Dewatering, waterproofing and drainage - Tunnel Engineering: Basics and Additional Services for Design and Construction - page 240

start in completed sections. Experience shows that sintering can be already recognised at
an early stage. The complete sintering behaviour can however only be analysed when the
drainage system is in operation. The already recorded data are also of assistance to obtain
information about the behaviour of the drainage system as soon as possible.
In the manholes, the following should be evaluated or measured:
- degree of sintering,
- water quantity and
- the calcite precipitation tendency of the drainage water according to DIN 38 404-10 [60].
5.4.3.1 Camera surveys of the pipe runs between the manholes
The condition of the drainage system should already be checked during construction as part
of normal quality assurance measures. This means that individual sections of drain runs
should be checked with a camera survey immediately after their construction in order to be
able to detect any defects as soon as possible. All these surveys should be undertaken inde-
pendently of the camera surveys undertaken as part of the acceptance of the drainage system.
The images fro the camera survey can then permit conclusions about the exact position
and intensity of individual water ingress locations and sintering. The RI-BWD-TU provide
their own evaluation model, which is based on the ATV (General technical specifications
for construction contracts) system for the recording of damage to pipe runs.
5.4.3.2 Data processing and administration
The protocols from the manholes can be used to enter the parameters
- water level, sintering magnitude,
- pH value,
- water temperature and
- saturation index
into plans of the drainage pipes. It is then easy to recognise areas with heavy sintering and
significant changes from the sintering behaviour, temperature curve, and the curves of the
water temperature and saturation index.
In order to evaluate the camera surveys, it is recommended to digitise the video images
every 5 m and still closer when anything interesting is discovered. Using the digital im-
ages and result sheets using a classification of the code system, a plan can be produced
showing the parameters:
- sintering of slots,
- sintering of pipe invert,
- water ingress locations,
- special features and
- damage.
The plan can then be used to identify any possible improvements. On the other hand, the
plans also deliver the first information about the condition of the drainage system in gen-