After insertion, the annular space between the old and new pipes is grouted with air entrained lightweight concrete or PU foam.

The annular space formed by the insertion of the lining pipe is grouted in order to achieve, among others, the following (not found):

• Fixing the liner;
• Avoiding the entrance of soil and water;
• Creating a defined bedding in the sewer;
• Even transfer of external loads;
• Prevention of dangerous gas bubbles.

Further advantages of grouting the annular space are:

• Preventing the collapse of …

Before the start of the grouting process, when not already carried out in the course of the liner insertion, the start and ends of the annular space or the grouting regions at the manholes and the side inlets, must be professionally closed off such that the grouting pressure can be absorbed and the control of the grouting process can be made possible. In order to prevent longitudinal changes, the liner must be secured against buoyancy [ATVM143-3].

The connection of the continuous pipe at the insertion excavation with liner insertion in both directions is generally carried out with stub ends with loose steel flanges . In addition, in this region, wall collars can be welded on or an adhesive strip can be wound around the pipe.

After insertion of the injection or venting nozzles, the transition region is concreted .

The grouting of the annular space corresponds with the principle of the injection of an artificial cavity.

Special here is the presence of a lining pipe of visco-elastic plastics that is subject to buoyancy and hydrostatic pressure during grouting.

In order to prevent deformation or bulges, the choice of the grouting material and the execution of the grouting process become especially important.

The maximum buckling values permissible for the lining pipe must not be exceeded.

Care must be taken especially for gravity pipes whose invert gradients must be strictly adhered to that the lining pipe does not float up.

For large cross sectional differences between the lining pipe and the sewer to be rehabilitated, the continuous pipe to be inserted can also be provided with spacers for preventing mechanical damage as well as for approximate positioning and to reduce the floating effect when grouting the annular space [Stein83c] […

Filling of the lining pipe with water may serve to exert internal pressure, which counteracts the buckling pressure.

In this case, the weight of the filled lining pipe also serves the purpose of ballasting.

If it comes to pressure changes of the water filling of the lining pipe, appropriate counteractive measures have to be taken …

The grouting of the annular space can be carried out in two ways:

• Pressure-less filling with the use of the natural slope of the section of the sewer; and
• Grouting under pressure.

For very long sections of the sewer and the high grouting pressures that this requires, as well as for large grouting volumes, the grouting work can be carried out in sectors.

During unpressurised grouting, this may be achieved by interrupting the grouting procedure between the different sections in which the grouting material hardens partly …

Variant with injection sockets

The filling material takes the "line of the least resistance" – with leaky pipes, it can infiltrate into the surrounding soil and fill adjacent cavities (basements, pipelines etc.) before it reaches the designated place.

If the actually inserted amount of filling material exceeds the calculated filling amount by more than 10%, the grouting procedures must be …

The grouting procedure is finished when the measured density of the material is equal at the filling and venting nozzle and when the grouting material remains visible at the filling and venting nozzle until its hardening.

Samples of the mixed grouting material must be extracted and density measurements must be carried out and documented before and during the grouting procedure.

In addition, sample cubes should be prepared in order …

If the pipe to be rehabilitated is still load-bearing and if a small annular space is available, one often refrains from a complete annular space grouting but fills only partly the ends or manholes as well as the range of the laterals. This should serve to avoid the stressing of the laterals by mechanical loads as a result of temperature-dependent length variations.

Modifications to the conventional sliplining process refer mainly to the structure of the pull head under the aspect of simplifying the grouting of the annular space and to remove flow obstacles in the section of the sewer to be rehabilitated within the scope of the relining measures.

The finishing work comprises in addition to testing :

• Manhole connection:
• Adapting the liner to the manhole channels;
• Restoring …