Efficient and safe: Novel Shaft Sinking equipment made by Herrenknecht proves itself in complex geology.
Since April 2003, one of the world?s largest sewer projects has been in progress. On behalf of the ?Ministry of Public Works? a total of nearly 100km of sewer pipes with diameters ranging from 200 to 2,250mm will be installed, 38km of this with the Pipe Jacking method. The construction works for this mammoth project are scheduled for completion in May 2006. The construction of shafts in this region is a huge challenge resulting from the geology with an extremely high water content.
Due to the proximity to the Persian Gulf, the groundwater level in Kuwait is in many places only 3 meters below the surface. The geology in this region of Kuwait mainly consists of sand, cemented sand, loam and limestone. Up to 40 launch and reception shafts have to be built in the course of this enormous construction project, all of them between 8 and 28m deep and with internal diameters ranging from 6 to 8m. State-of-the-art machine technology from Schwanau was chosen for the construction of the 15 shafts due to the complex geological and hydrological conditions, the required shaft depth and the tight schedule.
The M.A. Al Kharafi Group (Kuwait), being the main contractor, has subcontracted the installation of approximately 20km of sewer pipelines in the Shuwaikh Industrial Area to the KBC Greenline joint venture based in Kuwait. Together with KBC Greenline, a joint venture of the companies Kuwait Brückner Contracting Co. and Greenline (Kuwait), Herrenknecht developed a completely new Shaft Sinking equipment, named >>VSM 8000<<. In Kuwait, the Shaft Sinking equipment as well as two Microtunnelling systems from Schwanau for the installation of sewage pipelines at depths of up to 28m, have been working continuously since May 2004.
The Shaft Sinking equipment consists of two main components: the 78t lowering unit and the shaft boring machine with a weight of 59t and a power of 300kW. The shaft boring machine is assembled in a ?launch section? at the top of the shaft caisson and then starts excavating the ground mechanically with a cutting boom (cutting speed 85 rpm). The shaft is constructed with precast concrete segmental rings (segments), connected to the top of the shaft caisson. The lowering unit is anchored firmly to the shaft collar at the surface. From there, the segmental rings are connected with each other and vertically pushed into the ground by the jacking units of the lowering unit (max. pressure force 10,000kN).
To balance the surrounding groundwater pressure and to avoid blowouts, the shaft is flooded with water. The excavation of the material underwater is comparable to the mode of operation of a Microtunnelling slurry shield. The rotating cutter drum, positioned on the cutting boom, excavates the material across the entire base of the shaft. The mixture of excavated material and water is pumped to a settlement tank at the surface where the material is separated. A machine operator continuously monitors the whole process of material excavation and transportation from the control panel in the conrol container at the surface.
Besides the project in Kuwait, another Shaft Sinking equipment is currently in operation in Indonesia. It is being used for the exploitation of gigantic drinking water reservoirs and is planned to excavate a 100m deep shaft. The Shaft Sinking equipment, type VSM 2500 (for shaft diameters of 2.50m), started operation on the island Java in early July 2004. It was developed by Herrenknecht in cooperation with the Technical University of Karlsruhe (TU) and the German Ministry of Education and Research (BMBF). The equipment is operating in fissured carst with compressive strengths of up to 80 MPa. The concept of vertical tunnelling is comparable to that of a machine with partial face excavation in horizontal tunnelling. The roadheader boom on the machine excavates the material at the tunnel face. The excavated material is transported to an intermediate platform by a grab on a winch system and from there it is hoisted in a skip to the surface by a crane. The construction of the 100m deep shaft is scheduled for completion by October 2004. It will allow access to the underground drinking water storage system and provide 75,000 people with sufficient fresh water every day.
A third Shaft Sinking equipment of the type VSM 7700 (for shaft inner diameters up to 7,70m) is currently being manufactured on the Herrenknecht premises. The equipment has to prove itself during a highly demanding construction project in the city of Saint Petersburg in early 2005. With the Shaft Sinking equipment connections to existing pipelines and sewers will be constructed in a depth of 85m. Besides working temperatures down to 20 degrees below zero, the equipment has to master multilayer formations, groundwater and boulders up to 2.5m as well. This will demand everything from the novel machine technology since the formations beneath the first water-bearing layer, reaching a depth of 60m, consist of extremely hard and dry loam.
By the latest after this litmus test, the novel Shaft Sinking equipment made by Herrenknecht will prove its worth in the construction of launch and reception shafts for inner-city subway stations as well as foundations for offshore structures.
