Rocks and weathering 3.4

Question 1

Human impact on mass movement: excavations

Answer 1

In places where ground is removed, it can leave slopes that are too steep and therefore liable to failure

Question 2

Human impact on mass movement: waste heaps

Answer 2

Waste heaps from quarrying or mining often have steep slopes and are often made of material which is unconsolidated and highly porous.

Question 3

Human impact on mass movement: loading by building

Answer 3

Building on top of a slope liable to landslip can add sufficient mass to the ground that may trigger a landslide.

Question 4

Human impact on mass movement: loading by water

Answer 4

Water has a lubricating effect on unconsolidated material and saturated clays. Building project can lead to the disruption of drainage which diverts water to these areas.

Question 5

Human impact on mass movement: removal of vegetation

Answer 5

Deforestation, construction projects or leaving land bare can increase surface run off leading to mudflows.

Question 6

Strategies to reduce mass movement: pinning

Answer 6

Drilling a long hole through loose blocks into the table rock beyond before a metal rod is inserted and fixed in place which is then bolted into place.

Question 7

Strategies to reduce mass movement: netting

Answer 7

Metal netting is fastened to road cuttings to prevent loose blocks falling on the road below.

Question 8

Strategies to reduce mass movement: grading

Answer 8

Decreasing the angle of slopes to reduce the risk off mass movement by artificially creating the angle of the slope.

Question 9

Strategies to reduce mass movement: afforestation

Answer 9

Planting trees and other vegetation can reduce the risk of MM by absorbing water in the ground and by root action binding with loose rock.

Question 10

Case study HK 1966: causes

Answer 10

• 1650mm of rain fell within 5 days in early June.
• HK’s soil composition makes it susceptible to erosion with high proportions of granite.
• Slopes steeper than 30 degrees.
• Partly triggered by building projects - loading by building.

Question 11

Case study HK 1966: impacts

Answer 11

• 64 killed
• 2500 were made homeless
• 8000 evacuated

Question 12

Case study HK 1966: management

Answer 12

• The Slope Safety System manages and maintains 57,000 man-made slopes in HK.
• They do this by land use planning, upgrading, slope maintenance, and landscaping.
• Surface drains are used to reduce surface runoff.

Question 13

Case study HK 1966: greening techniques

Answer 13

• Using natural vegetation to reduce the risks of MM.
• The mulching system (protective vegetation cover) allows vegetation to grow and secure it in place whilst maintaining water capacity.
• Long-rooting grass is a quick and cost-effective way of securing slopes.
• Fibre-reinforced soil system helps strengthen soil particles to prevent erosion.

Question 14

Case study HK 1966: were the management techniques successful?

Answer 14

• The risk of landslides has been reduced by 50% since 1977.
• However, population growth has meant developers have continued to build on steep slopes.
• Confusion over responsibility has meant storage