Presentation on theme: "Landslip Preventative Measures Development of the Hong Kong System"— Presentation transcript:
1Landslip Preventative Measures Development of the Hong Kong System Slope ManagementandLandslip Preventative MeasuresDevelopment of the Hong Kong SystemMajor Landslide at Maracas, Trinidad - Late December 2002.
2Prevention of Landslides Database of SlopesType of SlopeConditionConsequencesCut SlopesFill SlopesRetaining WallsHybrids: 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.
3Development of Slope Registration Scheme Began in late 1970’s based on geographic map areae.g. 11SW-Afollowed by a codeC - Cut Slope : F - Fill SlopeR - Retaining Wall : N - Natural SlopeCR - Cut Slope with Retaining WallFR - Fill Slope with Retaining Wallfollowed by a numberi.e. 11SW-A/R188refers to Retaining wall 188 in Map area 11SW-A
4Hong Kong Slope Catalogue 12345678910111213141516Map ReferencingScheme11SW-AABCDNWNESWSE
5Cut Slopes and Fill Slopes e.g. North Coast Road “Natural” SlopeCut SlopeFill SlopeRetaining Wall
21LPM: Wing Lee Street (Bridges Street Market) Wall in 1982 prior to LPMNote: N.K. Tovey with assistantsWall in 2001
22Landslide Preventative Measures - Step 1 Slope catalogue - data collected quickly - Stage 1Very Simple Ranking SystemNOT necessarily accurate BUT gives a Rational Way to move forward.Evaluate a score systeme.g. (3 * height + drainage factor )* consequence factordrainage factor say 0 if good > 5 if poor)consequence factor - say1 for little consequence : 2 for minor roads3 for major roads : 4 for buildingsSlopes with High Rank Number SUGGESTS they are MORE CRITICAL
23Landslide Preventative Measures - Step 2 Limited Financial Resources available in any one yearsoFrom 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 correctprobe depth of weep holes in retaining wallsmake a thorough check for signs of distressdo a simple slope stability analysisshortlist (say 6) most critical based on this Stage 2 study for detailed study as Stage 3
24Landslide Preventative Measures - Step 3 Arrange for Site Investigation of shortlisted Slopestrial pitssoil sampling - shear testingbore holesinstall piezometersmonitor piezometersCheck History of SiteCheck responsibilityFull Stability AnalysisIf public responsibility move to design Stage - otherwise serve notice on person or authority liable for maintenance.
25Landslide Preventative Measures - Step 4 Design Preventative MeasuresCheck designsWorking DrawingsTender ProcessContractors on SitePreventative Work completeBegin Step 2 for next group of slopes for next year.After a number of years, most critical slopes should now be safe.
26Some recent Landslides in Trinidad There is NO proactive system in placeEverything is Reactive
27December 2004 – note the slide is much more extensive Landslide at MaracasDecember 2002December 2004 – note the slide is much more extensive
283 km beyond Las Cuevas as seen on TV half of road blocked December 9thLandslide3 km beyond Las Cuevas as seen on TVhalf of road blockedLandslide 11th December at approximately 13:001 km before Las Cuevashalf of road blocked
29Slope before failure at Couva Slope after LandslideSlide by Derek Gay, UWI