Special features of scheduling tunnel works - Tunnel Engineering: Basics and Additional Services for Design and Construction - page 284

7.4 Planning tools

General. For complicated construction projects, scheduling also undergoes a develop-
ment process, which means that it is not possible at the start to assemble all the works that
will be required and the associated durations of the actual construction works. Table 7-2
shows this process from conception through design to work preparation and construction.
The planning tools are the bar chart (Gantt chart), precedence diagram or critical path
diagram and the time-distance diagram.

Table 7-2 Stages of planning construction time [138].

Stages
Project phase

Construction
programme
Design phase

Construction
schedule
Before construction

Work sequence plan
Construction phase

Can be used as rough plan rough plan

fine plan fine plan

Process on the critical path
leading activity
supplementary activity

calculated
estimated

calculated
calculated

calculated
calculated

Process off the critical path
leading activity
supplementary activity

estimated
estimated

calculated
estimated

calculated
calculated

Consideration of the familia-
risation time no no yes

Planning tools bar chart

network diagram

distance-time diagram speed diagram

distance-time diagram

Bar chart. Bar charts, more specifically Gantt charts, have a time coordinate, on which the
construction activities of a project are entered in coarse structure. No complete marking
of the reciprocal dependencies of activities is normally undertaken. Considered overall,
bar charts are only of limited use because of their coarse divisions and the approximate
estimation of durations. Fig. 7-6 shows a bar chart produced as a construction schedule for
the Westerschelde Tunnel.

Figure 7-6 Construction schedule for the Westerschelde Tunnel [180].