Civil Engineering Reference
In-Depth Information
In summary, the town development plan and the planning decision differ in the following
points [255]:
Town development plan
- The main emphasis of the town development plan lies in laying down various types of
land use for a defined area (for example overground and underground transport areas,
building and green spaces).
- Construction problems are only covered to a limited extent by the town development
plan (for example tunnels passing beneath buildings, support with anchors).
- A town development plan is particularly suitable for the construction of transport facili-
ties with heavy interdependence of the interests of urban planning use, like for example
stops in densely built-up areas and where transport development requires intrusion into
existing building, demanding a decision about replacement building.
Planning decision
- A planning decision includes the precise specification of a tunnel construction measure,
which also includes construction aspects and regulates legal matters (for example water
protection law).
- A planning decision is particularly suitable for pure transport infrastructure projects,
which have little effect on other urban planning interests (for example building, green
spaces).
- The planning decision is suitable for longer tunnels without major impact above
ground.
The phase between the design of a construction project and the permission to start con-
struction is nowadays the longest. In addition to the planning permission process, there are
also political objectives, which can have a significant effect on the process.
The time taken for the pure construction work indeed seems short compared to the total
duration but it is exactly in this area that faulty design work or the lack of stringent dead-
lines can lead to delays, both to the project and to connecting works, which could have
been avoided by appropriately careful scheduling. Careful in this case means taking into
account the number of parameters that have to be included in the planning of the con-
struction schedule, a particularly large number for a tunnel project with the compound-
ing problem that some influential factors are difficult to determine; although their effect
on construction progress is known, their time of occurrence is not always foreseeable.
Examples would be unpredictable heavy water ingress or changing geological condi-
tions, for example karst features [157].
In order to produce a correct construction schedule, the evaluation of the preliminary
geological investigation of the ground around the tunnel alignment is thus of significance.
The determination of the duration of individual activities should be based on a calcula-
tion of performance, which is calculated for the most vital processes or at least should be
taken from experience (values derived from analysis of costs from completed projects of
a similar nature) [131].
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