Department of National Defence B-Jetty Reconstruction

Transcription

1 Department of National Defence B-Jetty Reconstruction CFB Esquimalt, BC Presented by: Stantec & Golder Associates February 2, 2016

2 Agenda 1 B-Jetty Project Background 2 Distinguishing Project Features 3 Structural Schemes Considered 4 Design Considerations 5 Structural Pile Considerations 6 Analysis 7 Dredging and Soil Remediation

3 ESQUIMALT VICTORIA

4 Project Background

5 Existing B-Jetty Finger pier constructed in early 1940 s Reconstructed in 1956 Timber pile/pile cap structure with pre- cast concrete deck panels Original design vessel 2000 tons About 190 m long and 18 m wide Fixed crane

6 B-Jetty Replacement Project To accommodate the next class of offshore patrol vessels, frigates and supply vessels (JSS, AOPS, CSC, Subs) Design vessel - 20,000 Tonnes displacement Finger pier About 270 m long and 26 m wide Rail mounted crane Services tunnel around jetty perimeter Stub section to align with future A-Jetty replacement project

7 B JETTY A JETTY C JETTY DRYDOCK

8 B JETTY A JETTY C JETTY DRYDOCK

9 Distinguishing Project Features

10 Geotechnical Field Investigations Geophysical and geotechnical investigations were undertaken to obtain information on subsurface conditions Geophysical investigations consisted of multibeam (high resolution) bathymetry survey and sub-bottom profiling of an area comprising both B- and A-Jetties Geotechnical investigations consisted of cone penetration tests and samples boreholes with rock coring and sampling to depths varying from 10 to 20 m Geophysical televiewer surveys were also carried out in the rock core holes

11 Geotechnical Results Geophysical Surveys (Non-intrusive) Inferred Glacial Till/Bedrock Surface Inferred Seabed Surface

12 Geotechnical Borehole Investigation Area-3 Area-1 Area-2

13 Geotechnical Subsurface Conditions Shallow bedrock near shore Bedrock slopes sharply down in seaward direction Marine sediments vary from non-existent near shore to 10 m thick offshore Marine sediments are underlain by Victoria Clay to depths in excess of 70 m from seabed Clay underlain by thin till layer and bedrock Bedrock quality varies with severe fracturing/ jointing and low intact strength in upper 1 9 m

14 Soil Stratigraphy - B Jetty

15 Geotechnical Shear Strength Profile Victoria Clay and Marine Sediments

16 Earthquakes

17 Earthquake Loading (2010 NBCC)

18 Earthquake Loading (2010 NBCC)

19 Tsunami Cause and Effects of a Tsunami M9 megathrust earthquake Mike 21 modelling package Water level rise 1.6 m to 1.8 m Time of arrival after EQ ~ 90 minutes Current speed ~ 6 m/s Wave hits broadside to finger pier Run-up

20 Tsunami

21 Tsunami B Jetty 0 m 50 m 100 m NAD83 UTM Zone 10 Projection

22 Tsunami

23 Tsunami

24 Tsunami Computed Run-Up (Shaded)

25 Structural Schemes Considered

26 Structural Schemes Steel Sheet Piles and Concrete Caissons Apply sustained loads to weak and compressible overburden soils Would result in large, on-going total and differential settlements Not acceptable Steel Pipe Piles Vertical loads transferred to bedrock No settlement Pile lengths vary from less than 5 m near shore to more than 90 m at the seaward end

27 Preferred Structural Scheme Steel Pipe Piles Rock anchored steel pipe piles Reinforced concrete pile caps, support beams and deck But still a significant challenge to construct due to thick overburden and deep bedrock at seaward end

28 Design Considerations

29 Vessels & Operational Loads Water depth 11.5 m max (varies) 20,000 Tonnes Displacement max Deck live load 30 kpa Rail mounted crane Berthing loads, Mooring loads (60 knots) Geotechnical Shallow bedrock at shoreward end, very deep bedrock at seaward end Bedrock quality varies with severe fracturing/ jointing and low intact strength in upper 1 9 m

30 Earthquakes 2,475 year return period (NBCC) Importance Factor 1.5 (Post-Disaster) Analyses based on both National Building Code of Canada and Canadian Highway Bridge Design Code Tsunami Current speed ~ 6 m/s Wave hits broadside to finger pier Current force on berthed Joint Supply Ship (JSS) Governs over earthquakes loads

31 Structural Pile Configurations

32 Concept 1 Mix of battered and vertical piles Battered piles provide lateral bracing Challenge to install in deep bedrock zones

33 Concept 2 All vertical piles More lateral movement under high loads (EQ, Tsunami) than battered piles Challenge to install in deep bedrock zones but less than for battered piles

34 Preferred Configuration Concept 2 All Vertical piles Main Consideration - Constructability

35 Analysis

36 Analysis SAP 2000 Classic Line Diagram Solid Surface Diagram

37 Displacement (Tsunami) TSUNAMI FORCE Governing load combination generally due to Tsunami Forces SOIL INTERACTION LINEAR SPRINGS AT DISCRETE POINTS, BUT NON-LINEAR ALONG THE LENGTH OF PILE

38 Jetty Deflection Tsunami West to East (Incoming) TSUNAMI 180 mm

39 Stresses - Tsunami Required: 1067 mm dia, rock anchored, concrete filled pipe piles Post-tensioned longitudinal beams and deck

40 Dredging and Soil Remediation

41 Dredging and Soil Remediation Contaminated Soil Remediation Significant effort to remove contaminated harbor sediment Remediated areas to be capped with a 300 mm thick layer of sand (Residual Management Cover). RMS Cover 14,000 m 2 Soft Sediment Dredging For soil remediation and for water depth at berths Estimated Quantity 40,000 m 3 All dredged material to be barged to offsite offload location for land disposal

42 Dredging and Soil Remediation Bedrock Dredging For infrastructure installation For water depth at vessel berths For rock removal adjacent to Future A-Jetty location Estimated Quantity 6,500 m 3

43 Limits of Dredging NON-REMEDIATED REMEDIATED

44 Limits of Dredging m m SED TO BR m SED TO BR - 15 m SLOPE UP TO - 4 m REMOVE 1 TO 2.2 m SOFT SEDIMENT DREDGING TO BEDROCK SOFT SEDIMENT DREDGING TO DEPTH (REMEDIATED)

45 Limits of Dredging m m m m SOFT SEDIMENT DREDGING TO DEPTH (NON- REMEDIATED) BEDROCK DREDGING

46 Bedrock Dredging/Blasting Bedrock removal both onshore and within the harbor, required for infrastructure installation and for water depth at vessel berths Must be carried out near existing historic structures including buildings, quay wall and drydock Mitigating effects on local marine mammals are also an important consideration for the blasting program Blasting program includes low yield charges, bubble curtain, marine life exclusion zone

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48 Questions?