Contractors working on the Crossrail project have been fined more than £1 million over the death of a worker and two other incidents.
A joint venture of three companies, Bam, Ferrovial and Kier (BFK), pleaded guilty to three offences following an investigation by the Health and Safety Executive (HSE).
Southwark Crown Court heard that Rene Tkacik died after being crushed by falling wet concrete in March 2014.
Two other men were injured in separate incidents within six days of one another in January 2015.
All three incidents took place in the tunnels around the Fisher Street area of central London.
Mr Tkacik, 43, from Slovakia, was working to enlarge the tunnel by removing rings of the existing pilot tunnel and spraying walls with liquid concrete, when a section of the roof collapsed, fatally crushing him.
On 16 January 2015 Terence 'Ian' Hughes was collecting some equipment from inside one of the tunnels when he was struck by a reversing excavator, suffering severe fractures to his right leg and injuring his left knee and shin.
Six days later Alex Vizitiu, who was part of a team spraying liquid concrete lining, was helping with the cleaning of the pipes that supply the concrete, when one of the lines was disconnected and he was hit by pressurised water and concrete debris.
He suffered head and hip injuries as well as a broken finger and was in hospital for six days.
HSE said its investigation found a failure to provide a safe system of work relating to the operations Mr Tkacik and Mr Vizitiu were working on and also found there was a failure to properly maintain the excavator which reversed into Mr Hughes.
On all three occasions, the investigation found a failure to properly enforce exclusion zones that would have helped protect workers from foreseeable harm.
BFK pleaded guilty to three offences. In relation to the death of Mr Tkacik, it admitted breaching Regulation 10(2) of the Work at Height Regulations 2005 and was fined £300,000.
It also pleaded guilty to two separate breaches of Section 22 (1a) of the Construction (Design and Management) Regulations 2007, relating to the two incidents in January 2015.
The joint venture was fined £600,000 for the incident involving Mr Hughes on 16 January, and £165,000 for the incident relating to Mr Vizitiu on 22 January.
The total fine is £1,065,000, and the consortium was also ordered to pay costs of £42,337.28.
HSE head of operations Annette Hall said: "The omission to implement exclusion zones in a high hazard environment was a consistent failure in this case.
"Had simple measures such as these been taken, all three incidents could have been prevented, and Rene Tkacik may not have died.
"We believe every person should be healthy and safe at work. Here, all three workers were taking part in one of the most important and challenging infrastructure projects of the decade.
"It was this joint venture's duty to protect its dedicated and highly-skilled workforce. On these three occasions, BFK failed in its duty, with tragic consequences for Rene Tkacik and his family."
The new Crossrail railway line, which runs from Reading in Berkshire through central London, will open in December 2018.
Unite union national officer Jerry Swain, said: "This is firstly a human tragedy where a husband went to work and didn't return home again. The tragedy is even greater as we know his death was wholly avoidable.
"There are clear and straightforward ways of creating a safe way of working when applying concrete to the roof of a tunnel, which would have ensured that no-one could have inadvertently entered the danger area.
"Following the tragedy, the companies responsible should have swiftly accepted their guilt rather than prolong the torment faced by the victim's family.
"The industry needs to learn the lessons from this tragedy, especially on major infrastructure projects. These projects often include potentially dangerous work but if proper procedures are put in place and workers are fully engaged in safe ways of working, deaths and injuries can be avoided."