Soil Cut Slopes
• Cutting back
• Using retaining wall
• Soil Nails
Methods of upgrading man-made slopes
Fill Slopes
• Recompaction
• Soil Nails
Retaining Wall
• Thickening
• Soil Nails
• Recompaction of the Fill Material
Fill Slopes
Before construction
The Recompaction Process
Excavate the loose soil
layer by layer
Lay drainage blanket on soil surface
Recompact the next layer
of soil
Apply grass and tree seeds on slope surface
Fill slope upgraded!
• Soil Nails
Fill Slopes
With Grillage Beams
Soil Cut Slopes
• Cutting back
• Using retaining wall
• Soil Nails
Fill Slopes
• Recompaction
• Soil Nails
Methods of upgrading man-made slopes
Retaining Wall
• Thickening
• Soil Nails
• Wall Thickening
Retaining Walls
Before
After
• The use of Soil Nails
Retaining Walls
•
Less susceptible to the weather
•
Avoid felling too many trees
•
Robust and can work well in weak soil layer
•
Can be coupled with other slope greening and landscaping treatments
Merits of using Soil Nails
After Before
3. Upgrade and Maintain Government Man-made Slopes
• Starting from 1977, the GEO has begun to implement the
“Landslip Preventive Measures (LPM)” to upgrade old man- made slopes
• Details to be covered:
Priority with respect to consequence to life
Methods of upgrading man-made slopes
Slope Greening
斜坡綠化 斜坡綠化斜坡綠化 斜坡綠化
Slope Greening
Pros:
Protect against surface erosion on steep soil slopes or fall of fractured rock pieces
Prevent ingress of water into the slope
Cons:
Visually unattractive
Light and heat reflective
Complaints skyrocketed in late 1990s
A road-side masonry wall
Cement paste applied as part of routine
maintenance
Conventional Shotcrete Cover
Vegetation Cover
Don’t forget:
Slope Stability
Future Maintenance
Cost Implication
Changes in Culture
Government Policy
•
To make man-made slopes look as natural as possible
•
Use sprayed concrete (噴漿) in slope works as last resort
•
Use landscape treatment (園境美 化方法 ) to beautify slopes with
hard covers (硬面)
Planter Holes + ColourCommon Methods of Vegetating Slopes
Greening
2002 – Before Works
2003 – After Works
2004 2005 – The slope vegetation cover blends in naturally with
the surrounding woodland
Slope No. 11NW-B/C48 Near Sai Yeung Choi Street
Slope Greening Examples in South Lantau
Greening
Before Works
Slope No. 10SW-C/FR70 South Lantau Road
Greening
Hong Kong Slope Safety System – Major Strategies
1977
Slope Safety System set up by GEO Landslide
risk in HK
1.Check new slopes 2.Plan land use
Contain the increased risk
1950 1960 1970 1990 2010
Reduce risk by improving slope stability
Reduce risk by reducing landslide consequence 2000
3.Upgrade & maintain government slopes 4.Promote private
slope maintenance
5.Clear squatters on hilly terrain 6.Educate the public
to take precaution
Private Old Slopes (11,500 Nos.)
Govt. Old Slopes (27,500 Nos.)
(8,500 Nos.) Govt. New Slopes
(12,500 Nos.)
40,000 Government slopes 20,000 Private slopes
Private New Slopes
Slope Maintenance Responsibility
3. Upgrade and Maintain Government Man-made Slopes
• The Government maintains all government man-made slopes
Provide information and advice to slope owners Meeting Owners Corporation
4. Promote Private Slope Maintenance
• Our “Community Advisory Unit” promotes slope maintenance to private slope owners and provides them with information and advice.
5. Clear Squatters on Hilly Terrain
• GEO reduces landslide hazards to squatters through clearance of squatter structures in concern.
Squatter villages around Diamond Hill area in 1987
After squatter clearance and redevelopment in 2003
6. Educate the public to take precaution
Teaching Support Materials for New Secondary Geography Curriculum
• Through various activities, we educate the public of all walks of life with a view to promoting their awareness in slope safety.
Site Visits for Teachers
6. Educate the public to take precaution
School Exhibitions School Talks
Computer Animation of Historical Landslides
TV API
6. Educate the public to take precaution
Communication with the Media
OP12 - Annual Plan
“Safer Slopes Safer Living” Fiesta 2010
Themed Exhibition
Roving Exhibitions
6. Educate the public to take precaution
6. Educate the public to take precaution
Community-based Outreach Activities with NGOs, e.g. The HK Red Cross
Keep Away from Slopes 遠離斜坡
6. Educate the public to take precaution
1 • Landslide History of Hong Kong
2
• Causes of Landslides
3
• Hong Kong Slope Safety System
4
• New Challenges and Initiatives
5
• Conclusion
Outline of Presentation
Outline of Presentation
Future Slope Safety Challenges
Aging of man-made slopes
Slope degradation and requiring improvement/repair
Aging of man-made slopes
Slope degradation and requiring improvement/repair
Increased Population
Development close to hillsides
Study and mitigation of natural terrain landslide risk
Increased Population
Development close to hillsides
Study and mitigation of natural terrain landslide risk
Threatened by more extreme weather conditions Threatened by more extreme
weather conditions
• Upgrade 150 government man-made slopes Target 1
• Conduct safety-screening studies for 100 private man-made slopes
Target 2
• Carry out landslide risk mitigation measures for 30 natural hillside catchments
Target 3
長遠防治山泥傾瀉計劃 長遠防治山泥傾瀉計劃 長遠防治山泥傾瀉計劃 長遠防治山泥傾瀉計劃 長遠防治山泥傾瀉計劃 長遠防治山泥傾瀉計劃 長遠防治山泥傾瀉計劃 長遠防治山泥傾瀉計劃
Landslip Prevention and Landslip Prevention and Mitigation
Mitigation Programme Programme ((LPMitP LPMitP))
1999 Debris Flow in Shum Tseng
Check Dam
防 防防 防防 防防
防止止止止止止止止山泥傾瀉山泥傾瀉山泥傾瀉山泥傾瀉山泥傾瀉山泥傾瀉山泥傾瀉山泥傾瀉
Prevention Prevention
防 防防 防防 防防
防治治治治治山泥傾瀉治治治山泥傾瀉山泥傾瀉山泥傾瀉山泥傾瀉山泥傾瀉山泥傾瀉山泥傾瀉
Mitigation Mitigation
Natural hillsides landslide risks can be mitigated in a more cost effective manner through mitigation measures.
Germany - Protection tunnel
Germany - Debris Trap
Examples of Mitigation Works in Other Countries
Japan - Protection tunnel
Japan - Check Dam Switzerland -
Flexible barrier
Natural Hillside Landslide Risk Mitigation Measures Applicable to Hong Kong
Boulder fence Debris barrier
Concrete Check Dam
Natural Terrain Landslide Risk Mitigation Measures at Tai O
Concrete Check Dam 大澳南涌大澳南涌
大澳南涌大澳南涌 Flexible barrier
Landscaping
Landscaping Treatment to Landslide Scars
Shotcrete for emergency works
Sprayed with Different Colours
土木工程拓展署土力工程
Yu Tung Court 裕東苑
Coastal Skyline Towers 藍天 海岸 and
La Rossa Towers影岸. 紅
Caribbean Coast 映灣園
Natural Terrain Landslide Risk Mitigation Measures at Yu Tung Road, Tung Chung
Natural Terrain Landslide Risk Mitigation Measures at Yu Tung Road, Tung Chung
Debris Flow at Yu Tung Road, Tung Chung, on 8 June 2008
Natural Terrain Landslide Risk Mitigation Measures at Yu Tung Road, Tung Chung
Flexible barrier
Concrete Check Dam
Proposed trees and shrubs planting Existing trees to be retained
Grasscrete Grasscrete
Existing trees to be retained
Grasscrete 小草磚
Crest and toe planter Climbers on
wire-mesh
Proposed trees and shrubs planting
Climbers on wire mesh Proposed climbers to soften the up-stand walls
Natural Terrain Landslide Risk Mitigation Measures at Yu Tung Road, Tung Chung
Natural Terrain Landslide Risk Mitigation Measures at Yu Tung Road, Tung Chung
Photo Montage showing completion of works
Natural Terrain Landslide Risk Mitigation Measures at Yu Tung Road, Tung Chung
Photo Montage showing establishment of plants
1
• Landslide History of Hong Kong
2
• Causes of Landslides
3
• Hong Kong Slope Safety System
4
• New Challenges and Initiatives
5
