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111 Cards in this Set
- Front
- Back
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I=
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H/L
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Overburden pressure =
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unit weight of soil X depth
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overburden pressure w/ water =
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(total soil unit weight - unit weight of water) X depth
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total soil unit weight =
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125 pcf
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unit weight of water =
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62.4 pcf
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at some point in time subjected to load greater than present overburden pressure
(normally consolidated clay or over consolidated clay) |
over consolidated clay
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only subjected to overburden pressure equal to present overburden pressure
(normally consolidated clay or over consolidated clay) |
normally consolidated clay
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these soils generally withstand greater loading with little or no settlement
(normally consolidated clay or over consolidated clay) |
over consolidated clay
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3 common causes of consolidation of soil and settlement of structures
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removal or overburden though erosion
melting of overriding glacial ice removal of an old structure |
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most settlement on sand occurs by...
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completion of construction
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with settlement on sand, the ____ of settlement is not a factor as it is with clay
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time
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is the time of settlement a factor with clay
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yes
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settlement (clay) results from (3)
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reduction in voids
rearrangement of soil grains compression of material in voids |
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is primary or secondary consolidation usually the greatest
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primary
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extrusion of water from voids of a fine grained soil (primary or secondary consolidation)
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primary
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plastic readjustments of soil grains (primary or secondary consolidation)
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secondary
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q =
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volume of water discharged
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L =
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length
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a =
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cross sectional area
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h =
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head
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water flow permeameter is ________, on site flow is __________
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downward
horizontal |
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in situ is latin for
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on site
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smooth walls of permeameter vary from...
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natural soils
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field soils are
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undisturbed
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soil ____________ occurs in the field
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satisfaction
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field soil is often...
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non-homogeneous
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difference in lab tests vs on site tests is the location of the...
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groundwater table
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darcy's law applies for ____-_______ ____ over a long ________
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well-defined flow
distance |
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if flow is short or irregular, use
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flow nets
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a path a water particle follows is a
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flow line
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these connect points on different flow lines having equal total energy heads
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equipotential lines
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water rises up through voids from water table
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capillary rise
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is an accurate calculation of capillary rise easy?
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no, virtually impossible
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smaller grain size = _______ ____ _____
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smaller void space
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smaller void space =
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greater capillary rise
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____ has low capillary rise and low permeability
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clay
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what has the greatest capillary rise
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fine grain sizes
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examples of fine grain sizes
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silts and very fine sands
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vertical expansion of soil
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frost heave
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what is the best defense against frost heave
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construct foundations deep enough to escape effects of frost heave
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entire void space filled with water
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saturated
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voids partially filled with water
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partially saturated
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water content greatly effects the characteristics and engineering behavior especially for
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fine grained soils
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soil characteristics and engineering behavior are greatly influenced by
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water content
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cohesive soils (clay) are hard as a rock when
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dry
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cohesive soils (clay) are soft and plastic when
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wet
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cohesive soils (clay) shrink when
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dry
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cohesive soils (clay) swell when
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wet
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these are weakened at high water contents
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fine grained soils
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sandy soil is _____ when dry and rather ____ when wet
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loose
hard |
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greater permeability means there is
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more void space
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the water flow through soil
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permeability
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low voids means there is
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low permeability
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fine grained soils (clay) high or low permeability
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low
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coarse grained (sand) high or low permeability
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high
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pressure which causes water flow in soils
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hydraulic head
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darcy's law analyzes _____ ____ in soils
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water flow
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i =
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hydraulic gradient
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k =
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coefficient of permeability
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velocity of flow varies directly with
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difference in hydraulic heads
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coefficient of permeability (k) may be quarantined in terms of
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grain size distribution
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flow rate through soil varies inversely with
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length in which hydraulic head occured
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compaction increases _____ strength
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shear
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compaction increases
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bearing capacity
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compaction decreases
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permeability
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compaction reduces soil _________ and _____
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shrinkage and swell
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compaction increases resistance to
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erosion
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to press the soil particles tightly together by expelling air from the void space
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compaction
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compaction is normally produced deliberately and proceeds rapidly during
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construction
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results in the reduction of voids, but as a result of extrusion of water from the void space
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consolidation
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is consolidation rapid
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no
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compaction is defined by (2)
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dry unit weight
moisture content |
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for a given compactive effort, there is a particular
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moisture content
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you reach 100% compaction at (2)
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maximum dry density
optimum moisture |
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density =
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weight/volume
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MDD range for organic
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60-80
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MDD range for granular, well graded
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120+ lb/ft cubed
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optimum moisture for gravel
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7%
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optimum moisture for sand
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10%
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optimum moisture for heavy clay
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17.5%
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typical clay optimum moisture is
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15-30%
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typical sands/silts optimum moisture is
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10-20%
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typical density of concrete
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200
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field test for in place density (3)
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troxler nuclear density device
sand cone rubber balloon |
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lab test for MDD
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5-point proctor
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field tests for MDD (2)
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MDOT T-99
MDOT 1-point cone test |
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5-point proctor lab test at
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5 moisture contents
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# of blows per layer
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25
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# layers with 25 blows each
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3
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weight of hammer
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5.5 lbs
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volume of mold was
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1/30 ft cubed
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sub grades and embankments
base courses pavement smooth finished grades what type of roller |
smooth wheeled
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clayey or silty soils
granular material - sandy soils what type of roller |
pneumatic roller
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best for compacting cohesive soils
fine grained soils (sand w/ clays and silts) moderate effectiveness on silts and clays not effective in uniformly graded sand what type of roller |
sheepsfoot roller
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can be combined with other roller types
granular material clean sands and gravels less effective in cohesive soils what type of roller |
vibratory roller
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used in trenches and narrow spots
hand operated - vertical blows |
tamper
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dynamic compaction:
weight from ______ height from ______ |
2-20 TONS
20-100 FEET |
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typically obtain ___-___ % + of MDD
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95-98
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for soil stabilization, chemicals can be added like
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lime
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for soil stabilization, fabric material can be used like
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geosynthetics (geotextile fabric)
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used to densify (stabilize) existing soils when compactors will not be used on the soil
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soil stabilization
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few points of contact
poor interlock high permeability |
poorly graded
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good interlock
low permeability |
well graded
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only limited sizes
good interlock low permeability |
gap graded
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3 types of grain size distribution
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poorly graded, well graded, gap graded
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what lubricates soil particles
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water
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what creates clay particle bonding
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water
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are clays of high plasticity good for compaction
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yes
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is uniformly graded sand good for compaction
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yes
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shape of grains
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angular
rounded |
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what is the typical optimum moisture of A1A
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7-15%
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