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2011-04-15 13:57:53
ASBOG Study Guide Chap Eleven

ASBOG Study Guide Chapter 11 - Engineering Characteristics of Earth Materials
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  1. A-line
    the line on the plasticity chart that divides clays from silts. Equations of the line is horiztontal at PI=4 to LL=25.5, then PI=0.73 (LL-20)
  2. Atterberg Limits
    water content at the boundaries between the states of consistency of a soil
  3. Bearing capacity
    the load per unit area whihc the ground ca safely support without excessive yield
  4. Bulk Density (ρ)
    The density of a material measured in mass per unit volume
  5. Bulk Modulus (K) or Incompressibility Modulus
    a modulus of elasticity which relates a change in volume to the hydrostatic state of stress.; It is the reciprocal of compressibiltiy
  6. Coefficient of Curvature (Cc)
    a measure of the curvature of the grain size distribution plot. Well-graded sands and gravels have coefficients of curvature between 1 and 3
  7. Coefficient of Uniformity (Cu)
    A measure of the grain size uniformity using the ratio of particle sizes D60 to D10.
  8. Compaction
    the process of increasin the density of a soil (usually fill) by rolling, tamping, vibrating or other mechanical means
  9. Consistency
    the degree of adhesion between soil particles that can resist deformation or rupture
  10. Consolidation
    Gradual or slow reduction in volume and increas in density of a soil mass in response to increased load or compressive stress
  11. Critical Void Ratio
    the final void ratio at ultimate strength achieved by loose and dense samples of the same soil after shearing
  12. Degree of saturation (SR)
    the raito of the volume of water to the total volume of void space. The value of SR can range from 0 (0%) to 1 (100%)
  13. Dilatancy
    an increase in the bulk volume during deformation, caused by a change from a close-packed structure to an open-packed structure
  14. Direct Shear test
    a laboratory test to measure the shear strength of a soil
  15. Dry density (ρd)
    The density of a soil when it is completely dry; bulk density divided by 1 + water content
  16. Dry Strength
    The strength of a soil when dry as determinded by the crushing test
  17. Effective Size (D10)
    The diameter D10 which corresponds to the precentages, by weight, of grains equal to 10% of the grain-size diagram. Ten percent of the particles are finer and 90% are coarser than the effective size
  18. Effective stress (σ')
    That part of the total stress that is due entirely to the solid particles of soil, and represents an excess over the neutral stress or pore-water pressure. Effective stress = total stress minus pore-water pressure
  19. Gap-graded
    a soil in which some particle sizes are missing
  20. Hooke's Law
    a statement of elastic deformation - the strain is linearly proportional to the applied stress
  21. Liquid Limit (LL)
    the upper limit of the plastic state. Water content, in percent of dry weight, at which two sections of a pat of soil, separated by a specific distance, barely touch each other but do not flow together when given a sharp blow
  22. Liquefaction
    The sudden large decrease in shearing resistance of a cohesionless soil, caused by a collapes of the structure by shock or strain, and associated with a sudden but temporary increase of the pore-water pressure. The material is transformed into a fluid mass
  23. Mohr Circle
    graphical representation of the state of stress (normal and shear) on a particular plane inclined at an angle ot the major principal stress
  24. Mohr-Coulomb Equation
    an equation describing the failure of a material in shear fracture. The rupture line is a Mohr circle can be approximated by this equation
  25. Normal stress (σn)
    the component of stress that acts perpendicular to the plane
  26. Optimum Moisture Content
    the moisture content at which the maximum dry density of a soil is attained
  27. Piping
    erosion by percolating waters or seepage in a layer of subsoil resulting in caving and the formation of tunnels or pips through which the soluble or granular material is removed
  28. Plastic Index (PI)
    range in water content between the liquid limit (LL) and the plastic limit (PL). PI=LL-PL
  29. Plastic Limit (PL)
    the lower limit of the plastic state. Water content at which the soil begins to crumble when rolled out onto thin threads
  30. Poisson's Ratio (υ)
    An elastic constant (does not exceed 0.5). The ratio of the lateral unit strain to the longitudinal unit strain in a body that has been stressed longitudinally within it's elastic limit
  31. Porosity (n)
    The percentage of the bulk volume of rock or soil that is occumpied by void space
  32. Quick condition
    the condition of a soil in which a decrease in intergranular pressure allows water to flow upward with sufficient velocity to reduce significantly the soil's bearing capacity
  33. Relative Density (R.D.)
    the raito of the difference between the void ratio of a cohesionless soil in the loosest state and any given void ratio to the difference between its void ratios in the loosest and in the densest states

    • emax - e = R.D.
    • emax - emin
  34. Relative compaction
    the amount of compaction relative to the moisture-density curve, or compaction curve
  35. Seepage
    the movement of water or other fluid through a porous material such as soil
  36. Settlement
    the gradual downward movement of an engineered structure due to compression of the soil below the foundation
  37. Shear Modulus (G) or Rigidity Modulus
    a modulus of elasticity in shear. It measures the shear strain resulting from shear stress on a plane
  38. Shear Strength (s)
    the internal resistance of a soil to shear stress consisting of a combination of friction and cohesion
  39. Shear stress (τ)
    the component of stress that acts along a plane through any point in the body
  40. Shrinkage Limit
    Water content at which the soil volume is lowest
  41. Specific Gravity (Gs)
    the raito of the density of the solid particles to the density of water at 4oC
  42. Toughness
    the property of a soil that is able to absorb strees by plastic deformation
  43. Triaxial test
    the most widely used shear strength test in which drainage conditions can be controlled. Three principal types of tests are: unconsolidated-undrained (UU), consolidated-undrained (CU), and consolidated-drained (CD)
  44. Unconfined Compressive Strength Test
    a special case of the triaxial test in which axial stress is applied to a specimen under atmospheric pressure to obtain the value of the shear strength
  45. U-line
    the line on the plasticity chart that marks the approximate uppper limit of the relationship between the plasticity index and the liquid limit for natural soils. It is a check agains erroneous data - if a data point plots above or to the left of the line, verify the information
  46. Unit Weight (γ)
    The weight of soil plus water per unit volume
  47. Void Ratio (e)
    the ratio of the volume of void space to the volume of solids
  48. Well-graded
    a soil with all grain sizes present with no excess in any size range. Equivalent to the geologist's term "poorly sorted"
  49. Young's Modulus (E) or Modulus of Elasticity
    an elastic constant given by the ratio of stress to it's corresponding strain under given conditions of load, for materials that deform elastically according to Hooke's Law