Landslides and Slope Stability in Hong Kong

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Questions and Answers

What primarily causes a slope to become unstable and potentially result in a landslide?

When the slope gradient is zero

When shear stress is greater than shear strength (correct)

When shear strength is greater than shear stress

When there is no rainfall

Which factor is indicated as reducing the cohesion of materials on slopes, making them more susceptible to landslides?

Increased vegetation on slopes

Heavy rainfall (correct)

Gradual temperature changes

The presence of granite rocks

How does shear stress influence the movement of materials on a slope?

It pulls materials downhill due to gravity (correct)

It increases the friction between soil grains

It helps to stabilize the slope

It adds cohesion to the slope materials

What effect does strong weathering have on rocks that can lead to landslides?

Makes hard rocks weak and easily broken Signup and view all the answers

Which of the following describes the relationship between slope gradient and shear stress?

Greater gradient leads to greater shear stress Signup and view all the answers

What happens to essential services and infrastructure during a landslide in built-up areas?

They may be damaged or destroyed Signup and view all the answers

What is the primary consequence of weakened slope materials due to heavy rainfall?

Increased tendency for landslides Signup and view all the answers

Which component of soil directly affects the force of friction among soil grains?

Cohesion Signup and view all the answers

What is one primary factor that contributes to landslides in Hong Kong?

Deep weathering of granite Signup and view all the answers

At what slope gradient does the risk of landslides significantly increase?

30° Signup and view all the answers

How do human activities contribute to landslide risks in built-up areas?

Cutting and filling slopes Signup and view all the answers

What is a significant consequence of poor maintenance of man-made slopes?

Cracked surfaces allowing more water intrusion Signup and view all the answers

What measure can be taken to prevent landslides from damaging settlements?

Building barriers on slopes Signup and view all the answers

Which organization is responsible for monitoring and maintaining slopes in Hong Kong?

The Geotechnical Engineering Office (GEO) Signup and view all the answers

What is the effect of heavy rain on landslide risks in Hong Kong?

It can trigger landslides Signup and view all the answers

Which of the following is a preventive measure that the government has implemented regarding slope management?

Setting up laws for slope development and maintenance Signup and view all the answers

What should be done to help people who have lost their homes due to landslides?

Providing financial aid and insurance compensation Signup and view all the answers

How does the removal of vegetation from slopes affect landslide stability?

It adversely affects slope stability Signup and view all the answers

Study Notes

Landslides in Hong Kong

Landslides are the rapid movement of soil and rock down a slope due to gravity.
Approximately 300 landslides occur annually on natural terrain in Hong Kong (60% of the land area).
Landslides in built-up areas can cause injuries, deaths, damage to buildings and infrastructure (e.g., pipes, powerlines), and disrupt traffic.

Slope Stability

Slope stability depends on the balance between shear stress (driving force) and shear strength (resisting force).
Shear stress is influenced by slope angle and weight of materials.
Shear strength is affected by soil cohesion and friction.
A stable slope has greater shear strength than shear stress; an unstable slope has greater shear stress than shear strength.

Factors Affecting Landslides

Heavy Rainfall: Increased rainfall weight increases shear stress and reduces the cohesion and friction of slope materials. Summer months are often high-risk periods.
Strong Weathering: Weathered rocks (e.g., granite) have lower shear strength, increasing landslide susceptibility.
Steep Slopes: Larger slope gradients increase shear stress, elevating landslide risk, especially above 30°. Hong Kong's hilly terrain contributes to high risk.

Human Activities and Landslides

Slope Modification: Cutting and filling slopes for development increases shear stress and reduces stability. Removal of vegetation has similar negative effects.
Poor Slope Maintenance: Inadequate maintenance of man-made slopes, such as cracked surfaces and improper drainage, reduces shear strength and increases the risk of landslides.

Preventing and Mitigating Landslides

Barriers: Barriers can be constructed on or at the base of slopes to prevent downward movement in natural terrains.
Slope Strengthening and Monitoring: Enhancing slope stability, inspecting slopes regularly (like GEO) using instruments, and maintaining records are crucial in managed areas.
Land Use Regulations: Laws restrict development on steep slopes, need for proper slope studies and government authorization.
Landslide Warning Systems: The government issues warnings during heavy rain, enabling people to reduce their exposure to potential hazards.
Public Education and Preparedness: Education programs inform the public about actions to take during warnings. Emergency plans should include well-trained rescue teams, emergency aid, temporary shelters, and financial assistance.

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Description

This quiz explores the phenomenon of landslides in Hong Kong, focusing on their causes, impacts, and the concept of slope stability. Discover the factors that contribute to these natural disasters, including weather conditions and geological properties. Test your knowledge on how these elements interact and influence the safety of the terrain.