|
|
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)
| | (Image: Positional deviation of the frame of a manhole top [City of Düsseldorf, Germany]) |
|
|
| 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 … |
|
|
| (Image: Suggestions for the rehabilitation of damages of manhole tops)
|
|
|
(Table: Standards regarding manhole tops (stand 2006-07) [FI-Steina]) |
|
|
|
|
| (Image: Rehabilitation variants for height levelling)
|
|
|
|
|
|
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. | |
(Image: Working sequence in the lifting of the frame of the manhole top by means of polymer concrete wedges [FI-AcoSe] - Lifting the manhole frame … |
|
|
|
| (Image: Lowering a manhole frame by means of joint cuts with the aid of a milling cutter with reference to [FI-Loos] [Image: S&P GmbH])
|
|
|
|
|
|
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. . | (Image: Positional deviation of the frame of a manhole top [City of Düsseldorf, Germany])
| |
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 |
(Image: Chiselling of the road surface in the manhole top region using a jackhammer)
|
(Image: Loosening the manhole frame from its support using the jackhammer)
|
(Image: Loosening the support ring using the jackhammer)
|
| Example: Drilling over the manhole top |
(Image: Manhole frame remover type "Shark")
|
(Image: Drilling out the asphalt cover using the manhole … |
|
|
|
|
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 |
(Image: Chiselling of the road surface in the manhole top region using a jackhammer)
|
(Image: Loosening the manhole frame from its support using the jackhammer)
|
(Image: Loosening the support ring using the jackhammer)
|
|
|
|
Procedure 2 |
(Image: Cleaning the working space with the aid of the dirt pan and a shovel)
|
(Image: Applying the mortar to the top surface of the manhole taper)
|
(Image: Adjusting the height of the support ring using a hammer and wooden edge)
|
|
(Image: Applying the mortar to the top surface of the support ring)
|
(Image: Adjusting the height of the manhole frame using a hammer and wooden edge)
|
(Image: Smoothing the mortar by means of a wet brush)
|
|
|
|
| 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]. | | (Image: Underfilling the frame of the manhole top with the aid of polyethylene equalising … |
|
|
|
A comparable construction is offered by the creation of the joint intermediate layers and surrounding the manhole top with mastic asphalt with the use of a metal manhole shell . | (Image: Manhole top with mastic asphalt inclusion [FI-Beck](Beck))
| |
Mastic asphalt is a dense mass of crushed stones, sand, fillers and road construction bitumens, the mineral compound of which is composed nearly free of cavities. The content of binders is adjusted to the … |
|
|
| In order to include the manhole top into mastic asphalt, the side bedding of the frame of the manhole top as well as the intermediate gap between the frame of the manhole top and the manhole taper is carried out by means of the same material – mastic asphalt. Mastic asphalt is a good alternative for the rehabilitation of manhole tops due to its sufficient strength and good resistance to loads deriving from frost alternations or from the application … |
|
|
| The application of steel spring elements for the height regulation of manhole tops has the following aims: - substitution for mortar joints and bearing rings,
- height regulation during operation,
- damping of dynamic traffic loads.
| | (Image: Vertically adjustable manhole top with spring element) |
|
|
| (Image: Separation of manhole and manhole top)
Other processes for re-installation and rehabilitation of manhole tops, in the case of a height levelling with cover removal, have the aims of a relief of the bedding of the frame of the manhole cover by transferring its loads to the bordering carrier layer of the street surface. The purpose of this is to achieve a longer useful life. | Load removal above manhole top (Image: Separation of manhole top and … |
|
|
|
(Image: Installing a Selflevel manhole top into a bituminous cover layer [FI-GAV] - Surface of approx. 1.20 x 1.20 m opened up)
|
(Image: Installing a Selflevel manhole top into a bituminous cover layer [FI-GAV] - Inner shuttering and joint tape placed into the adapter ring)
|
(Image: Installing a Selflevel manhole top into a bituminous cover layer [FI-GAV] - Introducing the bituminous materials)
|
(Image: Installing a Selflevel manhole top into … |
|
|
|
(Video: Repair of a manhole with reference to the SSU-System) |
|
|
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
| Example: Paving the frame by casting the joints with bitumen |
(Image: Height regulation of manhole top with removal [City of Düsseldorf] - Detail region)
|
(Image: Height regulation of manhole top with removal [City of Düsseldorf] - Pointing with … |
|
|
