GE

• The geological time scale is the chronology of events that have occurred during Earth's history.
• Geotechnical Engineering is a subdiscipline of civil engineering that involves natural materials found close to the surface of the earth
• Civil Engineers must study the properties of soil, such as its origin, grain-size distribution, ability to drain water, compressibility, shear strength, and load-bearing capacity
• Soil is defined as the uncemented aggregate of mineral grains and decayed organic matter with liquid and gas in the empty spaces between the solid particles
• Soil is used as a construction material in various civil engineering projects and it supports structural foundations
• Soil Mechanics is the branch of science that deals with the study of the physical properties of soil and the behavior of soil masses subjected to various types of forces
• Geotechnical Engineering includes the application of the principles of soil mechanics and rock mechanics to the design of foundations, retaining structures, and earth materials
• Soil is derived from the weathering of rocks
• Soil weathering can be mechanical, which is the process of rocks being broken into pieces by physical force, or chemical, which is the process of chemical decomposition of the original rock
• There are three basic types of rocks: Igneous Rock, Sedimentary Rock, and Metamorphic Rock
• Soil can be deposited as Residual Soil, which is formed by the weathered products at their place of origin, or Transported Soil, where the composition depends on the environment under which they were transported
• There are five major categories of transported soils: Colluvial/Gravity Transported, Lacustrine, Alluvial, Glacial, Aeolian, and Marine
• Soil minerals are crystalline materials that make up the solids constituent of soil
• Quartz is the principal mineral of coarse-grained soils and is composed of silicon dioxide in colored, colorless, and transparent hexagonal crystals
• Clay minerals are complex aluminum silicates made of two distinct structural units: Silicon tetrahedron and Alumina Octahedron
• The three main types of clay minerals are Kaolinite, Illite, and Montmorillonite
• Kaolinite consists of repeating layers of elemental silica-gibbsite sheets in a 1:1 lattice and is used in paints, paper, pottery, and pharmaceutical industries
• Illite consists of gibbsite sheets bonded to two silica sheets, also bonded by potassium ions, and is sometimes called clay mica
• Montmorillonite has a structure similar to that of illite, with one gibbsite sheet sandwiched between two silica sheets, attracting a large amount of water into the space between the layers
• Bentonite is a highly reactive clay from the montmorillonite family used in drilling mud, slurry trench walls, and to stop leaks
• Montmorillonite has a structure similar to illite, with one gibbsite sheet sandwiched between two silica sheets
• Potassium ions are not present in montmorillonite as in illite, and a large amount of water is attracted into the space between the layers
• Soil particles are assumed to be rigid and arranged into structural frameworks called soil fabric during deposition
• Two common types of soil fabric are flocculated and dispersed, formed during the deposition of fine-grained soils
• Flocculated structure in a saltwater environment has particles oriented parallel to one another, while in a freshwater environment, particles are oriented in a perpendicular manner
• Dispersed structure occurs when the majority of particles orient parallel to one another
• Particle shape can be categorized into bulky particles (angular, sub-angular, rounded, sub-rounded), flaky particles (predominantly clay minerals), and needle-shaped particles (less common, examples include coral deposits and attapulgite clays)
• Soil types include gravel (pieces of rocks with occasional quartz, feldspar), sand (mostly quartz and feldspar), and silt and clay (consisting of very fine quartz grain, flake-shaped microscopic and submicroscopic particles of mica, clay mineral, and others)
• Soils can be classified based on the size of particles present
• Mechanical analysis of soil involves sieve analysis for particle sizes larger than 0.075 mm and hydrometer analysis for particle sizes smaller than 0.075 mm
• Sieve analysis consists of shaking the soil sample through a set of sieves with progressively smaller openings
• Particle size distribution curve is determined through sieve analysis and hydrometer analysis
• Parameters determined from the particle size distribution curve include Effective Size (D10), Uniformity Coefficient (Cu), Coefficient of Gradation (Cc), and Sorting Coefficient (S0)
• Different types of particle-size distribution curves include poorly graded, well-graded, and gap graded soils
• A sample problem involves determining percent finer in each sieve, plotting a grain-size distribution curve, calculating D10, D30, D60, uniformity coefficient (Cu), and coefficient of gradation (Cc)
• Laboratory exercises involve visual classification and identification of soil following specific procedures and submission guidelines