LESSON 11 GEOLOGY

• Soil


  A fundamental element in Civil Engineering. It acts as the medium though which structures are going to be built.
• Understanding soil


  • Crucial in order to design and build structures that are safe and durable
  • Varies from projects to projects
• Soil properties


  • One of the most crucial part of design and construction
  • Includes the long-term performance of infrastructure
• Soil properties


  • Grain size distribution
  • Plasticity
  • Compressibility
  • Shear strength
  • Permeability
• Grain size distribution


  To determine the percentage of each size of train that is contained within a soil sample. The results can be used to produce the grain size distribution curve. We can also use this graph and information to predict its behavior.
• Plasticity


  The ability of the soil to undergo deformation without cracking
• Compressibility


  The tendency of the soil to decrease in volume under applied pressure
• Shear strength


  The ability to resist the deformation and failure under applied stresses
• Permeability


  A measure on how quickly water passes through the soil
• Sieve analysis


  An analytical technique used to determine the particle size distribution of a granular material with macroscopic granular sizes
• ASTM

  American Society for Testing and Materials
• ASTM D 422 is the standard for sieve analysis
• Sieve sizes

  • 4 (4.75 mm)
  • 8 (2.36 mm)
  • 16 (1.18 mm)
  • 30 (0.60 mm)
  • 50 (0.297 mm)
  • 100 (0.149 mm)
  • 200 (0.075 mm)
  • Pan
• Soil triangle


  The USDA classifies soil types according to the soil texture triangular chart which gives names to various combinations of CLAY, SAND, and SILTS
• Soil particle sizes

  • SANDS – 2.0 to 0.05 mm diameter
  • SILTS – 0.05 to 0.002 mm diameter
  • CLAY – less than 0.002 mm diameter
• Soil A

  • 75% sand, 10% silt, 15% clay
• Soil B

  • 10% sand, 83% silt, 7% clay
• Soil C

  • 42% sand, 21% silt, 37% clay
• Determining soil classification from percent sand, silt, clay

  Use soil triangle
• Modifying percent sand, silt, clay if gravel is present

  Modified % Sand = % Sand / (100% - % Gravel)

  Modified % Silt = % Silt / (100% - % Gravel)

  Modified % Clay = % Clay / (100% - % Gravel)
• Percent gravel 12%

  Percent sand 25%

  Percent silt 32%

  Percent clay 31%
• Bacteriology midyear