Exam one

Question 1

3 things that make soil different

Answer 1

1. Natural material
2. Individual unconnected particles
3. Has all three phases of matter, (air, water, soilds)

Question 2

Void ratio

Answer 2

e

Question 3

Porosity

Answer 3

n

Question 4

Degree of saturation

Answer 4

S cannot go over 100%

Question 5

moisture content

Answer 5

w, cannot go over 100%, = Ww/Wd, (Weight wet sample - Weight dry sample)/weight dry

Question 6

Relative density

Answer 6

Dr

Question 7

Specific Gravity

Answer 7

Gs

Question 8

Saturated unit weight

Answer 8

γ(sat)

Question 9

Moist unit weight

Answer 9

γ(m)

Question 10

appartent unit weight

Answer 10

γ’

Question 11

γ(w)

Answer 11

Specific weight of water

Question 12

what does relative compaction need to be (RC)

Answer 12

95%

Question 13

5 steps - Process of cut and fill

Answer 13

1. Remove vegetation and topsoil
2. Evaluate the subgrade
3. Place soils in lifts (do in 8-9 in thick max)
4. Compact soil
5. Evaluate compaction, relative compaction needs to be 95%

Question 14

Most common method to find dry specifc weight field

Answer 14

Nuclear method, it correlates gamma radiation to dry specific weight

Question 15

What are the two options if a soil is too wet

Answer 15

1. Scarify and let nature dry
2. add lime stabilization good for wetlands (downside - it makes soil not as dense)

Question 16

Lightweight fill

Answer 16

geofoam, weakness is gasoline

Question 17

Shinkage factor

Answer 17

= ((Dry unit weight in fill/ dry unit weight in cut) - 1) *100%

Question 18

what is the I value for large fills

Answer 18

1

Question 19

5 causes of settlement

Answer 19

1. applied loads
2. Lower groundwater table
3. Shrinkage from clay
4. Vibration from machinery or earthquake (hurts sandy soil)
5. thawing of frozen soil

Question 20

3 types of settlement

Answer 20

1. elastic (soil particles compress elastically
2. consolidation (water squeezes out of the soil
3. secondary compression (soil creeps over time)

Question 21

Normally consolidated (NC)

Answer 21

A soil that has never felt an effective stress greater than today (never had glaciers)

Question 22

Overconsolidated (OC)

Answer 22

Soil that has felt an effective stress greater than today (had glaciers on it)

Question 23

OCR ratio

Answer 23

max pressure ever/ pressure today, if over 1 OC, if less than 1 NC

Question 24

4 causes of overconsolidation (OC)

Answer 24

1. Glaciers
2. Lowering of GWT
3. Erosion from upper layers
4. Aging (older soil is more consolidated

Question 25

Log(sigma’ + Delta P/sigma’) is the same as

Answer 25

log(stress after dewater/stress before dewater)

Question 26

If the GWT goes down will the soil feel more stress

Answer 26

Yes when the water table lowers pressure felt goes up

Question 27

What test gets you sigma’ c (Highest stress ever felt)

Answer 27

1-D consolidation test (undisturbed sample from field, trim into hockey puck, slowly add load over a weeks time

Question 28

Steps to find sigma’ c from chart

Answer 28

1. sharpest point of curvature
2. draw horizontal at step 1
3. Draw a tangent at step 1
4. Bisect through step one between steps 2 and 3
5. extend straightline from Cc slope
6. intersection of 4 and 5 is sigma ‘ c

Question 29

who is the father of soil mechanics

Answer 29

Karl Teraghi

Question 30

Ʊ

Answer 30

Degree of consolidation

Question 31

Hdr

Answer 31

the longest distance a particle of water has to travel to get out

Question 32

Tv relates to Ʊ from table, time should be in days,

Answer 32

yes