be HP14x73
  14x102
• Piling will terminate in the high blowcount
  glacial till.
• Estimated pile length varies from 145 to 205 feet
  in length.
• Total Plan Length of Piling is 80,110 lf

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Riverbank Instability
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Stability Analysis

• Stability of Riverbanks on the Red River has and
  continues to be a problem.
• Documented stability problems on East end of
  Existing Bridge.
• Use information obtained from borings to conduct
  a stability analysis with FHWA program ReSSA
• Minimum FS allowed is 1.5
• Recommended 41 inslopes and 61 endslopes to
  maintain Min. FS
• Limited Embankment height

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Stability Analysis - Inslope

• Show cross section

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• It should be emphasized that both of these mass
  wasting processes are natural phenomena, that can
  be expected in regions of bank erosion along the
  Red River --- such as those along cutbanks on the
  outside of river meanders.
• However, man can inadvertently accelerate the
  process of slump development by
• the placement of a load on top or along the
  slope, itself
• tree removal
• increasing soil moisture content, by lawn
  watering or installation of drain fields within
  prone regions.

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Settlement Estimations/Recommendations

• East Embankment
• Max embankment height is 10 feet
• Total predicted settlement is 5.8 inches
• 90 5.2 inches in 1182 days
• Wick drains _at_ 10 ft spacing can achieve 90
  settlement in 320 days
• West Embankment
• Max embankment height is 17 feet
• Total predicted settlement is 14.4 inches
• 90 13.0 inches in 1641 days
• 5 ft. surcharge in addition to Wick drains _at_ a 9
  ft spacing can achieve 90 settlement in 340 days.

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East Embankment
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West Embankment
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Driving Wick Drains

• Show driven graph

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Using Wick Drains to Accelerate Settlement

• Pic of wicks

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Downdrag Concerns

• Settlement of soil after piles are driven applies
  additional loads to the pile.
• The additional load is caused by the friction or
  adhesion between the pile and the downward moving
  soil.
• Preboring and backfilling with Bentonite Slurry

Bridge
New fill
Consolidatingsoil
Bearing stratum
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Geotechnical Instrumentation

• Will Allow Monitoring of
• Settlement
• Rate of Settlement
• Pore Pressure (Water Pressure) in soil as
  Embankments are built
• Control Rate of Placement to Maintain Minimum
  Factor of Safety.

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Geotechnical Instrumentation

• Vibrating Wire Settlement Cell

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Settlement Plate
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Geotechnical Instrumentation

• Vibrating Wire Piezometer

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Special Thanks to Grand Forks District and the
Drayton Section for all their help.