Exam 1 Flashcards
(273 cards)
1
Q
Who cares about dirt (soil)?
A
- Geologists
- Contractors
- Hydrologists
- Farmers
- Agronomists
- Soil chemists
2
Q
Why does soil matter to a construction manager?
A
Most structures of all types rest either directly or indirectly upon soil. Proper analysis of the soil and design of the structure’s foundation are necessary to ensure a safe structure free of undue settling and/or collapse.
3
Q
Soil is composed of particles, ___ and
___.
A
large, small
4
Q
Soil includes :
A
solid matter, air, and water
5
Q
Particles are the result of
A
of weathering (disintegration and
decomposition) of rocks and decay of
vegetation.
6
Q
Cycles of rock disintegrating to form
A
soil, soil becoming consolidated under great pressure and heat to form rock, and so on.
7
Q
Difference Between Soil and Rock:
A
If material can be removed without blasting, it is usually considered to be “soil,” whereas if blasting is required, it might be regarded as “rock.
8
Q
Rock classification based on their origin and/or method of formation:
A
- Igneous 2. Sedimentary 3. Metamorphic
9
Q
form when magma (molten matter) such as that produced by erupting volcanoes cools sufficiently to solidify
A
Igneous rocks
10
Q
Being generally hard, dense, and durable, ______ often make good construction materials. Also, they typically have high bearing capacities and therefore make good foundation material.
A
igneous rock
11
Q
can be coarse-grained or fine-grained, depending on whether cooling occurred slowly or rapidly.
A
Igneous rocks
12
Q
Cool quickly and as a result these rocks are fine grained or has a lack of crystal growth.
A
Extrusive igneous rocks
13
Q
Are formed from magma that cools slowly and as a result these rocks are course grained.
A
Intrusive igneous rocks
14
Q
The most common coarse-grained igneous rock:
A
granite
15
Q
A hard rock rich in quartz, widely used as a construction material and for monuments
A
granite
16
Q
The most common fine-grained igneous rock. A hard, dark-colored rock rich in ferromagnesian minerals and often used in road construction.
A
basalt
17
Q
what type of rock is granite?
A
Igneous
18
Q
What type of rock is basalt?
A
Igneous
19
Q
compose the great majority of rocks found on the earth’s surface.
A
Sedimentary rocks
20
Q
They are formed when mineral particles, fragmented rock particles, and remains of certain organisms are transported by wind, water, and ice (with water being the predominant transporting agent) and deposited, typically in layers, to form sediments.
A
sedimentary rocks
21
Q
Over a period of time as layers accumulate at a site, pressure on lower layers resulting from the weight of overlying strata hardens the deposits, forming _________.
A
sedimentary rocks
22
Q
Can be identified easily when their layered appearance is observable.
A
Sedimentary rocks
23
Q
The most common sedimentary rocks are
A
shale, sandstone, limestone, and dolomite.
24
Q
The most abundant of the sedimentary rocks, is formed by consolidation of clays or silts.
A
Shale:
25
1. Organic matter or lime may also be present.
2. Have a laminated structure and often exhibit a tendency to split along laminations.
3. They can become soft and revert to clayey or silty material if soaked in water for a period of time.
Shales
26
vary in strength from soft (may be scratched with a fingernail and easily excavated) to hard (requiring explosives to excavate).
Shales
27
Relatively hard shale makes a good _______.
foundation material
28
consisting primarily of quartz, is formed by pressure and the cementing action of silica (SiO2), calcite (calcium carbonate, CaCO3), iron oxide, or clay.
Sandstone:
29
Strength and durability of sandstones vary widely depending on
the kind of cementing material and degree of cementation as well as the amount of pressure involved.
30
generally good Construction materials.
Sandstones
31
is sedimentary rock composed primarily of calcium carbonate hardened underwater by cementing action (rather than pressure); it may contain some clays or organic materials within fissures or cavities.
Limestone
32
Its strength varies considerably from soft to hard (and therefore durable), with actual strength depending largely on the rock’s texture and degree of cementation.
Limestone
33
Limestone with what type of texture is low strength?
(A porous texture means lower strength.)
34
If strong, can be good foundation and construction materials
Limestone
35
are similar in grain structure and color to limestones and are, in fact, limestones in which the calcite (CaCO3) interbonded with magnesium. If strong, can be good foundation and construction materials
Dolomites
36
_______ are much less common at the earth’s surface than are sedimentary rocks
Metamorphic rocks
37
They are produced when sedimentary or igneous rocks literally change their texture and structure as well as mineral and chemical composition, as a result of heat, pressure, and shear.
Metamorphic rocks
38
can be hard and strong if unweathered.
Metamorphic rocks
39
sometimes contain weak layers between very hard layers
Metamorphic rocks
40
what type of rock is marble?
Metamorphic
41
What are soil particles the result of?
Soil particles are the result of weathering of rocks and organic decomposition.
42
Weathering is achieved by
mechanical (physical) and chemical means.
43
disintegrates rocks into small particles by temperature changes, frost action, rainfall, running water, wind, ice, abrasion, and other physical phenomena.
Mechanical weathering
44
causes of rock disintegration
breaking, grinding, crushing
45
causes chemical decomposition of rock, which can drastically change its physical and chemical characteristics.
Chemical weathering
46
This type of weathering results from reactions of rock minerals with oxygen, water, acids, salts, and so on. It may include such processes as oxidation, solution (strictly speaking, solution is a physical process), carbonation, leaching, and hydrolysis.
Chemical weathering
47
What are the three things chemical weathering can do?
Chemical weathering can
(1) increase the volume of material, thereby causing subsequent material breakdown;
(2) dissolve parts of rock matter, yielding voids that make remaining matter more susceptible to breaking; and
(3) react with the cementing material, thereby loosening particles.
48
The type of soil produced by rock weathering is largely dependent on _____.
rock type.
49
Soils can be categorized according to where they are ultimately deposited relative to the location of the _____.
parent rock
50
They remain where they were formed, simply overlying the rock from which they came.
Residual soils
51
They are formed when rock weathers at one site and the particles are moved to another location.
Transported soils
52
What are the four common transporting agents for particles?
(1) gravity, (2) running water, (3) glaciers, and (4) wind.
53
Geological Foundations of the Greater Cincinnati, including SW Ohio, N Kentucky, and SE Indiana are made up of what?
The Ordovician bedrock
54
It has layers of hard gray limestone alternating with soft gray shale. One thick rock unit, the Kope Formation, is mostly shale and therefore is particularly prone to failure.
The Ordovician bedrock, glacial deposits, and riverbank deposits.
55
They are more variable and their distribution is harder to predict.
The glacial deposits
56
Till, outwash sands and gravels, which are mined for construction aggregate in many stream valleys, and lake bed clays, the culprit in many damaging landslides. These are all classified as what?
Glacial deposits
57
They are lower in clay, consisting mostly of sandy silts. They make very attractive land for farming and for real estate development, but are prone to flooding.
The riverbank deposits
58
What are the three soil types?
Cohesive, Cohesionless, Organic
59
sticks together and acts in a plastic manner
Cohesive
60
like sand, will not hold a unified shape
Cohesionless
61
spongy, crumbly and highly compressible which is undesirable in construction
Organic
62
Three common types of cohesionlesssoils are ________.
gravel, sand, and silt
63
```
• Large Bearing capacities
• Small settlements (movements)
• Good foundation materials for roadway
• Excellent retaining wall backfill material
Easily compacted
Well draining
•High shear strength for embankments
• Loose sand is poor for construction
```
Construction properties of Granular soils
64
high permeability make them bad for earthen dikes or dams
Granular materials
65
The common type of cohesive soil is ____, which has particle sizes less than about 0.005 mm.
clay
66
* Lower shear strength, properties change with water content
* Plastic, expansive and compressible
* Creep (deform) under long‐term loading
* Prone to landslides (related to Shales; limestone, sandstone)
* They expand when wetted and shrink when dried
* Low permeability causing high lateral pressures (bad for retaining walls)
* Impervious ‐excellent material for earthen dams and dikes
Cohesive soils construction properties
67
* On the border between clayey and sandy soils.
* Fine‐grained like clays but cohesionless like sands.
* Undesirable engineering properties.
* exhibit high capillarity and susceptibility to frost action, yet they have low permeabilities and low densities.
silty and organic soilds
68
What are three properties of silts?
1. Undesirable for construction
2. Susceptible to frost
3. Low permeability
69
Five properties of organic soil
1. Undesirable for construction
2. Contains organic matter
3. Highly compressible
4. Strong odor
5. Low shear strength
70
What are the two classifications of the soil types by particle size?
1. The American Association of State Highway and Transportation Officials (AASHTO) system
2. The Unified Soil Classification System (USCS)
71
Coarse‐grained(granular): Gravel and sand, with soil grains coarser than ____ , or a ____ sieve size.
1. 0.075 mm
| 2. No. 200
72
_____ will a natural soil be encountered in which all particles are exactly the same size and shape.
Never
73
The Atterberg Limits, Hydrometers tests are for what kind of soils?
for fine Grained Soils
74
Sieve Analysis is for what type of soils?
for Coarse Grained Soils
75
If soil is varied what should you do to test the soils?
Modifications to tests may occur
76
In the case of most cohesionless soils, distribution of grain size can be determined by _____.
sieve analysis
77
Is similar to a cook’s flour sifter: It is an apparatus containing a wire mesh with openings the same size and shape.
A sieve
78
When soil is passed through a sieve, soil particles smaller than the opening size of the sieve will pass through, whereas those larger than the opening size will be ______.
retained
79
Certain sieve‐size openings between _______ mm are designated by U.S. Standard Sieve Numbers
4.75 and 0.075
80
1. Diameter of soil particles at which 50% passes (i.e., 50% of the soil by weight is finer than this size)
2. Median size gives an “average” particle size for a given soil sample
(D50)
81
The diameter at which 10% passes
(D10)
82
CU is the what?
Uniformity coefficient, it describes the steepness of the curve.
83
What is the equation for CU?
CU = D60 / D10
84
Indicates the irregularity of the curve. Where D60 and D30 are the soil particle diameters corresponding to 60% and 30%, respectively, passing on the cumulative grain‐size distribution curve.
Cc= Curvature Coefficient
85
What is the equation used to find the curvature coefficient?
Cc = (D30)2 / (D10 x D60)
86
1. Indicates the irregularity of the curve
2. where D60 and D30 are the soil particle diameters corresponding to 60% and 30%, respectively, passing on the cumulative grain‐size distribution curve.
Curvature coefficient
87
Particle sizes varying over a wide range and have
| higher Cu values (15 or higher).
Well‐graded soils:
88
Poorly graded soils:
1. A deficiency or an excess of some particle sizes (gap‐graded or skip‐graded)
2. Most soil particles approximately the same size and have low Cu (uniformly graded soils)
89
What is Good—Cu, Cc, when it comes to Gravel well grade?
Gravel Well Grade
| • Cu≥4 and1
90
What is Good—Cu, Cc, when it comes to sand well graded?
1. Sand Well Graded
| • Cu≥6 and1
91
Distribution of grain size is not determined by sieve
| analysis because the particles are too small.
Cohesive soils:
92
Cohesive Soils Analysis Techniques:
1. Hydrometer method:
Process for indirectly observing the settling
velocities of the particles in a soil–water mixture.
2. Atterberg limits
93
1. Calculates the drag force on a sphere as it travels through a fluid.
F=viscous drag force acting on the sphere.
r=radius of the sphere
n= viscous drag of the sphere
v = velocity of the sphere
F = 6 pie r Nv
Strokes law
94
• Relates the terminal velocity of a freely falling sphere to the diameter of the sphere
• ________ is applied to soil particles in the _______.
• The individual particles will fall at different rates
• Taking readings over time w
ill indicate the particle sizes
1. Stoke’sLaw
| 2. hydrometer test
95
determines particle sizes
Hydrometer
96
The big difference between silt and clay is its behavior in the _________.
presence of water
97
In 1911 Atterberg defined the states of soils based on the ________.
Moisture Content
98
Plastic and Liquid Limit tests combined to form _________, which classifies the firmness of silts and clays. Evaluate soil for shrink/swell with changes in moisture
Atterberg Limits Test ASTM C4318
99
Consistency refers to clays or silts degree
| of _______.
firmness
100
What are the four states of soil in Atterberg limits?
1. Liquid state
2. Plastic state
3. Semi-solid state
4. solid state
101
1. The dividing line between the semi‐solid and solid states
2. Quantified for a given soil as a specific water content, and from a physical standpoint it is the water content that is just sufficient to fill the voids.
Shrinkage limit
102
Below the ________, any water content change
will not result in volume change; above the shrinkage limit, any water content change will result in an accompanying volume change.
shrinkage limit
103
Soil moisture content when a reduction of water causes the soil to act as a solid. From semi‐solid to plastic state.
Plastic Limit
104
What are the sets to the plastic limit test?
1. Water is added to soil in small amounts.
2. Soil is molded into balls and then rolled into a thread or snake.
3. If the snake crumbles before it reaches 1/8” diameter, it is too dry and more water is added.
4. When the snakes is rolled and reaches 1/8” diameter,
moisture is removed by remolding or evaporation.
5. Continue the process until the snake crumbles at 1/8”.
6. Determine weight with moisture.
7. Repeat process with additional samples.
8. Dry all samples and compare dry weight to
wet weight.
9. Not all soils have a plastic limit
10. A material with no plastic state is called non‐plastic “NP” (silts or organics)
105
1. Soil moisture content when an increase in water causes the soil to act as a liquid.
2. From liquid state to plastic state
3. Casagrande device & grooving tool
Liquid limit
106
1. Three samples are used.
2. Water is added to the sample.
3. The sample is placed in the Casagrandedevice and smoothed until flat and 1/3” deep.
4. Groove placed in the sample
5. Casagrandedevice is tapped in order to close the gap
7. Moisture content is determined by oven drying the sample
liquid limit test
107
What is the equation for plastic index?
PI = LL - PL
108
The ___ gives an indication of how much a soil will expand and contract. The higher the ___ the more exp./cont.
PI
109
Typical PI’s range from ____.
2-30
110
1. In the field, _______ are a guide for how much settlement or consolidation will occur under load.
2. Find the field moisture content and compare it to the _________.
3. Field Moisture is near the Liquid Limit, >> settlement is likely
Atterberg limits
111
Why is it important to use atterberg's limit to figure out how much soil will expand?
1. All loads transfer to the soil
| 2. If foundations move...there is a problem!
112
Three reasons for movement:
1.Settlement –downward movement of foundations due to consolidation of underlying materials.
2. Shrink / Swell –vertical movement, either downward or upward, caused by moisture changes.
3.Shear Failure –downward movement of the foundation by lateral
movement of underlying soils
113
What are the three types of settlement?
1. Uniform settlement
2. Tipping settlement (mostly without cracks)
3. Differential settlement (with Cracks)
114
1. Geological Classification System
2. Agronomic Classification System
3. Textural Classification System (USDA)
4. American Association of State Highway Transportation Officials System (AASHTO)
5. Unified Soil Classification System (USCS)
6. Federal Aviation Agency System (FAA)
Various soil classification systems
115
Soil classification systems must be:
1. Based on a Scientific Method
2. Simple
3. Permit Classification by Visual and Manual Tests
4. Describe Certain Engineering Properties
5. Should be Accepted to All Engineers
116
1. Used by the US Department of Agriculture
2. Limits are assigned for the soil fractions
3. Mostly sand, some clay–So, sandy clay
4. Deal with superficial soils
Textural classification
117
1. Silty clay
2. Clayey sand
3. Sandy gravel
4. Need size limits on soil fractions
5. Establish percent compositions
6. US Department of Agriculture
7. Particularly where characteristics of only superficial soils are of principal concern, which for construction purposes they frequently are.
Textural classification USDA
118
When using Textural classification USDA, Gravel is not in chart. If soil contains ____ or more gravel, a gravelly prefix is added to classification.
20%
119
Grain Size Distribution
1. Mechanical Sieve Analysis
| 2. Well, Poor, or Gap
120
When dealing with coarse grained soils, what affects the Shape of Particles/ Angularity?
1. Manufactured Aggregate‐Angular
2. Crushed Stone or Interlocking
3. Natural Deposits
4. Rounded or River Rock
121
When dealing with _______is the ( % passing #200).
| silt of clay
Fines Content
122
1. Do not retain the in‐situ properties
of the soil during the collection process.
2. Consider these samples to be representative of underground soils except for tests that do not rely on the structure of the soil itself.
3. For soil type and texture, moisture content, and nutrient and contaminant analysis, among other evaluations.
4. The majority of soil samples engineers and geologists collect are disturbed samples because they are easier to collect and the precision necessary for collecting an undisturbed sample is not required for many soil tests.
Disturbed soil samples
123
1. soil samples retain the structural integrity
of the in‐situ soil.
2. Collecting a perfectly undisturbed sample is difficult and the samplers may contain a small portion of
undisturbed soil at the top and bottom of the sample length.
3. Undisturbed samples allow an engineer to determine the geotechnical properties of strength, permeability, compressibility and fracture patterns among others.
4. Results of these analyses are instrumental in the design of a new building.
Undisturbed soil samples
124
1. Shelby Tube (Thin Walled)/SPT (Standard Penetration Test):
2. Retrieve a sample with an auger and tube leaves soil as intact as can be (almost in situ...):
3. Truck mounted, like drilling rig
Undisturbed (kind of)
125
1. Taken by shovel, post hole digger, handheld auger
2. Sealed to retain moisture
3. All granular soils are taken this way
Disturbed soil sample
126
Types of soil samples:
1. Disturbed
| 2. Undisturbed kind of
127
When doing Visual Soil Classification identify soil by using what three easy methods?
1. Color (e.g. brown, gray, brownish gray)
2. Odor (if any)
3. Texture (coarse or fine‐grained)
128
When doing Visual Soil Classification Identify the major soil constituent ________.
(>50% by weight)
129
When using Visual Soil Classification Identify the major soil constituent (>50% by weight) for what types of soils?
1. Coarse gravel
2. Fine gravel
3. Coarse sand
4. Medium sand
5. Fine sand
6. Fines (clay and silt)
130
Visual Soil Classification:
| Estimate percentages of all other soil constituents by weight:
1. Trace ‐0 to 10%
2. Little ‐10 to 20%
3. Some ‐20 to 30%
4. More ‐30 to 50%
131
Little
10 to 20%
132
Trace
0 to 10%
133
When doing a visual soil classification test, if major soil constituent is Sand or Gravel:
Identify particle distribution. Describe as well graded or poorly graded
134
soil consists of particle sizes over a wide range.
Well‐graded
135
Consists of particles which are all about the same size or gap graded
Poorly graded soil
136
Visual Soil Classification: Identify particle shape (granular soils)
1. Angular
2. Sub‐angular
3. Rounded
4. Sub rounded
137
Visual Soil Classification: If major soil constituents are
| Fine particles, perform the following tests:
1. Dry strength test
2. Dilatancy Test
3. Plasticity or Toughness (Snake) Test
138
Field / Visual Classification:
1. Rely on eyes to determine coarse vs. fine
2. Well graded vs. poorly graded
3. If soil is coarse but has fines:
Must run field tests to determine the classification of the fines.
139
1. Passing #40 material, moist soil
2. Shake, squeeze
3. The rapidity appearance of water during shaking, and disappearance when squeezing
4. Is the soils reaction to shaking.
Dilatancy
140
1.Fine clean sands reaction to dilatancy:
quick reaction
141
2. Plastic clay reaction to dilatancy:
no reaction
142
3. Inorganic silts reaction to dilatancy:
Moderate reaction
143
Visual classification of fine grained soils:
1. crushing characteristics of soil
2. Passing #40 material, dry it
3. Test its strength by breaking with fingers
4. Fat clays –high strength
5. Silt –slight strength
Dry strength
144
Visual Classification of Fine Grained Soils:
1. ________ –consistency near plastic limit
2. Passing #40 material, moist
3. Roll out like the Plasticity Index test
4. Lean Clays –weak thread near plastic limit
Toughness
145
Why Do We Classify Soils?
1. Engineering applications based on the soil characteristics
2. Safety Regulations on Trenching
3. Max allowable slope for a Clayey Soil vs. Sandy Soil
4. Suitable Fill
5. Low Volume Change (LVC)
146
Soil is made up of solids, liquids and gas.
Soil Components
147
Are the soil that are visible.
Solids
148
Are typically water, although petroleum and other _____ may be present.
Liquids
149
Gas is also called _____ and has many constituents.
air
150
The volume of the liquid and gas is known as the ____.
void
151
Soil components
Air, Water, Solids
152
Relative Density:
1. For cohesionless soils
2. Relative density can be defined in terms of ______.
Void Ratio; e
153
Highest void ratio possible for a given soil (void ratio of the soil in it's loosest condition)
e max
154
Void ratio of the soil in place
e0
155
lowest void ratio possible for the soil (void ratio of the soil in its densest condition.
e min
156
1. Developed by Arthur Casagrade
2. To classify soils for use in roads or airfields
3. Permits Field or Lab Classification
4. ASTM D2487
Unified Soil Classification System
157
Unified soil classification system classifies soils into six major soil types based on?
1. Particle size
2. Liquid limit
3. Plasticity index
158
Unified soils classification system uses a _______.
Two-symbol designation
159
The first symbol in Unified soils classification system classifies what?
soil type
160
G
gravel
161
S
sand
162
M
silt
163
C
clay
164
O
organic
165
Pt
Peat
166
is an accumulation of partially decayed vegetation or organic matter.
Peat
167
What does the second symbol in the Unified Soils Classification system designate?
Condition of soil with respect to Gradation or plasticity
168
W
Well Graded
169
P
Poorly Graded
170
L
Low liquid limit: LL less than 50
171
H
High liquid limit: LL greater than 50
172
NP
Non-plastic
173
M
silty
174
C
clayey
175
If less than 5% passes the No. 200 Sieve Gravels and Sands are classified as?
GW, GP, SW, or SP
176
When dealing with Gravels and Sands, the well verses poorly graded depends upon the ______.
particle size distribution
177
When dealing with Gravels and sands, if more than 12% passes the No. 200 Sieve
GM, GC, SM, or SC
178
When dealing with gravels and sands, iff between 5% and 12% of the material passes the No. 200 Sieve
GW‐GC Well‐graded gravel with clay
179
SW‐SC
Well‐graded sand with clay
180
GP‐GC
Poorly‐graded gravel with clay
181
SP‐SC
Poorly‐graded sand with clay
182
When dealing with gravels and sands, if between 5% and 12% of the material passes the No. 200 Sieve.
1. GW‐GM Well‐graded gravel with silt
2. SW‐SM Well‐graded gravel with silt
3. GP‐GM Poorly‐graded gravel with silt
4. SP‐SM Poorly‐graded sand with silt
183
Fine grained soils:
ML, OL, CL, MH, OH, CH
184
1. If more than 50% passes the No. 200 sieve
| 2. If the Liquid Limits are less than 50
ML, OL, or CL
185
1. If more than 50% passes the No. 200 sieve
| 2. If the Liquid Limits are greater than 50
MH, OH, CH
186
This determines whether sample is Coarse or Fine Grained.
% Passing the No. 200 Sieve
187
This separates gravel from sand
% Passing No. 4 Sieve
188
(Difference between liquid limit and plastic limit; ___ )
LL‐PL
189
Coarse
(More than 50% on #200)
190
less than 5% fines, greater than 12% fines (#200)
clean or dirty
191
1. Determine Cu, Cc
| 2. Determine Well or Poor
Clean
192
Determine LL, PI –Plot on Plasticity Chart
| Determine Silty or Clayey
Dirty
193
To determine is a soil is fine grained, ___ or more passes #200.
50%
194
Determine if organic:
must be told it is organic or has odor
195
Plot on Plasticity chart to determine if ____.
Silt or Clay
196
If soils have less than 5% fines_________.
Atterberg’s limits are irrelevant
197
_____ should be determined by their dark color and smell.
Organic soils
198
1. Can determine by running LL on sample after air drying and oven drying.
2. If LL is <3/4 the standard value due to drying it is ____.
organic
199
1. Describe soils with seven basic soil groups
2. A-1(best) through A-7(worst)
3. A-8 is for organic soils
4. A-1 through A-3 are sands and gravels
5. A-4 through A-7 are silts and clays
AASHTO classification system
200
Best soil in AASHTO
A-1
201
Worst soil in AASHTO system
A-7
202
Organic soils in AASHTO system
A-8
203
Sands and soils in AASHTO are classified as what?
A-1 through A-3 are sands and gravels
204
Silts and clays are classified as what in AASHTO?
A-4 through A-7 are silts and clays
205
What is the difference between ASSHTO and USCS?
Fine and course soils:
AASHTO defines fines as greater than 35% passing
USCS defines it as 50% passing .
206
GI = (F - 35) (0.2 + 0.005(LL-40)) + 0.01(F-15) (PI - 10)
GI = group index
207
For A-2-7 and A-2-6 use what?
Partial Group index
208
PGI = 0.01 (F-15) (PI - 10)
Partial Group Index
209
F = fines _______.
(#200 or 0.075 mm passing)
210
If you have a negative GI what should you do?
report it as zero
211
Refers to a volume of earthen material that is placed and compacted for the purpose of raising the grade of a roadway (or railway) above the level of the existing surrounding ground surface.
Embankment
212
1. Grain size distribution
2. Particle shape
3. Specific gravity of solids
4. Clay
5. Maximum dry unit weight (density)
6. Optimum moisture content
The factors that affect Compaction of soils.
213
1. Typically 8” loose compacted to 6” at finish
2. Typically accomplished in 6-10 coverages
3. Scarifying between layers: to provide bonding between layers
Field Compaction
214
1. Tampers deliver a succession of light blows
2. Held in place
3. Operated by hand
4. Used in areas not accessible by larger equipment
Ramming or tamping foot compactors (Wacker Packer)
215
1. Uses 1 or more rollers
2. Self-propelled or pulled by tractors
3. Compacting base courses, and provides a smooth finished grade
Smooth Drum
216
1. Vibration frequencies of 1,500-2,000 cycles/min
| 2. Effective for clean sands & gravels
Vibratory rollers
217
1. rotating drum with metal “feet”
2. Creates greater pressures
3. Provides kneading action for fines-grained soils (clays & silts)
Sheepsfoot roller
218
–are the index values for fine particles
1. Not always enough information to draw conclusions about soils.
2. Need info on
3. Soil Unit Weight
4. Water Content
5. Other correlations between air-water-soil
LL, PL, and PI
219
1. This number indicates how much heavier/lighter a material is than
water.
2. In soils, SG refers to the mass of solid matter of a given soil sample as
compared to an equal volume of water.
Specific Gravity
220
When dealing with specific gravities soil solids = what?
W= 187.2 lbs
221
When dealing with specific gravities of water, it equals what?
W = 62.4 lbs
222
If the W of the soil solids w=187.2 lbs and the w of the water w=62.4 lbs what is the specific gravity.
SG = 187.2 / 62.4 = 3.0
223
Specific gravity of Sand is:
2.65-2.67
224
Specific gravity of silty sands is:
2.67-2.70
225
Specific gravity of Inorganic Clay is:
2.70-2.80
226
Specific gravity of soils with mica/iron:
2.75 - 3.00
227
Specific gravity of organic soils:
less than 2.00
228
Soil Consists of the following:
1. Solids
2. Water
3. Air
229
What is the equation for the volume of soil.
Volume = volume of soil + volume of water + volume of air
230
What is the equation for weight of soil?
water = water weight + water weight
231
Vt=
Total soil volume
232
Va =
Air volume
233
Vw =
Water volume
234
Vs =
solids volume
235
Vv
voids volume
236
What is the equation for void volume?
Vv = Va + Vw
237
Wt =
total weight
238
WW=
Water Weight
239
WS=
Solids Weight
240
What is the equation for void ratio?
e = Vv / Vs
241
What is the Porosity (N) ratio?
n = Vv/V x 100%
242
What is the degree of saturation (S) Stopped on page 8 of 2.6. A little confused.
S = Vw/Vv x 100%
243
```
1. Natural decrease in soil volume w
hen subjected to an increased
effective stress
2. Foundations (surface loads)
3. Embankments (fill)
```
Compressibility
244
1. Results in surface settlement
| 2. Which in turn can cause damage to structures
compressibility
245
Total settlement as a two‐phase process:
1. Immediate settlement : occurs very rapidly—within days or even hours after a structure is loaded.
2. Consolidation settlement: occurs over an extended period of time (months or years) and is characteristic of cohesive soils.
246
1. ________ involves expelling water from soil voids.
| 2. Due to permeability and void ratio (e)
consolidation
247
High permeability = ______ soils (sandy)
| 2. Consolidation happens quickly; i.e. during construction
coarse grained
248
1. Low permeability = ________
2. Consolidation happens slowly: Because of lower permeabilities, cohesive soils compress much more slowly because the expulsion of water from the small soil pores is so slow.
fine grained soils (clays)
249
1. Change in height can be predicted based on the loaded void ratio.
2. Consolidation tests predict Δh
3. Consolidation removes water without replacing
the water with air.
loaded compressible stratum
250
1. Moist sand has _________.
apparent cohesion
251
2. Surface tension holds the _____.
sand together
252
3. Loose sand when shaken will ___.
densify
253
4. For water filled voids, water must be expelled before _______.
densification
254
1. When water is expelled, pressure
between soil grains is reduced
2. When the pressure reduction is sufficient, the soil has no strength (like unconfined sand) or has liquefied
3. Liquefaction can occur after earthquakes causing mudslides
Soil liquefaction
255
1. Cohesive strength based on
2. Water content
3. Plastic limit
4. Liquid limit
5. Stiff to hard _____ pose problems in construction
6. Must be excavated or remediated
7. Unsatisfactory for foundations of shoring
Clays
256
1. Soils are loaded in compression
2. NATURAL so strength and properties vary as the RULE
3. Designs and methods must change to match the soil property encountered.
Soil strength
257
Load carrying capacity of soil is dependent on its _____.
shear strength
258
The ability of soil to support an _____ is determined by its shear strength
imposed load
259
1. Made in advance of construction
2. Assist in design of structures
3. Subsurface exploration
4. Made available to the contractor during estimating
period
Soil exploration
260
1. Locate and define vertical and horizontal boundaries of:
a. Various soils and rock strata
b. Underlying the site of proposed construction
2. Locate the groundwater table
3. Determine engineering properties of subsurface material
Field exploration
261
a. Preliminary examination or survey of a job site.
b. Some useful information on the area (e.g., maps or aerial photographs) will already be available
c. Astute person can learn much about surface conditions and get a general idea of subsurface conditi
ons by simply visiting the site.
d. The geotechnical engineer should then visit the site in person.
e. Observe thoroughly and carefully, and interpret what is seen.
1-Reconnaissance
262
What are the steps of soil exploration?
1. Boring
a. Direct exploration
b. Semi‐direct exploration
2. Sampling
a. Disturbed
b. Undisturbed
3. Testing
263
Direct Exploration is Performed by visual inspection through:
1. Test pits
2. Test trenches
3. Test holes
264
Preferred when groundwater is 20’or more below the surface: Because most saturated soils will not cling sufficiently to the auger for lifting.
Direct Exploration
265
1. excavations into the earth t
hat permit a direct, visual
inspection of the soil along the sides of the pit.
2. They may be large enough to allow a person to enter : make inspections by viewing the expos
ed walls, taking color photographs of the soil in its natural condition, testing in situ, and taking undisturbed samples.
Test pits:
266
1. Press the thumb firmly into the soil in question
2. If the thumb makes an indentation in the soil only with great difficulty, the soil is probably Type A
3. If the thumb penetrates no further than the length of the thumbnail, it is probably Type B soil
4. If the thumb penetrates the full length of the thumb, it is Type C soil.
Thumb penetration test
267
1. The _______ is subjective and is therefore the least accurate method.
2. Used for determining shoring requirements: For deeper pits, the excavation may need to be shored to protect persons entering the pits.
thumb test
268
Support system to hold soil back during excavation for
| underground construction or exploration
Shoring:
269
1. Determines unconfined compressive strength of soil (qu) through penetration of soil.
2. Direct exploration method
3. Based on allowable pressure(psf), not density (pcf)
4. Have error rates in the range of ±20‐40%
Pocket Penetrometer
270
Direct exploration advantages:
1. Permits observation in natural state
| 2. Can obtain undisturbed samples
271
Direct exploration disadvantages:
1. Usually depth is restricted
| 2. By equipment or groundwater
272
1. Auger drilling rig
2. Drills and samples
3. Solid Stem
4. Hollow Stem
5. Rotary Drilling
6. Uses Slurry or Drilling Mud
Semi-direct exploration
273
1. Thin walled tube sampling
2. Shove sample tube into bottom of boring
3. 2‐5 in in diameter
4. Up to 4’ in length
5. Obtain an undisturbed sample
Shelby Tubes
