HYDRAULICS AND GEOTECHNICAL ENGINEERING

• GEOTECHNICAL ENGINEERING is the science and practice of the part

  of civil engineering that involves natural materials found close to the

  surface of the earth. It includes the application of the principles of soil

  mechanics and rock mechanics to foundation design problems.

  SOILS are materials that are derived from the weathering of rocks.

  SOIL ENGINEERING is the application of the principles of soil

  mechanics to practical problems.

  MINERALS are chemical elements that constitute rocks.

  ROCKS are the aggregation of minerals into a hard mass.
• Alluvial soils


  Fine sediments that have been eroded from rock and transported by water, and have settled on river and stream beds
• Calcareous soil


  Contains calcium carbonate and effervesces when treated with hydrochloric acid
• Caliche


  Consists of gravel, sand, and clay cemented together by calcium carbonate
• Collovial soils (collovium)


  Soils found at the base of mountains that have been eroded by the combination of water and gravity
• Eolian soils


  Sand-sized particles deposited by wind
• Expansive soils


  Clays that undergo large volume changes from cycles of wetting and drying
• Glacial soils


  Mixed soils consisting of rock debris, sand, silt, clays, and boulders
• Glacial till


  Soil that consists mainly of coarse particles
• Glacial clays


  Soils that were deposited in ancient lakes and subsequently frozen. The thawing of these lakes revealed soil profiles of neatly stratified silt and clay, sometimes called varved clay. The silt layer is light in color and was deposited during summer periods, while the thinner, dark clay layer was deposited during winter periods
• Gypsum


  Calcium sulfate formed under heat and pressure from sediments in ocean brine
• Lacustrine soils


  Mostly silts and clays deposited in glacial lake waters
• Lateritic soils


  Residual soils that are cemented with iron oxides and are found in tropical regions
• Loam


  Mixture of sand, silt, and clay that may contain organic material
• Loess


  Wind-blown, uniform, fine-grained soil
• Marine soils


  Sand, silts, and clays deposited in salt or brackish water
• Marl (marlstone)


  Mud cemented by calcium carbonate or lime
• Mud


  Clay and silt mixed with water into a viscous fluid
• Three Major Types of Soil according to Particle Sizes

  • Gravel – particle size greater than 4.75 mm
  • Sand – particle size ranges from 0.075 mm to 4.75 mm
  • Silt & Clay – particle size lesser than 0.075mm
• Mechanical Analysis of Soil

  Determination of the size ranges of the particles present in a soil, expressed as a percentage of the total unit weight
• Sieve Analysis


  For particle sizes larger than 0.075 mm in diameter
• Hydrometer Analysis


  For particle sizes smaller than 0.075 mm in diameter
• Three Basic Soil Parameters Used to Classify Granular Soils

  1. Effective Size - This refers to the diameter of the particle size

  corresponding to 10% finer

  2. Uniformity Coefficient, Cu - This is the ratio of the particle size

  corresponding to 60% finer to the effective size.

  3. Coefficient of Gradation, Cc - This is the ratio of the square of

  the particle size corresponding to 30% finer to the product of the

  particle size corresponding to 60% finer and the effective size.

  
• Water Content (w)


  The ratio of the weight of water to the weight of solids
• Void Ratio (e)


  The ratio of the volume of void space to the volume of solids
• Porosity (n)


  The ratio of the volume of voids to the total volume
• Specific gravity (Gs)


  The ratio of the weight of the soil solids to the weight of water of equal volume
• Degree of Saturation (S)


  The ratio, often expressed as a percentage, of the volume of water to the volume of voids
• Unit Weight (γ)


  The weight of a soil per unit volume
• Effective or Buoyant Unit Weight

  The weight of a saturated soil, surrounded by water, per unit volume of soil
• Relative Density (Dr)


  An index that quantifies the degree of packing between the loosest and densest possible state of coarse-grained soils as determined by experiments
• LIQUID LIMIT (LL)


  The boundary between the plastic and liquid state. It is the moisture content required to close a distance of 1⁄2 inch along the bottom of the groove at 25 blows using the liquid limit device
• PLASTIC LIMIT (PL)


  The boundary between the semi-solid and plastic states. It is the moisture content at which the soil when rolled to 1/8 inch or 3.2 mm in diameter crumbles
• PLASTICITY INDEX (PI)


  The difference between the liquid limit and plastic limit of the soil
• SHRINKAGE LIMIT (SL) – It is the boundary between the solid

  and the semi-solid state of a soil.

  CLASSIFICATION OF SOIL

  Methods:

  1. AASHTO – American Association of State Highway and

  transportation Officials

  2. USCS – Unified Soil Classification System