3.1.4.6 PACT system
The PACT slab track system was developed in Britain and first constructed in 1969 at Radcliffe
for testing purposes (Round8
). It is consisted of a continuous paved unreinforced concrete layer
on which a paved, profiled continuous reinforced track slab is based (Bastin31). The connection
between these two layers is achieved by shear links in the reinforcement of the upper slab
(Round8
). This system has a 22.9 cm thick concrete slab that is 2.43 m wide (Canadian Pacific
Railway) (Bilow,Gene & Randich9
). After the curing of concrete is complete, holes are drilled
(diamond-core) and the continuous welded rail is laid on a continuous rail pad and fixed to
inserts embedded in the slab (Bilow,Gene & Randich9
, Bastin31). Although it was designed for
high speed lines, this has not happened. It has mainly used in tunnels (wet tunnels) because of its
low construction height and low maintenance needs comparing to ballasted track. The maximum
speed in a PACT system nowadays does not exceed the 150 km/h (Round8
). Although this
system was at the forefront of slab track development, the lack of any significant new
construction in Britain did not allow for many further developments. The PACT system is outdated
for the current standards and high speed train demands (Bastin31). The advantages of this
system are the low construction costs and the high quality geometry. The disadvantages are, that
requires special laying equipment, the out-dated construction method (bottom-up) combined with
the continuous support of the rail make it harder to achieve the levels of accuracy required for
high speed, as well as that the drainage is often hindered resulting to debris collection which lead
to corrosion of the railway fastenings (Round8
, Bastin31). The exact dimensions and structural
features of the PACT system are schematically illustrated in figure 56