- Selection criteria and location of quarries
- Preparation stages for natural stone extraction
- Extraction techniques
Contrary to what might be expected, choosing to open a quarry does not only depend on the presence of the material one intends to quarry, but there are many more factors that are to be taken into consideration. In addition, there are several quarrying techniques but it is crucial to choose the right one basing on the type of quarry in order to avoid issues later on. In this article we will discuss how quarry locations are selected and what extraction techniques can be employed.
Selection criteria and location of quarries
Engineers and contractors must take many factors in consideration when choosing where to locate a quarry. Selection must occur primarily on the basis of public safety pertaining the characteristics of the site, the farming method, and the presence of private and public works such as aqueducts, railways, building and bridges in the vicinity. Another factor to be considered is the distance between the site and the centres of use of the extracted material, as well as the craftsmen’s residence, the supply centres for spare parts and the repair and maintenance centres of the machinery employed. When selecting where to locate a quarry, it is important to take into account whether infrastructures and resources vital to a quarry, such as streets, electric energy and water are present nearby the site. Lastly, it is important to consider any protective restrictions.
Preparation stages for natural stone extraction
Once the location of the quarry has been chosen, there are some necessary steps that must be taken prior to the extraction itself. The first one is selecting the appropriate extraction technique. Nowadays, this can be done manually or using specific machines. It is fundamental that the method be chosen beforehand: the choice will depend on the dimension of the quarry, the nature of the rock and the demand for building stone. Subsequently, according to the selected technique, a diagram or layout for the extraction will be realized. This will determine which side the bedrock will be extracted first, as well as how the extraction will be conducted in the following phases.
At this point, it is necessary to remove the thick layer of soil and various materials that have leaked and accumulated on the natural stone. Regardless of the extraction technique employed, this overload of materials is to be removed before the actual extraction can be started. Similarly, any rocks held loosely on the slopes need to be removed to prevent accidents in later operations.
The removal of the stones from their natural bed through multiple operations is called extraction. Extraction techniques include:
- Excavating: this technique is employed when a quarry is made up of small, soft chunks of stone;
- Heating: this technique is used when the bedrock is thin and positioned horizontally;
- Wedging: questo metodo viene utilizzato quando la roccia dura è costituita da fessure naturali. Quando esse sono assenti, quelle artificiali vengono preparate praticando dei fori.
- Use of explosives: this technique involves the use of monitored explosives which fill the crevices of the stone.
Let’s take a closer look at the steps that must be followed to extract natural stone using explosives:
- Realisation of drilling holes: blast holes are performed using a drilling machine.
- Charge: explosive powders are placed inside the cleaned and dried holes.
- Infill: the remaining blast holes are filled with clay, cinder, fuses and wiring.
- Firing: the fuses of the blasting holes are activated using the power supply or rods.