The example for this method of coating is the creation, securing or lining in galleries and tunnels with the aid of the shuttering common there [DGEG86b] [Maak86] [Maidl84b]. In this process, convertible shuttering or special shuttering carts (Bild 5.3.1.6.1) (Bild 5.3.1.6.1) are used. Depending on the size of the tunnel shuttering, mechanical or hydraulic devices can be built in for helping to install and remove the shuttering.

In contrast to the water supply sector, there is at present no experience in the application of in-situ concrete lining processes for rehabilitation of non-man-accessible sewers.

A representative of this group of …

In the displacement process, a displacement body whose outside diameter is smaller than the inside diameter of the pipe to be coated by the amount of the layer thickness to be applied, is pulled or pressed centrally through the respective section of the sewer. The coating material in front of it, in the direction of flow, is displaced into the annular space between the piping and displacement body and is pressed by it against the pipe inner wall.…

According to DIN 18551 [DIN18551:1992], gunite is a "concrete that is conveyed in a closed pressure-resistant hose or pipe to the site and is there applied by means of spraying and thus consolidated."

In principle it is not differentiated in its composition from the usual in-situ concrete. The difference is in the conveying, insertion and consolidation, i.e. in the working that is combined into one working step, the spraying. Shuttering and vibration …

The Hochtief AG has developed a special gunite lining process of a two-layer rehabilitation system in which the first layer is used as a back anchor for the second layer [Hille87]. The back anchoring is created by means of a plastics-modified gunite (SPCC) with polyacryl-nitrile fibres.

In order to create the SPCC preparatory mixture (gunite plastics-modified cement mortar), water-emulsified epoxy resin is used that, according to [ZTVSIB90], particularly …

A large part of the accident and health dangers mentioned in the section "Gunite and gunite mortar" are avoided by the "Ruswroe System" specially developed in England for the coating of sewers [FI-Alpha] [Marti84].

It is based on the wet gunite lining system with the utilisation of a very low pressure (comparable to the application of plaster with plaster spray machines).

The mortar used is applied onto a galvanised mesh wire mat with a mesh thickness …

(Image: Sketch of the principle of an automatic spray machine for dry (right) and wet (left) gunite process for coating large boreholes in the coal mining industry [Großk85])

In order to improve coatings based on the gunite lining process as regards costs, material quality as well as accidents and injuries, present efforts are aimed at mechanisation.

A first attempt in this respect was with the spray machine used in the Pre-load process [Atkin50] …

(Image: Applying cement grout by spray lining in non-man-accessible sewers - Rotary spray heads with coupled smoothing cones [FI-Heitkb])

The Centriline process or cement mortar coating with the spray lining process was developed specially for water supply pipes or pipelines of steel or cast iron.

Even today, this is the main use of the application for nominal sizes from DN 80 and almost without limits upwards (Bild 5.3.1.9.1.1).

For this purpose there …

(Image: Working opening in the opened-up semi-cylinder channel [FI-Teerb])

The work can generally be carried out from the manholes. Depending on the dimensions of the machines to be used, excavations may be necessary.

For pressure piping of steel, the required working openings are effected in an excavation by removing a piece of the piping approximately 2 m in length or by cutting open a semi-cylindrical section with chamfered, or even better, rounded, …

After insertion and centring the spray lining machine at one end of the section of the sewer to be rehabilitated, the machine is pulled or driven backwards through the section of the sewer at a constant velocity during which the spraying of the mortar onto the inner surface of the pipe is carried out by means of a rapidly rotating spray head operated by compressed air or an electric motor (Bild 5.3.1.9.1.2.2) (Bild 5.3.1.9.1.2.2). The mortar is …

The advantages of the spray lining procedure are:

• Can be applied almost independently of the nominal size and length of the section of the sewer;
• Coating possible on concrete, vitrified clay, asbestos cement, steel, cast iron and brickwork (limited);
• Besides cement grout, also plastics-modified cement grouts can be used with suitable machine modifications;
• Achievement of higher mortar densities and strengths compared to the displacement process;
• Layer …

The CSL Polyspray process was developed in England in 1984 for the coating of sewers in the nominal size range of DN 225 to DN 1000 [FI-Costa].

The spray lining machine consists of three main elements:

• Mixing chamber;
• Gelling section;
• Rotary spray head with drive motor.

The two components of the polyurethane resin are pumped separately up to the mixing chamber and are there mixed intensively by an integrated plastics static mixer.

Between the mixing …