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Engineers Australia Professional Interview

Application for Chartered Membership - Ryan Eales
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Ryan Eales

on 24 September 2013

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Transcript of Engineers Australia Professional Interview

Application for Chartered Membership
Professional Interview
Friday 12th April 2013
9:30AM

By Ryan Eales
B.Eng Civil (Hons)
METHODOLOGY AND PRODUCTION RATES OF MSE WALLS AT YANDI
8) Conclusion
6) Lessons Learnt
7) The (Nearly) Finished Product
5) Budget Vs. Actual Cost
4) Production rates
3) Installation Methodology
2) Yandi Scope of Work
1) What is an MSE Wall and why do we need one?
OVERVIEW
WHAT IS AN MSE WALL?
AND WHY DO WE NEED ONE?

Reinforced Earth Wall
MSE Wall = Mechanically Stabilised Earth Wall.

DEFINITION:
A Reinforced Earth wall is designed based on the reinforcement of the earth through metal intrusions allowing the earth to stand vertical. Friction stresses develop between the reinforcing intrusions and the soil.

MSE Walls are also called REINFORCED EARTH WALLS and/or GRAVITY WALLS.
The MSE Wall acts as a dumping pad to enable trucks fully laden with unprocessed ore to tip the raw material into the mechanical crushing infrastructure to begin the refining process.

The design height of the MSE Wall was governed by the height of the mechanical crushing infrastructure in front of the wall (by others).
WHY DO WE NEED ONE AN MSE WALL?
WHAT IS AN MSE WALL?
YANDI SCOPE OF WORKS
YANDI SCOPE OF WORK
INSTALLATION METHODOLOGY
MSE Wall is designed to be approx 20m high, made up of 56 Panel lifts (56 x 0.35m = 19.6m).

Total Wall face of 1,880m².

Steel Panels are 350mm high.

Select Fill material is required over the
steel reinforcing straps.

Select Fill needs to be compacted to
above 95% Maximum Dry Density.

Hand compaction only within 1.5m of the
wall face.

General back fill is used behind the reinforced
earth block.
Specifics of the Wall
PANEL INSTALLATION CREW
1 x Supervisor
6 x Labourers

1 x IT Loader
1 x 18T Smooth Drum Roller

2 x Wacker Packers
2 x Jumping Jacks


BULK INSTALLATION CREW
1 Fleet of Dump Trucks
1 x D8 Dozer
1 x Grader
Crew Size and Project Resources
Construction of the MSE Wall is a repetitive process.

Each lift starts in the same fashion. Lets assume we are installing Lift #14.

The lift below the lift being installed (Lift #13 in this case) is fully compacted over the straps accept the infill from the wall.
STEP 1 - Beginning of Lift
To remove Working at Height issues, a handrail system utilising sacrificial scaff-tube was utilised.

The Vertical Handrail supports are raised by sliding Scaff-clips and horizontal bars up.

The panel for the lift above the one we are working on is installed.
STEP 2 - Raise Handrails and Connect Panels
Using an IT Loader with forks, bundles of straps are moved over and laid out as required.

Straps are bolted to the facing panels using hand held impact wrenches and laid flat on the ground.

A combination of Strap length is utilised. To ensure correct design strap length is installed the engineer inspects works prior to moving onto the next stage of installation.
STEP 3 - Install Straps
Using a D8 Dozer and a fleet of Moxies, select fill is carted in and dumped on top of the straps.

The dozer pushes the select fill out into a uniform layer thickness in order to obtain a 350mm thick compacted layer.
STEP 4 - Select Fill Over Straps
Using a Grader, the select fill surface is graded and a safety earth ramp is installed as per SWP-27.

The ramp will be 1 roller drum width wide and elevated to 200mm min.

This safety ramp is in place to prevent the roller from falling against the wall.
STEP 5 - Install Safety Ramp
The roller is then used to compact the edge of the safety ramp by rolling perpendicular to the wall face.

This compacts the edge surface to ensure the roller does not encounter any soft ground which may cause a fall against the wall while rolling parallel to the wall.
STEP 6 - Roll Edge of Ramp Section
The roller is then used to compact the remaining select fill material above the straps by rolling parallel to the wall.

The safety ramp section remains in place to ensure the roller stays away from the wall face.
STEP 7 - Roll Select Fill Material
Using a grader with the blade extended the ramp section is removes and pushed into the infill hole.

Where the ramp was is then compacted using hand compaction.
STEP 8 - Remove Ramp and Hand Compact
Using a Loader, select fill material is dropped into the infill hole.

Hand compaction is used within 1.5m of the wall.

This completes the installation of one lift of the wall.

Construction continues repeating these same steps.
STEP 9 - Fill the Infill Hole and Compact
RENO MATTRESS

Installed up the batter adjacent to the MSE Wall.
Excavator pulls the batter, Bidim laid out, Baskets pegged in place and filled with rock.
HDPE LINER

Liner is installed at the top of the wall to prevent water seeping through and compromising the reinforced soil block.

Excavator is required to cut back the shape of the liner. Crews then cut the liner to shape and roll it out on the ground between back fill lifts. No HDPE Welding is used, just a 0.5m overlap.
VERTICAL DRAIN

Runs up behind the Reinforced Earth block to prevent water compromising the block. Excavated every 3-5 lifts, lined with Bidim, filled with Aggregate and filled over. Slotted pipe is installed at the bottom of the drain for free drainage.
Other Aspects of the MSE Wall
PRODUCTION RATES
RECO recommends the following construction rates;
30m² per day for small structures with difficult areas.
80m² per day for large structures.

At tender, Thiess estimated the following;

50 m² per day.

What we achieved;

Start Date = Friday 6th November 2009.
Finish Date = Sunday 21st March 2010.
TOTAL = 110 Days.
MSE Wall Construction
Having worked with these walls, seen where we went wrong, how we could do things differently, and where we lost time…

For future tenders I would recommend a wall of this size should take 12 weeks (78 Days).

~ 25m² per Day
Lost Time Activities:

Interface LOR is estimated to have cost 8 Days.
Roller incident cost 5 Days.
Strap Displacement incident cost 3 Days.
Traffic Site closure cost 3 Days.
Miscellaneous Hazard Cards cost 3 Days.
TOTAL =
22 Days
What Slowed us Down?
This works out at 17.16m² per day
BUDGET Vs ACTUAL COSTS
The following Cost-Codes were set up to track costs during MSE Wall installation;
Percentage of
Total Budget

73600 MSE Wall Supply 59%
73650 MSE Wall Installation 25%
73670 MSE Wall Select Backfill 16%

TOTAL 100%
Cost Codes
MSE Wall Supply was awarded to a sub consultant on a Schedule of Rates contract.

The Supply Contract was awarded for 90.7% of the Supply Budget allowed at Tender.

The Budget for these works constituted 59% of the total wall construction budget, however only 53.2% of the budget was utilised.

Hence, a 5.8% profit was made against the total MSE Wall Construction Budget.
COST CODE 73600 - MSE Wall Supply
MSE Wall Installation was carried out by the Thiess labour force.

Costs incurred were directly proportional to crew size and installation duration.

The Wall production rate ($/m2) is plotted below.
COST CODE 73650 - MSE Wall Installation
The MSE Wall Installation was completed for 86.7% of the Budget.

The Budget for these works constituted 25% of the total wall construction budget, however only 21.7% of the budget was utilised.

Hence, a 3.3% profit was made against the total MSE Wall Construction Budget.
COST CODE 73650 - MSE Wall Installation
MSE Wall Select backfill was carried out by the Thiess labour force.

Costs incurred were directly proportional to crew size and installation duration.

The Wall production rate ($/ccm) is plotted below.
COST CODE 73670 - MSE Wall Select Backfill
The MSE Wall Installation was completed for 224% of the Budget.

The Budget for these works constituted 16% of the total wall construction budget, however 36.0% of the budget was utilised.

Hence, a 20% loss was made against the total MSE Wall Construction Budget.
COST COST CODE 73670 - MSE Wall Select Backfill
SUMMARY
LESSONS LEARNT

REALISTIC PRODUCTION RATES AT TENDER

Put simply… the wasn’t enough time allowed for to install this wall, hence there was never enough dollars in the budget.
Production Rates

Consistent Manning Levels

We struggled to keep the required manning levels on each wall. Instead of a dedicated crew for each wall we have a hybrid 1 and a half crew that floated between both walls.

1 Wall required: -

1 x Supervisor (not necessarily full time)
6 x Labourers
1 x IT and Operator
1 x 18 T Smooth Drum Roller
2 x Wacker Packers
2 x Jumping Jacks
Manning Levels

Alternate Products

The RECO Terramet system is very time consuming and labour intensive
Laying and bolting of straps is incredibly tedious.

Atlantic Civil offer a Wire Wall.
Instead of reinforcing straps it has reinforcing mesh
Front of the wall is filled with rip-rap rock, or concrete facing panels
Alternate Products
THE (NEARLY) FINISHED PRODUCT
MSE Wall Before and After
This presentation has covered off on;

1) What is an MSE Wall, and why did we
need one at Yandi?


2) Yandi Scope of Works.


3) Installation Methodology.


4) Production Rate.


5) Budget Vs Actual Costs.


6) Lessons Learnt.


7) The Finished Product.
Conclusion
Aerial View
Yandi MSE Wall
At BHP Yandi, ore is excavated from the pit, trucked to the processing facility, crushed, conveyed, stockpiled and then loaded onto trains for transport to Port Hedland where it is loaded onto boats and exported. All processing of the ore is done at the mine site.

The MSE Wall is required at the front end of the processing cycle.
Crew size and resources required was originally determined based on allowance made in estimate, this was later revised based on input from our specialised supervisor.
Full transcript