Mechanical Shaft Construction Uses Herrenknecht VSMIn Kuwait, the first Herrenknecht VSM mechanical shaftsinking rig recently completed a 25 m-deep x 8 m-diameter microtunnelling launch shaft in just a week. Of a total of nearly 100 km of sewer pipes with diameters ranging from 200 to 2,250 mm to be installed over 3 years, 38 km will be pipejacked. The groundwater level in Kuwait is in many places only 3 m below the surface, with geology of mainly sand, cemented sand, loam and limestone. Up to forty launch and reception shafts have to be built, all of them between 8 and 28 m-deep, and with internal diameters ranging from 6 to 8 m. Some fifteen of these are in complex geological and hydrological conditions, where the required shaft depth and the tight schedule demand VSM 8000 technology, jointly developed by Herrenknecht and contractor KBC Greenline. This comprises two main components: the 78 t lowering unit; and the 59 t 300 kW shaft boring machine. The shaft boring machine excavates the ground mechanically with an 85 rev/min cutting boom while the segmental lining is pushed downwards into the ground by the 10,000 kN jacking units of the lowering unit.To balance the surrounding groundwater pressure and to avoid blowouts, the shaft is flooded with water. The rotating cutter drum, positioned on the cutting boom, excavates the material across the entire base of the shaft, which is then pumped to a surface settlement tank for separation. A similar unit is at work in Java, Indonesia, where a 100 m-deep shaft is being excavated by a VSM 2500, and a third unit, a VSM 7700, is currently being manufactured by Herrenknecht for use in the city of St Petersburg, Russia. Other applications in the construction of launch and reception shafts for inner-city subway stations are being appraised. For more, e-mail: PR@herrenknecht.de, or visit www.herrenknecht.de 48/04.