GEOTECH

• 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.
• SOIL ENGINEERING is the application of the principles of soil

  mechanics to practical problems.
• SOILS are materials that are derived from the weathering of rocks.
• MINERALS are chemical elements that constitute rocks.
• ROCKS are the aggregation of minerals into a hard mass.
• Alluvial soils are 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.
• Eolian soils are sand-sized particles deposited by wind.
• Expansive soils are clays that undergo large volume changes from

  cycles of wetting and drying.
• Glacial soils are mixed soils consisting of rock debris, sand, silt,

  clays, and boulders.
• Glacial till is a soil that consists mainly of coarse particles.
• Gypsum is calcium sulfate formed under heat and pressure from

  sediments in ocean brine.
• Glacial clays are 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.
• Collovial soils (collovium) are soils found at the base of mountains

  that have been eroded by the combination of water and gravity.
• Lacustrine soils are mostly silts and clays deposited in glacial lake

  waters.
• Lateritic soils are residual soils that are cemented with iron oxides

  and are found in tropical regions.
• Loam is a mixture of sand, silt, and clay that may contain organic

  material.
• Loess is a wind-blown, uniform, fine-grained soil.
• Marine soils are sand, silts, and clays deposited in salt or brackish

  water.
• Marl (marlstone) is a mud (see definition of mud below) cemented by

  calcium carbonate or lime.
• Mud is clay and silt mixed with water into a viscous fluid.
• 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
• Sieve Analysis – for particle sizes larger than 0.075 mm in diameter
• Hydrometer Analysis – for particle sizes smaller than 0.075 mm in

  diameter
• Effective Size - This refers to the diameter of the particle size

  corresponding to 10% finer
• Uniformity Coefficient, Cu - This is the ratio of the particle size

  corresponding to 60% finer to the effective size.
• 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.
• Void Ratio (e) - the ratio of the volume of void space to the

  volume of solids.

  A) e

  
• Porosity (n) - is the ratio of the volume of voids to the total

  volume.

  A) n

  
• Specific gravity (Gs) - is the ratio of the weight of the soil

  solids to the weight of water of equal volume

  A) GS

  
• Degree of Saturation (S) - is the ratio, often expressed as a

  percentage, of the volume of water to the volume of voids

  A) S

  
• Unit Weight ( ) – or bulk unit weight, is the weight of a soil

  per unit volume.

  A) Y

  
• Saturated Unit Weight: The weight of a unit volume of a liquid at its saturation point

  A) YSAT

  
• Dry Unit Weight (S=0)

  A) YDRY

  
• Effective or Buoyant Unit Weight is the weight of a

  saturated soil, surrounded by water, per unit volume of soil.

  A) Y'

  
• Relative Density (Dr) – is an index that quantifies the degree

  of packing between the loosest and densest possible state of

  coarse-grained soils as determined by experiments

  A) DR

  
• PLASTIC LIMIT (PL) – It is 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.