Abstract
The hard coal seams in the Jiu Valley mining basin have been mined with different mining methods and technologies, including with the complete caving of the surrounding rocks and with top coal caving. These mining systems have led to the degradation of the ground surface by producing subsidence of the land, ranging from a few meters up to tens of meters, in the areas with thick coal seams with high dips. When the limits of the main safety pillars are accidentally exceeded whilst mining, buildings situated either below the ground or on the surface are affected. In the future, the possibility exists of mining some of the very large reserves that are immobilized in the main safety pillars, where the gentle dip seams are stored. In consideration of the above, in order to study the behaviour of typical buildings that are under the influence of underground mining and to develop a model of the stress state in the structural elements of the structures, finite element modelling is used. As such, several modelled buildings with one, two, and three levels were generated, as well as buildings with two levels and with different lengths. These buildings were built of reinforced concrete panels or brick masonry and were subjected to the mining influence of a panel specific to the mines in the Jiu Valley basin, sequentially extracted with a longwall coal face method at different operating heights, with the use of roof control by caving of rocks and with top coal caving methods. Following the analysis of the major principal (tensile) stresses and minor principal (compressive) stresses, a series of conclusions regarding the behaviour of these buildings that are under the influence of the underground mining is revealed. In this context, it was concluded that the value and location of the stresses developed in the structure of the buildings depend mainly on the extension of the panel and the volume of the goaf, the relative position of the building in respect to the coal face line, and the length of the building.
Highlights
The coal basin of the Jiu Valley (Figure 1) is geographically located in the center of the country and contains the most important hard coal deposit in Romania, both in terms of balance reserves exceeding one billion tons and in relation to the special coking characteristics of the western coal seams in the basin
As a result of the mining of thick coal seams in the Jiu Valley coal basin, deformations have appeared on the ground surface, which in some cases have even led to the destruction of buildings located on the surface and of some main underground mining works
Underground mining operations lead to significant disturbances in the balance of the roof rocks, and sometimes in the floor of the mined coal seam. Under certain conditions, this movement is transmitted to the surface, causing damage to both the ground surface and the objects located in the area of influence of the coal seam mining area [12,13]
Summary
The coal basin of the Jiu Valley (Figure 1) is geographically located in the center of the country and contains the most important hard coal deposit in Romania, both in terms of balance reserves exceeding one billion tons and in relation to the special coking characteristics of the western coal seams in the basin. As a result of the mining of thick coal seams in the Jiu Valley coal basin, deformations have appeared on the ground surface, which in some cases have even led to the destruction of buildings located on the surface and of some main underground mining works. Under certain conditions, this movement is transmitted to the surface, causing damage to both the ground surface and the objects located in the area of influence of the coal seam mining area [12,13] The magnitude of these deformations depends on the following parameters: number of seams worked on; their thickness; the dimensions of the fields worked on within each seam; the exploitation method; liquidation of the space worked on; geological and hydrogeological overburden structures; and tectonics, strength, and strain properties of the rock mass and rock strata [14]. Examples of Deformation of the Ground Surface as a Result of the Underground Mining of the
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