Quarrying case study: Rosa Portugal marble in Vila Vicosa, Portugal

Due to the hardness of the stone and the size of the sites, Rosa Portugal quarries such as the one owned by Florival Rocha Marmores LDA in Vila Vicosa, Portugal, have presented a challenge to operators.

The Rosa Portugal marble quarries in Vila Vicosa and neighboring areas are deep, often difficult to access, and the marble is hard to cut. But the challenging extraction offers a substantial reward, as the beautifully colored pink marble is wear-resistant and durable, containing hard and colorful minerals. Consequently, the precious stone is one of the best-selling materials worldwide for floors, wall panels, tiles and furnishings.

A major challenge for area quarriers is to open new levels on closed quarry floors. Overburden, deep erosion and fractures at the surface of the deposits make a deep quarry more economical and attractive in this region than a wide and shallow mine. Therefore, opening new levels and the need to extract blocks from closed levels and benches play a major role in successful and economic quarrying of Rosa Portugal marble. A closed quarry floor in a space-confined deep quarry can become a headache, and lowering it one more level is a major challenge. Time-consuming drilling work was done, and blasting was also used on occasion, often damaging and wasting considerable amounts of the precious marble, yet not achieving the desired level floor.

Korfmann ST 450 VH chainsaws, equipped with Stratapax polycrystalline diamond inserts from GE Superabrasives, have provided a new option for fabricators of Rosa Portugal marble, such as Joaquim Mendes Nobre LDA.

Chainsawing

One solution was introduced in Vila Vicosa some years ago. Giant Korfmann chainsaws with a cutting depth of up to 3 meters were equipped with Stratapax polycrystalline diamond inserts. These saws cut directly into the quarry floor and undercut benches horizontally. This offered the advantage of allowing a new quarry level to be cut, while also extracting blocks at the same time. And by horizontally undercutting a whole bench, diamond wire could be used with great ease. Since every vertical hole drilled will hit the horizontal cut, there was no time-consuming drill alignment and no missed holes. The diamond cut quarry floor is smooth, level and straight.

Additionally, widening the quarry area and creating rooms and tunnels deep in the quarry is made easier, as the chainsaws can cut directly into the walls horizontally and vertically.

The Stratapax diamond insert was originally developed by GE Superabrasives for drilling applications in the oil industry. The blanks consist of a layer of polycrystalline, manmade diamond and cemented tungsten carbide, produced as an integral blank through a high-temperature, high-pressure technique. The resulting blank has the hardness and wear resistance of diamond, which is complemented by the strength and impact resistance of cemented tungsten carbide. The polycrystalline layer on the Stratapax blank permits a continually sharp edge as the blank wears in the application. As diamond crystals are slowly worn away, sharp new crystals are exposed. The desired re-sharpening process continues through the life of the blank.

The depth of some Rosa Portugal sites is evidenced by the quarry owned by Cecchinelli, LDA.

Quarrying results

According to figures compiled by GE Superabrasives, production totals of 2 meters per hour and over 6 square meters are now reached with the new-generation Korfmann ST 450 electro-hydraulic chainsaws in the Rosa Portugal marble. Without the polycrystalline Stratapax diamond inserts in the specially developed cutting tools, the quarries had previously used diamond wire cutting techniques alone. Now, the combination of chainsaw and wire technology is reaching new and higher levels in quarry block production.

At the quarry of Joaquim Mendes Nobre LDA an increase in raw block production up to 50% was noted with the addition of the chainsaw. At Florival RochaÂ¿s quarry, a straight horizontal cut of 19 meters long and 3 meters deep was achieved in 9 hours. With a width of 42 mm, the cut is wide enough to put supports in, it does not clog up with debris, and it is easy to find the drill holes for the diamond wire.