Rehabilitation and Maintenance of Drains and Sewers / Publisher: Prof. Dr.-Ing. D. Stein & Partner GmbH, Editorial: D. Stein, R. Stein (2004)

Quantitative Condition Acquisition

The results of optical inspections (Abschnitt 4.3.2.1) are often not sufficient to describe the condition of the sewers comprehensively and to provide satisfactory answers to questions of damage as well as type and extent of rehabilitation measures. In order carry out technically and economically based rehabilitation measures it may be necessary to carry out qualitative as well as quantitative determination of the actual condition (Abschnitt 4.2).

Affected by this are examples of damage such as non-visible leaks and the condition of the bedding. Furthermore, for mechanical wear (Abschnitt 2.5) and for corrosion damage (Abschnitt 2.6.3.2) information is required on the remaining wall thickness or the amount of removal in order to evaluate the extent of the damage. For the case of damage due to deformation (Abschnitt 2.7.1) a quantification or measurement of the deformation figure is indispensable under certain conditions.

The quantitative acquisition of the actual condition of sewers is not practised much at present. This is not only due to the fact that there are relatively few suitable measuring instruments and systems, which for instance, permit continuous measurements in combination with sewer TV inspection, on the market, but there are also missing corresponding requirements and guidelines for carrying out this type of inspection. Making matters more difficult is the fact that our sewers were not, and are still not, planned and built with a view to rehabilitation (Abschnitt 1.9.1), which inhibits and makes more difficult many tests such as leaktightness tests (Abschnitt 4.5.1).

The following measuring instruments and methods (Image 4.4.3.3.1-1) mentioned as examples, are a first attempt at the complete acquisition of the actual condition of sewers, they make possible the quantitative determination of:

  • Deposits;
  • Positional deviation;
  • Displacement and deformation, internal corrosion and mechanical wear (cross sectional measuring);
  • Bedding conditions (structure / foundation).

With some of the measuring instruments for the quantitative determination of positional deviations, as with the correspondingly equipped and described in (Abschnitt 4.3.2.1) sewer TV cameras, crack width measurements in rigid sewers can be carried out. This possibility is expressly mentioned.

The latest, but not yet ready for practical applications, instruments for multi-sensor sewer inspection are presented in (Abschnitt 4.3.2.3).

Rehabilitation and Maintenance of Drains and Sewers / Publisher: Prof. Dr.-Ing. D. Stein & Partner GmbH, Editorial: D. Stein, R. Stein (2004)