Z powrotem do publikacje Jerzy Cabała

Abstract

On the basis of surveying data the development of subsidence trough in the region of the Kazimierz syncline (USCB) has been presented. The size of subsidence and its variability have been analysed in the period 1973-97. The influence of geological-mining factors on the dynamics of ground surface deformation has been determined. Standardised subsidence curves for individual bench marks have been calculated. This allowed to define the status of dynamics of individual bench marks. Curves described with formulae may form the basis to forecast the dynamics of deformation in subsequent years. The influence of a tectonic fault on the deformation transfer rate has been analysed. It was pointed out that the created trough is incomplete and that positive deformations originated in its border, external part. That resulted from horizontal displacements generating periodical and local tensile stress state.

The area included in the investigations is highly urbanised and because of developing surface deformations is systematically flooded and during the flood-time in 1997 was virtually totally flooded.

The described subsidence trough resulting from repeated mining carried out by the coal mine “Kazimierz-Juliusz” is an incomplete trough with transient deformations. Direct influences of not-deep mining of beds 510, 418 and 409 carried out in the period 1978-94 had a primary effect on its formation. On the other hand small direct influences could affect its formation from residual deformations originating from the oldest mining in bed 420 in the period 1940-50 carried about 200 m north of the analysed profile.

The observed dynamics of vertical movements is very diversified and ranges from 13 to 250 mm per month (8 mm per day) at a substantial fluctuation, that expressed by the variability factor amounts to 0.98. The obtained subsidence rates reach 40 mm per day at a variability factor in the range of 0.4 – 0.7 and in the coal mine “Czeczott” (Chudek, Strzałkowski 1995) the maximum subsidence amounted to 28 mm per day. A significant subsidence dynamics observed in the coal mine “Staszic” and “Czeczott” results from a very fast advance of mining operations amounting on average to 5 m per day. The investigations carried out recently in the USCB (Kowalski 1995, Kwiatek 1997) show that the rate of mining results also in an increase of subsidence dynamics, and the breaks in mining affect the value of fluctuations. After analysis of subsidence in the region of the fault (bench mark No 6) the following conclusion may be presented: tectonic faults in a substantial way affect the rate of subsidence and in the case of mining carried out in a uplifted and downthrown sides of faults unpredicted accelerations of subsidence and formations of steeply inclined internal border parts of subsidence troughs may occur. Such zones will feature a short relaxation period and a quick settlement of secondary equilibrium state in the rock mass. Forecasting of subsidence for tectonic zones covered with mining shall take into account:

- a possibility of formation of narrow deformation zones,

- quick transfer of deformations to the surface,

- occurrence of main deformations on the active, most often thrust side of the fault.

Calculation on the basis of many years subsidence of curves standardised my means of polynomials or another function allows to indicate which parts of the trough are already in a state of relative equilibrium and in which subsidence has got the greatest dynamics. From the shape of curves one can forecast at what time a given point may reach the state of equilibrium. Such forecasting is purposeful for regions in which renewed mining of a new bed will not occur and the existing mining will proceed in hitherto mined beds.

Z powrotem do publikacje Jerzy Cabała