5 minczytania
Circular cut or breaking out with a hammer? The methods compared
The demolition method decides three things at once: how much material goes to the tip, how long the lane stays closed and whether the repair survives to the next winter. Here is how the methods differ in practice.
You have to get to the manhole somehow. The surface around the cover has to come off down through the wearing and binder courses, so usually to around 10 cm. There are three methods and each leaves a different mark behind.
The breaker and chipping out
The fastest way into the job and the most expensive way out of it. A breaker has no line to stop at, so the demolition area always ends up larger than planned. The edge is ragged, and the vibration travels into the binder course and leaves micro-cracks beyond the visible damage.
The second problem is the shaft itself. A breaker working close to the load-relief ring can damage it, and then a height adjustment turns into a structural repair.
Straight saw, cutting a square
The edge is even and vertical, so the joint with fresh asphalt holds far better than after a breaker. The price is geometric: to enclose a round manhole in a square you have to cut an area clearly larger than what actually has to come out. Add four saw passes and the corners the blade does not close, which come out with a hammer anyway.
The circular cut
The machine mounts in the manhole frame and swings the arm around the shaft axis. The ring you cut is close in shape to what has to come out, the edge is vertical and even, and the reference point is the manhole itself, not the surface. No setting out, no corners, no finishing with a hammer.
Side by side
| Criterion | Breaker | Saw, square | Circular |
|---|---|---|---|
| Edge | ragged | even | even, vertical |
| Demolition area | hard to control | excess at the corners | close to what is needed |
| Number of passes | — | four plus corners | one |
| Risk to the shaft | high | moderate | low |
| Repeatability | none | moderate | high |
Repeatability is underrated. If every opening has the same diameter, the material for restoring it is counted once for the whole stretch instead of separately for each manhole.
When is a breaker still needed?
A circular cut opens the surface. It does not replace removing the frame, cleaning the shaft or setting the new level. The breaker stays in the crew’s kit, it just stops being the tool the job starts with.
What is worth counting before deciding?
- The demolition area per manhole, multiplied by the number of manholes on the stretch.
- The volume of rubble and the number of tipper runs.
- The mix to be laid when restoring.
- The running metres of joint that has to be sealed.
- The hours of lane closure, if you pay for occupying the road.
With one manhole the differences are bearable. With a dozen they start to decide the result of the job. See the HornetCut R650 specifications or how the cutting sequence looks.