Innovative pile plugging Musandam Rock Loading Facility

Transcription

1 DGF meeting : Pile foundation Innovative pile plugging Musandam Rock Loading Facility Jørgen S. Steenfelt COWI A/S, Denmark 1 Innovative pile plugging

2 Outline - introduction Project location and site conditions Concept & challenges Temporary Barge Berth (Dana Jetty) - piling experience - horizontal load testing Main Jetty - alternative piling method - results Conclusions &lessons learned 2

3 Project location & site conditions Musandam Rock Loading Facility Aisha Bay, Oman Rock material for Gulf region infrastructure projects 3

4 Project location & site conditions Client: Rock Equipment S.A Marine contractor: MEDCO Piling subcontractor GeoSea Consultant: COWI Gulf & DK 4

5 Project location & site conditions Main jetty for bulk loading - vessels & barges 80,000 dwt Causeway - access & conveyor system to jetty Temporary barge berth Dynamic & single point mooring analysis 5

6 Project location & site conditions Causeway soft marine sand deposits at seabed high PGA: liquefaction risk site specific study 6

7 Major challenges Ground conditions -20 m Few boreholes -15 m Facility moved after boring campaign New drilling equipment failed Marine sand -10 m Upper Calcarenite Limestone gravel Lower Calcarenite Limestone (at depth) 7

8 Major challenges Ground conditions Marine deposits PGA Marine deposits Caprock Limestone gravel Site specific seismic study by WLA 0.43 g reduced to g for 475 yrp (10% in 50 y) g for 238 yrp (10 % in 25 y) Position & extent of Calcarenite? Limestone Depth to Limestone? Use pile driving as GI-tool? 8

9 Major challenges - Jetty concept 1422 m driven steel tube piles Ø1.422 m, t = 25 mm Design: shaft adhesion and end bearing (plugging or refusal in bedrock) Driving depth: - embedment for horizontal loads - vertical capacity Contractor's choice: Hydrohammer S150 (E=150kNm) Wirth PBA612 top drilling system 9

10 Major challenges Piling Position & extent of Calcarenite Marine deposits Caprock Limestone gravel Limestone Effect on driving - sloping caprock? Plugging/no plugging? - and where? Drilling out when? Pile length versus capacity of hammer Evaluation method? 10

11 Temporary Barge Berth Fender piles V ~ 0 H = 609 kn Platform piles V = 3000 kn H = 20 kn 11

12 Pile driving as investigation tool? Required pile length m To substitute GI up to 34.5 m piles Evaluation? - Danish pile driving equation - automatic record of E, N Required vertical capacity: - ULS: 6,322 kn (platform piles) Horizontal: py-curves 12

13 Pile driving results Loading platform Caprock layer (merit in drilling) Partial or full plugging - at 14 m depth Refusal in Limestone - at -24 m acc. to BH Uniform results Problems foreseen for Main Jetty 13

14 Pile driving results Fender piles Caprock layer - depth varies - shadow effect Influence from ground conditions Overall same trend 14

15 Horizontal capacity? P7 P6 15

16 Test set-up 16

17 Measurements Total station Walkie talkie (E, N) Hydraulic jack pressure gauge 17

18 Horizontal load test results Fender piles Lpile - no hysteresis - caprock? 600 kn mm elastic mm LPile 18

19 Main Jetty Dolphins V ~ 3300 kn H ~ 650 kn Platform piles V ~ 3000 kn H ~ 400 kn Required dynamic capacity: plugged: kn unplugged kn 19

20 Pile driving initial Main Jetty Weld-on when required Initial penetration 20

21 Pile driving initial Main Jetty Dynamic Capacity Q> 7300 kn Piles excessively long Caprock a problem? Drilling adverse influence Innovation required 21

22 Plugging method 22

23 Pile driving results Main Jetty Min 10 m embedment Plugging above caprock High capacity Huge savings - time and steel High confidence 23

24 Pile driving results Main Jetty Difference from initial record remarkable Also valid for loading platform! 24

25 Conclusion & lessons learned 25

26 Conclusion & lessons learned Positive effect of plugging obvious More inference to come from data Pile driving elucidated ground conditions Co-operation designer & contractor pays off! 26