Technical Seminar No. 5 LAND RECLAMATION. Works in Singapore. 22 nd April, 2012

Transcription

1 Technical Seminar No. 5 LAND RECLAMATION Works in Singapore 22 nd April, 2012

2 History of Land Reclamation Projects in Singapore Singapore Land Area km 2 (1960s) km 2 (Present) A. Kallang River..1960s (Industrial & Housing) B. Kranji 1960 (Indstrial) C. Jurong swamps.1960s and 1970s (Industrial) D. Pasir Panjang.1970s (Pasir Panjang Port) E. Marine Parade.1970s (Housing) F. Changi Airport.1980s (Infrastructure) G. Jurong Island.1990s (Joined 7 islands for Industrial) H. Seletar.1980s (Housing) I. Reclamation Work at Marina Bay and Tanjong Rhu.Completed 1994 J. Changi East (Changi Airport Extension) K. Pulau Semakau off Shore Land Fill Project L. North Eastern Coast Reclamation Project (Punggol 21) M. Pasir Panjang Terminal Phase-1. Completed 1997 N. Tuas Reclamation.Completed 1999 O. Pasir Panjang Terminal Phase 2. Completed 2009

3 Marine Vessels and equipments

4 Trailer Suction Hopper Dredger (TSHD) -For sand mining and sand discharging -Hopper capacities range from 4500 to m 3 -Dredgable depths range from 12 to 90 m below seabed Large and small TSHD

5 Cutter Suction Dredger -For sand dredging and sand rehandling -Discharge capacities range from 8,400 to 80,000 m3/day -Dredgeable depth 15 to 35 m below seabed

6 Grab or Clamp Shell Dredger -For clay/sand dredging -Common grab size 5 to 8 m3 -Dredging range from 10 to 60 m below seabed

7 Sand Spray Pontoon / Barge -For sand spraying/spreading at sand mat construction -Sand spreading is implemented when a shallow seabed is encountered or when the seabed soil is too soft.

8 Floating Dock - For Caisson Launching Main Dimension 31.5m 27m 6.5 m 1.5 m 1. Capacity : 20,000 Ton 2. Full Length : m 3. Width : m 4. Inner Width : m 5. Top Deck Height : 31.5 m 6. Safety Deck Height : 27.0 m 7. Pontoon Deck : 6.5 m 8. Draft (Empty) : 1.5 m 9. Ballast System : m3/hr 10. Ballast Tank Capacity: 36,790 tons

9 Pre-construction activities -Pre-construction survey - obtained original seabed level before start work -Soil Investigation - boreholes - in-situ testing -Toxicity test - chemical test of the dredged material

10 Toxicity samples depth, grid and sample size Samples depth Seabed level 0.9 m 1.9 m 2.9 m Every 3 m until 1 m below design dredged level Samples grid As the site is unlikely to be contaminated m x 200 m As the site is likely to be contaminated m x 100 m Sample size At least 100 mm long (SPT samples can be used) Design dredged level 1 m below design dredged level

11 Coastal Protection

12 Types of coastal protection - Stone Revetment - Retaining Rock Bund - Breakwater - Headland -Vertical Wall -Cantilever, counterfort and gravity walls -Sheet pile wall -Caisson sea wall -Box gabion - Quay Wall - Composite Retaining Structures

13 Construction sequences of Stone Revetment - Soil Investigation - Design Process - Sand Key Trench Dredging - Sand Key/Bund Filling - Deep Compaction - Sand Trimming - Geo-fabric laying - Stone filling and pitching - Cement motar

14 Sand Key Trench Dredging Rough Dredging Final Dredging Sea Trench Dredging Hard Layer

15 Sand Key Trench Dredging Sampling TESTING OF SOIL SAMPLE BY USING POCKET PENETROMETER

16 Determination of Dredging Depth 0.00mCD Grab Dredger Water level Chart datum Tide (mcd) Bucket depth (m) Dredge depth (mcd) Seabed level E.g. Bucket depth = 20 m Tide = +2.0 mcd Dredged depth = mcd

17 Chart Datum Chart Datum is the plane below which all depths are published on a navigational chart. It is also the plane to which all tidal heights are referred, so by adding the tidal height to the charted depth, the true depth of water is determined. By international agreement, Chart Datum is defined as a level so low that the tide will not frequently fall below it. Chart Datum is shown on charts as the zero metre contour.

18 Sand Key Trench Dredging

19 Sand key/bund filling and deep compaction Acceptance Criteria line Sand Bund Qc value Sea Sand Key Hard Layer

20 Stone Revetment Construction Quality Control of the Geo-textile material Field drop test Checking the A stone weight (379.5 kg) Dropping the stone from 1.5m high Criteria -Total should have 16 cells (1.2 m * 1.2 m) - A stone weight not less than 350 kg -Drop from 1.5 m high (free fall to center) -Not more than 8 cells should have holes -Each cell should not have more than 2 holes -Holes should not exceed or equivalent of diameter 10 mm. 1 hole at cell no.2

21 Sequences of Stone Revetment Construction v Sand Trimming Geo-textile laying v Stone placing and pitching Cement mortar

22 Construction sequences of Caisson Sea Wall - Soil Investigation - Design Process - Caisson Fabrication - Sand Key dredging - Sand Key Filling and deep compaction - Rock mound filling and tamping - Final grading and Rock crust leveling - Caisson Installation - Rock filtering at caisson base - Caisson infilling and compaction - Caisson preloading - Caisson Joints - Scour protection

23 CAISSON SEA WALL

24 FABRICATION OF CAISSON CAISSON MOVED BY HIGH TONNAGE CARRIERS

25 FABRICATION OF CAISSON Step-4 Step-3 Step-2 Floating Dock

26 Caisson Launching

27 Flows of Caisson construction Caisson Installation

28 Laying of geo-textile for caisson joint Rolled geotextile Installation of anchor bolts on to the caisson wall in progress, using 1 underwater hydraulic hammer drill 2 Anchor bolt ( M10 )installed on caisson wall 3 Unfolding of geotextile, as the steel pipe is lowered 4 Use of steel plates and anchor bolts to hold the geotextile

29 Flows of Caisson construction Frequency of Monitoring Before Infilling Baseline reading During Infilling/Sand filling behind Caisson times per day After Filling Once daily for 7 days and twice weekly until reading stabilized Preloading on Caisson----- Once daily After preloading Twice weekly until reading stabilized Long term performance monitoring----- Once weekly until end of Defect Liability Period (DLP) Caisson instrumentation & monitoring

30 Flows of Caisson construction Rock Filtering

31 Flows of Caisson construction Caisson infilling and cells compaction

32 Flows of Caisson construction Caisson preloading and Caisson joint casting

33 Flows of Caisson construction Scour Protection Seabed Scour Protection

34 Land Reclamation by Soil Improvement Method

35 Reclamation Fill (Without Soil Improvement) Sand Fill Sand Fill Compressible layer Consolidation settlement completed after 5 years Compressible layer Hard Layer Hard Layer

36 Reclamation Fill (With Soil Improvement) Sand Surcharge Consolidation Settlement completed After 5 months Sand Fill Compressible layer Hard Layer

37 Reclamation sequences Soft clay/dredged material filling Sea Sand Key Normally allowed up to -2.0 mcd Hard Layer

38 Reclamation sequences Sand spreading/spraying at sand mat construction Sea Sand Key Hard Layer

39 Sand pumping by TSHD

40 Magnetometer survey

41 Prefabricated Vertical Drains Installation & Calibration PVD calibration for actual penetration depth and data logger record PVD installation in progress

42 Geotechnical Instrumentation for Reclamation Shallow Settlement Plate (SSP) SSP sketch diagram SSP installation

43 Geotechnical Instrumentation for Reclamation Magnetic Extensometer

44 Geotechnical Instrumentation for Reclamation Deep Settlement Guage

45 Geotechnical Instrumentation for Reclamation Pneumatic Piezometer Piezometer monitoring Bentonite pallets and clean coarsegrained sand

46 Sand preloading / surcharging

47 Dynamic compaction and surface compaction Dynamic compaction Roller compaction and field density testing (sand cone method)

48 Thank you!