Training the key to reducing in-tunnel incidents 12 Oct 2017

TBMs today are capable of excavating in a startling array of conditions. They are driven by state-of-the-art computers and can be equipped with monitors and data acquisition programs to track nearly every tunneling parameter.

As a result, tunneling today is certainly much safer and more precise than in decades past, and it is getting more efficient all the time. But there is room for improvement.

We would venture a guess that a large percentage of incidents in tunnel excavation projects that result in significant project downtime - whether that means a stuck TBM, a sinkhole, or other occurrences - are rarely due to the TBM or equipment operations at all. Human error has been, and continues to be, the greatest source of in-tunnel incidents in our industry.

In-depth theoretical and simulation classroom programs

This is an issue for everyone, including equipment manufacturers, whose equipment is often blamed or framed in a bad light as the investigation of an incidence ensues. Of course, local media reports on sinkholes, project delays, and cost overruns are a benefit to no one, and give tunneling in general a bad reputation. Luckily, human error is an issue that can be remedied fairly easily if we band together as an industry to change regulations.

So how can we reduce human error? The answer is through training.

While there are many highly qualified engineers in our industry, those actually driving the machine often lack basic training in the optimal operating parameters for given conditions and for equipment maintenance and more.

Even when these operators are experienced (and there are many well qualified, experienced operators in our industry), these qualifications have been gained through trial-and-error and on-the-job training on multiple projects. While on-the-job training is invaluable, it is not the best way to gain an elementary understanding of how to operate a TBM as conditions change. In such conditions mistakes can prove very costly and time consuming.

Certified EPBM training at the Colorado School of Mines

With TBM training in mind, ITAtech, the committee of the International Tunneling and Underground Space Association (ITA-AITES) to promote new technologies for development of underground space through the publication of guidelines that deal with aspects such as terminology, methodology, design, and construction techniques, is part of a huge push for TBM operator training. Made up of manufacturers and suppliers that support the ITA, the ITAtech committee has set their sights on training through simulator technology.

Working in collaboration with the Colorado School of Mines (CSM), Robbins is taking a leading role on a curriculum for training EPBM operators. EPBMs are selected for the initial programme of training as they are the most commonly used type of TBM in the world and are also often used in urban settings below roadways, buildings and existing tunnels and utilities, making settlement control of the utmost importance.

Training up operators

The Certified EPB Operator Training Program currently consists of classroom training combined with a TBM control simulator operated via PC. The program could also be linked with an actual TBM operator’s cab in the future. There are an endless number of scenarios that can be created on the simulator program for EPB operator training. These can depend on any particular project on which a machine is deployed in known ground conditions.

EPB simulator training based on five geological scenarios

PC simulator program could be used on the jobsite or on a command chair

At the moment five case study conditions and scenarios have been developed. These scenarios focus on EPB operation during excavation and while standing still, for example during segmental lining ring build, although ring build itself is not part of the simulation. For each of the five scenarios, the geological parameters and tunnel depth can be modified and are based on operating the TBM through sand; through clay; through transitional geology; through mixed face conditions; and through homogeneous conditions.

The simulation program is developed to be used in conjunction with a schedule of theoretical training, which is being developed at several universities and by ITA-CET, the ITA-AITES Committee on Education and Training.

While another simulator has been developed by the construction company Bouygues in France, its six-week training program is available to its employees only. The CSM program would be one to two weeks long ideally, and will be open to students and those who want to purchase the program. There are also plans to extend the simulations to hard rock and slurry type TBMs.

Ergonomics of the commander’s chair

Operating the TBM is not the only issue. Working hours on TBMs are often long and carried out in hot, humid environments. While operators now control machines from sound proofed, air-conditioned control cabins, one of the biggest complaints from TBM operators is the comfort of the chair itself.

Operator stations are also becoming so big, they are often placed on the boring machine back-up with little or no thought being given to what the operator sees visually. They rely on CCTV systems when in some cases it would be better for the operator to have a first-hand view of the situation. We could argue that, as per a ship or other large piece of machinery, the operator should be in a location that gives him or her an overview of some of the more critical functions and operations of the boring machine.

New commander chair with modular touch screens and designed for the ‘bridge’

Should the operator, for example, be able to see the material on the conveyor belt or be able to see the ring build area, particularly the top 120 degrees of the head? In effect, the operator should be located on the ‘bridge’ of the boring machine for the best view.

With this in mind, and with consideration to providing training to operators on the controls, a more compactly designed operator station or command chair needs to be developed. The chair would need to be removable from the cab to allow on- or off-site training and would need to be a self-contained unit with all machine control systems included within the design of the chair.

Taking all the above into consideration, designers, with input from manufacturers of other industry command chairs, and actually operators of machines in the field, came up with an innovative design based on the chair of the ship’s helmsman.

Two panels on either side of the operator have been designed with modular and interchangeable control panels. Each modular panel is specific to the type of machine and is designed to be instinctive for the operator to start and control the machine. Functions on the control panels have been reduced to the absolute minimum with all other functions - to control, monitor or stop and start systems - being transferred to two touchscreen panels also incorporated in the command chair.

The command chair concept is currently being developed for use on several Robbins machines and the company is looking forward to testing it in the field.

New commander chair with modular touch screens and designed for the ‘bridge’

In addition, there are several ways the command chair and simulator technology could become useful in the future. With the ever-improving connectivity of machines via high-speed internet, there may in some circumstances be a valid case for remote operation of boring machines. While this has been done in the past, particularly for slurry machines, most control cabins due to their size and cost have not been replicated outside a tunnel. Command chairs do not require operator cabins and can be easily installed in an office environment. Having the ability to operate a machine utilizing identical controls as those on the machine rather than from a keyboard can only give boring machine operators more confidence.

With the incorporation of highly sophisticated data acquisition systems, it is only a matter of time before a real-time database of every project and of all the ground conditions encountered can be stored on the simulator to give operators first hand experience of actual conditions that any particular machine can encounter.

Ergonomics of the commander’s chair

The net effect of all these developments – from theoretical training to simulator training and location of command chairs in the best area for visualization - is to set up the operator for a successful bore.

But there is yet more to the process than that.

It is our overall recommendation that training becomes mandatory for all TBM operators. Until training is seen as a risk management tool, and calculated in potential cost savings, perhaps we will not see it written into contracts as a requirement. But it should be written into contracts. It is an effective way to reduce risk. Only with well-trained crews can we reduce the most common risk in tunneling: that of human error.