Author: Lok Home

Notice of Retraction and Apology

To all Visitors of our Site:  I declare that our website contained information that was inaccurate, and in retrospect, was offensive and disrespectful to our longtime Customer and highly qualified construction Client, Obayashi Corporation of Japan, along with their Joint Venture (JV) Partners, Taisei Corporation and Kosei Corporation.  The referenced Project Site name is Hiroshima Expressway 5 Shield Tunnel Project and the Robbins Technical Article titled https://www.robbinstbm.com/grout-or-not/, which states as if the JV selected the wrong type of TBM for the Hiroshima Project.

We retract the statements made in our article such as, “Contractors who are used to tunneling in soft ground may not realize that when using a Slurry TBM in rock, inspections must be frequent due to increased cutter consumption.  We have seen this borne out on recent projects such as the Hiroshima Expressway Line 5 in Japan” because these statements were not based on facts and were incorrect. This statement reads as if the contractor did not review other optional TBM types, when in fact, the JV did indeed study all TBM types and methods to excavate this Express Tunnel.

There were additional incorrect statements made in the Article as follows:

• The same paragraph of the Article continues,”…, and they (contractor) were expecting up to 13 bar water pressure. This high pressure water zone was only in a small section of the overall tunnel length, about 5 percent.“
• The Article further states, “The contractor in Hiroshima had grouted off from the surface a planned safe zone in which to inspect the cutterhead without requiring a hyperbaric intervention, but this strategy did not go according to plan. The abrasive rock damaged the cutters and cutterhead before they could reach the safe zone, resulting in unplanned delays“.
• The same paragraph of the Article continues, “…grout off from the surface a planned safe zone…“.

The reason for choosing a Slurry type TBM was not solely based on the high water pressure but was also a result of the JV’s extensive review of all aspects of the tunnel requirements.

There was no plan to grout a “safe zone/safe haven” from the surface as other plans for cutter changes were in place and such plans have proven to be effective over numerous cutter change events.

Robbins commits to have more peer review and where a Client is involved, to have the Client review prior to presenting such data on our website.

 

 

 

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Let’s Be Clear: Transparency is a Boon, not a Bust, for the Tunneling Industry

The idea of transparency is one that we most often hear touted in politics and policies.  But transparency is a concept that applies to our underground industry as well.  Widespread knowledge sharing can and should be the policy in our industry, but all too often jobsite politics, confidentiality agreements, and fear of poor public opinion limit what is ultimately divulged.  I argue that transparency in tunneling is a help, not a hindrance, and we can make steps today towards clearer communication.

Why It’s Needed

• Learn from Experiences in the Field: Tunneling professionals deserve full access to the successes and the problems that have been encountered in the field. If we were to employ universal knowledge sharing, tunneling operations themselves could become safer and more efficient and overall project costs could be reduced.
• Improve Tunneling Technology: Knowledge of advance rates, performance in specific ground conditions, wear rates for cutters and other surfaces in contact with the cutting face, performance of ground conditioners and foams, and many other types of info are imperative to improving technology. Tunnel boring could be made faster, safer, and more cost effective with such knowledge.  It could also improve willingness to try new and emerging technologies in the industry, which benefits all stakeholders.  With a good knowledge of TBM performances in specific ground conditions, TBM specifications could also be written to greater accuracy and result in using the most cost effective solutions.
• Improve Risk Sharing: Risk is often apportioned unfairly on today’s tunneling projects. In many cases the TBM supplier is required to shoulder a larger part of that burden than their potential returns. With a better understanding of the risks through knowledge of past projects, as well as knowledge of past risk sharing strategies, this problem can be resolved.
• Ensure Fair Financial Practices: With transparency in terms of contractual pricing and project spending, payments for work performed, etc. and other unsavory practices can be lessened.
• Reduce Litigiousness: Claims in tunneling projects are on the rise worldwide. Recent projects have resulted in separate and duplicate claims against different parties, such as the equipment manufacturer and the owner, for the same issues and without their mutual knowledge. Such claims are unfair, and through transparency and equal access by all parties to a Dispute Review Board, the frequency and extent of lawsuits in our industry could be reduced.

From the Equipment Supplier Perspective

As equipment suppliers, we strive to share the information that is available to us.  We’ve opened up about stuck TBMs, challenging drives, and how we’ve overcome those issues.  We’ve also tried to share whenever possible why we think fast advance rates and good efficiency were achieved on various projects.

Unfortunately knowledge is sometimes not shared even within parties on the same project, such as the contractor, project owner, owner’s representative, and equipment supplier.  Time and again we see that communication between all parties is key to overcoming challenging conditions. The road to transparency starts here: with clear communication between all coordinating parties on a given project.

Not Without Precedent

Transparency is not an untested idea in our industry.  A great recent example is that of the U.K.’s Crossrail project.  The project follows governmental codes of practice for data transparency and the country’s Freedom of Information Act.  Details such as project and equipment costs, spending budgets and records, safety records, and more are available for download on their website, and special requests can be made for additional data. Multiple reports have also been up front about TBM performance, advance rates, and other experiences on the project. The Crossrail project was highly successful and, arguably, transparency played a large part in that. Crossrail is also just one example of transparency at work in the U.K.—governmental programs such as Transport for London’s Transparency Strategy aim to give clear and consistent information to the public about all road and public transit spending.

A Call for Clarity

Transparency is possible in the tunneling industry, but it may require things like international regulations, or at the very least certifications that could be provided by an international organization like the ITA.  Such a certificate would be highly beneficial to all stakeholders: It could certify corruption-free practices, and guarantee knowledge sharing.  Transparency is not an easy thing to achieve, and there are certainly barriers to the process in various areas of the world. But we can start with transparency requirements within projects, and then move outward.  To be clear: knowledge sharing is something that can only benefit our industry. It is our recommendation we start today.

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Are You in Tough Ground? Learn from our Trials and Tribulations in some of the Tunneling World’s Most Difficult Projects

Squeezing Ground, Fault Zones, Water Inflows, and More

True story: In a mountain range, crews worked on a shielded TBM more than 500 m below the surface. The TBM had excavated several kilometers in worsening conditions.  The crew encountered karstic aquifers filled with mud and water.  Personnel were pumping polyurethane through the cutting face to staunch the water inflows.

Suddenly, water inrushes climbed to a rate of 1,500 liters/second, creating a knee-deep underground river and causing the machine to become stuck. Thankfully, the crew was able to exit the tunnel, unharmed. The massive inrush created a damming effect with enough pressure to crush the TBM shields and send cylinders catapulting into the back-up.

As quickly as it had started, the machine ground to a halt, deep underground.

What happens when you encounter an unforeseen condition? A severe water inflow, fault zone, or squeezing ground? A geological feature that seems like it might stall your tunneling operation altogether? Some of our most difficult challenges—spanning from New York to Peru to the Republic of Georgia—are detailed below.  These case studies are meant to pass on our knowledge and experiences to help you overcome obstacles, unforeseen or otherwise.

How to Overcome an Epic Flood: New York’s Harbor Siphons project

Sometimes an unforeseen condition requires a rescue effort to overcome. In October 2012, a storm was coming to New York City’s Harbor Siphons Project on the shores of Staten Island. The undersea tunnel and its 3.6 m CAT EPB ground to a halt when hit by Superstorm Sandy.  The monstrous hurricane battered the eastern seaboard of the U.S. with winds of 145 kph.

The launch shaft was inundated with seawater despite contractor Tully/OHL’s best efforts.  Flood water entered the tunnel and stopped the TBM just 460 m into its 2.9 km long drive. A 2013 post-storm survey of the tunnel showed a damaged machine extensively corroded by saltwater. All electrical components needed to be replaced.

Contractor OHL turned to Robbins for help. During the downtime, the original TBM manufacturer had exited the tunneling industry. Robbins worked with the contractor to come up with a multi-pronged approach to bring the TBM back to life.

Hiring a Dedicated Team

Per the scope of work, defined jointly by OHL and Robbins, crews temporarily excluded the cutterhead and main bearing of the TBM for refurbishment, as they were under earth pressure and not accessible. The Robbins team would need to complete the refurbishment taking into account unknowns, such as the condition of the cutterhead. The segmented concrete tunnel lining would not permit the removal of many of the larger TBM components, so these would have to be refurbished onsite.

The Robbins crew was contracted to guide onsite personnel in replacing corroded hydraulic components and installing all new electrical components. Variable Frequency Drives, PLCs, and wiring were replaced inside the small tunnel under atmospheric pressure of 3 bar. Crews constantly monitored earth pressure during the refurbishment. The machine had been stopped with its thrust cylinders in, and thus the crew could not replace or evaluate certain components before the machine started up.

Reverse-Engineering Electrical Components

By mid-December 2013, Robbins PLC technicians were reverse engineering the TBM’s control system. The team understood early on that the previous control programming would be unusable given the PLC change. The technicians had only limited assembly drawings from the CAT manual, so much of the refurbishment, including the PLC system, had to be built from the ground up. The team at site understood how the machine should work and therefore were able to build the correct PLC system.

Coordinating Success

Despite all of the challenges, the refurbishment project was a success. Crews had gone from a shipwrecked TBM—rusted, corroded, and abandoned in the tunnel—to a successful tunneling operation. It was a monumental task, scheduled to be completed in four months, and finished on schedule.

In the final phase of the refurbishment, a Robbins PLC technician was able to complete the commissioning of the TBM and on April 14, 2014 the machine officially returned to mining. The machine successfully completed its tunnel in February 2015.

Read more in the white paper here.

Make Rock Bursting Conditions Safe for Your Crew: The Olmos Trans-Andean Tunnel

If 16,000 recorded rock bursting events in the world’s second deepest tunnel weren’t enough, the crew at Peru’s Olmos Trans-Andean Tunnel had another problem. As the machine progressed and the cover grew higher—up to 2,000 m at the highest point—the rock bursts became more violent. Crews experienced large over-breaks and cathedralling in fractured and unstable ground. Teams of personnel had to inject concrete into large cavities that had formed during stress-relieving activities and stabilize these cavities with spiling.  Then, several kilometers into the tunnel, a major rock bursting event occurred that twisted ring beams and caused damage in 45 m of lined tunnel. Damage was extensive to the TBM gripper, which was ballooned and blown off its mountings. Damage also occurred to other hydraulic cylinders.  Thankfully crew members were not harmed, but downtime for repairs would be substantial.

A Century-Long Effort

The Olmos tunnel is a 12.5 km long water transfer tunnel that was bored through the Andes Mountains to bring irrigation to drought-ridden areas on the pacific coast. The project was more than 100 years in the making, with several attempts being made and thwarted by incredibly difficult geology as recently as the 1950s.

In 2007, with Odebrecht as the main contractor, the tunnel was finally completed using a 5.3 m diameter Robbins Main Beam TBM after other attempts with conventional methods failed. The route is the world’s second deepest civil works tunnel with overburden of up to 2,000 m.  The tunnel alignment traverses complex geology consisting of quartz porphyry, andesite, and tuff with rock strengths ranging from 60 to 225 MPa UCS. The machine crossed over 400 fault lines including two major faults of approximately 50 m wide.

A Rocky Start

The machine was launched in March 2007, in ground conditions that immediately became more complex than anticipated. As the height of the overburden increased, long stretches of extremely loose, blocky ground were encountered. TBM utilization was as low as 18.7% of working time because rock support installation was requiring a very high 43.5% of the working time.

One of the main problems faced was ground deterioration and the resulting falls of blocky ground. The majority of these events occurred during the time taken for the newly excavated bore to pass behind the rear fingers of the roof shield, where ring beams and mesh were installed.

Modifying the Machine in the Tunnel

During consultations between Robbins and Odebrecht, a decision was made to modify the machine in the tunnel. The TBM would be reworked to use the McNally roof support system, which allows support to be installed directly behind the main roof shield. Crews removed the roof shield fingers and installed a series of rectangular pockets in their place. The pockets ran from the rear side of the cutterhead to the trailing edge of the roof support. These pockets were designed to be used with rebar, which is part of the McNally Roof Support System. At a later stage when the ground conditions worsened these pockets were extended to cover the sides of the TBM as well.

The McNally Support System

One big advantage of the McNally support system is that it is possible to install ground support closer to the face than other ground support methods used on TBMs. It holds loose rock in place, which in turn helps to activate the strength of the rock mass and maintain the inherent strength of the tunnel arch. When used correctly the system can significantly reduce the time taken to provide adequate support. It can also offer reductions in the level of support required, and contain rock bursts and collapsing ground.  The greatest benefit of the system, by far, is its ability to provide a much safer work area.

Incorporation of the McNally support system and various other modifications to the TBM resulted in a steady increase in production rates in spite of continuous rock bursting events. The machine broke though in December 2011 having achieved production rates in excess of 670 m a month.

Read more about the McNally Support System here.

Make short work of an unforeseen cavern: The MKTVARI project

The Republic of Georgia’s Mktvari Hydropower Plant Construction project, along the river of the same name, was a challenge from the outset. The initial contractor used drill and blast for the 9.5 km long headrace tunnel through hard rock, but after 1.5 years they had only advanced about 200 m. The new contractor took over a previously-ordered non-Robbins hard rock machine but enlisted Robbins to help with the TBM assembly. They also wanted Robbins to be available if problems occurred.  The machine did well at the outset, boring up to 900 m per month.  But then, the machine hit bad ground.

Cavernous Conditions

Crews hit an unforeseen cavern above the TBM and were unsure of how to proceed through mixed layers of breccia, andesite, and bands of clay with light water inflows.   A Robbins Field Service Manager was sent to the site, where he determined that the cavern was part of a fault zone consisting of unstable material that fell onto the cutterhead. At the time of his arrival, the TBM had passed through most of the fault zone but huge voids were left behind the segments.

Using pea gravel pumped through holes drilled in the segments, combined with cementitious grout, the crew was able to stabilize the existing segments and safely advance through the cavern in about 10 additional segments.  There was also a probe drill onsite that had not been used; the Robbins manager persuaded the crew to install the probe drill and conduct systematic probing ahead of the machine, in case a larger section of clay was encountered.

Key Takeaways

As can be seen in these examples, planning is key. But, even the best-laid plans can go awry. When conditions go from bad to worse, having an expert team of personnel on your side is by far the most valuable tool and the most positive predictor of a project’s ultimate success.  That true story I started off with certainly wasn’t the first such incident in the tunneling world, and it won’t be the last.  Be prepared by arming yourself with knowledge, and with a knowledgeable team.

Information at your Fingertips

Learn more about our vast experience in difficult ground conditions.  Our selection of white papers covers some of the world’s most challenging projects, while our Project Solutions section offers many examples of past successes.

 

 

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From Risk Aversion to Risk Reduction: How Elon Musk could usher in a New Era of Tunnel Boring

 

It has been some time since I have written on the Robbins blog page, but I am inspired to do so by the announcement that Elon Musk is entering our business—the tunnel boring business.  It is great to see people with a vision of an improved world enter our industry.  I agree with Musk that the advance rate of tunnels can be significantly improved if development money comes into the industry.  Development money in tunneling, however, is at best minimal and is more often essentially nonexistent.  Nearly all tunnels are heavily specified to avoid risk taking by owners (therefore discouraging new development).  Nearly all tunnels go to the low bidder and low bidders try to buy the TBMs at the lowest price; a further discouragement of development. The industry has therefore been slow to improve advance rates, but with Musk bringing the issue into the spotlight, perhaps things will change.

Risk Aversion and How to Reverse it

There are some exceptions to this practice of risk aversion for new technology, and one is the Delaware Aqueduct Repair. This tunnel corrects heavy water leakage occurring from the 1940’s-built aqueduct tunnel for New York City.  We are just completing Factory Acceptance in our plant in Solon, Ohio of this unique Single Shield TBM.  The tunnel is at significant depth (approximately 300 m / 900 ft) with the distinct possibility of encountering very high water pressure (up to 30 bars).  The contractor JV of Kiewit/Shea have shown their willingness to move forward with several new developments for this project.  The concept of grouting off high water pressure as the primary means to allow advance in such conditions, rather than use an EPB or Slurry TBM, is in my view a significant step forward for our industry.  Granted there have been halfway attempts with a combination of grouting and pressurized tunneling at recent projects like the Arrowhead Tunnels and Lake Mead Intake No. 3, but these have come at high cost and sometimes long delays.  The Delaware Aqueduct TBM, by contrast, is designed to hold up to 30 bars of pressure while grouting occurs.   Boring and cutter changes are done in atmospheric pressure.

Chemical grouting and grouting technology in general have advanced multifold in recent years, and it is commendable to see it used extensively on several aspects of the Delaware Aqueduct Project. It’s a great example of what can be done when a contractor is willing to use new technology to address potential risks—it appears it can actually reduce risk in the long run.  It is a great honor to be working with the capable Kiewit/Shea JV team to be a part of advancing technology.

Areas Ripe for Change

The Delaware Aqueduct Repair project is a flagship project for what I hope will become more common in the industry: instead of low bidding with the cheapest possible machine, offering a reasonable bid with a specialized TBM that has a higher initial investment, but ultimately a lower cost overall. The project’s use of technology is wide-reaching, particularly atmospheric cutter changes and chemical grouting, which have the potential to reduce downtime and increase safety. I do not see the future of rock tunneling under high water pressure being left to divers to change cutters and repair the cutterhead.  We all know it is not cost effective to send divers to work in confined spaces over 10 bars.  It should be noted that the long-duration Hallandsås Tunnel, for example, finished the majority of its TBM advance by relying on effectively this technique of grouting and advance after failing with a Slurry System.  There are lots of tunnels to be built with above 10 bars pressure that will use this technology.  The industry needs to automate cutter and bit changes as much as possible, and increase the integration of chemical grouting in tunneling.

Certainly there are many areas for advancement in our industry, and major public figures like Musk drawing attention to it is ultimately a good thing.  After all, getting the general public to think about solving traffic by going underground is no easy feat. Even more so, getting the tunneling industry to think about its own risk-averse practices has a big potential benefit. Hopefully all of this attention will result in more tunnels, more business, and better infrastructure. Musk’s willingness to take a risk aimed at making the underground construction industry potentially faster and more stable is a good bet to take.

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The Light at the End of the Tunnel: The Positive Side of Seattle’s SR99 Project

Seattle is the founding city of The Robbins Company, and a place where I lived for nearly 15 years and commuted on SR99 while working at Robbins early in my career. As such, the new SR99 Viaduct Replacement Tunnel Project is of great interest to me.

The industry is all too familiar with Seattle’s SR99 Tunnel and its TBM, known as “Big Bertha”. More specifically, much has been written with regards to the TBM needing repairs after about 300 m of boring. The TBM is the world’s current largest at 17.5 m in diameter, and is excavating a 2.7 km long drive.

TBM Tendering

Robbins was a relatively new entry into the EPB/soft ground tunneling business when tenders were called for the latest SR99 project in 2011, and we made a concerted effort to get the order for this particular TBM. We teamed up with Japanese TBM manufacturer Mitsubishi Heavy Industries (MHI) to get the order. Robbins has had an association with MHI for more than 20 years, with jointly-designed machines operating around the world on projects in India, China, the U.S., and more. MHI has built over 1,000 EPB machines and in my opinion, the Japanese TBM manufacturers are further advanced in EPB technology than their European and American counterparts.

Through the process of trying to receive this order, we learned a lot about the geology, as well as the contractors’ and TBM’s specification requirements. The contractor Dragados, one of the JV partners and very well-experienced in soft ground tunneling technology, developed a high-level specification for the TBM suppliers. All of the prospective TBM suppliers were required to quote and if successful, supply to this standard. We eventually stepped out of the tendering process to supply this TBM, as the lower prices and greater assumption of contract risk offered by our competitors made the TBM supply an impractical business option for us.

Tough Tunneling

The current situation at the SR99 project is more positive than media tend to paint it. The project design consultant did a commendable job on laying out the tunnel route and building in a contingency plan. Boring through glacial till, even with modern TBMs, is never an easy task as previous projects like the Brightwater Conveyance Tunnels have taught the city of Seattle. This is doubly so along the Seattle waterfront, which includes manmade fill, utilities, and buried refuse. In such ground, TBMs can encounter rapidly changing geology; pockets of groundwater; abrasive soil; and manmade objects such as unmapped disused pipes; foundation piles; etc.

Aware of the problems that can develop while using an EPB TBM in glacial till under a city with a lot of backfill, the SR99 designer wisely developed a contingency plan. The strategy, in addition to pre-planned safe havens, involved a “shake down” stretch of tunnel, which ran under no buildings. If problems did occur repairs to the TBM could be made by sinking a surface access shaft at this location. Unfortunately the need for that repair event occurred shortly after the machine commenced excavation.

Why there were failures of the cutterhead seals, and potentially the cutterhead main bearing, is yet to be determined. I doubt there will be any signs of failure of the main bearing when the crews get to inspect it. However, all parties involved are wisely taking precautions and installing a new main bearing in addition to the seals.

Bertha’s Lessons

The Seattle Tunnel Partners and WSDOT have in place a panel of experts to advise them on the highly technical details of the TBM design. I personally know several of these experts and they are well qualified to recommend and supervise the necessary repairs and procedures to get the TBM into a condition where it is able to finish this tunnel.

Having been in the TBM supply business for quite a few years, I unfortunately have to admit having been in a similar (fortunately not as well published) situation as the TBM supplier on more than one occasion. This situation–significant TBM problems at the beginning of boring—can result from many different factors and is not unique to the SR99 project. In fact, Robbins recently had a similar situation (admittedly on a smaller scale in terms of both public and financial impact) on a project in Turkey known as the Kargi HEPP. Despite extensive pre-planning, unexpected ground was encountered, which resulted in several in-tunnel stops and machine modifications in the first few hundred meters of the tunnel. What happens in these situations is you pull in the best minds with the most experience and immediately analyze the problem. The ultimate fix often ends up as a multi-level solution. You must ensure you have the problem under control, plus take additional measures to monitor the vulnerable components and operating procedures. At Kargi, this process resulted in the remainder of the project being finished without significant TBM problems. Without a doubt a similar process is going on at SR99 with Hitachi Zosen engineers, the contractor’s specialists, and the city’s board of experts.

Being one who is keenly interested in this project, I believe that this TBM will soon be back to boring with a new completion date, which will be fulfilled. I am optimistic that this project will one day be seen as a positive in the tunneling industry, where many lessons were learned and advancements were made. Such advancements will be put to use in Seattle and in other cities that greatly benefit from the excavation of more underground infrastructure.

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Research and Development: A Sneak Peek at the Next Generation of Disc Cutters

R & D is important in any industry, and it is no less true for the tunneling industry.  Evolution, even if it is incremental, is where most research and development successes are made.  Such improvement forms part of the competitiveness among manufacturers and thus begets further improvements.  I also believe it is our obligation, as equipment manufacturers, to assist the market in driving down the costs of tunneling in general by improved product performance and product life.

Take, for example the research and development going on with our disc cutters: Robbins disc cutters have improved dramatically since the 1950s when they achieved their first success at 11 inches in diameter in crystalline limestone of 190 MPa (28,000 psi) UCS.  Today’s disc cutters do reach 20 inches in diameter and cost-effectively excavate rock strengths of 400 MPa (60,000 psi) UCS, all while lasting much longer than their predecessors.

That being said, we believe there is always room for improvement.  We are working hard right now to develop customized cutters for EPB tunneling in soft and mixed ground, and to optimize those designs so they can excavate under high pressure.  In hard rock, we are researching and testing new steels, and developing monitoring systems to allow contractors to plan cutter changes.

Here’s a snapshot of what research and development is going on in the cutter department, both in the lab and in the field:

Improved Metallurgy

Working with the University of Trondheim and the Norwegian government, we are commencing a program of laboratory and field testing to improve the materials making up the disc ring itself.  We are always testing new materials in order to find the most durable materials based on the ground conditions. An example of past cutter research in the lab can be seen below:

Pressure Compensated Disc Cutters

We are currently developing improved disc cutters specifically for use on EPB and Slurry TBMs at high pressures of plus 10 bars, using a testing module in our Kent, Washington facility.  The module duplicates a pressurized operational environment so that we can analyze how the cutter seals perform under pressure—the design is in its 3^rd or 4^th generation with continuous improvements being made.

Remote Cutter Monitoring

Our remote cutter monitoring system is a breakthrough that we have been field testing for four years.  The system is now undergoing full scale testing on three Main Beam TBMs at Malaysia’s Pahang Selangor Raw Water Tunnel.  The setup allows crews to more closely monitor the actual working conditions and cutter wear.  We project, through this system, to increase the TBM utilization of each machine by 3 to 4% and to reduce cutter cost by 10%.

We’re also working on expanding this wireless system to EPB and Slurry machines, so that monitoring of cutter wear and rotation can be used while those machines are in closed mode.  This would be a highly beneficial development, because under pressure the detection of tool wear is difficult.  Our goal here is to reduce or better plan interventions because of tool wear.

Robbins Atmospheric Cutter Change System (RACCS)

Finally, we are developing a system to allow cutter changes at atmospheric pressure on large diameter EPBs.  This atmospheric cutter change system is superior to other systems on the market because it allows muck to flow through.  Other systems on the market are very prone to clogging. Each spoke of an EPB cutterhead will contain a chamber at atmospheric pressure.   Cutters can be rotated from the pressure zone into the chamber to allow for efficient and relatively fast cutter changes.

The development is also significant because a huge cost of operating large diameter EPBs is associated with intervention for cutter inspection and change.  We are currently building a large test fixture for this system, which will analyze how RACCS reacts in sand, gravel, boulders, clay, and mud conditions under pressure.

 

Conclusions

These research and development projects are all aimed at solving a particular problem or shortfall—with the objective to bore more meters per month.  It is not the only area where we have research and development underway, as we have similar programs to investigate improvements of the probe drilling and lube systems on our TBMs.  The process is usually rigorous, as designs need to be tested and re-tested in both the lab and the field.

I am not a big believer in “Big Step” research and development as was tried in earlier days at Robbins with the Mobile Miner and the Bore Pack.  Such “Big Step” research and development usually leads to disappointment and heavy cost for the client and the company.

However, improvements like the 19” cutters and the cutter monitoring systems are and will be big wins for the contractors and for Robbins.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

R & D is important in any industry, and it is no less true for the tunneling industry.  Evolution, even if it is incremental, is where most research and development successes are made.  Such improvement forms part of the competitiveness among manufacturers and thus begets further improvements.  I also believe it is our obligation, as equipment manufacturers, to assist the market in driving down the costs of tunneling in general by improved product performance and product life.

Take, for example the research and development going on with our disc cutters: Robbins disc cutters have improved dramatically since the 1950s when they achieved their first success at 11 inches in diameter in crystalline limestone of 190 MPa (28,000 psi) UCS.  Today’s disc cutters do reach 20 inches in diameter and cost-effectively excavate rock strengths of 400 MPa (60,000 psi) UCS, all while lasting much longer than their predecessors.

[Photo of a disc cutter]

That being said, we believe there is always room for improvement.  We are working hard right now to develop customized cutters for EPB tunneling in soft and mixed ground, and to optimize those designs so they can excavate under high pressure.  In hard rock, we are researching and testing new steels, and developing monitoring systems to allow contractors to plan cutter changes.

Here’s a snapshot of what research and development is going on in the cutter department, both in the lab and in the field:

Improved Metallurgy

Working with the University of Trondheim and the Norwegian government, we are commencing a program of laboratory and field testing to improve the materials making up the disc ring itself.  We are always testing new materials in order to find the most durable materials based on the ground conditions. An example of past cutter research in the lab can be seen below:

Pressure Compensated Disc Cutters

We are currently developing improved disc cutters specifically for use on EPB and Slurry TBMs at high pressures of plus 10 bars, using a testing module in our Kent, Washington facility.  The module duplicates a pressurized operational environment so that we can analyze how the cutter seals perform under pressure—the design is in its 3^rd or 4^th generation with continuous improvements being made.  [Photo of testing facility?]

 

Remote Cutter Monitoring

Our remote cutter monitoring system is a breakthrough that we have been field testing for four years.  The system is now undergoing full scale testing on three Main Beam TBMs at Malaysia’s Pahang Selangor Raw Water Tunnel.  The setup allows crews to more closely monitor the actual working conditions and cutter wear.  We project, through this system, to increase the TBM utilization of each machine by 3 to 4% and to reduce cutter cost by 10%.

We’re also working on expanding this wireless system to EPB and Slurry machines, so that monitoring of cutter wear and rotation can be used while those machines are in closed mode.  This would be a highly beneficial development, because under pressure the detection of tool wear is difficult.  Our goal here is to reduce or better plan interventions because of tool wear.

[Show screen shot of monitoring system]

Robbins Atmospheric Cutter Change System (RACCS)

Finally, we are developing a system to allow cutter changes at atmospheric pressure on large diameter EPBs.  This atmospheric cutter change system is superior to other systems on the market because it allows muck to flow through.  Other systems on the market are very prone to clogging. Each spoke of an EPB cutterhead will contain a chamber at atmospheric pressure.   Cutters can be rotated from the pressure zone into the chamber to allow for efficient and relatively fast cutter changes.

The development is also significant because a huge cost of operating large diameter EPBs is associated with intervention for cutter inspection and change.  We are currently building a large test fixture for this system, which will analyze how RACCS reacts in sand, gravel, boulders, clay, and mud conditions under pressure.

 

Conclusions

These research and development projects are all aimed at solving a particular problem or shortfall—with the objective to bore more meters per month.  It is not the only area where we have research and development underway, as we have similar programs to investigate improvements of the probe drilling and lube systems on our TBMs.  The process is usually rigorous, as designs need to be tested and re-tested in both the lab and the field.

I am not a big believer in “Big Step” research and development as was tried in earlier days at Robbins with the Mobile Miner and the Bore Pack.  Such “Big Step” research and development usually leads to disappointment and heavy cost for the client and the company.

However, improvements like the 19” cutters and the cutter monitoring systems are and will be big wins for the contractors and for Robbins.

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