1. Landslip Preventative Measures Development of the Hong Kong System
Slope Management
and
Landslip Preventative Measures
Development of the Hong Kong System
Major Landslide at Maracas, Trinidad - Late December 2002.

2. Prevention of Landslides
Database of Slopes
Type of Slope
Condition
Consequences
Cut Slopes
Fill Slopes
Retaining Walls
Hybrids: Cut/Retaining Wall / Fill/Retaining Wall
“Natural” Slopes - slopes where there has been no anthropogenic activity, or where such activity is causes small changes to the geometry of the slope so that the Factor of Safety is largely unaffected.

3. Development of Slope Registration Scheme
Began in late 1970’s based on geographic map area
e.g. 11SW-A
followed by a code
C - Cut Slope : F - Fill Slope
R - Retaining Wall : N - Natural Slope
CR - Cut Slope with Retaining Wall
FR - Fill Slope with Retaining Wall
followed by a number
i.e. 11SW-A/R188
refers to Retaining wall 188 in Map area 11SW-A

4. Hong Kong Slope Catalogue1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
Map Referencing
Scheme
11SW-A A B C D NW NE SW SE

5. Cut Slopes and Fill Slopes e.g. North Coast Road
“Natural” Slope
Cut Slope
Fill Slope
Retaining Wall

6. Fill Slope
Fill Slope

7. Home Page for Hong Kong Slope Information System

9. Main Menu for Slope Information System

10. Click once on Slope to display data for 11SW-A/CR175
Slope Catalogue: Slope 11SW-A/CR175: Po Shan Road
Click once on Slope to display data for 11SW-A/CR175

11. Centred Map for Cut Slope 11SW-A/CR175: Po Shan Road

12. Photographs of Slope 11SW-A/CR175: Po Shan Road
Failure of slope in June 1972
Aerial Photograph of Slopes
11SW-A/CR175 and
11SW-A/FR30

13. Landslide Preventative Measure
Feature Registration Form for Po Shan Road Slope
11SW-A/CR175
Major Disaster in June 1972
Landslide Preventative Measure

14. Field Observation Form for Po Shan Road Slope
11SW-A/CR175

15. Example of Fill Slope from Slope Catalogue: Street Reference

16. Fill Slope 11SW-A/FR 30: Reconstructed slope from lower part of 1972 Po Shan Road Failure

17. Photographs of Slope 11SW-A/CR175: Po Shan Road
Failure of slope in June 1972
Aerial Photograph of Slopes
11SW-A/CR175 and
11SW-A/FR30

18. Example of Retaining Wall from Slope Catalogue: Street Reference

19. Landslip Preventative Measures
Peel Street:
Wall: 11SW-A/R188
before LPM in 1984
Same Wall in from Slope Catalogue

20. Po Hing Fong: LPM 33
NK Tovey inspecting Walls
11SW-A/R53
11SW-A/R64
Oct. 15th 1982

21. LPM: Wing Lee Street (Bridges Street Market)
Wall in 1982 prior to LPM
Note: N.K. Tovey with assistants
Wall in 2001

22. Landslide Preventative Measures - Step 1
Slope catalogue - data collected quickly - Stage 1
Very Simple Ranking System
NOT necessarily accurate BUT gives a Rational Way to move forward.
Evaluate a score system
e.g. (3 * height + drainage factor )* consequence factor
drainage factor say 0 if good > 5 if poor)
consequence factor - say
1 for little consequence : 2 for minor roads
3 for major roads : 4 for buildings
Slopes with High Rank Number SUGGESTS they are MORE CRITICAL

23. Landslide Preventative Measures - Step 2
Limited Financial Resources available in any one year so
From the thousands of slopes in catalogue, select the 20 with the highest RANK Number for more careful analysis.
e.g.
Check initial catalogue data is correct
probe depth of weep holes in retaining walls
make a thorough check for signs of distress
do a simple slope stability analysis
shortlist (say 6) most critical based on this Stage 2 study for detailed study as Stage 3

24. Landslide Preventative Measures - Step 3
Arrange for Site Investigation of shortlisted Slopes
trial pits
soil sampling - shear testing
bore holes
install piezometers
monitor piezometers
Check History of Site
Check responsibility
Full Stability Analysis
If public responsibility move to design Stage - otherwise serve notice on person or authority liable for maintenance.

25. Landslide Preventative Measures - Step 4
Design Preventative Measures
Check designs
Working Drawings
Tender Process
Contractors on Site
Preventative Work complete
Begin Step 2 for next group of slopes for next year.
After a number of years, most critical slopes should now be safe.

26. Some recent Landslides in Trinidad
There is NO proactive system in place
Everything is Reactive

27. December 2004 – note the slide is much more extensive
Landslide at Maracas
December 2002
December 2004 – note the slide is much more extensive

28. 3 km beyond Las Cuevas as seen on TV half of road blocked
December 9th
Landslide
3 km beyond Las Cuevas as seen on TV
half of road blocked
Landslide 11th December at approximately 13:00
1 km before Las Cuevas
half of road blocked

29. Slope before failure at Couva
Slope after Landslide
Slide by Derek Gay, UWI