Rock excavation is a basic technological operation during tunnelling and drilling roadways in underground mines. Tunnels and roadways in underground mines are driven into a rock mass, which in the particular case of sedimentary rocks, often have a layered structure and complicated tectonics. For this reason, rock strata often have highly differentiated mechanical properties, diverse deposition patterns and varied thicknesses in the cross sections of such headings. In the field of roadheader technology applied to drilling headings, the structure of a rock mass is highly relevant when selecting the appropriate cutting method for the heading face. Decidedly differentiated values of the parameters which describe the mechanical properties of a particular rock layer deposited in the cross section of the drilled tunnel heading will influence the value and character of the load on the cutting system, generated by the cutting process, power demand, efficiency and energy consumption of the cutting process. The article presents a mathematical modelling process for cutting a layered structure rock mass with the transverse head of a boom-type roadheader. The assumption was made that the rock mass being cut consists of a certain number of rock layers with predefined mechanical properties, a specific thickness and deposition pattern. The mathematical model created was executed through a computer programme. It was used for analysing the impact deposition patterns of rock layers with varied mechanical properties, have on the amount of cutting power consumed and load placed on a roadheader cutting system. The article presents an example of the results attained from computer simulations. They indicate that variations in the properties of the rock cut – as cutting heads are moving along the surface of the heading face – may have, apart from multiple other factors, a significant impact on the value of the power consumed by the cutting process.
This article describes stability issues of main excavations in deep copper mines in Poland, from the perspective of mining work safety. To protect main transportation and ventilation routes, parts of rock are left untaken to form so-called protective pillars. The problem was to determine the size of main excavations protective pillars in deep underground copper mines in which provide stability of main excavations. The results of numerical simulations of the stability of protective pillars under specific geological and mining conditions are presented, covering: underground depth and width of protective pillar, number, size and layout geometry of protected excavations, as well as the impact of parameters of surrounding gob areas. Problem was solved applying numerical simulations based on the finite element method which were performed in a plane state of strain by means of Phase2 v. 8.0 software. The behavior of the rock mass under load was described by an elastic-plastic model. The Mohr-Coulomb criterion was used to assess the stability of the rock mass. The results of numerical modeling have practical applications in the designing of protective pillars primarily in determining their width. These results were used to prepare new guidelines for protective pillars in Polish copper mines in the Legnica-Glogow Copper District.