The extraction process of the marble and Vicenza Stone blocks can be summarized as follows:
1 | Identification of the area
The marble extraction process begins by identifying potential quarry sites through a comprehensive review of geological maps for the area and from site inspections to evaluate any emerging masses from which to deduce the characteristics and quality of the material. This happens usually in areas where ancient quarries pre-existed. The cultivable layer materializes at a certain altitude, with a fairly constant power. Cultivation takes place underground, as the cultivable layer is located beneath rock covers and other material. Underground cultivation is an obligatory choice, however it also presents notable advantages. First of all, the visual impact can be considered limited - only the entrance is visible - and in this way the profile of the mountain is kept unchanged, without further affecting the vegetation. There is practically no noise pollution (due to the mechanical means at work), and also the diffusion of dust is limited.
2 | Opening of a new access to the underground
first the rock mass is exposed, then we proceed with the first phase of creating the area in front of the future entrance to the quarry. A flat space is created by working on the floor with a bench sawing machine, allowing to obtain a front sufficiently high to position the self-propelled chain sawing machine.
3 | Gallery creation for the marble extraction process.
once the self-propelled chain saw has been positioned, a series of horizontal and vertical cuts are made for a maximum useful depth of 2.8 metres, with a cutting width of 38 mm and a variable advancement speed of a few centimeters per minute. Once these cuts have been made, we continue with the detachment of part of the blocks by inserting steel wedges into the cuts. These wedges are then struck forcefully until the block is detached from the hill side. The same result can be achieved by using steel retractor cushions filled with water. Each single block is then removed with the aid of a loader. Finally the work continues with the creation of rear cuts (with a chain saw) of the remaining blocks, thus completing the advancement.
4 | Excavation deepening
To deepen the excavation, we proceed instead with the bench chain saw. The blocks are identified by making cuts in the ground, longitudinally and transversely with respect to the axis of the tunnel; then they are cut at the base so that they can subsequently be removed by a loader. In this way, the height of the tunnel increases. The blocks obtained are then transported to the Nanto factory for the following processing phases.
In general, we pay particular attention to the definition of the geometric development of the excavation, always aiming for the maximum recovery of useful material.
This type of structure (full-empty, unreinforced) exploits the fact that the useful benches are located between the roof and the bed of the quarry, and are generally intact or in any case with good continuity. This in order to homogeneously distribute the load increases on the various pillars following the excavation. The size of the chambers and pillars is directly dependent on the mechanical resistance of the intact stone, as well as on the resistance of the entire rock mass, influenced in turn by the presence of discontinuities and cracks.
Cultivation planning generally involves, depending on the position and power of the layer, the development of a series of large-section chambers, cultivated from top to bottom in successive horizontal phases.