Client: Empresa Urra S.A. E.S.P Colombia, S.A.

Location: Urra Dam, Colombia, South America

Combined was asked to overcome a range of logistical and engineering challenges to successfully complete the structural modification of a remote hydro-electric dam in Colombia, South America.

The project – to raise the full supply level of the Urra Dam in the state of Cordoba – required removal of a 5.2m high section of the existing spillway and structural modifications to the crest to accommodate new fuse gates.

This contract was the first work of its kind by an Australian company in South America and worth an estimated 5% of Australia’s annual export trade with Colombia.

KEY CHALLENGES

Design engineers were concerned that conventional demolition would cause micro-cracking across the remaining structure and damage sensitive monitoring equipment.

For this reason Combined technical experts recommended using concrete bursters and wire-sawing to complete the unusually deep cuts with a high degree of accuracy.

Access to the work area was difficult and working platforms had to be designed and constructed on both the upstream and downstream faces of the dam.

A 120 tonne crane was erected on the abutments to maintain vehicle access to the bridge spanning the dam spillway.

Numerous comprehensive studies had to be undertaken to determine the complex rigging required for removing concrete blocks from under the deck.

PROJECT SUCCESSES

Despite encountering significantly more steel reinforcement than shown on the as built drawings, the work was successfully completed with the client expressing surprise and satisfaction at the accuracy of finished surfaces.

With the successful completion of projects like Urra Dam, Combined has confirmed its reputation as a world leader in large scale structural modifications.

Client: BHP Billiton & Monadelphous Group

Location: Port Hedland iron ore car dumper

Due to the increase in demand for iron ore, the rail car dumper at the BHP Billiton Port Hedland Iron Ore Loading Wharf required upgrading.

Each carriage has a capacity of about 100 tonnes of ore.

KEY CHALLENGES

Steel I-beams encased 400mm deep in concrete had to be left in place while the structure was strengthed, and then cut by wire saw for removal at 25 separate locations.

The cut concrete surface had to be coated with a moisture inhibiter and the newly exposed reinforcing steel had to be cut back 50mm and painted with an anti-rusting agent before filling over the hole.

Work was carried out in extreme conditions during the summer months where the outside temperature regularly reached 45°C, making it considerably hotter inside the dumper. This necessitated the cutting of over 50 openings for ventilation in floors that were up to 3m thick.

Two 12 man shifts, which included supervisors and mechanics, operated day and night with monitoring fluid intake a critical part of the working day.

The project required significant plant resources to be deployed including:

“Blind” recesses had to be formed in sloping walls to accommodate the stabilizers for the new dumper, requiring the bottom to be formed first to enable the back and sides to be cut.

As the removed concrete had to be transported by road, most of the concrete was cut into 20 tonne pieces.

PROJECT SUCCESSES

In total about 500 square metres of wire sawing was completed with over 700m of drilling for wire and lifting holes.

As part of the upgrade over, 700 tonnes of concrete was successfully cut and removed from the dumper.

Client: Hinze Dam Alliance

Location: Hinze Dam, Gold Coast Hinterland Queensland

With a rapidly growing population and widespread drought, the pressure on water supply continues to increase.

The Hinze Dam Stage 3 project was designed to increase water storage capacity and delay the release of floodwaters down stream thereby decreasing the number of properties vulnerable to flooding.

The existing stage 2 spillway bridge consisted of 4 spans totalling 85m in length, with each span made up of 15 pre-stressed beams totalling 9m width. The largest of these spans contained beams weighing 32 tonnes each.

The bridge is situated over the Hinze Dam Spillway and serves as the local traffic access across the dam.

KEY CHALLENGES

Raising the spillway and embankment required the existing bridge to be removed to make way for construction of the new spillway and bridge.

3 – STAGE SOLUTION

PROJECT SUCCESSES

Combined successfully employed precision cutting and hydraulic jacking techniques to complete the necessary de-construction work safely and efficiently.

Client: Baulderstone Hornibrook & Bilfinger Berger

Location: Sydney NSW

As part of the Cross City Tunnel project, which links the Eastern and Western suburbs of Sydney, the feeder road from Sir John Young Crescent to the Cahill Expressway and Sydney Harbour Tunnel required widening.

This involved extensive modification to the abutment of the Art Gallery Road bridge.

The project was carried out in 3 stages:

KEY CHALLENGES

As the work was being carried out within 1m of the road, the carriageway had to be closed and that was only possible between 10.00pm and 5.00am.

The abutment consisted of five columns each 5.3m high by 600mm thick and between 1.4m and 1.2m wide.

Between each column was a 200mm thick curtain wall.

The weight of each column was about 10.3 tonnes with the weight of each section of curtain wall about 5.3 tonnes, making a total weight of almost 73 tonnes of concrete to be removed.

PROJECT METHODOLOGY

The first stage involved core drilling and wire sawing to cut and remove the columns in 1 tonne sections.

Each column was divided into four pieces, the top pieces weighing just less than 1 tonne, and the bottom piece around 3 tonnes.

The second stage involved core drilling and pre-cutting to allow lifting chains to be put in place prior to making the final cut to free the 2 tonne section of wall for removal.

PROJECT SUCCESSES

The work was safely and effectively carried out within 1m of the carriageway, within the allocated time and without any damage to the public environment.

Client: NSW RailCorp

Location: The Argyle Cut, Sydney NSW

The NSW Rail Corporation required an emergency exit door installed in the concrete tunnel wall of the Shore Down Line, close to the Argyle Portal, which forms part of freeway approach to the Sydney Harbour Bridge.

The tunnel wall is 1.2m thick and the opening needed to be 1.5m wide by 2.2m high.

KEY CHALLENGES

The floor of the tunnel was found to be 670mm lower than the outside ground level, so the top and bottom cuts had to cut on an angle of 28° from horizontal.

A further complication was that the concrete had to be cut and lifted out and the opening made safe in a 40 hour closure from 6am Saturday to 10.00pm Sunday.

As the project was taking place in Observatory Park in central Sydney, the working area had to be fenced o and fail-safe slurry control measures implemented.

Various signal and communication cable ducts were within 100mm of the planned top of the opening.

All personnel had to be RailCorp Track Awareness inducted, and stringent Occupational Health and Safety precautions observed.

PROJECT METHODOLOGY

150mm diameter lifting holes were drilled and used to check the construction drawings and to verify the height difference of 670mm;

Four 150mm diameter corner holes were drilled on the 28° angle, and two 50mm diameter intermediate holes were drilled horizontally;

Two side cuts were made, followed by the sloping bottom cut, the horizontal middle cut and the sloping top cuts using a wire saw;

A 20 tonne crane was used to remove the two pieces of concrete weighing just under 10 tonnes in total.

PROJECT SUCCESSES

With the cutting finished and concrete removed we cut and formed stairs and fitted a door before leaving the site clean and secure well before the Sunday deadline!

Client: Thiess Hotchieff

Location: Chatswood to Epping, Sydney NSW

For the construction of the Chatswood to Epping rail tunnel, Theiss’ design plans required the rail lines to be fixed to a concrete track slab by the use of Delkor rail base plates.

There was 5.5km of floating slabs and 3.1km of DFF drill and grout slabs existing in the tunnel, requiring 96,000 50mm diameter holes to be drilled.

To get the job done in time and to the accuracy specified, Combined designed a fully-automated, multi-head drill rig capable of drilling 16 holes at a time. It was operated by two men and required only 1 x 32amp lead and one waterhose.