Dewatering, waterproofing and drainage - Tunnel Engineering: Basics and Additional Services for Design and Construction - page 192

1. The bidder is to provide details for water obstructions categorised according to rising
and falling advance depending on the groundwater quantity and water obstruction clas-
ses (Table 5-8).
The different effects of water on the rock mass and the location of water occurrence in
the tunnel cross-section are to be described and assigned to water obstruction classes
according to Table 5-7 for each project.
In case the partial cross-sections bench and invert are not on the critical path (meaning
they are excavated parallel to the top heading), only the items for the mining crew and
the time-dependent costs are to be provided for these partial sections. A separate deter-
mination of the payment units for the bench and invert is not provided, but rather the
number of invoicing units is to be taken from the top heading.
In case the partial cross-sections bench and invert are just as time-critical as the top hea-
ding, and thus have their own advance rate details and items for time-dependent costs,
the payment units for water obstruction are separated analogously to the top heading.
In this case the reduction factors (Table 5-8) are also to be requested for these partial
cross-sections.
2. The maximum water quantity to be considered in the estimation is to be determined for
each project. If required, the lower limit of water quantity, up to which any obstructions
are included in the excavation prices, is also to be laid down for each project. If no
figures are agreed for the lower and upper limit values, the figures in Table 5-8 apply.
3. The employer is to lay down a number of working days with water obstruction for
the individual partial cross-sections and assign these to obstruction classes and water
quantities. The number of invoicing units is calculated from the number of working
days laid down by the employer and the reduction factors according to Table 5-8 to be
stated by the contractor within the limits laid down by the employer. The number of
working days laid down by the employer are calculated from the tunnel sections with
water obstruction and the advance rates without water obstruction that are assumed by
the employer.
4. The payment units for water obstructions that determine the construction time are to be
considered in the sum of the payment units for tunnelling.
5. The type, location and frequency of measurements of groundwater quantity are to be
given separately for rising and falling advances for the individual working areas.
6. Payment items for water obstruction to the installation of support measures and inner
lining are also to be provided for each project if required.

Table 5-7 Obstruction classes according to ÖNorm B 2203-1 [170].

Influence of water on the ground

Location of water ingress in the partial cross-section
invert

sides and face

negligible 1 2

medium 2 3

heavy 3 4

REMARKS
In this table, the relevant location is defined as follows:
tunnel sides and face is the area from 1.0 m above the actual invert (top heading invert) up to the
crown; invert is the area from the relevant actual invert (top heading invert) up to 1.0 mm above it.