In 1953, the Memorial Tunnel in Standard, WV, was constructed as a two-lane, 2800 ft (853 m) tunnel with semi-transverse ventilation. The owner operated the tunnel until the mid-1980s when a four-lane bypass was constructed to upgrade the turnpike to current Interstate standards. The tunnel was abandoned until 1989 when the Federal Highway Administration (FHWA), in conjunction with the American Society of Heating, Refrigerating, and Air Conditioning Engineers (ASHRAE), embarked on the Tunnel Fire Ventilation Test Program using funding from the Central Artery Project.
The test program consisted of performing controlled test ï¬res up to 100 megawatts. These intense ï¬res then provided valuable information for the design of ceiling wall partitions and the protection of facilities for power, ventilation, and lighting. In addition, it provided the opportunity to develop and evaluate methods of proper ventilation control of a tunnel under various ï¬re scenarios.
Parsons Brinckerhoff was retained to perform the test program. As part of that test program, an evaluation of the structural condition of the tunnel was performed and structural repairs were designed. A critical part of the design was to insulate structural portions of the tunnel for temperatures in excess of 2000 °F (1143 °C).
The rehabilitation program for the reuse of the tunnel required the sealing of all cracks in the tunnel liner because the bedrock around the tunnel contained low-flashpoint cannel coal. In addition to sealing the cracks, extensive structural rehabil-itation of the liner was performed to repair damage caused by the excavation for the bypass on the adjacent highway. Numerous products were evaluated to determine which would provide suitable fire protection for the structural elements of the ceiling and for mechanical equipment anchorages. The test program included the use of traditional venti-lation with a tunnel ceiling and tests with the ceiling removed for the use of jet fans. The construction contract for the rehabilitation of the tunnel and the removal of the ceiling had a projected cost of $10 million.
During the test program of 98 ï¬res, routine inspection of the tunnel was performed to evaluate the performance of the ï¬reprooï¬ng. Based on the performance of certain structural elements, changes were made in the use of structural ï¬re-prooï¬ng and code requirements for the protection of equipment. After the test program in 1991, the
The Use of Macro-Synthetic Fiber-Reinforced Shotcrete in Australia
Macro-synthetic ber-reinforced shotcrete (SnFRS) has rapidly gained popularity in Australia over the past 5 years. This can be attributed mainly to the huge improvement in post-crack performance that has been demonstrated over recent years and the almost universal adoption of this material for ground support by the underground mining industry.
Use of Fiber-Reinforced Shotcrete
As many of you Shotcrete readers know, there have been many articles published here on FRS, and many more where FRS is mentioned. Two articles in the premier issue of Shotcrete in February, 1999, mentioned FRS. I have been keeping a bibliography of Shotcrete articles on FRS and, through Summer 2004, I have over 20 listed. These, of course, are available on the American Shotcrete Association (ASA) website. For example, in an editorial in the May 2000 issue, Mike Ballou says, œSteel Fiber Reinforced Concrete”It is time to ï¬ nd out about it, and in a Spring 2003 Technical Tip, Denis O™Donnell discusses where ï¬ bers should or should not be used in ground support for hard rock mining.
Restoring the Century-Old Wachusett Aqueduct
Every day, residents of Eastern Massachusetts quench their thirsts, bathe, flush toilets, do the dishes, and water their lawns with water drawn from the Massachusetts Water Resources Authority (MWRA) water system. Thanks to the Quabbin and Wachusett Watersheds and Reservoirs, 2.2 million people and 5500 industrial users have one of the most abundant and high-quality water supplies in the world.
The Wachusett system was constructed in 1897 to originally service the 29 municipalities within the 10 mile radius of the State House. At the time, the Wachusett Reservoir was the largest public water supply reservoir in the world. The Wachusett Aqueduct extends from the Wachusett Reservoir in Clinton, through Berlin to Northborough, MA. This 9 mile-long water system consists of 2 miles of hard rock tunnel and 7 miles of 11 ft-high horseshoe-shaped underground aqueduct constructed of nonreinforced concrete with a brick-lined invert.
From its completion in 1903 until the early 1960s, the Wachusett Aqueduct was the primary water transmission system from the Wachusett Reservoir to the City of Boston and surrounding communities. As Boston™s water demand steadily increased, a new system called the Cosgrove Tunnel was developed in the 1960s to provide increased capacity. The Cosgrove Tunnel is a deep rock tunnel running roughly parallel to and deeper than the Wachusett Aqueduct. Since its completion, the Cosgrove Tunnel has essentially replaced the Wachusett Aqueduct as the main delivery system of Boston™s water supply.
Today, a 10-year improvement program, initiated by MWRA with a series of projects to protect watersheds and build new water treatment and transmission facilities, is nearly complete. The Wachusett Watershed is just one
Sissach’s Saved by a Bypass
The small village of Sissach, near Basel, in Switzerland is one of the nicest Swiss villages in the country, but the serenity is plagued each rush hour by heavy commuter traffic. The solution was a bypass tunnel running through the Chienberg hill to the north side of the village. Shallow cover, unconsolidated material at the portals, a TBM pilot tunnel, and the potential for squeezing ground conditions distinguish the Sissach tunnel from many tunnels currently under construction in Switzerland.
The 2284 m (7500 ft) long Sissach bypass tunnel runs a maximum of 120 m (395 ft) beneath the Chienberg hill and beneath the picturesque homes of the Sissach village. It was originally intended to run the two-lane bidirectional bypass up and over the hill on the surface, but protests by the local villages forced the local Canton government to adopt an underground route for the heavy commuter traffic currently passing through the village.
To accommodate the shallow underground route, the alignment is divided into three separate sections: a section of 550 m (1800 ft) cut-and-cover and 200 m (656 ft) cover and cut on the west end, followed by a 1440 m (4725 ft) length of mined tunnel, and a 94 m (308 ft) section of cut-and-cover at the east end.
The first 550 m (1800 ft) of cut-and-cover on the west end of the project was completed under a separate contract and included the boxed section over the Ergolz River. The contract for the main bypass civil works, including the mined tunnel, was awarded to the Arge Chienbergtunnel Sissach, a joint venture led by the Batigroup, Switzerland™s
Shotcrete for Underground Support IX
The Japan Tunnelling Association (JTA) and International Tunnelling Association (ITA) sponsored the Shotcrete for Underground Support IX Conference held in Kyoto, Japan, from November 17-20, 2002. It is a cooperative conference with the United Engineering Foundation, New York, which sponsored the previous eight conferences, the first of which was held 30 years ago. A total of 35 papers were presented at the conference, 34 of which are published in a proceedings available from the JTA. The conference was chaired by Koichi Ono, Professor, Kyoto University, Japan, and co-chaired by D. R. (Rusty) Morgan, Chief Materials Engineer, AMEC Earth & Environmental Limited, Vancouver, British Columbia, Canada.
The conference was a resounding success. It was attended by over 70 delegates, with papers from Japan, South Korea, Vietnam, India, Canada, Brazil, France, Finland, Norway, and Switzerland. Keynote addresses were given by Koichi Ono from Japan on œShotcrete Use in Tunnelling Works in Japan (over 2 million m3 per annum); Minema Ikoma from the Japan Railway Construction
Silica Fume in Shotcrete
Silica fume is a highly pozzolanic mineral admixture that has been used mainly to improve concrete durability and strength and as portland cement replacement. Silica fume has been used primarily in the United States, Canada, and the Scandinavian countries, but is now finding increasing use elsewhere in the world.
Development of a Centrifugal Sprayed System for Shotcrete Application
A new Japanese Ministry of Health document provides regulations and guidelines for the allowable dust concentration in tunnel works. The recommended maximum concen-tration should be less than 3.0 mg/m3 (2.3 mg/y3) at 50 m (164 ft) from the tunnel face. To observe this guideline, it is a serious problem as to how to reduce the generation of mineral particles of dust during shotcreting operations. In general, shotcrete is placed using pneumatic energy. This is a main factor causing dust generation during shotcrete operations. It may be easily imagined that if shotcrete application can be conducted by centrifugal force, dust concentration would be dramatically reduced. In this paper, we describe the development of a centrifugally sprayed shotcrete system named Dustless Shotcrete and also provide the results of a practical application of this technology at the Hishino Tunnel.
Steep Slope Stabilization with Fiber-Reinforced Shotcrete
For the past 150 years or so, roads have been built through the mountain passes in the western U.S. and Canada. Sometimes these roads led to mines; sometimes they started as logging roads. Some were built for access roads for the railroad. Many were built so that people could drive wagons, stagecoaches, and later, automobiles to their destinations. As time went on, some of these roads were abandoned, while others were turned into highways and scenic byways. These roads can be seen on maps, criss-crossing through mountain passes, valleys, and wherever passage was possible. Many of these roads were constructed along mountain slopes, carved out using the largest equipment available at the time, sometimes by hand work, and sometimes by blasting through rocky areas. Road conditions in some of these areas can change dramatically throughout the year. In the mountains, vast amounts of snow can accumulate during the course of just a few days. Sometimes there are heavy rain storms. There can be snow avalanches and mudslides from the rain and snow. In times of drought, vegetation might dry out and die, leaving slopes exposed to erosion, increasing the probability of avalanches and mudslides. Because of varying climactic conditions, freezing-and-thawing cycles, radical changes in the amount and nature of moisture, steepness of slopes, and other factors, slopes need to be stabilized so that rocks, trees, debris, and other factors not listed do not unearth them-selves and become hazards to all things below them. One of many ways to secure and stabilize highway slopes is by the use of ï¬ber-reinforced shotcrete (FRS), usually along with either rock bolts or some other mechanical device drilled into the rock or slope. This paper provides an overview of why ï¬ber-reinforced shotcrete is an excellent choice in lieu of plain shotcrete reinforced with either welded wire mesh or rebar mats for such slope stabilization work.
Specification of Shotcrete Toughness
Fiber-reinforced shotcrete has become an established material for ground support in tunnelling and mining applications as well as in new construction and infrastructure repair. Designers and speciï¬ers frequently require such shotcrete to maintain some quantiï¬able postcrack strength or toughness. Until the newly published round panel test method (ASTM C 1550-03)1 becomes more widely used, North American designers and speciï¬ers will likely continue to refer to toughness parameters as determined by the beam test method (ASTM C 1018).2 The following sections discuss various toughness parameters associated with this beam test and their signiï¬cance.