Skip navigation

Old Busch Tunnel

The Busch Tunnel was driven in Hauset Sand from 1841 to 1843. The tunnel was originally 741 m but it was shortened by 50 m in 1884. The maximum overburden amounts to roughly 51 m. The tunnel is mainly lined with small bricklets. Compact sandstone blocks have, however, been used for the abutments for parts of the southern section. The tunnel vault was destroyed by blasting during the Second World War between tm 109 and 134 but it could be reopened again by 1949. The route was electrified between 1965 and 1966 making it necessary for the gradient in the tunnel to be lowered. in order to accomplish this the base invert at the centre of the tunnel had to be reduced over a distance of some 340 m and strengthened through the installation of 90 cm wide reinforced concrete ribs set 3 m apart. 2 m wide cap beams, whose upper edge lies approx. 1 m above the rail upper edge, link up with the ribbing. A number of redevelopment measures followed, including the sea ling of numerous sections of the masonry using reinforced shotcrete. Extensive damage to the masonry has again been evident since the start of the 1990s, which took the form of up to 12 cm thick spalling and bursts affecting the brickwork. These sectors are partially sealed with shotcrete. The shotcrete seal that was added in 1976 reveals large-scale bursts and spalling in some places. On account of the spalling and the insufficient concrete covering the matting reinforcement is corroded. In 1991, the Deutsche Bahn decided to investigate the causes of damage by examining the quality of the brickwork and the load imposed on the tunnel vault. The masonry thicknesses as determined by core boring amount to roughly 0.7 m in the tunnel roof, 0.85 to 1.27 m in the abutment and approx. 0.20 to 0.75 m in the base invert. The reinforced concrete ribs in the floor are about 0.75 m thick and in a very compact state. On the other hand, the old base invert consisting of brickwork, which was reduced to residual thicknesses of 0.2 to 0.5 m as a result of lowering the floor, is of far worse quality so that its bearing capacity can only be assessed as limited. Two measurement cross-sections in the section with reinforced concrete floor ribbing and one measurement cross-section in the section without ribbing - with a total of 17 test points on the inner side of the tunnel wall - were installed to measure stress. AII measurement cross-sections were in sectors with around 50 m overburden. The measured normal stresses amounted to 1.3 MN/m² in the roof and rose to around 3.2 MN/m² in the side walls. Whereas the 2 m wide cap beams for the base ribbing made of reinforced concrete had practically no load to sustain owing to a lack of positive connection, the loads were concentrated in the approx. 1 m wide masonry strips between them. There the stresses measured in the masonry were as much as 10MN/m².  The outcome was that these investigations revealed that it can be assumed that there is reduced support bearing capacity in certain sections. With the aid of the measured stresses, it was proved that the permissible limit values for brickwork masonry according to DIN 1053-1 have clearly been exceeded. Tensile strength measurements with the aid of pressure pad tests in situ and uni-axial pressure tests on large brickwork samples served to determine the actual bearing reserves. The results show that the bearing capacity of the brickwork masonry in the sector where the base ribbing was retrofitted is practically exhausted. Pronounced damage in the form of bursts at the base of the abutment testifies to this. In 2002, in order to assure operational safety until the scheduled tunnel redevelopment, the deteriorating brickwork in the vicinity of the base ribbing was secured over large areas by means of reinforced shotcrete and a positive connection attained by grouting between the concrete base ribs and the masonry. After the New Busch Tunnel goes into service, the Old Busch Tunnel will be converted for single-track operation at the beginning of 2007.


  • Country: Germany
  • Region: Aachen, North Rhine Westphalia
  • Tunnel utilization: Traffic
  • Type of utilization: Main-line rail
  • Client: DB Netz AG
  • Consulting Engineer: DB Projektbau GmbH NL West
  • Construction Monitoring: Prof. Dr.-Ing. Bernhard Fröhlich, gbm
  • Contractor: Hochtief Construction AG, Hartung Bau, Eichholz
  • Main construction method: Refurbishment
  • Lining: Shotcrete
  • No. of tubes: 1
  • Tunnel total length: 691 m
  • Contract Volume: € 7.0 million
  • Construction start/end: early to late 2007