Quay Wall Options - 1113 - Rev00

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DESIGN NOTE

Checked by: Compiled by: / 6

Project:

Section:

Saldanha GMQ Ext. FEL3

Quay wall options assessment

Date:

Note No.:

29/10/2012

1113/QW/001 Rev00

-

Task Description:

As part of the FEL3 Study for the Phase 2 Extension of the GMQ and Rock Quays in the Port of Saldanha Bay a number

of quay wall types were considered. This note documents the work undertaken as part of the options assessment and

presents the preferred quay wall section for the extension.

Layout:

Two quay wall sections are required for the Phase 2 Extension:

1. Infill area - No existing structures, construct new wall along cope line and backfill. 2. Rock Quay - Existing sheet pile wall (unsafe), (1.0m between berthing line of old and new cope lines).

In addition the quay wall must provide an interim depth of -6.5mCD with the ability of deepening to -11.5mCD.

Available Information:

The following information has been utilised:

PRDW Design Note 1113/GEO/001 Rev00 (Geotechnical Desk Study)

Quay Wall Requirements:

Berth Function Berth Depth

(m CD)

Cope Level

(m CD) Design Loads

Offshore Supply Base Interim depth : -6.5

Final depth : -11.5 +3.8

40 kN/m² Apron Load

Hydrostatic head (tidal lag) 0.5m

Bollard: 60t (30 kN/m)

400t Crane Load – (150t point load)

Design Life:

50 yr design life with minimal maintenance

Design Geotechnical Parameters:

Material

Unit weight above water

table (kN/m

3)

Unit weight below water

table (kN/m

3)

Undrained shear

strength (kPa)

Effective Cohesion

(kPa)

Effective friction

angle (°)

Drained Young's Modulus

(MPa)

Poisson's Ratio

QUARRY RUN - 20.0 - - 38 50 0.25

53mm STONE - 19.0 - - 40 50 0.25

Backfill SAND 17.0 18.0 - - 34 25 0.30

loose fine SAND - 18.0 - - 32 20 0.25

fine to coarse SAND - 19.0 - - 34 20 0.25

coarse SAND - 19.0 - - 35 20 0.25

Quay Wall Options:

The following quay wall options have been considered at Concept level* as part of this assessment:

1. Steel Sheet Pile Wall

2. Mass Concrete Blockwall

3. Reinforced Concrete Counterfort Wall

4. Reinforced Concrete Deck on Steel Tubular Piles

*Main structural elements have been roughly sized and ROM costs have accuracy levels of -40% to +50% (costing is only for comparison purposes and the R/m rates .

Assessment Criteria:

The quay walls have been assessed against the following criteria:

a) Ability to meet functional requirements

b) Constructability

c) Maintainability

d) Ease of Deepening from -6.5 to -11.5mCD

e) Cost and Value

f) Construction programme

g) Environmental Impact

A summary of the information contained in this note is presented in the form of a Multi Criteria Assessment, see

Figure 7.

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1. Steel Sheet Pile

Assessment Criteria Comments

Ability to meet functional requirements

Meets all requirements

Constructability

Availability of skills: Limited – Local marine sheet piling skills are limited but available

Availability of materials: Required AZ section and tie rods not fabricated locally will require overseas procurement. Fabricated steel work and concrete coping and paving will be locally sourced

Extent of temporary works: Minimal – Only pile guide frame required

Contractors site camp:

Minimal – Small footprint required mostly sheet pile stock pile, and spoil stock pile from the tie rod excavation.

Risk associated with unknown ground conditions:

High – very hard layers and very soft layers pose potential design, cost and duration risks to a sheet piling solution

Interaction with existing wall Limited - Drive new wall ahead of existing – requires NO removal and excavation of existing sheet piles – Simple tie in with existing blockwall GMQ

Maintainability

Access for maintenance: Easy access to face of structure, no access to anchor system

Localisation and repairability of damage:

Damage to steel AZ sheeting easily repaired with welded steel patch, damage to tie system would require excavation and careful replacement

Ease of Deepening From -6.5mCD to -11.5mCD Simple – Structure designed for -11.5mCD and when required easily deepened to -11.5mCD

Cost and Value

Capital Cost:

R 740 000/m (ROM -40 to +50% quay wall only construction cost, items common to all walls types excluded i.e. quay furniture, paving, berth pocket dredging etc – Not to be used to calculate project costs - for comparison purposes only)

Maintenance and Operational Cost:

Medium –Anode replacement (3 x during life), patching at tyre fender locations

Construction programme Duration: ± 12 Months (Excluding procurement ) Fast - Speed of construction is rapid – with option for acceleration through the mobilisation of additional piling rigs

Environmental Impact Low – no dredging required to install wall

SEE FIGURE 2 & 3:

The sheet pile wall has the advantage over the other options as it does not require the complete removal of the existing wall. The AZ46 piles

can be driven ahead of the rock quay providing significant programme and capital cost advantages.

The major concern with this wall type centres around the ground conditions - hard Calcrete layers will prevent driving, while soft silty SAND

layers will limited passive soil response. This represents a potential fatal flaw, which the results of the current geotechnical investigations will

inform.

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2. Mass Concrete Blockwall




Constructability

Availability of skills: Satisfactory – Local concreting skills and marine placing skills for heavy precast block are available

Availability of materials: All materials can be locally procured

Extent of temporary works: Significant – Reasonable sized casting yard, load out facility


Extensive – Large footprint required mostly precast block stock pile, and spoil stock pile from the foundation trench excavation.


Low – GMQ is a blockwall structure - excavate material and extend stone bed if poor sub strata is encountered

Interaction with existing wall

Extensive – Requires complete removal of existing sheet pile wall at Rock Quay wall as well as extensive excavation for the foundation trench or construction of a significant temp retaining wall – Temp support or removal of blocks required for tie in with existing blockwall

Maintainability Access for maintenance: Easy access to face of structure


Easy to repair with FRP or concrete patch

Ease of Deepening From -6.5mCD to -11.5mCD Structure constructed at -11.5m CD – no interim (-6.5mCD) option

Cost and Value

Capital Cost:

R 1 520 000/m (ROM -40 to +50% quay wall only construction cost, items common to all walls types excluded i.e. quay furniture, paving, berth pocket dredging etc – Not to be used to calculate project costs - for comparison purposes only)


Very Low – Serviceability crack repairs to capping beam as required

Construction programme

Duration:

± 20 Months Slow - Speed of construction is slow – limited by production rate of casting yard, foundation trench construction and placing rate of marine plant –numerous interfaces between unit production, trench excavation, stone bed placing, unit placing, preloading and backfilling

Environmental Impact Significant – The construction of the foundation trench for the wall requires the removal of ± 60 000m³ of material, most of this this material will be stock piled and reused

SEE FIGURE 4:

The block wall requires significant volumes of concrete, making it the most material intensive option. Combined with the necessity to

completely remove the existing wall and create a large foundation trench – this options has the highest cost /m.

This wall type has been successfully used in the Port of Saldanha at the GMQ and there are life cycle advantages to its robust design and

construction method.

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3. Reinforced Concrete Counterfort Wall




Constructability

Availability of skills: Satisfactory –– Local concreting skills and marine placing skills for heavy precast block are available – the availability of large heavy lift marine plant is limited.


Extent of temporary works: Extensive – Reasonable sized casting yard, launching dock


Extensive – Large footprint required mostly precast block stock pile, and spoil stock pile from the pla trench excavation.


Low – MPT is a counterfort structure - excavate material and extend stone bed if poor sub strata is encountered

Interaction with existing wall Extensive – Requires complete removal of existing sheet pile wall at Rock Quay as well as extensive excavation for the foundation trench - Temp support or removal of blocks required for tie in with existing blockwall

Maintainability

Access for maintenance: Easy access to face of structure


Easy to repair with FRP or concrete patch (joints require diver)

Ease of Deepening From -6.5mCD to -11.5mCD Structure constructed at -11.5m CD – no interim option

Cost and Value

Capital Cost:



Low – joint maintenance and Serviceability crack repairs to capping beam as required


Duration:

± 17 Months Average - Speed of construction is average – limited by production rate of casting yard, foundation trench construction and placing rate of marine plant –numerous interfaces between unit production, trench excavation, stone bed placing, unit placing, preloading and backfilling – The size of the units does have a positive impact on the placing speed.

Environmental Impact Significant – The construction of the foundation trench for the wall requires the removal of ± 60 000m³ of material, most of this this material will be stock piled and reused

SEE FIGURE 5:

The counterfort wall presents a more efficient concrete gravity option than the blockwall. However, TNPA have expressed concerns over the

joints in the counterforts at previous quay wall MCA meetings.

This option also requires the full removal of the existing wall and extensive dredging to create the foundation trench. In addition the extensive

temporary works required for the unit construction of this quay type must be considered.

This wall type has been successfully used in the Port of Saldanha at the MPT and has the advantage of Saldanha TNPA being familiar with

operational and maintenance requirements.

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4. Reinforced Concrete Deck with Steel Tubular Bearing Piles



Heavy lift loading on a deck structure is a concern

Constructability

Availability of skills: Satisfactory – Local marine piling skills are available


Extent of temporary works: Minimal – Pile headstocks and deck support, casting yard for precast deck elements


Minimal – Small footprint required mostly pile stock pile, and spoil stock pile from existing sheet pile removal


High – very hard layers and very soft layers pose potential design, cost and duration risks to a piling solution

Interaction with existing wall Extensive – Requires complete removal of existing wall as well as extensive excavation for the revetment slope – Construction of a return wall required for the tie in at the existing blockwall GMQ

Maintainability

Access for maintenance: Easy access to face of structure and deck top, limited access to underside of deck


Deck easy to repair, damage to pile is much harder

Ease of Deepening From -6.5mCD to -11.5mCD Cutting slope and installing revetment after construction of the deck is difficult therefore will construct to -11.5mCD at

Cost and Value Capital Cost:



Medium – Anode replacement, serviceability repairs to cracking deck concrete, revetment maintenance


Duration:

± 22 Months Slow - Speed of construction is slow – with option for acceleration through the mobilisation of additional piling rigs (additional cost) – Number of interfaces with excavation, pile driving, precast beam and panel placing and insitu concreting of deck

Environmental Impact Significant – Installation of the wall requires the removal and disposal of ± 40 000m³ of material - - Revetment is a positive

SEE FIGURE 6:

The deck on piles option provides an alternative to the material intensive gravity options. The piling risks associated with the sheet pile are still

a concern. However the use of steel tubular piles allows for grabbing out or chiselling through the tube to progress through the harder layers.

This option also requires the full removal of the existing wall and extensive dredging to create the revetment slope.

The heavy lift requirement for the deck structure results in heavy beams, a thick deck and a close pile spacing, which result in higher

construction costs and a longer construction programme.

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Figure No.

Title:

SALDANHA GMQ Ext. FEL3 STUDY

Interpreted Geological Section 1

loose fine SAND fine to coarse SAND coarse SAND clayey SAND CALCRETE

S.B.28 S.B.29 S.B.30

E.O.H. E.O.H.

E.O.H.

(-6.3 to -7.3)

(-9.2 to -9.4)

(-10.7 to -11.0)

-13.3

-20.1

-5.3 -5.4

-3.6

-7.0

-5.3

-13.3 -13.5

-15.6

(-10.0 to -10.2)

(-17.6 to -17.7)

(-8.3 to -8.5)

0.0 (MLWS)

Source: Historical borehole logs from 1973 (Conducted by Salcon) – Made available by TNPA Saldanha, 2012

-19.5

-21.3 -21.1

South

side of blockwall

North

side of blockwall

Figure No.

Title:


Steel Sheet Pile – Infill Section 2

Existing material

-24.0mCD

+3.8mCD

Quarry Run

Backfill Sand

AZ46 (430 MPa) Main Wall

AZ18 (350 MPa) Anchor Wall - Length of 7m - oversized due to increased liquefaction risk in upper soil strata

Design dredge depth -11.5mCD

Interim dredge depth -6.5mCD

0.0 mCD

Stone Drain

Filter Layer

M100(500 MPa) 35m long

Reinforced concrete capping beam

Precast cope panel – extended to -0.5m CD and

grout filled behind to protect against corrosion

Potential Calcrete layers

(50MPa)

Method:

1. Drive AZ46s

2. Install AZ18 anchor wall

3. Place to interim level - quarry run, filter layer and backfill material

4. Install M76 tie rods

5. Backfill anchor

6. Tension tie rods

7. Complete Back fill

8. Install cope, services, paving and furniture

Figure No.

Title:


Steel Sheet Pile – Rock Quay Section

3

Existing material

-24.0mCD

+3.8mCD

Existing sheet pile

Backfill Sand

AZ46 (430 MPa) Main Wall

AZ18 (350 MPa) Anchor Wall - Length of 7m - oversized due to increased liquefaction risk in upper soil strata


0.0 mCD Stone Drain Existing anchor

M100 (500 MPa) 35m long


Precast cope panel – extended to -0.5m CD and

grout filled behind to protect against corrosion

Potential Calcrete layers

(50MPa)


Method:

1. Drive AZ46s ahead of Rock Quay

2. Excavate down to just above tie lvl of Rock Quay

3. Cut existing Rock Quay sheet piles to just above tie lvl

4. Install AZ18 anchor wall

5. Install M100 tie rods

6. Backfill anchor and gap between walls

7. Tension tie rods

8. Install cope, services, paving and furniture

Figure No.

Title:


Blockwall

4

Quarry Run

1.0m thick stone bed

+3.8m CD

Backfill SAND



Filter layer

Existing material

Stone infill

Unreinforced precast concrete blocks

0.0m CD

1:3


Figure No.

Title:


Counterfort

5

1.0m thick stone bed

+3.8m CD

Backfill SAND



1:3

Reinforced concrete counterfort unit

(5m width)

0.0m CD


Figure No.

Title:


Deck-on-Piles 6

Existing material

-24.0mCD

+3.8 mCD

Backfill Sand

Reinforced concrete abutment


Quarry Run

+0.0 mCD


Insitu reinforced concrete deck Precast panels

Precast beams

Ø800mm steel tubular piles

1:3

1:1.5

Figure No.

Title:


MCA Results 7

Quay Wall Options - 1113 - Rev00

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