A 245-meter section of a new motorway tunnel in Sydney, which is plagued by dolines, and a “challenging” geological feature will bring a transport project of USD 3.1 billion to standstill, unless a contract for 11 hours is achieved.
The new Twin 4 -km tunnel of the M6 with the south of Sydney with the wider motorway network were approved in 2019 and are to be opened in 2025.
This date was pushed back to 2028 after two large dolines over the tunnel and under an industrial area in Rockdale opened in March 2024.
But even this extended timeline is now doubted that the consortium has announced with the construction of the tunnels between Kogarah and Arncliffe that from June 30th after the discovery of a “high -angle debt” in the basic rock near the thinker, it would go back after the discovery of “high -angle debt”.
David Jackson, the director of the first stage of the M6 project -was a joint venture from CPB, Ghella and UGL, collective as CGU -said in an e -mail to employees, which was published in May by The Sydney Morning Herald.
Jackson said the design and construct contract had become “frustrated” and “ended by the operation of the law”.
He wrote that the tunnel “Excavation … for almost a year in the queue in the queue in the queue in the queue on the queue on the loop of unique negative ground conditions in the queue in the queue in the queue in the queue in the queue in the queue in the queue in the queue, which is put on hold by a complex False zone were caused, including a reverse reverse (never before in the pool in Sydney) ”.
“The presence of such soil conditions could not be expected by anyone,” he said, adding that they were only discovered after the tunnel excavation was carried out.
“It is now obvious that a compliant design solution cannot be achieved in order to overcome these challenging soil conditions.”
NSW government remains “optimistic”
The government was drawn to the intention of the CGU to go away before the e -mail was sent to the staff, a spokesman for Transport for NSW (TFNSW) said Guardian Australia.
The project is otherwise 90% completed. CGU's above -ground work in Kogarah can continue and can be completed by the end of the year.
The New South Wales Premier Chris Minns criticized the one -sided step and claims that the contractor is still responsible for the design and construction of the tunnels.
“My best advice for the contractor today is to send the lawyers home and bring the engineers back,” he said in May. “I will not allow NSW taxpayers to transfer a barrel for these large projects.”
A TFNSW spokesman said the department was still “optimistic” about an agreement with CGU.
They previously said that the government had worked with the contractor to “determine a technical solution for the problems that occurred on the project” and claimed that the consortium had not demonstrated that it had exhausted all the technical options to advance the work.
“It is unhappy that CGU has now found that it is in its commercial interest to take off tools instead. We consider the position of transport in terms of the contract in view of the one -sided steps of CGU,” said TFNSW.
As part of the tender procedure for the main project, potential contractors received geotechnical reports about the soil in which the work would be carried out, said TFNSW. Guardian Australia could not provide Guardian Australia from every phase of the project of the geotechnical reports.
CPB as a senior contractor for CGU says that it cannot comment on.
“Of course it can be ready”
Grahame Campbell, an engineer whose project managed the M4, which was completed in half of the forecast period and the budget, has written a paper for the Center for Independent Studies on “Bungles”, which leads to costs and time outbreak for important infrastructure projects in Australia.
However, he is confident that the M6 will be completed at some point, but it is of the opinion that it is a budget – like other major projects, including Sydney's Metro and Light Rail Builds and Melbourne's North East Link.
“Of course it can be ready and it's about doing it right and doing the right team,” he says.
According to Campbell, blowouts were not always so common. They can be caused by various factors, including contractors who start building before ending designs, changes to designs, governments that transfer the risks to risks for contractors, and lack of specialist knowledge within the government or at the level of contractors.
“An contractor is pretty good at throwing concrete into the ground,” he says.
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“But they are [sometimes] Not particularly good in project management. Keep open and understand the widest problems and deal with them. Unfortunately, these concepts in the government are not very big … at the moment and they come to this disorder.
“You would think that after you have lost billions of dollars over decades, [governments] Had learned in the meantime – but unfortunately it doesn't seem as if they have it. “
The establishment and decommissioning of workplaces is expensive, but it is not uncommon for building contractors to change in the middle of the builds, says Campbell. Stakeholders should learn from previous major projects, he argues.
“Thousands of projects were built in the Sydney basin. You can go back and see how they were managed.”
Soil or geological anomalies should ideally be discovered before work begins. Water management that can lead to dolines is “always the biggest problem in large -scale projects,” says Campbell.
Survey techniques are not bulletproof
Prof Prof
“Reverse errors”, in which a layer of rock is pressed up and over a different layer, are less common and difficult to see, since the angle of errors is often very steep. Drill holes that are drilled into the ground five to 10 meters apart can miss the opposite fault, says the professor.
According to Fatahi, survey techniques, including seismic surveys, are not “bulletproof … there is always the possibility to lack things.
The risk of building a tunnel at the location of a rock error is based on potential movement in the fault zone. While Sydney is not a very seismic area, even a small amount of rock movements could affect a tunnel, he says.
A new way to protect underground pipelines from land movements includes the damping of pipes with foam, its research has shown. The solutions for preventing dolines include joint, tunnel food and freezing the soil before excavations.
All Civil Geotech Designs have some strangers, he says. “There is no risk of zero … but that doesn't mean that there will be big surprises.”
The two dolines that opened above the M6 tunnel were not a normal risk associated with the ditch, says Dr. Francois Guillard.
The high -ranking lecturer at the School of Civil Engineering at the University of Sydney says that dolines can occur wherever water penetrates into the ground, although karb regions – often consist of soluble limestone – are usually more susceptible to dolines.
In view of its mainly sandstone geology, Sydney is not particularly susceptible to the phenomenon, says Guillard.
In order for a sinkhole to develop, material must be removed under the surface of the soil, usually through water erosion or chemical decomposition. In urban areas, the disturbance of the usual water drainage patterns can lead to sinkhole formation below the asphalt surface.
It agrees that studies of soil and geology from the surface are “not perfect”.
According to Guillard, dolins made by people, which are triggered by engineering or construction work, are “rare” like urban dolines in general. “I would not recommend worrying, it's a little risk,” he says.