| Tunnel boom |
来源：World Highways 发布日期：2007-11-7
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Large numbers of tunnelling projects are now underway, with contractors and clients able to choose from a wide array of more efficient solutions The tunnelling industry is seeing huge growth around the world, due to a pressing need for major infrastructure projects. Road tunnel construction is underway in many countries, as a way of bypassing both mountainous and environmentally sensitive areas or providing traffic links under rivers and in congestion clogged cities. Large tunnel projects are underway at present in parts of Asia such as India or China, in Latin America''s Andes Mountains and across Europe. The tools available to engineers have improved enormously, with sophisticated geological mapping and software design packages that allow projects to be planned far more efficiently. Meanwhile, tunnel excavation hardware has also developed enormously, becoming more reliable and more productive. Drill and blast methods remain popular in some applications and have been helped by the development of new and more efficient equipment, although continuous methods such as tunnel boring continue to progress as the leading firms introduce new solutions. One of the leading players in terms of tunnel boring solutions, German firm Herrenknecht, is seeking to raise its profile further on the global market. Herrenknecht is establishing a plant for tunnelling systems and service in Chennai on the eastern coast of South India. This 100% owned subsidiary, Herrenknecht India, will have modern assembly, steel production and storage capacities and will cover an area of 40,000m2, representing and investment of e6 million. The move follows the firm''s stronger presence in neighbouring China, with its role in large projects such as the new road tunnel under the Yangtze River in Shanghai. The company has made this move because India represents a key growth market for tunnelling as there is massive demand for new infrastructure. Herrenknecht tunnelling technology is working on the subway extension scheme in New Delhi and numerous other projects. The new subsidiary was established in Chennai on the Bay of Bengal because it has good transport links through its seaport into the mainland, an established industrial zone and a ready availability of trained personnel. The first construction phase will be to build an efficient assembly plant for tunnelling machines, as well as to set up production capacities for components and tools. The assembly hall will cover 3,000m² and the site also has a production plant for the manufacture of cutter discs and a warehouse for spare parts. Construction work is underway on the assembly hall with commissioning planned for spring 2008 and the facility will employ 100 staff, including a service team that will support Herrenknecht TBMs operating in India. The first Herrenknecht Double Shield Machine with a diameter of 7.96m will begin excavating an 18.8km water supply tunnel near Hyderabad in Southern India this winter. In addition, Herrenknecht is supplying a lining segment production facility as well as providing technical support. Meanwhile, Herrenknecht has received orders to supply eight Earth Pressure Balance Shields to bore 18km of new tunnels in downtown New Delhi, as part of the city''s subway extension scheme. A number of new road tunnels are also planned in Northern India, to provide improved communications in the country''s mountainous regions. Herrenknecht has also been involved in a project to build a new road tunnel in the Spanish capital of Madrid. The southern section of the congested M30 urban motorway will run through tunnels that are being built by a consortium comprising the Spanish construction firms FCC and Dragados. The work is expected to cost some �740 million (US$ 1 billion) and take 30 months to complete. Driving of the two tunnels using TBMs has now been finished. One of the TBMs was built by Herrenknecht and the other by Mitsubishi and these drove tunnels of around 3.6km. Both units were fitted with earth pressure balance (EPB) shields for this project, weigh over 4,000tonnes and feature a further 160tonnes of trailing machinery and bored drives of over 180m² through the clay and gypsum. As the TBMs progressed, 2m wide tubbing rings each comprising nine elements and a keystone were set in place. A number of Putzmeister pumps have been used for placing concrete and for backfilling the tubbing with special mortar. However the concrete placing work was not easy due to pumping distances of 600m, high air humidity and continuous operation. While the southern bore was being driven, six KOV DUO 550 PM pumps with ball valves were used to fill the annular gap between the 15.2m diameter tunnelling face and the external radius of the concrete rings, which measured 14.65m in diameter. Four further ball valve pumps were used to carry material from the silos, with all ten Putzmeister pumps integrated for this application. As the site was working a three-shift system, the PM ball valve pumps were in use 24 hours/day, seven days/week in 95% air humidity. The delivery systems ran in a fully automatic mode as the tunnel was driven from the centre control room of the EPB. The two tunnel bores have an internal diameter of 13.45 m and will carry three lanes as well as two strips at the side. The carriageway floor features 600mm thick pre-stressed concrete prefabricated components which lie on brackets concreted into the inside of the tubbing. The ventilation system is mounted in the roof of the tunnel, with a service and rescue route beneath the carriageway and cross tunnels connecting the two bores every 200m. Meanwhile, four shotcrete machines from the Sika/Putzmeister alliance have been used by the Schmücke tunnel consortium for 14 months to strengthen the sides of this key German highway project, which is costing around �100 million. The two tunnels measure 1.72km and 1.729km long long and form part of the A71 autobahn between Erfurt and Sangerhausen. In total, the section is 7.5km long and is being constructed by a consortium consisting of the contractors Baresel, Herman Kirchner Hoch- und Ingenieurbau and Alfred Kunz Untertagebau. The construction costs for the project are. Section lengths vary in this tunnel due to the range of geological conditions present, so extensive support has had to be used in some areas. The construction work continues on this project and the four stationary PM pumps are now concreting the inner shell using cast in place concrete.
However the difficult ground conditions mean that a full face excavation method would have been difficult to control. Instead the engineering team decided to excavate the east and west tunnel using separate crown/side wall blasting and crown/side wall/base blasting drive methods respectively. As the tunnelling work progressed simultaneously from the north and south side, the consortium opted to use four Sika-PM500 shotcrete machines for the concrete spraying work. Because of the need to ensure a continuous supply of concrete, two additional machines were kept on standby. Despite the technical problems imposed by the poor geology, the consortium has managed to stay on schedule since the tunnel driving operation began in late 2005 and by the end of November 2006 the semicircular crown profile had already been excavated in both tunnels. However, different section lengths of between 0.8-2m were necessary for the headwork due to the varying load bearing behaviour of the surrounding mountains. And for safety reasons, five emergency galleries, which run in parallel at a distance of 20m, connect the two tunnels.
A further problem arose from the high water table. The ground in the central area of the two tunnels was so saturated with water that excavation with the chosen drive method would not have been possible. To deal with this and provide sufficient drainage, a gallery consisting of 35 wells had to be sunk in a depression on the rear of the Schmücke at depths up to 90m. When the construction work is completed the wells will be restored to their previous state, allowing the groundwater conditions to return to normal levels though. As soon as the first cross heading was reached after 140m in the crown drive, the consortium began the side wall and base drives. The cut sections also varied significantly from each other here, with lengths ranging from 2-12.6m due to the tricky geological conditions. After an initial application of shotcrete to stabilise the rock, a second layer of shotcrete is applied as a sealant carrier. Due to the very smooth surface (80% of the aggregate granulation measures up to 4mm, 20% up to 8mm) the shotcrete shell is being lined directly with fleece and plastic sealing sheeting. On average, the wall thickness of the outer shell is from 200-300mm, while around 75,000m³ of shotcrete in total is used for the two tunnels and the four entrances of the Schmücke tunnel. In delivering the large quantities of concrete required for this project, the six shotcrete machines have required regular maintenance, with steady wear seen on components such as spray nozzles. But to minimise downtime, two of the six shotcrete manipulators were kept available as reserves during the service intervals. Before the start of 2007, the placement of concrete began on the north and south side of the Schmücke tunnel for the base and the arch in the inner formwork. When doing this, the consortium used formwork carriages and up to four stationary Putzmeister concrete pumps (two BSA 1408 E pumps as well as a BSA 1405E and BSA 1005E pump). Before concreting the arch, a section of the base measuring around 60m in length had to be installed to support the arch formwork carriage. The BSA pumps follow directly behind the formwork carriages and are pulled along section by section. Meanwhile, the delivery lines are deliberately kept to a maximum of 10m to ensure a good supply. The respective 12m long inner shell blocks are made from cast-in-place concrete and measure from 0.4-0.6m thick. The time that the concreting crew requires for placing some 135m³ of concrete for each arch section is around 5.5 hours, while the teams require around 3-3.5 hours to place the 75m³ or so of concrete for the base sections. By varying the proportion of cement, the engineers were able to achieve an optimum performance for the conditions and application. The aim is to concrete one base and one arch block/day, for each tunnel section but this requires striking times of less than 12 hours in the arch, so efficient operations are crucial. Each of the tunnels is being concreted in 144 blocks and each block is approved by the site management, while the total requirement of concrete for the inner shell is around 65,000m³. The construction team has been receiving supplies of shotcrete and the cast-in-place concrete from several mixing works in the region. Work is generally conducted in two 12-hour shifts, seven days/week to meet the schedule, with the headwork having been concluded in May 2007 and the inner shell due to have been completely concreted by the end of 2007 · Herrenknecht Putzmeister Drilling faster Atlas Copco says its powerful COP 2238 rock drill combines a high penetration rate with low running costs. This new 22kW hydraulic rock drill can be used for holes from 51-76mm in diameter and suits tunnelling applications. Because it features the firm''s proven dual-damping system, the rock drill ensures that the bit stays in contact with the rock, which helps tighten drill-string joints with each impact and prevents the loosening that can cause heat builds-ups and lead to early wear. The rock drill operates at a high frequency, which allows a high penetration rate, while the damping system absorbs excess energy from each impact and this further reduces wear on the rock drill and drill string. A long slender piston ensures a percussion energy that suits the harmonics of the strong for best drilling efficiency. The company claims that the COP 2238 is easy to service as key wear parts can be replaced without having to demount the rock drill from the drill rig. Service and maintenance issues are further improved as the COP 2238 shares many parts with the firm''s COP 1838-series. Highly versatile, the COP 2238 can be used with short or long shank adapters and can use R32, R38 and T38 threads, while the customer can choose four different rotation motors |
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