Simex has strengthened its range of MP cutter heads for profiling with the MP 1000HD for removing damaged surfaces in tunnels.
It was created for Amplia Infrastructures, formerly Pavimental, a subsidiary of Autostrade per l'Italia, a company specialised in construction and maintenance of motorway civil works and plant engineering.
Designed for excavators from 35-60 tonnes customised for tunneling, the HD version differs from the MP model of the same width in several ways. Piston motors in direct drive with the drum release a hydraulic power of 200kW and a cutting force of 65kN. Hydraulic depth adjustment is up to 150mm via side wheels. There is also independent depth adjustment on both right and left wheels to easily make side-by-side passes.
The cutter has a 360° hydraulic rotation and a nebulizer kit for enhanced dust suppression.
Because the operating weigh of the MP 1000HD is over 4,000kg, it requires a dedicated excavator with enough high hydraulic capacity for performance in tunnel vaults.
For the construction site commissioned by Amplia Infrastructures, a remote-control telescopic arm – called the Joker - was created by Laurini Officine Meccaniche of Busseto, Italy. The Jocker allows the entire profile of the tunnel to be milled in a single pass, for a width of 240°. The next pass, in the opposite direction to reposition the prime mover, is made by advancing only with the tracks, without interrupting the work.
Simex MP 1000HD cutter head for profiling was used to remove the deteriorated layers of concrete inside the several tunnels along the stretch of A1 motorway, towards Florence. The depth and uniformity of the scarifications are hydraulically done thanks to the independently controlled side wheels and by the hydraulically adjustable attachment. Both are controlled remotely by the operator – for profiling the tunnel lining from the ground, along the side walls, up to the crown, with controlled descent on the other side.
There was widespread deterioration of the lining concrete, with cracks and gravel pockets that arise due to infiltration of water. These required immediate remediation and refurbishment. In the driest points, where the problem was linked only to concrete deterioration, the scarification was 5cm. Scarification was up to 10cm in areas where water infiltration was evident.
The restoration took into account the previous damage: after scarifying dry surfaces it was enough to proceed with grout restoration. However, in the presence of infiltration, it was necessary to install draining membranes to convey excess water into special channels.
Simex says that because the MP 1000 - a completely new piece of equipment - simplifies the work, the work takes less time to complete, crucial for the profitability on the industry. Concluding the milling activities earlier not only allows to avoid penalties but allows for an earlier start to the next phases of tunnel work - restoration with grout, installation of ribs and finally the placement of drainage membranes, cables and pipes.
