General Geotechnical Presentation
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General Geotechnical Presentation

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Basic Geotechnical Presentation recently given at a Lunch and Learn at Galloway

Basic Geotechnical Presentation recently given at a Lunch and Learn at Galloway

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General Geotechnical Presentation General Geotechnical Presentation Presentation Transcript

  • Geotechnical Engineering Presented to October 21, 2009
  • Geotechnical Engineering Approach
    • Four Components
    • Field Exploration/Site Reconnaissance
    • Laboratory Testing
    • Report of Findings and Recommendations
    • Future Additional Studies/Construction Observation
    • All are relative to what’s being proposed
  • Geotechnical Engineering Report
    • What we knew and what we did…
      • Based on our sometimes limited knowledge of the project at the time of the study
    • What we encountered…
      • Expansive soils/bedrock, collapse-prone soils, shallow groundwater, etc.
    • What it means…
      • Design: Foundations, Floor slabs, Retaining Walls, Pavements
      • Construction: Dewatering, Earthwork, Surface Drainage, and Maintenance
  • Geotechnical Engineering Report
    • What it means…is different for each reader
      • Owner
      • Architect
      • Civil Engineer
      • Structural Engineer
      • General Contractor
      • Earthwork Contractor
      • Foundation Contractor
      • Pavement Contractor
      • Landscape Contractor
      • Municipality
      • End User
  • Project Description and Site Conditions
    • The scope of the study and recommendations are based on these assumptions provided by client and project design team
    • Changes are often made after the Report is issued (Building Location, Number of stories, Finished floor elevation, Basement construction, Proposed Traffic, etc.)
    • Sometimes, even site location changes!
    • Some owners have not seen the site
      • Are there stockpiles? Debris?
      • Drainages? Trees?
      • Does the site drain well?
  • Field Exploration – Drilling
  • Boring Location Map Details the location of our borings and the location and elevation of the temporary bench mark (if applicable)
  • Field Exploration – Sampling
    • Solid or Hollow-Stem Augers
    • Ring Barrel Sampler or standard Split-spoon
    • Standard Penetration Test
    • Coring (very hard bedrock)
    • Other advanced methods such as…
  • Exploratory Methods
    • Pressuremeter
    • Seismic Refraction
    • Cross-hole Seismic
    • Thermal Conductivity
    • Dilatometer
    • Cone Penetrometer
    • Borehole Shear / Vane Shear
    • Ground Penetrating Radar
  • Subsurface Characterization
    • This is a description of the subsurface soil, bedrock, and groundwater conditions encountered at the time of the exploration
    • May also include assessment of geologic hazards
  • Boring Logs YOUR PROJECT HERE Your Name Here 1 2 3 4 5 Boring No. and Project Info Soil Types and Descriptions Sample Depth, Soil Classification and Field and Lab Test Data Swell Test Result(s) Water Level Measurements 1 2 3 4 5
  • Laboratory Testing
    • Common Soil Tests
      • In-situ Moisture Content, Dry Density
      • USCS and AASHTO Classification
      • (Grain Size, Atterberg Limits/Plasticity Index)
      • Expansion/Consolidation Potential
      • (Denver Swell Test)
      • R-Value/CBR (Pavements)
      • Sulfate Content (for Cement type)
      • pH & Resistivity (Corrosion)
  • Laboratory Testing, (cont.) Denver Swell Test in Laboratory Dial Gauge Sample in Water Pot
  • Laboratory Testing, (cont.) Swell Test Results Percent Swell Measured After Water is Added to Sample Surcharge Load (500 psf) Consolidation with Increasing Surcharge Load Swell Pressure (15,000 psf) YOUR PROJECT HERE
  • Engineering Recommendations
    • This is the part of the report that provides the design parameters and construction recommendations.
    • Geotechnical Considerations – Provides a brief overview of subsurface conditions that will impact the project from a geotechnical standpoint
      • Expansive soils
      • Existing fill materials
      • Shallow groundwater
      • Soft soils
  • Foundation Systems
    • Relevant geotechnical design parameters
    • Based on soil conditions, proposed bottom of foundation elevations, and anticipated structural loads
  • Foundation Systems, (cont.)
    • Drilled Piers (Caissons) or Helical Piles
        • Heavy Loads
        • Expansive Clays / Claystone Bedrock
        • Resist axial loads, lateral loads, and uplift by socketing into bedrock
        • Socket must be below anticipated wetting
    • Spread Footings/Slabs/Mats
        • Light Loads
        • Non- to Low Expansive Materials
        • Alternative with Overexcavation of expansive soils, usually requires additional evaluation
  • Lateral Earth Pressures
    • This section provides recommendations for the design and construction of CIP retaining or basement walls
    • Information used to resist soil pressure/movement
    • For MSE walls there are special considerations
  • Lateral Earth Pressures
    • Special Wall Projects
      • Not a standard recommendation, but design plans and/or design parameters can be provided for specialty retaining walls
      • May require additional exploration
      • MSE walls are cheap and flexible, but movement may be unacceptable
      • Imported, granular backfill almost always is recommended
  • Floor Slabs-On-Grade
    • This section provides recommendations for design and construction of floor slabs-on-grade including subgrade preparation to mitigate unsatisfactory conditions (fill, swelling soils, etc.)
    • Generally cannot eliminate movement
    • Owner, Design Team
    • may want alternatives
    • Risk vs. Cost
  • Pavements
    • Pavement sections are based on: Traffic and Soils
    • Traffic is rarely known
    • Assumptions should be confirmed
    • AASHTO
    • CDOT
    • NAPA
    • ACI
    • FAA
  • Pavements, (cont.)
    • Swell Mitigation - Every Agency is different
    • Overexcavation and moisture-conditioning
    • Removal and replacement
    • May include Chemical treatment – Lime, fly ash, cement
    • Surface drainage main key in long term pavement subgrade performance
      • Base course can provide a pathway for water and formation of a bathtub if roadway grades are not right
      • Backfill curb and maintain good drainage
      • (silt fence can be a problem!)
      • May need to install edge drains behind curb
  • Earthwork- Overview
    • This section provides recommendations for stripping, subgrade preparation, dewatering, fill materials, moisture/compaction specifications, maximum slopes, shrink/swell estimates, etc.
  • Earthwork Recommendations
    • Observation and testing of Engineered Fill and Structural Fill are key to long-term performance
      • Breakdown/processing of materials is key to achieve proper compaction and swell mitigation
      • Water almost always required to achieve compaction and swell mitigation. Higher moisture contents required in expansive clays to reduce swell/settlement potential, but may lead to pumping
      • Higher compactive effort may be needed to limit settlement of deep fill zones
  • Earthwork Recommendations
    • Provide Recommendations for maximum permanent slopes
      • Generally 3:1 (H:V) is recommended for clays and loose sands
      • Retaining walls (often tiered walls) are used to steepen slopes; however, without thinking about slope stability analyses, this can be dangerous
      • Tiered walls tend to be designed to make an overall slope of 1:1
      • This is generally unsafe, especially with landscaping
  • Additional Recommendations
    • Seismic Site Classification (ReMI)
    • Exterior Flatwork - subgrade preparation, swell mitigation
    • Underground Utility Design/Construction – groundwater, flexibility, corrosion, etc.
    • Cement Type
  • Additional Recommendations
    • Entire report depends on Surface Drainage…
      • Slope grades away from buildings and onto pavements (no ponding behind curbs)
      • May require swales, chases, area drains
      • Landscaping recommendations for areas near buildings/infrastructure
      • Recommendations for discharge of downspouts away from the building
      • Available for Geotechnical review…Observation of finished product
  • Appendices
    • Boring Location Map
    • Logs of Borings
    • Laboratory Test Results and Summary
    • Report Terminology and General Notes
      • USCS
      • Definitions
    • Other: Traffic/Pavement Calculations
  • Construction Observation and Materials Testing
    • Important for proper documentation that recommendations have been followed per geotechnical report, project plans, and specs
    • Provides a high level of quality assurance for owners/buyers
    • Does not replace contractor’s quality control
  • Construction Observation and Materials Testing
    • Proofroll observation
    • Fill compaction testing
    • Bearing strata evaluation
    • Utility Trench Backfill
    • Subgrade testing
    • ICC Reinforcing and Structural Steel Inspections
    • Masonry observations and testing
    • Mix Design Review
    • Concrete, asphalt, and other materials testing
    Services Offered, but not limited to…
  • Foundation QC Testing
    • Osterberg Cell/Load Testing
    • Pile Dynamic Analyses
    • Cross-hole Sonic Logging
    • Pulse-echo Integrity Tests
    • Small-strain Dynamic Load Tests
    • Geotechnical Instrumentation
            • Slope Inclinometer
            • Settlement Devices
            • Pore Pressure Devices
  • Geotechnical Field Methods
    • Polymer Slurry-Drilled Shafts
    • Cast-in-place Displacement Piles
    • Secant/Tangent Walls
    • Ground Improvement
    • Soil Nailing
    • Soil Rock Anchors
    • Mini-piles
    • Light-Weight Fill
  • Questions and Discussion Reliable ■ Responsive ■ Convenient ■ Innovative