Bezpieczeństwo Pracy i Ochrona Środowiska w Górnictwie Number 09/2014

The paper recalls the measurement methods and devices used since 1945 to control the level of natural threats in coal mines. The development of system-wide monitoring over the last 20 years is discussed in more detail. The measurement devices used for continuous monitoring of aerologic and geospheric threats is reviewed based on a selected example. The directions of development of system-wide monitoring of the threats and the locations of the crew and machinery are presented.

Designing the longwalls located in the vicinity of high-methane content deposit, with planned high concentration of the mining, requires meeting ventilation-methane and fire safety criteria and appropriate cross-sections of the longwall faces. The ventilationmethane criteria defined in “The rules of mining the longwalls in methane threat conditions” [4], implemented the uniform rules of methane threat assessment in Polish mines. The issues related to appropriate cross-sections of the longwall faces is becoming more important in the conditions of increasing concentration of mining in the longwalls with high absolute methane content. The forecasting of the changes of cross-sections of the longwall faces during the mining designing stage allows to conduct the simulation calculations for the variants of possible method of ventilation of a designed longwall. The results of the conducted underground studies of the changes to cross-sections of longwall faces before and behind the front of the longwalls, upon conducting the comparative analysis with the forecasted results determined high usefulness of the developed forecasting methods. These methods should constitute a tool allowing to design appropriate ventilation method of the longwall in the conditions of methane threat and endogenic fire threats.

The paper presents experiences gained during the drilling of the bore-holes within the scope of NCBiR project: “Development and verification on a pilot scale of underground gasification technology”. The issues related to drilling three precise, few-dozen metre deep cored boreholes in underground workings at KWK “Wieczorek”, communicating in a single point, are presented in relation to mining-geological conditions observed in the drilling area, causing the need to take measurements of bore-hole trajectory. The assessment of behaviour of the bore-holes along their course was conducted through analysis of correlation and regression of the values of the deviation of actual axis from the designed axis in relation to bore-hole depth. The results of the studies of actual course of the bore-holes determined by magnetic inclinometer indicate that the deviations from the planned trajectory increase along with the length of the bore-hole, and the highest determination factors were showed by linear and polynomial regression. The maximum deviation along the total length of the bore-holes was 1.57 m, while the minimum deviation was 0.17 m.

The mine seismic observations have been focusing to date on identification of the shock and rock burst threat conditions. However due to the number and configuration of the network of seismic stations this assessment concerned rather the mining areas than individual workings or mined longwalls. Due to difficulty of locating weak seismic events, the analysis of effectiveness of applied preventive measures or determination of the impact of mining-geological parameters on the level of released seismic energy was similarly difficult. The utilisation of the possibilities offered by the enhanced seismic monitoring enabled to improve the quality of recording of the shocks of the bed rock and to use the longwall passive tomography, analyse the changes of coefficient b of Gutenberg-Richter distribution and parameters of PPV factor for the assessment of the seismicthreat conditions. The obtained qualitative and quantitative data in respect to the rock burst threat assessment allows to better select the appropriate preventive measures concerning the conducted mining works and react quickly and accordingly to a changing threat status.