Page 48 - Built Expressions - Online Construction Magazine - November 2014 Issue

Cover Feature one.aecom.com and combine the functional features of a hard-rock shield tunnel boring machine and optionally, of a slurry shield or a hydro shield machine. They are always used when tunnels have to be driven alternately in stable and unstable sections. • New style machines: Dual-mode tunnel boring machines are still a new type of machines and have been developed to meet the requirements of complex projects in strongly varying geologies. Where conventional tunnelling techniques had to be used Earth Pressure Balance Tunnel Boring Machine (EPB TBM ) formerly, these machines now open the way to lower-risk and lower- cost tunnelling in diffcult geological conditions. Earth Pressure Balance Tunnel proven the SBUA works better than Boring Machine (EPB TBM ) any other method of excavating small 9. Cranes If the geology ranges from soft soils to diameter, hard rock bores. Different types of equipment ranging weathered rock, then Earth Pressure from Tower Cranes to Lifting Hoists Balance Machine (EPBM) is the Slurry Pressure Balance Tunnel to simple site fabricated systems using correct technical solution for project. Boring Machine (SPB TBM) electrically or mechanically operated This is particularly true when project Bentonite slurry, consisting of a specifc winches can be adopted. They are is located in an urban environment clay and water mixture is universally frequently used for shifting of concrete, and ground surface subsidence cannot used in boring and digging operations. masonry blocks, labour, reinforcement be tolerated. EPBMs are utilized The slurry has numerous properties: and many other miscellaneous in the construction of rail tunnels, sealing of the cutting face, reduced materials. metropolitan subway systems, highway friction on the TBM's structure and The construction equipment tunnels, and other projects where the transport of cuttings to the separation that falls under the term “cranes” tunnel will be constructed either partly plant outside the tunnel. represents a broad class of machines. or completely in soft soil beneath the The basic principle of this TBM is The typical crane is used to lift and water table. to maintain the tunnel's cutting face place loads. Modifcations on the basic From "Smooth Flow" cutter during the excavation phase by flling crane structure allow it to be used for heads that reduce friction to super- the working chamber, located behind other activities such as dredging and reliable sealing systems and Variable the cutter head, with slurry. pile driving. Frequency Cutter head Drives, has Slurry pressure is carefully A crane is a lifting machine, taken the traditional EPB design to the controlled by a large air bubble which is generally equipped with a winder (also next level. maintained by a separately-controlled called a wire rope drum), wire ropes or air supply system. This air bubble acts chains and sheaves that can be used Microtunneling Boring Machine as a damper by absorbing sudden both to lift and lower materials and to (MTBM) variations in mucking output. move them horizontally. It uses one Small Boring Units (SBU-A) is a small or more simple machines to create diameter rock cutting head (from Mix shield Tunnel Boring mechanical advantage and thus move 24"/600 mm to 72"/1.8 m) that can be Machine (TBM) loads beyond the normal capability used with any Auger Boring Machine Dual mode-two process technologies in of a human. Cranes are commonly (ABM) to excavate hard rock on drives one as the term 'dual mode' indicates, employed in the construction industry, less than 500 ft (150 m). SBU-A has two process technologies are combined lifting of heavy material, girders etc. been proven on hundreds of jobs across in these machines. Different types of cranes available are: the U.S. Over one hundred contractors • Shield machines-these machines are • Truck mounted Cranes in locations around the world have externally similar to shield machines • Rough Terrain cranes PG 48 Built Expressions Vol: 3 Issue: 11 November 2014