Stream 2
Dumbe Fomation Repair
Project Scope
The 34km long Dumbe deviation is characterized by long
adverse inclines, much of them at the 1:60 ruling gradient. Even
though formation rehabilitation was undertaken here prior to the
above mentioned study, the site visit review indicated that there
were signs of failure. The formation rehabilitation in the Dumbe
deviation was undertaken under the 71Mtpa expansion program,
as the failure of the formation had the potential to lead to slacks
and derailments in that area. The project began in March 2013
and the bulk of the work was done in May 2013 (during the
2013 Coal line shutdown).
The Dumbe formation rehabilitation project required for the
upper 400 mm of the formation layer works to be removed and
replaced, and the ballast to be replaced. The subgrade (SSB) of
the track was imported from the nearby Mahulumbe formation
rehabilitation project and the ballast was imported from a quarry
nearby. This had to be done prior to the coal line shutdown as
part of the preparation of the work.
During the shutdown, the rail was cut and removed along with
the sleepers and the ballast. The top 400mm of the formation
was removed; new material was brought in and compacted in 2
by 200mm layers before the placement of the new ballast bed
and the installation of the skeleton track. Thereafter welding of
the rails and final tamping of the ballast took place. On the last
day of the 12 day shut the rehabilitated formation was
commissioned.
The plant that was used included HGR machines used to lift the
rail off the track, TLBs, a roller compactor and excavators to
remove the ballast and do the bulk earth works, front end
loaders to do the layering works, AY wagon trains to place the
ballast on the skeleton formation, a ballast regulator and a
ballast tamping machine. The movement of all the abovementioned plant caused a significant amount of dust on the
farmers’ land, thus the contractor had to provide a water lorry to
spray water on the barren soil during the works
Background
The coal line formation (subgrade below the track
superstructure) was developed during the 1970’s. During the
early 1990’s, it began to show signs of failure such as cracking
of the stabilized sub-ballast layers, weathering and
decomposition of the layers due to issues such as cyclic loading,
temperature and moisture changes, inadequate drainage and
issues with the original construction. Transnet has been
rehabilitating this formation at various locations along the coal
line since 1995. Formation rehabilitation is a time consuming
process and requires the section of track that is being worked on
to be out of service for the duration of the work, which impacts
the capacity of the coal Line1. It is thus in the best interest of
Transnet to optimize the amount of time spent on such
rehabilitation.
As part of the 81Mtpa rail capacity expansion program, through
which Transnet aims to increase the coal export capacity to
81million tonnes per annum and sustain it at this level, a work
package for formation rehabilitation was put in place. This work
package aims at limiting the formation rehabilitation to areas
that show excessive signs of failure as well as in critical areas
along the line, while ensuring the sustainability of the formation
as a whole.
Formation rehabilitation is an essential part of the 81 Mtpa
program and indeed as part of previous expansion programs,
because if it is not undertaken; mud holes will form in the
formation, the track will sag, there will be ingress of moisture
into the formation, formation drainage problems and ballast
fouling will occur. These formation issues can result in potential
derailments, speed restrictions and potential rail breaks which
could mean high maintenance costs, reduced slot capacity due to
speed restrictions, reliability issues and additional rolling stock
procurement.2
A geotechnical study to investigate the railway formation along
the coal line was undertaken between 1998 and 2004 and a
report was compiled. In the report, areas with poor geotechnical
data, possible track geometry issues, significant maintenance
effort, speed restrictions and visual problems were used as a
basis to determine critical areas. In order to identify the areas
that require formation rehabilitation and to what extent,
Formation Condition Index (FCI) data, Track Quality Index
(TQI) data, information on maintenance depot-identified areas
of concern , visual inspection of the track and information on
speed restriction areas was obtained and reviewed. 2
The critical sections were identified, however, only some have
been rehabilitated over the past ten years due to the time it takes
and the extent of work that needs to be done on each section that
was identified. Some of the remaining areas are being addressed
as part of the 81 Mtpa program.
1
2
(Transnet Capital Projects, 2009)
(Transnet Capital Projects, 2009)
Status of Project
Formation rehabilitation is necessary along the coal line in order
for Transnet to achieve and sustain the 81 Mtpa export capacity.
The above mentioned challenges, encountered during the project
life, were dealt with accordingly. Unfortunately some of the
challenges led to some increase in cost, but the project proved to
be an overall success and completed within budget.
The senior project manager was Uli Guttenbrunner, the Project
Manager was Lebese Ramohlale and the Construction Manager
was Daniel Kidane. A total of 60 people worked on this project
at different time slots. 20 people from the civil team worked up
to day 8 of the shut, 40 people from the perway team worked up
to day 9 of the shut, the Overhead Track Equipment (OHTE)
team was needed on day 7 and 9 to check the height and stagger,
while the signals team was needed on day 93.
Benefits of Project
Cost
Project
Management
Transnet Capital Projects
EPCM
Client
Contractor Phase 1
Contractor Phase 2
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3
(Transnet Capital Projects, 2013)