Damming the entry of the water with a single -component polyurethane foam

Due to the rapid foaming of the injection medium on contact with the water, an enclosed blocking layer is created that temporarily prevents the entry of water and thus an uncontrolled flushing away of the subsequent injection medium until the end of the reaction of its components. This step can be left out if there is only a weak flow of water.

Injection with two-component polyurethane resin

This fills the cavity and the previously introduced polyurethane foam, if it was injected, is compressed. A soft elastic resin is formed with a high modulus of expansion, which seals the entry of the water and retains its sealing properties even with later movement of the structure e.g. through temperature and alteration of loading.

Second injection with two-component polyurethane resin

At the contact surface concrete / polyurethane resin there can occur, in the injection at b), in the enclosed water in the concrete pores with the polyurethane, a "foam reaction" and this can impair the local adhesion of the resin to the concrete, which might require a second injection under certain circumstances. For this reason, local pressures of 250 bars must be applied …

An important share of the repairs to manholes is the regulating and exchange of manhole tops because today, as compared to earlier, much greater demands are made on the evenness of the traffic lane and these are subject to higher loads due to the heavier traffic conditions .

The following points of damage occur especially often:

• Crack formation at cover, grating or frame;
• Wear of the frame and/or the lid especially on the support surfaces between the lid and frame;
• Positional deviation of the frame of the manhole top ;
• Settling differences between the traffic lane or pavement and the manhole top .

Damages of cover or frame according to DIN EN 13508 [DINEN13508-2] :

• cover broken (A)
• rocking cover (B)
• cover missing (C)…

Consequences of damage:

• traffic hazards (material damages and personal injuries)
• traffic obstruction
• noise disturbance (due to clanging manhole covers or uneven road)

The most common cause for the last two named types of damage is the failure of the grout between the frame of the manhole top and the throat of the manhole or possibly the support ring through a combination of dynamic loading from passing vehicles and chemical / physical stressing caused, for instance, by:

• Effects of thawing salt;
• Temperature differences;
• Differences in moisture content;
• Freezing / thawing change stresses.

Further causes that can …

In this rehabilitation measure, neither the manhole tops, nor the surrounding covering and carrier layers, are removed. There follows only the lifting or lowering of the frame that has previously been loosened with the aid of special mechanical or hydraulic machines [WPCFFD6] [NASSCO85a] [WPCF85].

Procedure:

• lifting the manhole frame up to the required level
• cleaning the joint that has thus emerged
• inserting a shuttering (metal or hose shuttering)

In the patented bedding with wedges of polymer concrete, joints between 2.5 and 5.5 cm can be pointed up.

The exact and stepless height regulation is achieved by means of mutual movement together of two different types of wedges with different heights , whose radii are adapted to that of the manhole top.

The height levelling of manhole tops with removal is always carried out when the surrounding cover layer is also damaged by the formation of cracks, deformation, etc. .

Procedure:

• removal of the surrounding covering and carrier layers as well as the damaged manhole top and bearing rings
• cleaning of repair area
• installation of the new manhole top and level regulation

Removal:

• stemming out, milling, cutting, drilling

Level regulation by means of:

• regulation mortar
• plastic adjusting units
• mastic asphalt inclusion
• steel spring elements
• separation of manhole top and manhole

Reinsertion of cover and carrier layer:

• paving the frame by casting the joints with bitumen
• inclusion with mastic asphalt without and with the application of meltable or self-adhesive bitumen joint strips

Removal:

• stemming out, milling, cutting, drilling

Example: Stemming out the manhole top

Example: Drilling over the manhole top

Level regulation by means of:

• regulation mortar
• plastic adjusting units
• mastic asphalt inclusion
• steel spring elements
• separation of manhole top and manhole

Height levelling by regulation mortar: Procedure 1

Procedure 2

Other developments have the aim, instead of cement grout, of inserting equalising rings of plastics, which, because of their lower modulus of elasticity, reduce the loading peaks of the dynamic loads on manhole top and manhole caused by the traffic. The suitability of such special rings has been proven by comprehensive in-situ and laboratory tests [Stein98a].