Soil Mechanics

• Rock can be defined as a natural aggregate of minerals connected by strong and permanent attractive forces and considered as a consolidated materials
• Soil is defined as unconsolidated sediments and deposits of solid particles resulting from the disintegration of rock
• Topsoil is the top layer of regolith.
• Igneous rock results from the cooling and hardening of molten rock called magma, originating deep within the Earth
• Sedimentary rock is formed from accumulated deposits of soil particles or remains of certain organisms that have become hardened by pressure or cemented by minerals
• Two types of igneous rock:

  • Extrusive/Volcanic rock type: when molten materials cool rapidly at or near the Earth's surface (e.g., Basalts, Rhyolites, Andesites)
  • Intrusive/Plutonic type: when molten rock is trapped deep below the surface of the Earth and cools slowly (e.g., Granites, Syenites, Diorites, Gabbros)
• Rocks with chief minerals as Quartz or Orthoclase (high in silica content) decompose to predominantly sandy or gravelly soil with little clay (e.g., Granite and Rhyolite)
• Acidic rocks are light-colored, classified as acidic due to high silica content (e.g., Granite and Rhyolite)
• Regolith protects the rock below from weathering because bedrock weathers easier than regular rock.
• Most non organic materials that are identified as soil originated from rock as the parent material.
• The source of soils.

  Rock
• Basic rock are very dark colored rock.
• Rocks like granites, which are acidic, are considered good construction materials
• Sedimentary rocks:

  • Shale: formed predominantly from deposited clay and silts soils, relatively stable when exposed to the environment but some expand or delaminate after contact with water or air.
• Plastic flow refers to slow viscous movement and rearrangement within the rock mass as it changes and adjusts to the pressures created by external forces
• Soil categories:

  • Residual soil: formed from weathering of rocks and remain at the location of their origin, the weathering process may be attributed to mechanical weathering or chemical and solution weathering.
• Metamorphic rock results when igneous rock or sedimentary rocks are subject to a combination of heat, pressure, and plastic flow, changing the original rock structure and mineral composition
• The rate of weathering is greater in warm humid regions than in cool dry regions
• Sand stone is predominantly quartz cemented together with silica.
• Which are generally considered good construction materials

  Calcium carbonate or Iron compounds
• Cemented sand and gravel

  Conglomerate
• Cemented rock fragments which are similar to sand stones.

  Breccia
• Predominantly crystalline calcium carbonate formed under water.

  Limestone
• A variety of limestone, but harder and more durable.

  Dolomite
• Softer forms of limestone.

  Marl and Chalk
• A good foundation material provided that the formation is sound and free of cavities.

  Marl and Chalk
• Refers to the effect of wind rain, running water and tectonic forces (such as earthquake)

  Mechanical Weathering
• Is a rock decomposition due to chemical changes in the rock minerals brought about by exposure to the atmosphere, temperature changes, water or other materials.

  Chemical and Solution Weathering
• Are those materials that have been moved from their place of origin.

  Transported Soil
• Most common example of intrusive/plutonic type of rock

  Granites
• When molten materials cooled rapidly at or near the Earth’s surface.

  Extrusive or volcanic rock
• Example of Extrusive or Volcanic rock

  Basalts, Rhyolites, Andesites
• Intrusive or Plutonic Rock is when molten rock trapped deep below the surface of the Earth and cooled slowly.
• Example of Intrusive or Plutonic Rock


  Granites, Syenites, Diorites, Gabbros
• Classified as Basic Rocks

  • Gabbros
  • Diabeses
  • Basalts
• Rock whose high in Silica content

  Quarts or Orthoclase
• Two types of Igneous Rock

  • Volcanic Rock
  • Plutonic Rock
• 3 Rock Types

  • Igneous Rock
  • Sedimentary Rock
  • Metamorphic Rock
• Two broad categories of soil

  • Residual Soil
  • Transported Soil
• Types of Sedimentary Rock

  • Shale
  • Sand stone
  • Cinglomerate
  • Dolomite
  • Marl and Chalk
  • Sound limestone
  • Breccia
  • Limestone