The term’microtunnelling’ was firmly coined during the years that preceded the spring of 1984, during a period in our industry that has become known as the "Trenchless Revolution." Engineers and innovators in Japan, UK and Europe are credited with the rapid development of "slurry tunnelling" or "mud recirculation tunnelling" techniques in order to meet the needs of aging urban infrastructure and population growth. In order to comprehend the scale of industry at that time, reference is made to the 180km of utilities that was built annually using the microtunnelling technique in Japan alone. Several manufacturers, such as Iseki, Tekken, Soltau, and Komatsu were marketing remote "high-tech" tunnelling systems, many with unique trade names such as Iron Mole, Telemole, Telemouse and Unclemole. Incredibly, several of these original microtunnel boring machines (MTBMs) are still in operation today around the globe.
Microtunnelling originally encompassed any tunnelling method that was used to construct underground utilities of up to 900mm ID. Today it is universally accepted that microtunnelling is any remote controlled pressurised excavation method (slurry or earth pressure balance) that installs a pipe behind the MTBM by jacking from a defined drive shaft. The jacking pipes in today’s market can be composed from precast concrete, steel or glass-fiber-reinforced, polymer mortar. Microtunnels provide a significant safety benefit in that they are generally non-personnel entry, except for scheduled and controlled periods to conduct equipment maintenance or perform the all important survey checks.
The lion’s share of the work in modern microtunnels is conducted within a drive shaft, while the TBM operator and slurry plant operators reside in climate-controlled containers, surrounded by an array of computer screens and keyboards – a far cry from the conditions experienced by conventional pipejacking tunnellers.
In this article reference will be made to seven microtunnels that were constructed during the period 1980 to 2000 in Ontario using remote-controlled, steerable MTBMs, slurry excavation and a slurry separation/recirculation plant. At this point it is important to make reference to the first successful slurry excavated microtunnel constructed in North America. This significant event took place under the I-95 Highway in Fort Laurderdale, Florida, for the Miami Dade Water and Sewer Authority. The project involved the construction of a single 182m-long, 1.8m OD steel casing, through coral soil conditions. Salgado Eastern Corporation rented an Iseki Crunchingmole for the tunnel drive and soon after this drive several other microtunnels were built across the US. However it wasn’t until June 1987, when an opportunity presented itself for the introduction of microtunnelling into Ontario.
WELCOME TO ONTARIO
Buoyed by the success of more than 8km of constructed microtunnels, the American Thrustboring Corporation had been marketing Iseki microtunnel equipment throughout Ontario. These adverts caught the eye of Roger Woods, the owner of R.H Woods of Watford, Ontario. Woods had been awarded a sub-contract to construct sanitary sewers for the expansion of the nearby E.S Fox Holding properties, along Thorold Road, Welland, Ontario. Recognising that the soil conditions consisted of _ owing saturated silts and clay, Woods decided to rent an Iseki TCC500 MTBM to install more than 320m of 600mm ID concrete sewers. The concrete pipe was shipped in to Ontario from Lafarge’s plant in Edmonton and all but one of the three microtunnel drives were completed without issue. During the second microtunnel drive the MTBM was stopped dead in its tracks by a large boulder, bigger than the MTBM, which was hastily removed to permit the MTBM to pass and complete the drive. The project naturally stirred up a lot of local interest at the time, however, more than three years would pass before the next slurry microtunnel project would be built in Toronto. In August of 1990, the highly experienced tunnelling contractors S. McNally & Sons (McNally Construction) was awarded a contract to construct a 458m-long, 750mm ID storm sewer along Keele Street., due north of Bloor Street. in Toronto. After much discussion between the City of Toronto Public Works and Engineering and in order to minimise local traf_ c disruption, an Iseki Unclemole MTBM was sourced and subsequently rented from Iseki Polytech USA to undertake the work. Tunnelling operations commenced during the winter of 1990 and the project was completed in three drives, through sands, silts and gravel using locally sourced concrete pipe, manufactured by Waterloo Concrete Products. One unique attribute of this project, was that it involved the first use in Ontario, of a designed Interjack Station and concrete pipe sleeve (IJS) to overcome predicted jacking forces. This project attracted a large municipal audience that, upon viewing the operations, would soon specify the method in forthcoming contracts. Yet again three years would pass before a microtunnel project would be constructed in Ontario.
In September 1994 the Regional Municipality of Durham, awarded the first specified microtunnel contract to S. McNally & Sons for the construction of a 300mm ID sanitary sewer, along Gould Street in the Town of Uxbridge, Ontario This project would take the honor of being the smallest microtunnel constructed in Ontario at the time, and what is even more interesting is that the microtunnel pipe used in this project was composed from 300mm ID Vitrified Clay No-Dig pipe. The author believes that this is the only such section of sanitary sewer constructed in Ontario using vitrified clayware pipes and the slurry microtunnelling method. An Iseki TCC430 Unclemole MTBM was rented from Iseki Polytech USA and the tunnel was successfully driven in two drives through saturated silts, clays and gravel. The year 1994 was certainly busy for microtunnelling in Ontario. In addition to the project in the Town of Uxbridge two other projects were underway in Western Ontario. The _ rst of these projects was built for the Ontario Department of Transportation, in Waterloo, Ontario. Bonlot Construction Ltd. of London, Ontario, sourced a Soltau RVS 400 to construct a 64m-long, 900mm ID steel storm culvert through boulder clay. This was the _ rst use of a welded steel lining behind a MTBM and following the successful completion of this project, Bonlot Construction decided in 1995 to use a similar MTBM to construct a 900mm ID sanitary sewer along Cheapside Street, in London, Ontario.
The microtunnel drives were constructed through boulder clays and the consisted of locally sourced 3m concrete pipes. This project featured a record-breaking microtunnel drive of over 253m and despite this achievement, the TBM had to be recovered mid-drive to re-tool the cutterhead, after it had been almost completely worn down by the challenging soil conditions.
CLOSING OUT THE CENTURY
Microtunnelling is well known to provide an effective solution to highly sensitive environmental situations. In 1995 a project called the Devils Creek Sanitary Trunk Sewer was to be constructed beneath an active railway, highways and through natural wetland, in an area known as the Devils Creek, which was located in the City of Cambridge, Ontario. The project received substantial media attention locally, due to the fact that the microtunnelling took place below the natural habitat of an endangered species of salamander.
The City of Cambridge speci_ ed one-pass microtunnelling as it offered the least environmental disruption and awarded the construction of the 750mm ID trunk sewer microtunnel contract to Regional Sewer and Watermain, of Cambridge, Ontario. An Iseki TCC800 MTBM was rented for the project and this MTBM proceeded to construct the microtunnels, in three drives, achieving typical pipe-push times of under 25 minutes. Which is very respectable even by today’s standards. The first drive was under an active CP railway, making this drive the first ever railway microtunnel drive to be driven using reinforced concrete pipe, which was supplied by local manufacturer Water Concrete Products.
The second and third drives were tunnelled beneath the wetlands and highway respectively. The second drive did experience significant boulder obstructions, such that the MTBM went of grade. The contractor elected to attach cables to the MTBM and effectively hoist it back on grade and complete the drive. Sometimes you just can’t beat simple engineering ingenuity.
The last microtunnel project to be constructed in Ontario, prior to the Millennium year 2000, was awarded to S. McNally & Sons in Janurary 1998 and proved to be a very difficult project in many respects.
The City of Vaughan awarded the contract for the construction of a 1,050mm ID storm sewer, close to the intersection of Jane Street and Rutherford Road. The soils in this area are defined as classic glacial tills, which are known to contain boulder nests.
An Iseki TCC1100 MTBM was rented from Iseki Polytech USA and featured the innovative and trusted four spoke epicyclic cutterhead, which was designed to crush boulders down to a suitable particle size, to the "chippings" to be removed from the cutterhead in the return slurry. The microtunnel pipe for this project was again supplied by Waterloo Concrete Products.
Unfortunately after only completing 85m of its first drive the MTBM began to lose grade and alignment, and an emergency shaft was excavated to investigate. Once the MTBM was exposed, no such boulders were observed, thus the machine was relaunched, but had only advanced 45m before it was halted by a boulder nest, containing boulders of up 600mm in diameter. The remaining 392m of this first drive was constructed using traditional pipejacking techniques, while the MTBM was relaunched in the opposite direction to complete the final 158m drive.
This was to be the last microtunnel completed in Ontario until the summer of 2011.
Conclusion
Having reviewed and studied the seven microtunnel projects that were constructed in Ontario during the period 1980-2000 it is clear that the Ontario tunnelling industry was certainly keeping the pace with its global counterparts. Anyone in our industry would be the first to admit that there is no such thing as a straightforward project.
This article serves to recognise and more importantly acknowledge the vision and microtunneling firsts that were achieved In Ontario during the period 1980 to 2000.
Today the microtunnelling market is experiencing steady growth, fueled by a strong economy, consistent suburban expansion, the requirement to replace aging infrastructure, and the reduced impact the method has on our sensitive environment. It is questionable as to whether we are experiencing a microtunnelling revolution in Ontario at present, perhaps the word revival fits the picture better.
Finally to conclude the article one must be reminded by the poignant words spoken by one of the worlds foremost trenchless veteran James Thompson, on the conclusion of his address at the No- Dig 1985, "Engineers of the world – go under. You have nothing to lose but you prejudices, your shovels and your holes in the road"
