(MODULE 9.2) ENGINEERING BEHAVIOR AND PROPERTIES OF SOIL AND ROCKS Flashcards
soils are derived from the ___
weathering of rocks
soils are broadly described by terms such as ___, ___, ___, and ___
gravels, sands, silts, and clays
physical weathering causes ___ of the parent rock without ___
reduction in size; change in its composition
chemical weathering causes ___ and ___.
reduction in size of the parent rock and change in chemical composition
gravels, sands, silts, and clays are used to identify specific textures in soils. these soil textures are referred to as ___
soil types
sands and gravels are grouped together as ___
coarse-grained soils
clays and silts are ___
fine-grained soils
coarse-grained soils feel ___
gritty and hard
the coarseness of soils is determined from knowing the ___, which is the primary means of classifying coarse-grained soils
distribution of particle sizes
fine-grained soils feel ___
smooth
to characterize fine-grained soils, we need ___
further information on the minerals present and their contents
fine-grained soils have a ___ arrangement
flaky
soil minerals
the principal mineral of coarse-grained soils
quartz
the mineral particles of fine-grained soils are ___
platy
the main groups of crystalline materials that make up fine-grained soils are the minerals ___, ___, and ___
kaolinite, illite, and montmorillonite
minerals are ___ and make up the solid’s ___
crystalline materials; constituent of a soil
during deposition, the mineral particles are arranged into structural frameworks that we call ___
soil fabric
the environment under which deposition occurs influences the ___
structural framework that is formed
in particular, the ___ has the greatest influence on the kind of soil fabric formed during deposition of fine-grained soils.
electrochemical environment
two common types of soil fabric are formed during deposition of fine-grained soils:
1.
2.
- flocculated
- dispersed
a flocculated structure, formed in a saltwater environment results in ___
many particles arranging parallel to one another
a flocculated structure, formed in a freshwater environment, results in ___
many particles arranging perpendicular to one another
this structure of soil fabric occurs when a majority of the particles orient parallel to one another.
dispersed structure
the spaces between the mineral particles are called ___, which may be filled with
1.
2.
3.
voids; liquids, gases, and cement minerals
coarse-grained soils have ___, ___, and ___
good load-bearing capacities, good drainage qualities, and strength
course-grained soils are incompressible when dense, but ___ can occur when they are loose
significant volume changes
___ accentuate volume changes in loose, coarse-grained soils by ___.
vibrations; rearranging the soil fabric into a dense configuration
coarse-grained soils with ___ have ___, ___, and ___ than coarse-grained soils with rounded particles
angular coarse-grained soils; higher strengths, higher compressibility, lower densities
why are angular particles of coarse-grained soils sturdier than rounded particles?
if you have angular particles, the contact between them would increase friction. the increase in friction would let it have higher strengths and compressibility. due to it being angular, it tends to have lesser voids than rounded particles.
coarse-grained soils are generally described as ___
free draining
free draining means that ___
the soil allows free passage of water in a relatively short time
___ can significantly alter the flow conditions in these soils
fines content (silts and clays)
gravel, boulders, and coarse sands with fins content less than ___ are ___
5%; free draining
__, especially if it exists as a thick layer, is not free draining.
fine sand
___ means it has high permeability, meaning there is a lot of seepage that can happen within the coarse-grained soils.
free draining
fine-grained soils have ___ compared with coarse-grained soils.
poor load-bearing capacities
fine-grained soils are practically ___, ___. and are ___.
impermeable, change in volume and strength, susceptible to frost
___ control, the engineering properties of fine-grained soils, in contrast to course-grained soils whose properties depend on grain size and shape.
mineralogical factors
___ have been responsible for many geotechnical failures.
thin layers of fine-grained soils, even within thick deposits of coarse-grained soils
when there are no joints, ideally, the rock mass and the intact rock should have the same properties, provided the rock is ___
homogeneous
joints within a joint set are approximately ___
parallel
intact rock: ___
isotropic properties
isotropic: ___
same properties in all directions
a collective term used for all structural breaks (bedding planes, fractures, and joints) in solid geologic materials that usually have zero to low tensile strength
discontiniuity
the discontinuities make the rock mass ___
anisotropic
the amount of joint sets can be identified by ___
seeing the differing orientation of joints, linking a set to joints with the same angle.
factors affecting discontinuities
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
- orientation
- spacing
- persistence
- roughness
- wall strength
- aperture
- filling
- seepage
- number of joint sets
- block size and shape
measured by the dip and dip direction of a discontinuity, very critical to stability; in the right direction, the stability of a rock can be affected significantly, positive or negative.
orientation
if the discontinuity plane or fracture continues from the top of the slope to the bottom, the steep dip angle will ___
cause mass wasting because of the discontinuity plane lying like a bed underneath the mass above.
the perpendicular distance between two adjacent discontinuities of the same set
spacing
it affects the ___ of the rock mass and the ___.
hydraulic conductivity; failure mechanism
closely spaced joints can imply ___
highly permeable rock
if the spacing is too close to each other, ___, increasing permeability
water can find a path to flow through
the measure of the extent to which the discontinuity extends to the rock
persistence
what is the surface area of the discontinuity?
this is the area that takes part in any possible sliding, and hence is an important parameter in determining stability.
refers to the large-scale surface undulations observed over several meters and the small-scale unevenness of the two sides relative to the mean plane, observed over several centimeters.
roughness
roughness
large-scale undulations can be called ___, ___, or ___.
stepped, undulating, or planar
roughness
small-scale unevenness can be called ___, ___, or ___.
rough, smooth, or slickensided
roughness is measured using the ___ method.
linear profiling
this tool provides useful basis for examining some of the issues associated with estimation of roughness.
profile gauge tool
refers to the compressive strength of the rock that makes up the walls of the discontinuity
wall strength
wall strength is an important factor that governs the ___ and ___
shear strength and deformability
the perpendicular distance between the two adjacent rock walls of an open discontinuity where the space is filled by air or water.
aperture
a joint is called either tight or open, depending on whether the ___
aperture is small or large
the term used to describe the material that occupies the space between the adjacent rock walls of a discontinuity
filling
filling affects the ___ and ___ of the rock mass
permeability and deformability
the permeability of a given rock mass
seepage
determines the ability of the rock mass to deform without undergoing failure
number of joint sets
as the number of joint sets increases, the ___ decreases and their ___ increase
individual block size; degrees of freedom to move
the rock mass consists of ___ formed by intersections of several joints
blocks
