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Krzysztof Tajduś and Antoni Tajduś

Abstract

Mining-induced deformations of the ground surface and within the rock mass may pose danger not only for surface constructions but also for underground objects (e.g., tunnels, underground storages, garages), diverse types of pipelines, electric cables, etc. For a proper evaluation of hazard for surface and underground objects, such parameters as horizontal displacement and horizontal deformations, especially their maximum values, are of crucial importance. The paper is an attempt at a critical review of hitherto accomplished studies and state of the art of predicting horizontal displacement u, in particular the coefficient B, whose value allows determination of the value of maximum displacement if the value of maximum slope is known, or the value of maximum deformation if the value of maximum trough slope is recognized. Since the geodesic observations of fully developed subsidence troughs suggest that the value of the coefficient depends on the depth H, radius of main influences range r and properties of overburden rock, in particular the occurrence of sub-eras Paleogene and Neogene layers (old name: Quaternary and Tertiary) with low strength parameters, therefore a formula is provided in the present paper allowing for the estimation of the influence of those factors on the value of coefficient B.

Open access

Krzysztof Tajduś

Abstract

The paper presents a wide-ranged analysis of horizontal displacements in the region of underground mining exploitation. Initially, various theories pertaining to the determination of mining-induced horizontal displacement are discussed, followed by a complex study on horizontal displacements measured for a selected example region of the German coal mine BW Prosper Haniel, as well as the determination of displacement factor B.

Open access

Krzysztof Tajduś

Abstract

The paper presents the analysis of the phenomenon of horizontal displacement of surface induced by underground mining exploitation. In the initial part, the basic theories describing horizontal displacement are discussed, followed by three illustrative examples of underground exploitation in varied mining conditions. It is argued that center of gravity (COG) method presented in the paper, hypothesis of Awierszyn and model studies carried out in Strata Mechanics Research Institute of the Polish Academy of Sciences indicate the proportionality between vectors of horizontal displacement and the vector of surface slope. The differences practically relate to the value of proportionality coefficient B, whose estimated values in currently realized design projects for mining industry range between 0.23r to 0.42r for deep exploitations, whereas in the present article the values of 0.33r and 0.47r were obtained for two instances of shallow exploitation. Furthermore, observations on changes of horizontal displacement vectors with face advancement indicated the possibility of existence of COG zones above the mined-out field, which proved the conclusions of hitherto carried out research studies (Tajduś 2013).

Open access

Krzysztof Tajduś

Abstract

Underground mining exploitation may result in mining damages to building objects located on a terrain surface. Considering high harmfulness of this phenomenon, the scientists from all over the world have tried to describe impact of underground exploitation on deformations of terrain surface and objects located thereon. The first theories, based on the Gaussian distribution, have emerged in the 1950s and are in use until now. Later on, in connection with development of computational techniques, their availability and numerical methods, a possibility of numerical computations use for forecasting of deformations has emerged. These methods, when suitable numerical models are adopted, enable to include higher number of factors influencing the results being obtained. When constructing numerical model, particular attention should be paid on selection of: appropriate geometry of model, proper constitutive model describing behavior of rock and soil layers, adequate values of rock mass parameters prior to execution of mining exploitation, and after it. The author presented in this article part of these problems, based on own experience.

Open access

Krzysztof Tajduś

Abstract

The article presents an analysis of the horizontal land surface displacements taking place as an effect of coal exploitation on the Girondelle 5 seam in the Friedrich Heinrich-Rheinland mine in Germany. The paper presents changes in displacement vectors measured on the surface following the progress of the exploitation face and an analysis of horizontal displacement measurements assuming that their magnitude is proportional to the profile of subsidence trough slope. Then, the values of horizontal displacement coefficient B are assessed for selected longitudinal and transversal calculation cross-sections of longwall No. 537.

Open access

Krzysztof Tajduś

Abstract

The paper presents results of numerical calculations and modeling of mining-induced surface deformation based on Finite Element Method (FEM). Applying the numerical method discussed to calculations allows us to assume a larger number of factors, such as rock mass structure, fracture network, rock properties, etc., which essentially affect the results obtained. On the basis of an elastic transversely isotropic model, an analysis of horizontal displacement distribution and surface subsidence was carried out for two sample regions of mines. The results of numerical calculations were later compared with the measured values. Such an analysis proved that the applied numerical model properly described distribution and values of subsidence and slope of subsidence trough, though there were serious differences in the values of calculated horizontal displacement, especially in areas of far influence range. In order to improve the matching, the influence of boundary conditions of the model on the value of calculated horizontal displacement was analyzed. The results are presented in graphs.

Open access

Antoni Tajduś, Jerzy Cieślik and Krzysztof Tajduś

Abstract

The paper presents the results of analyses on tendency of bedded rock mass towards rockburst, carried out on the basis of laboratory tests of rock samples and determined indices, as well as by means of numerical calculations. The first part of the paper discusses selected parameters evaluating the tendency of rocks towards burst, on the basis of which the analysis was carried out in order to assess rockburst hazard in selected complexes of strata in Upper Silesian Coal Basin. Rockburst hazard in bedded rock mass is also analyzed with the use of numerical methods and the results of calculations of rock damage development in the exploitation front during coal deposit extraction are presented. Burst hazard of rock mass is studied through the changes of intensiveness of damage process in the area of exploitation front.

Open access

Antoni Tajduś, Marek Cała and Krzysztof Tajduś

Abstract

Determination of original state of stress in rock mass is a very difficult task for rock mechanics. Yet, original state of stress in rock mass has fundamental influence on secondary state of stress, which occurs in the vicinity of mining headings. This, in turn, is the cause of the occurrence of a number of mining hazards, i.e., seismic events, rock bursts, gas and rock outbursts, falls of roof. From experience, it is known that original state of stress depends a lot on tectonic disturbances, i.e., faults and folds. In the area of faults, a great number of seismic events occur, often of high energies. These seismic events, in many cases, are the cause of rock bursts and damage to the constructions located inside the rock mass and on the surface of the ground. To estimate the influence of fault existence on the disturbance of original state of stress in rock mass, numerical calculations were done by means of Finite Element Method. In the calculations, it was tried to determine the influence of different factors on state of stress, which occurs in the vicinity of a normal fault, i.e., the influence of normal fault inclination, deformability of rock mass, values of friction coefficient on the fault contact. Critical value of friction coefficient was also determined, when mutual dislocation of rock mass part separated by a fault is impossible. The obtained results enabled formulation of a number of conclusions, which are important in the context of seismic events and rock bursts in the area of faults.

Open access

Anton Sroka, Stanisław Knothe, Krzysztof Tajduś and Rafał Misa

Abstract

The geometric-integral theories of the rock mass point movements due to mining exploitation assume the relationship between the progress of subsidence and horizontal movement.

By analysing the movement trace of a point located on the surface, and the influence of the mining exploitation in the rock mass, an equation describing the relationship between the main components of the deformation conditions was formulated. The result is consistent with the in situ observations and indicates the change of the rock mass component volume due to mining exploitation. The analyses and in situ observations demonstrate clearly that the continuity equation adopted in many solutions in the form: i=1i=3εii=0 is fundamentally incorrect.

Open access

Anton Sroka, Stanisław Knothe, Krzysztof Tajduś and Rafał Misa

Abstract

Underground mining exploitation creates damage in surface building structure and in underground constructions as well. For this reason, many mining companies gave up carrying out excavations in safety pillar shafts. Currently, the situation on the market is changing. The continuous increase in excavation depth combined with an increase in exploitation costs resulted in many mining companies trying to find cheaper solutions. One of the methods is to carry out partial exploitations inside safety pillar shafts. Such exploitation is much cheaper than ordinary, because it decreases the exploitations depth, the length of transportation drifts, etc. The functionality of the shaft and its infrastructure have to be fulfil.

The authors present a methodology for calculating the effects of mining on mine shafts using geometric integral methods. The paper presents the assumption of the first method developed by Bals (1939), a method based on the so-called Professor Knothe Theory (1951) and the German method of Ruhrkohle (Ehrhardt and Sauer 1961). Based on these methods, operational planning rules are given for mining in protective pillars during coal bed exploitation; additionally, the dimensioning method for shaft pillars is specified. Presented solutions are illustrated with examples from mining practice, where the continuous miner system was planned in the direct area of the mining shaft.