ASBOG - Engineering Geology Exam
Questions with Correct Answers
Strain - Answer-An alteration in the shape or volume of a soil related to stress. It is
calculated as the ratio of the new shape compared to the original shape
Effective Stress - Answer-The total amount of stress placed on a soil minus the pore-
water pressure
Normal Stress - Answer-The component of total stress that acts perpendicular to the
plane.
Shear stress - Answer-The component of total stress that acts parallel to any point in
question.
Dilatancy - Answer-Tendency of a material to increase in volume when subjected to a
shape change. Assume a closed-packed structure from an open-packed structure
Quick Condition - Answer-Tendency of some soils that lack cohesion to allow water to
flow rapidly between grains and to liquefy the material. Soil does NOT possess
significant bearing capacity
Elastic Modulus - Answer-Measure stiffness in a material (bulk, shear, Young's(Elastic))
Triaxial Test - Answer-Test for mechanical properties of deformable solids.
Direct Shear test - Answer-Measure shear strength when sample is surrounded
withstand subjected to mechanical stresses.
Unconfined compressive strength test - Answer-Similar to triaxial but without external
confining pressure.
Consistency - Answer-General amount of cohesion in soil particles
Critical void ratio - Answer-Void ratio of soil that stays the same even during shearing
events.
Mohr circle - Answer-Graph showing stresses that act on a single point on a plane. The
x-axis - normal stress. Y-axis - shear stress
Seepage - Answer-The flow of a fluid through soil pores.
4-inch diameter; three lifts; 25 blows by 5.5 lb hammer; falling 12-inches - Answer-
Proctor Test
,five lifts; 10lb hammer; 18-inches - Answer-Modified Proctor Test
Differentiate between the three different types of modulus: bulk
(incompressibility) modulus, shear (rigidity) modulus, Young's
(elasticity) modulus. - Answer-There are three different kinds of modulus, or ways to
measure the
stiffness of the material:
• bulk modulus (K; otherwise known as incompressibility
modulus): a measure of a substance's resistance to uniform
compression. It is defined as the pressure increase needed
to affect a given relative decrease in volume
• shear modulus (G; also known as rigidity modulus): refers
to the deformation of a solid when exposed to a force
parallel to one of its surfaces as its opposite face is exposed
to an opposing force. This will cause an object that is
shaped like a rectangular prism to be deform into a
parallelpiped
• Young's modulus (E; also known as the modulus of
elasticity): a measure of the stiffness of a given material.
Defined as the ratio, for small strains, of the rate of change
of stress with strain
Define the terms used to describe volume changes in soils:
dilatancy, dry strength, quick condition. - Answer-The following terms are used to
describe volume changes in soils:
dilatancy: the tendency of a material to increase in volume
when subjected to a shape change. Also refers to material
which can assume a close-packed structure from a openpacked
structure
• dry strength: the resistance that a dry soil possesses to
being crushed. A soil that is composed of clays and gravels
will have relatively high dry strength
quick condition: the tendency of some soils that lack
cohesion to allow water to flow rapidly between grains and
to liquefy the material. Such a soil does not possess
significant bearing capacity. Bearing capacity is the ability
of soils to support the loads imposed by buildings or
structures
Distinguish between the following types of tests: direct shear test,
triaxial test, unconfined compressive strength test. - Answer-The following tests are
designed to quantify engineering parameters
of soils:
• triaxial test: a common method to measure the mechanical
properties of many deformable solids. The test is used for
, soil, sand, clay, and other granular material. Test involves a
cylinder of soil which is subjected to uniform fluid pressure
from all sides. After being checked for deformation, the
sample is then subjected to a vertical load. Drainage
conditions are controlled
• direct shear test: laboratory tests to measure the shear
strength of soil in which the soil or rock sample is
surrounded with sand and subjected to a series of
mechanical stresses which are analyzed by computer. The
sample is normally saturated before the test is run, but can
be run at the in-situ moisture content
• unconfined compressive strength test: similar to a triaxial
test but without external confining pressure applied
Discuss the terms used to describe soil grain size: well-graded, gap
graded, effective size, coefficient of curvature, coefficient of
uniformity. - Answer-The following terms are used to describe the grain size of soil:
• well-graded soil: soil or unconsolidated sediment consisting
of particles of several different sizes and having a uniform
or equal distribution of particles from coarse to fine. A
graded sand or sandstone containing coarse, medium, and
fine particle sizes is an example
• effective size: corresponds with the weight percentage of
material equal to a certain size amount. Measures the
distribution of grain sizes; for example, a grain with an
effective size of D3o would be finer than 70% of the other
grains in the sample
• gap-graded soil: any soil that is missing distinct particle
size ranges.
• coefficient of curvature (Cc): a measure of the curve on a
grain size distribution plot
• coefficient of uniformity (Cu): a measure of the degree to
which grain sizes are uniform. Found by determining the
ratio of particle sizes
Define the following terms related to soil strength investigations:
bearing capacity, consistency, critical void ratio, Mohr circle, Mohr Coulomb
equation. - Answer-The following terms are related to soil strength investigations:
• bearing capacity: the maximum load per unit area that a
particular soil can be subjected to before it collapses.
Bearing capacity is the ability of soils to support the loads
imposed by buildings or structures
• consistency: the general amount of cohesion in soil
particles
• critical void ratio: the void ratio of soil that stays the same
even during shearing events
Questions with Correct Answers
Strain - Answer-An alteration in the shape or volume of a soil related to stress. It is
calculated as the ratio of the new shape compared to the original shape
Effective Stress - Answer-The total amount of stress placed on a soil minus the pore-
water pressure
Normal Stress - Answer-The component of total stress that acts perpendicular to the
plane.
Shear stress - Answer-The component of total stress that acts parallel to any point in
question.
Dilatancy - Answer-Tendency of a material to increase in volume when subjected to a
shape change. Assume a closed-packed structure from an open-packed structure
Quick Condition - Answer-Tendency of some soils that lack cohesion to allow water to
flow rapidly between grains and to liquefy the material. Soil does NOT possess
significant bearing capacity
Elastic Modulus - Answer-Measure stiffness in a material (bulk, shear, Young's(Elastic))
Triaxial Test - Answer-Test for mechanical properties of deformable solids.
Direct Shear test - Answer-Measure shear strength when sample is surrounded
withstand subjected to mechanical stresses.
Unconfined compressive strength test - Answer-Similar to triaxial but without external
confining pressure.
Consistency - Answer-General amount of cohesion in soil particles
Critical void ratio - Answer-Void ratio of soil that stays the same even during shearing
events.
Mohr circle - Answer-Graph showing stresses that act on a single point on a plane. The
x-axis - normal stress. Y-axis - shear stress
Seepage - Answer-The flow of a fluid through soil pores.
4-inch diameter; three lifts; 25 blows by 5.5 lb hammer; falling 12-inches - Answer-
Proctor Test
,five lifts; 10lb hammer; 18-inches - Answer-Modified Proctor Test
Differentiate between the three different types of modulus: bulk
(incompressibility) modulus, shear (rigidity) modulus, Young's
(elasticity) modulus. - Answer-There are three different kinds of modulus, or ways to
measure the
stiffness of the material:
• bulk modulus (K; otherwise known as incompressibility
modulus): a measure of a substance's resistance to uniform
compression. It is defined as the pressure increase needed
to affect a given relative decrease in volume
• shear modulus (G; also known as rigidity modulus): refers
to the deformation of a solid when exposed to a force
parallel to one of its surfaces as its opposite face is exposed
to an opposing force. This will cause an object that is
shaped like a rectangular prism to be deform into a
parallelpiped
• Young's modulus (E; also known as the modulus of
elasticity): a measure of the stiffness of a given material.
Defined as the ratio, for small strains, of the rate of change
of stress with strain
Define the terms used to describe volume changes in soils:
dilatancy, dry strength, quick condition. - Answer-The following terms are used to
describe volume changes in soils:
dilatancy: the tendency of a material to increase in volume
when subjected to a shape change. Also refers to material
which can assume a close-packed structure from a openpacked
structure
• dry strength: the resistance that a dry soil possesses to
being crushed. A soil that is composed of clays and gravels
will have relatively high dry strength
quick condition: the tendency of some soils that lack
cohesion to allow water to flow rapidly between grains and
to liquefy the material. Such a soil does not possess
significant bearing capacity. Bearing capacity is the ability
of soils to support the loads imposed by buildings or
structures
Distinguish between the following types of tests: direct shear test,
triaxial test, unconfined compressive strength test. - Answer-The following tests are
designed to quantify engineering parameters
of soils:
• triaxial test: a common method to measure the mechanical
properties of many deformable solids. The test is used for
, soil, sand, clay, and other granular material. Test involves a
cylinder of soil which is subjected to uniform fluid pressure
from all sides. After being checked for deformation, the
sample is then subjected to a vertical load. Drainage
conditions are controlled
• direct shear test: laboratory tests to measure the shear
strength of soil in which the soil or rock sample is
surrounded with sand and subjected to a series of
mechanical stresses which are analyzed by computer. The
sample is normally saturated before the test is run, but can
be run at the in-situ moisture content
• unconfined compressive strength test: similar to a triaxial
test but without external confining pressure applied
Discuss the terms used to describe soil grain size: well-graded, gap
graded, effective size, coefficient of curvature, coefficient of
uniformity. - Answer-The following terms are used to describe the grain size of soil:
• well-graded soil: soil or unconsolidated sediment consisting
of particles of several different sizes and having a uniform
or equal distribution of particles from coarse to fine. A
graded sand or sandstone containing coarse, medium, and
fine particle sizes is an example
• effective size: corresponds with the weight percentage of
material equal to a certain size amount. Measures the
distribution of grain sizes; for example, a grain with an
effective size of D3o would be finer than 70% of the other
grains in the sample
• gap-graded soil: any soil that is missing distinct particle
size ranges.
• coefficient of curvature (Cc): a measure of the curve on a
grain size distribution plot
• coefficient of uniformity (Cu): a measure of the degree to
which grain sizes are uniform. Found by determining the
ratio of particle sizes
Define the following terms related to soil strength investigations:
bearing capacity, consistency, critical void ratio, Mohr circle, Mohr Coulomb
equation. - Answer-The following terms are related to soil strength investigations:
• bearing capacity: the maximum load per unit area that a
particular soil can be subjected to before it collapses.
Bearing capacity is the ability of soils to support the loads
imposed by buildings or structures
• consistency: the general amount of cohesion in soil
particles
• critical void ratio: the void ratio of soil that stays the same
even during shearing events
