SOIl

Question 1

BsCs considers soils in 2 categories, what are they?

Answer 1

Fine(>35% passing 63mm sieve)
or
Coarse (<35% passive 63mm sieve)

Question 2

What size is cohesionless soil

Answer 2

D>0.06mm

Question 3

Explain what is the Double diffuse layer,

Answer 3

The double diffuse layer is a region near a charged surface where ions from a solution gather, with an outer layer of ions being more spread out.

Question 4

DDL role in the behaviour of clays

Answer 4

The double diffuse layer helps to stabilize charged surfaces and affects interactions between particles in solutions, influencing processes like colloid stability and electrochemical reactions

Question 5

DDL factors
affecting its thickness (and how).

Answer 5

The thickness of the DDL decreases when:
* The concentration of salt increases (NaCl)
* Temperature decreases
* The valence of cations increases

Question 6

2 methods to determining the Liquid Limit (LL)

Answer 6

Casagrande method or Falling cone method

Question 7

Plasticity Index formula

Answer 7

PI = LL - PL

Question 8

Moisture Conten Formula

Answer 8

W= Mw/Ms

Question 9

Void Ratio Formula

Answer 9

Vv/Vs

Question 10

Porosity

Answer 10

e/1+e

Question 11

Degree saturation

Answer 11

Sr=Vw/Vs

Question 12

Bulk Density formula

Answer 12

p=(Ms+Mw)/Vt

Question 13

Density

Answer 13

p=M/V

Question 14

Submerged Density

Answer 14

ρ’ = ρ - ρw

Question 15

Specific Gravity formula

Answer 15

Gs = Ps/Pw = Ms/(Vs Pw)

(𝜌=P)

Question 16

Describe in a short paragraph what critical flow conditions are about

Answer 16

Critical flow conditon- If the seepage force is > gravity force, the soil exerts a downward force

Question 17

Ways to mitigate critical flow conditions

Answer 17

1.Proper design and sizing.

2.Using flow control devices.

3.Installing pressure relief systems.

4.Monitoring and controlling systems.

Question 18

Comment on how the benefits of falling
head test

Answer 18

Suitable for materials with low to moderate permeability.

Mimics natural drainage conditions more closely by allowing the hydraulic gradient to decrease over time.

Question 19

Comment on how the benefits of constant head test

Answer 19

Suitable for materials with high permeability.

Maintains a constant hydraulic gradient throughout the test, which simplifies calculations.

Question 20

What relationship must an equipotential have with a flow line if the flow net
is to produce credible predictions of seepage flow?

Answer 20

For credible predictions of seepage flow in a flow net, equipotential lines must intersect flow lines at right angles.

Question 21

how does cut off walls help in seapage

Answer 21

Cut-off walls stop water from seeping through soil or rock, preventing potential damage to structures and controlling environmental risks.