Department of National Defence B-Jetty Reconstruction · Department of National Defence B-Jetty Reconstruction ... Design Considerations 5 Structural Pile Considerations 6 ... •

Presented by:

Stantec &

Golder Associates

February 2, 2016

Department of National Defence B-Jetty Reconstruction CFB Esquimalt, BC

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

VICTORIA

ESQUIMALT

Project Background

DND B-Jetty Reconstruction Stantec I Golder Associates

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


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

A JETTY

B JETTY

C JETTY

DRYDOCK

A JETTY

B JETTY

C JETTY

DRYDOCK

Distinguishing Project Features


Geotechnical Field Investigations

•  Geophysical and geotechnical investigations were undertaken to obtain information on subsurface conditions

•  Geophysical investigations consisted of multi-beam (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


Geotechnical Results – Geophysical Surveys (Non-intrusive)

Inferred Glacial Till/Bedrock Surface

Inferred Seabed Surface


Geotechnical Borehole Investigation

Area-3

Area-1

Area-2


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


Soil Stratigraphy - B Jetty


Geotechnical Shear Strength Profile Victoria Clay and Marine Sediments


Earthquakes


Earthquake Loading (2010 NBCC)


Earthquake Loading (2010 NBCC)


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


Tsunami


Tsunami B Jetty

0 m 50 m 100 m

NAD83 UTM Zone 10 Projection


Tsunami


Tsunami


Tsunami

Computed Run-Up (Shaded)

Structural Schemes Considered


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


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

Design Considerations


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

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)


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

Structural Pile Configurations


Concept 1

•  Mix of battered and vertical piles •  Battered piles provide lateral

bracing •  Challenge to install in deep

bedrock zones


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


Preferred Configuration •  Concept 2 – All Vertical piles •  Main Consideration - Constructability

Analysis

Analysis – SAP 2000

Classic Line Diagram

Solid Surface Diagram


Displacement (Tsunami)

SOIL INTERACTION

TSUNAMI FORCE

LINEAR SPRINGS AT DISCRETE POINTS, BUT NON-LINEAR ALONG THE LENGTH OF PILE

Governing load combination generally due to Tsunami Forces


Jetty Deflection – Tsunami West to East (Incoming)

TSUNAMI

180 mm


Required: •  1067 mm dia, rock anchored, concrete filled pipe piles

•  Post-tensioned longitudinal beams and deck

Stresses - Tsunami

Dredging and Soil Remediation


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 m2

Soft Sediment Dredging •  For soil remediation and for water depth at berths •  Estimated Quantity 40,000 m3

•  All dredged material to be barged to offsite offload location for land disposal


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 m3

Limits of Dredging

NON-REMEDIATED

REMEDIATED


Limits of Dredging

SOFT SEDIMENT DREDGING TO BEDROCK

SOFT SEDIMENT DREDGING TO DEPTH (REMEDIATED)

SED TO BR

SED TO BR

-‐13.9 m

-‐13.7 m

-‐12.2 m

-‐15 m

SLOPE UP TO -‐4 m REMOVE 1 TO 2.2 m


Limits of Dredging

SOFT SEDIMENT DREDGING TO DEPTH (NON-‐REMEDIATED)

BEDROCK DREDGING

-‐13.4 m

-‐11.9 m

-‐13.7 m

-‐12.2 m


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


Questions?

Documents

Department of National Defence B-Jetty Reconstruction · Department of National Defence B-Jetty Reconstruction ... Design Considerations 5 Structural Pile Considerations 6 ... •