SURFACE COMPACTION OF HYDRAULIC FILLS OF LIMITED THICKNESS

Transcription

1 SURFACE COMPACTION OF HYDRAULIC FILLS OF LIMITED THICKNESS Patrick Mengé

2 Outline of the presentation Problem description Common project requirements Possible Soil Improvement Techniques Surface Compaction Techniques with large depth of influence Quality Control Specific Problems Conclusions / Research needed

3 Hydraulic fill with limited thickness Nearshore landwinning projects Granular material (non-cohesive material) Subsoil can vary from soft soil with soil improvement over granular soil to rock Thickness considered: from 0 m to approximately 6 m thickness Water table is always at limited depth Fill is realised partly under water and partly above the water table by means of hydraulic fill

4 Execution

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8 RESULT

9 RESULT

10 Outline of the presentation Problem description Common project requirements Possible Soil Improvement Techniques Surface Compaction Techniques with large depth of influence Quality Control Specific Problems Conclusions / Research needed

11 Material type Grain size distribution % fines (< 63 micron): e.g. max 10% % clay (< 2 micron): e.g. max 3% % stones limited: e.g. >200 mm max 10% Maximum size limited: e.g. no stones larger than 300 mm Coefficient of uniformity

12 Compaction Absolute density % Maximum Dry Density: e.g. 95% % Relative Density: e.g. 70% CBR-value: e.g. 15% E-modulus (how defined?) Plate load tests: from small to large = Zone Load Tests (Long Term) Settlement Requirement CPT-q c values of SPT-N values Minimal q c or N values, increasing with depth? DPT values

13 Outline of the presentation Problem description Common project requirements Possible Soil Improvement Techniques Surface Compaction Techniques with large depth of influence Quality Control Specific Problems Conclusions / Research needed

14 Compaction of Granular Soil Deep compaction techniques Heavy Tamping (or Menard Compaction) Vibratory compaction (vibroflot or special needletype compaction probes) Surface compaction techniques Conventional roller or plate compaction engineered fill: thin layers not appropriate for hydraulic fill Alternative techniques with large influence depth HEIC: High Energy Impact Compaction RIC: Rapid Impact Compaction Polygonal Drum Special Probes/Methods

15 Outline of the presentation Problem description Common project requirements Possible Soil Improvement Techniques Surface Compaction Techniques with large depth of influence Quality Control Specific Problems Conclusions / Research needed

16 HEIC High Energy Impact Compaction Companies: Landpac, Broons, Geoquip, others Comparison static-vabrotory-impact

17 HEIC principle and advantage

18 Depth of influence

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23 Method of working Driving at 12 km/h 20 to 40 passes Driving large loops Each loop shifts 1 drum width Depth of influence: up to 4 m

24 Parameters Soil type and moisture content Stratigraphy Type of equipment Drum Weight Drum Shape Contact pressure Rotational drop height Energy loss Impact roller Mass Lift (m) (h) Potential Energy Kinetic Energy kj Number of sides (p) Propulsion (p) Geoquip 16.2 t m 37 kj 169 kj 3 Drawn Landpac 11.0 t m 25 kj 115 kj 3 Self propelled Broons 7.9 t m 12 kj 55 kj 4 Drawn Broons 11.5 ECSMGE t MADRID m September kj / TC kj 17 Workshop 4Ground Improvement Drawn Landpac 10.5 t m 15 kj 69 kj 5 Self propelled

25 Depth of influence

26 RIC Rapid Impact Compaction Driving on a steel plate 1 m diameter Each Impact point blows Special Pattern with 2 or 3 passes Equipment: BSP Depth of influence: up to 6 m

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29 Depth of Influence

30 Depth of Influence

31 Polygonal Drum = vibratory roller compaction with special drum Drum has polygonal shape for larger depth of influence Method of working = classic vibratory roller compaction More passes (up to 20 sometimes) Depth of influence: up to 4 m Equipment BOMAG (14 and 25 tons rollers)

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33 Polygonal drum principle

34 Depth of influence

35 Depth of influence compaction value vs depth ,2 depth (m) -0,4-0,6-0,8-1 -1,2 24 passes 18 passes 12 passes 6 passes 0 passes -1,4-1,6 com paction value (%)

36 Other Probes / Methods Large vibrating plates Large static mass rollers (200 ton) NRG Cone method Others. Depth of influence:???

37 Large vibratory plates

38 Large vibratory plates

39 Advantages Why using these Alternative Techniques? Limited thickness: deep methods less efficient to compact the full height Uniform compaction result (depending on the technique) Speed of execution Non-specialist methods: can be performed with local labour and easy to adapt to ever changing project planning Flexibility in application Quality control methods during compaction

40 Outline of the presentation Problem description Common project requirements Possible Soil Improvement Techniques Surface Compaction Techniques with large depth of influence Quality Control Specific Problems Conclusions / Research needed

41 Conventional surface QC methods Density testing Involves In situ density (e.g. sand replacement method Involves lab testing: MDD (proctor) CBR testing (lab or in situ) Nuclear density testing E-modulus testing: plate load test

42 Problems related to such tests Depth of influence versus layer thickness (hydraulic fill). Execution in excavated pit: undisturbed soil? Unclear how much tests to be performed. Not possible to test under water. Based on classical testing ratio s: very large number of tests. Material type sometimes does not alow for these tests (sand-gravel-stones).

43 Example material type

44 Methods over large depth CPT testing and SPT testing More appropriate Flexible and fast Full depth testing, under and above water Requirements: have to be realistic; e.g. increasing with depth when passing water table is not possible Requirements and Interpretation on basis of literature correlations: Is this valid? Effect of mineralogy? To prepare local correlation is difficult and time consuming. Not possible when high % of stones occur in the reclamation material (damage to cones and equipment) Time effect is demonstrated in literature Rare: PMT testing

45 Performance testing Specification requirement based on allowable settlements and expected loading Principle of PLT but at larger scale: Zone Load Tests

46 ZLT

47 ZLT 3 m x 3 m plate at 150 kpa: 1350 kpa 125% is 1688 kpa 200 ton setup Same principle as pile load test Testing during 24h, 48h, 1 week Settlement criterion: 25 mm on long term under 100% load 125% testing allows for prediction of creep deformations on long term

48 Testing during compaction Different techniques are (being) developped: E-vib method Continuous Impact Response (Landpac) others?? Overall testing is possible during compaction Automated systems with real time information More experience needed for interpretation and requirement specification Ideal to combine with local performance testing

49 CIR example Principle based on acceleration measured on the compactor (from Landpac)

50 Outline of the presentation Problem description Common project requirements Possible Soil Improvement Techniques Surface Compaction Techniques with large depth of influence Quality Control Specific Problems Conclusions / Research needed

51 Specific Problems Fines control Mineralogy: crushable sands Not worked out in this presentation because of limited time

52 Outline of the presentation Problem description Common project requirements Possible Soil Improvement Techniques Surface Compaction Techniques with large depth of influence Quality Control Specific Problems Conclusions / Research needed

53 Conclusions Landwinning projects with hydraulic fill are much different from normal earth moving works Conventional surface compaction techniques are not appropriate In some situations deep compaction techniques not optimal Search for new techniques in the layer thickness range 0 to 6 m

54 Conclusions Research needed Special Surface Compaction Methods In landwinning business these methods are rather new and unknown Promising in specific soil and stratigraphic conditions Need for more knowledge on their performance and on the effect of external factors such as water table, mineralogy and time

55 Quality control Conclusions Research needed On landwinning projects, density testing and related surface tests is cumbersome and unreliable Performance testing is more appropriate and should be promoted

56 Question Thank you for your attentio