EXAM 1 Flashcards
1
Q
Void Ratio
A
e = Vv / Vs
2
Q
Porosity
A
n = Vv / V
3
Q
Void Ratio and Porosity Relations
A
e = n / (1-n) n = e / (1+e)
4
Q
Degree of Saturation
A
S = Vw / Vv
5
Q
Water Content
A
w = Ww / Ws = Mw / Ms
6
Q
Total Unit Weight
A
γ = W / V
7
Q
Dry Unit Weight
A
γd = Ws / V
8
Q
Relationship between γ and γd
A
γ = γd * (1+w) = Ws * (1+w) / V
9
Q
Unit Weight of Water
A
γw = 9.81 kN/m^3
= 62.4 lb/ft^3
10
Q
Solid Unit Weight
A
γs = Ws / Vs
11
Q
Specific Gravity
A
Gs = γs / γw
G water = 1 @ 4 C
12
Q
Total Density
A
ρ = M / V
13
Q
Dry Density
A
ρd = Ms / V
14
Q
Solid Density
A
ρs = Ms / Vs
15
Q
Density and Unit Weight Relation
A
γ = ρ * g g = 32.2 ft/sec 9.81 m/sec
16
Q
Coarse
A
Rel bigger
Large voids
Low SSA
Equidimesnsional
17
Q
Fine Soil
A
Very small voids
Large SSA
Platy shape ( sheets of paper )
Important surface forces
18
Q
Main Mineral Group
A
Silicates
19
Q
Basic Structural Unit of Silicates
A
Silica Tetrahedron
20
Q
Composition of Coarse Materials
A
Gravel and sand fractions of soil are composed of non-clay materials
Quartz
21
Q
The building blocks for clay materials
A
Silica Sheets
Octahedral Sheets (Tri and Di Octahedral)
22
Q
Dioctahedral
A
Octahedral sheet with +3 element such as Al instead of +2 element
More holes than trioctahedral
23
Q
Trioctahedral
A
Formed by octahedral units consisting of 6 hydroxyl (OH) surrounding an magnesium atom
24
Q
Kaolinite
A
1:1 or 2 sheets per layer One silica sheet and one tetrahedral sheet Large platy shaped particle Strong glue between layers Low SSA (5-15 m2/g)
25
Isomorphous Substitution
Occurs in the formation of silicate materials
Substitution of one atom for another
Instead of Si atom +4 there is Al atom +3
Net unit charge deficiency increases
Distortion of the lattice
26
Illite
```
2:1 or 3 sheets per layer
More charged than kaleonite
Octahedral sheet bonded to 2 silica sheets
Glue is not very strong
Platty shaped particles
Low SSA (80-100 m2/g)
```
27
Montmorillonite
2:1 or 3 sheets per layer
Dicotahdedral sheet bonded to 2 silica sheets
Cations can quickly come in and out (loose)
Due to small amount of iso sub makes exchangeable
Large amount of water in the space of the layers
Modest amount of glue ( Na, Ca, Mg)
Very high SSA
28
Specific Surface Area
SSA= Surface Area / mass
29
The two faces of all platy particles have a
The edges of particles have
Negative charge caused by iso sub that is not neutralized by interlayer cation bonding
Positive charge
30
Diffuse Double Layer (DL)
When water is present cations and anions can float around the clay particles forming a diffuse double layer
The water is held to the clay particles by forces of attraction
Richer in cation the close to the particle
31
Absorbed water layer
The first 10-15 Angstroms of water adjacent to the mineral surface
Essentially acts as part of the structure of the clay particle
So close that it doesn't freeze
32
Double layer repulsion
Water molecules want to enter the double layer to reduce cation concentration by separating particles by reducing alkalinity which creates an edge to face electrical attraction
33
Flocculate
Two particles tend toward each other and become attached edge to face
34
Disperse
Two particles tend to move away due to no attraction
35
Unified Soil Classification System (USCS)
Standard soil identification test baed on particle size analysis and Atterberg limits
Soil types - Gravel, sand, silt, clay organic, peat
36
Gravel
less than 50% passing sieve #4 (4.75 mm)
37
Sand
more than 50% passing sieve #4 (4.75 mm)
| less than 50% passing sieve #200 (0.075 mm)
38
Silt (M)
More than 50% passing sieve #200 (0.075 mm)
| Below A-line
39
Clay (C)
More than 50% passing sieve #200 (0.075 mm)
| On or above A-line
40
Organic (O)
More than 50% passing sieve #200 (0.075 mm)
| (Liquid Limit dried / Liquid Limit not dried) less than 0.75
41
Peat (Pt)
More than 50% passing sieve #200 (0.075 mm)
| Mostly organic matter
42
Particle Size Distribution Plot
```
Logrimithic Scale
x axis - Particle Size (mm)
y axis - Percent Finer by Weight
s curve
use to find percent finer than 0.075 mm
```
43
Soil Uniformity Coefficient
Cu = D60 / D10 = Diameter at 60% / Diameter at 10%
The higher Cu , the less uniform the soil, more horizontal curve
Cu = 1 means very uniform, straight curve
44
Coefficient of Curvature or Gradation
Cc = (D30)^2 / (D10 * D60)
| Smaller and higher numbers show gaps in the curve (two types of soil)
45
Plasticity Atterberg Limits
Liquid Limit, Plastic Limit, Shrinkage Limit
46
Liquid Limit
Fluid soil-water mixture
| The water content (%) after 25 blows of Casagrande cup
47
Plastic Limit
Enough water where the soil doesn't crack after working with it
Water content at which 1/8" diameter thread crumbles
48
Plasticity Index
The difference between the liquid limit and plastic limit
PI = LL - PL
Equals the water content within which soil is in the plastic state
49
Compaction
Densification of soil by the application of mechanical energy
50
Methods of compaction
Fine : Impact and kneading using rollers controlled by relative compaction
Coarse : Static or dynamic/ vibration using vibratory and tamping controlled by relative density
51
Proctor Test
A compaction test to determine the optimum moisture content and density for a soil
52
Compactive Effort
Measure of the mechanical energy applied to the soil mass
| The more applied, the more dense the material and dry unit weight increases
53
4 key variables in compaction of fine grained soils
- Dry density or dry unit weight
- Water content
- Compactive effort
- Soil type
54
Optimum water content is located on proctor test plot
Where the dry unit weight (densification) is maximized
55
Parabolic shape on on proctor test plot
Water acts as lubricant until a point
56
The compaction curve never reaches 100% saturation
Due to voids
57
On proctor test plot, as compactive effort increases
The dry unit weight increases and the optimum water content decreases (left)
58
On proctor test plot, as plasticity increases
Dry unit weight decreases
