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This lecture "Rehabilitation" is part of the lecture series "Trenchless 101" and serves to provide an overview of the rehabilitation process of supply and disposal lines. Further individual lectures of this lecture series will separately present and discuss the main process groups repair, renovation and replacement. |
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| (Image: Rehabilitation)
According to EN 752-1 [DINEN752-1] rehabilitation is understood to be: All measures for restoring or upgrading the performance of existing drain and sewer systems. |
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According to EN 752 [EN752:2008] "in principle the performance requirements for a rehabilitated system shall be the same as those for a new system". | In the following, examples in which this requirement was not realized: |
(Image: Liner - Insufficient internal pressure / hardened too early / influence of groundwater)
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(Image: Folds in a cured in place pipe)
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(Image: Folds in a cured in place pipe)
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(Image: Buckled stainless steel sleeve)
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| (Image: General structure of a drain and sewer system)
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Section: A section between two manholes and/or special constructions. (Image: Principle sketch of a section)
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(Image: Street cross section wih combined system)
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(Image: Street cross section with separate system)
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With regard to drainage methods, i.e. the "discharge type of sewage" [DIN4045:2003], the following distinctions can be drawn: Combined system:
Drain and sewer system designed to carry both foul wastewater and surface water in the same pipeline(s) [EN752:2008]. Separate system:
Drain and sewer system, usually of two pipelines, one carrying foul wastewater … |
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The possible attempts at solutions can consist of hydraulic, environmentally relevant or structural aspects and achieve improvements in one or more of these fields [DINEN752-5:1997]. | Environmentally relevant effects (Image: Environmentally relevant)
| Hydraulic
effects (Image: Hydraulic)
| Structural
effects (Image: Structural)
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| (Image: Structural)
Particular emphasis will be placed in the following on the structural solutions (also called structural rehabilitation). According to EN 752-5 [DINEN752-5:1997] they comprise: - Protection of the sewer substance by means of suitable linings or inner coatings
- Rehabilitation of the sewer substance by means of:
- Repair
- Renovation
- Replacement.
| Repair (Image: Repair)
| Renovation (Image: Renovation)
| Replacement (Image: Replacement by trenchless … |
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The processes belonging to the rehabilitation of the sewer substance for structural rehabilitation comprises several main groups of processes with numerous special processes (Bild null). (Image: Overview of the main processing groups for the structural rehabilitation of drain and sewer systems)
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| (Image: Attention!)
As description of damage, its extent and its cause as well as the piping-specific limiting conditions in sewer systems are so different, the correct selection of the respective application case and the applicable structural rehabilitation measures are of great importance [Stein89c] [Stein95f]. | | | (Image: Pros and cons)
All repair, renovation and replacement processes have advantages and disadvantages as well as limitations for their … |
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| (Image: Attention!)
For reasons of economy, locally limited damage is repaired. Repeated and extensive damage at the same place in which a repair is no longer possible can be rehabilitated either by renovation or by replacement. If hydraulic overloading or a reduction in cross section caused by renovation measures cannot be accepted, then only replacement comes into question. | Locally limited
damage (Image: Locally limited damage)
| Repeated and
extensive … |
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| (Image: Decision process for the selection of structural solutions with reference to DIN EN 752-5 [DINEN752-5b])
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Repair | | (Image: Parts of section)
| (Image: Discrete pipes)
| (Image: Pipe joints)
| (Image: Branch connections)
| Renovation | | (Image: At least one section)
| | | | Replacement | | (Image: At least one section)
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Depending on the type of rehabilitation within the trenchless method, the existing substance of the old pipeline is fully used, partially used or not used at all. | Repair (Image: Repair)
Full or partial use of the original substance of the old pipeline | Renovation (Image: Renovation)
Full or partial use of the original substance of the old pipeline | Replacement (Image: Replacement)
No use of the original substance of the old pipeline |
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Depending on the structural condition of the rehabilitation section, the rehabilitated pipeline must take on the following loads: - groundwater load
- soil load
- traffic load
- dead load of construction
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(Image: Loading of the rehabilitated pipeline - Groundwater load)
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(Image: Loading of the rehabilitated pipeline - Traffic load)
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(Image: Loading of the rehabilitated pipeline - Soil load)
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(Image: Loading of the rehabilitated pipeline - Dead load of … |
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This lecture is part of the series "Trenchless 101" and serves to provide an overview of rehabilitation of gas, water and wastewater pipelines. |
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The dimensioning of plastic pipes is carried out on the basis of the minimum strength and a security factor. The security factors depend on the type of application and the hazard risk. DIN 8074 suggests three different security factors SF (1.25, 1.6 und 2.0) for HD-PE. Using the design coefficient C, DIN EN ISO 12162 only defines two different security factors (1.25 for water pipes; 2.0 for gas pipes). A low security factor increases the operating … |
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| (Image: Attention!)
The previously used term "PN" = "nominal pressure" has been taken out of the German standards for plastic pipes and is not used anymore. | |
The nominal pressure depends on the wall thickness and on the diameter of the pipe as well as on the applied security factor. PN = (20 ยท MRS) / ((SDR - 1) ยท SF)) = (10 ยท MRS) / (S ยท SF)
PN = maximum permissible nominal pressure (bar)
SDR = standard dimension ratio (OD/s)
MRS = minimum required … |
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In order to illustrate this change, the pipe series S and the diameter/wallthickness ratios SDR are compared with the previous PN-values in the following table. (Table: Correlation between S, SDR and PN [DIN8074b]) |
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In groundwater and during annular space grouting, hydrostatic load is imposed on the lining pipe. This pressure must not be higher than the permissible buckling pressure Pk,perm of the pipe. |
(Image: Buoyancy force Fv with reference to [FI-Hoech] [Koch85] [Bild: S&P GmbH])
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(Image: Buckling of the liner during annular space grouting)
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Modern alignment of jacking spans poses constantly increasing requirements for jacking pipes. Looking back to recent years, it is apparent that jacking lengths are getting longer and longer while narrow curves are becoming more and more frequent. Even complicated curve combinations, partly with multiple S- or three-dimensional curves, are no longer a rare sight in calls for tenders. Conventional pipe joints with pressure transfer rings made of wood … |
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The concept is described below for the CoJackHydra system. In CoJackHydra, the CoJack calculation and control system is combined with a new pressure transfer system (hydraulic joint) consisting of a water-filled high-pressure hose. The "Hydraulic Joint" replaces the pressure transfer ring between the jacking pipes, which usually consists of a chipboard or oriented strand board (OSB). Among other things, the system allows a better angular deflection … |
