Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Geology > Mass Movement Hazards > Flashcards

Mass Movement Hazards Flashcards

1
Q

Define Porosity

A

The % of cavities between grains, fractures and joints

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Porosity =

A

Total volume of pore spaces/Total volume of rock x 100

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Define Primary Porosity

A

Pore spaces between grains

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Define Secondary Porosity

A

Fractures, joints and faults in a rock

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are four factor affecting porosity?

A

Degree of sorting, Amount of diagenesis, Grain shape, Packing of grains

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

How does degree of sorting affect porosity?

A

A poorly sorted rock has low porosity because the finer grains fill the spaces between the coarser grains

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How does amount of diagenesis affect porosity?

A

A loose unconsolidated sediment has a much higher porosity than a rock that has undergone compaction and cementation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

How does grain shape affect porosity?

A

Rocks containing rounded grains have a higher porosity than rocks containing angular grains that fit together

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How does packing of grains affect porosity?

A

With depth compaction from the overburden pressure will cause the grains to pack closer together, reducing the pore spaces

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Define Permeability

A

Measures how fast fluid can flow through a rock, governed by the connectivity of the spaces

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Permeability =

A

Distance fluid has travelled/Time taken

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What factor affects permeability?

A

Grain size

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

How does grain size impact permeability?

A

The smaller the grain size, the lower the permeability because there is more resistance to flow

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What are the seven types of mass movement?

A

Rockfall, Sliding, Slip, Slump, Flow, Creep, Solifluction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Define Mass Movement

A

The movement of a mass of rock, debris or earth down a slope under the direct influence of gravity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What are the four forces acting on a slope?

A

Shear strength, Normal force, Gravity, Shear force

17
Q

If the angle of a slope increased, what would happen to shear force, shear strength and gravity?

A

Shear force = increase
Shear strength = decrease
Gravity = never changes

18
Q

Define Angle of Repose

A

The maximum steepness (angle) a sediment can be at before it will move downslope

19
Q

What are three factors influencing the angle of repose?

A

Size, Shape, Sorting

20
Q

Define Pore Pressure

A

Pressure exerted by water in pore spaces

21
Q

Define Cohesion

A

The tendency for water molecules to stick together

22
Q

What are six factors influencing slope stability?

A

Groundwater, Dip amount, Dip direction, Weathering, Ground vibration, Vegetation

23
Q

How does groundwater affect slope stability?

A

(1) Pore pressure increases (2) Decreased cohesion and friction (shear strength) (3) Increase shear force (4) Slope becomes unstable as the forces are unbalanced

24
Q

How does dip amount of rock strata affect slope stability?

A

Horizontal or very shallow dipping beds are more stable than beds with a high angle of dip

25
Q

How does dip direction of rock strata affect slope stability?

A

Beds dipping towards the cliff face are more unstable than beds dipping away

26
Q

How does weathering affect slope stability?

A

Weathering loosens the sediment, making it less stable due to there being less friction

27
Q

How does ground vibration affect slope stability?

A

More vibration means more grains are shaken, so slopes become less stable

28
Q

How does vegetation affect slope stability?

A

Vegetation holds the sediment together, preventing it from becoming unstable

29
Q

What are seven monitoring techniques?

A

Ground levelling and surveying, Microseismic survey, Surface strain measurement, Borehole distortion, Tiltmeter, Electronic distance measurement, Water table and pore pressure

30
Q

Describe Ground Levelling and Surveying

A

Conventional surveying equipment or GPS to monitor the change in height of the land, Height of land should drop over time if mass movement is about to happen

31
Q

Describe Microseismic Survey

A

Sound is detected through geophones around the slope as rocks break or slide past each other, Increases in size and frequency before a mass movement

32
Q

Describe Surface Strain Measurement

A

Inclinometers and extensometers are placed across cracks that have developed on a cliff face, If cracks get bigger the inclination of the bar will increase

33
Q

Describe Borehole Distortion

A

Inclinometers are placed in permanent boreholes which are drilled into the hillside, Any change in the tilt of the borehole could suggest movement along the plane

34
Q

Describe Tiltmeters

A

A network of tiltmeters are set up around the head of a mass movement, Any increase in tilt suggests a mass movement could occur

35
Q

Describe Electronic Distance Measurement

A

Lasers are used to measure the distance between two fixed points, If there is a decrease in distance a mass movement might be about to occur

36
Q

Describe Water Table and Pore Pressure Surveys

A

Piezometers are used to measure the pore pressure in boreholes around a mass movement, If pore pressure increases it could indicate there is a trigger for mass movement

37
Q

What are three methods of modifying slope geometry to stabilise slopes?

A

Removal of material, Adding material to the toe, Reducing the angle of the slope

38
Q

What are three methods of drainage to stabilise slopes?

A

Surface drains, Deep drains, Vegetation

39
Q

What are seven methods of retaining structures and slope reinforcements to stabilise slopes?

A

Retaining walls, Rock armour, Gabions, Retention nets, Rock traps, Rock bolts and anchors, Vegetation

Geology (16 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions