Volumetric changes in the focal areas of seismic events corresponding to destress blasting
|نوع نگارش مقاله||
scopus – master journals – JCR
۴٫۲۷۶ در سال ۲۰۲۰
۲۶ در سال ۲۰۲۱
۰٫۹۰۱ در سال ۲۰۲۰
|شاخص Quartile (چارک)||
Q1 در سال ۲۰۲۰
خرید محصول توسط کلیه کارت های شتاب امکان پذیر است و بلافاصله پس از خرید، لینک دانلود محصول در اختیار شما قرار خواهد گرفت و هر گونه فروش در سایت های دیگر قابل پیگیری خواهد بود.
فهرست مطالب مقاله:
The typical development of total volumetric change in the focal areas of seismic events, corresponding to destress blasting, is characterized as an explosive phase followed by an implosive phase and with alter- nating additional phases following on from that. In a few cases, a non-typical development of volumetric change was identified, where the first phase was implosive and the second phase, explosive. This devel- opment is mainly typical for induced seismic events recorded during mining, not for destress blasting. Seismic events were recorded during longwall mining in the Czech part of the Upper Silesian Coal Basin, where the destress blasting technique is used as a rockburst prevention active measure. Kinematic source processes in the focal areas of selected seismic events were analyzed by the seismic moment tensor inversion method, as well as by studying geomechanical rock mass conditions at the localities of the seismic events. The main goal of the analysis was to attempt to identify the reasons for non-typical development of volumetric changes in these cases. Volumetric changes were analyzed for seismic events with energy greater than 104 J, recorded in the period of time from 1993 to 2009 (1109 events). 80% (891) of the recorded seismic events were induced seismic events that were registered during longwall mining and 20% (218) corresponded to destress blasting events. Research shows that the main reason for the non-typical development of volumetric changes in the focal areas of seismic events is an association with destress blasting in the rock mass, which is very close to rock mass overstressing. The detonation of explosives in boreholes, which would dominate the first phase of volumetric changes, prob- ably obscured stress release in the rock mass, as manifested in the first implosion phase of the volumetric changes in this case.
|بخشی از متن مقاله:|
Rockbursts in the Upper Silesian Coal Basin-USCB (Fig. 1) have been a dangerous phenomenon for a long period of time . The rockburst problem relates primarily to the existence of competent rocks in the rock mass and the irregular stress fields induced by long-term excavation. The occurrence of a critical stress field leads to brittle failure of not only the coal but also the adjacent rocks. Such rockbursts are usually the result of combined, long-term for- mations of unfavourable stress conditions in specific geological structures . According to their origins, two main types of rock- burst can be distinguished in the Czech part of the USCB: (1) rock- bursts with an activation mechanism in the seam (coalburst or seam rockburst), and (2) rockbursts with an activation mechanism in the overburden. While rockbursts in the coal seam are localised
and linked to the stress state in the coal seam, rockbursts in the overburden lead to regional events caused by instability in the mined-out heterogenic and anisotropic rock mass . Destress blasting is used as a rockburst mitigation technique in the case of the second type of rockburst.
Seismic events corresponding to destress blasting as well as high energy induced seismic events (with energy levels more than
۱۰۴ J) were recorded during longwall mining between 1993 and
۲۰۰۹ (a total of ۱۱۰۹ events) and were analysed in detail. 80% (891) of recorded seismic events were induced seismic events registered during longwall mining and 20% (218) of the analysed events were seismic events corresponding to carrying out destress blasting. Based on analysis of the development of volumetric changes in focal areas, five events were identified with non- typical development of volumetric changes and these are the sub- ject of this paper. Two events were selected for presentation in detail. The typical development of volumetric changes in the focal areas of seismic events corresponding to destress blasting is characterised by an explosive phase followed by a phase of implo- sion and then alternating phases of explosion and implosion after that (Fig. 2). A few cases were identified as having a non-typical development of volumetric changes, where the first phase was implosion which had been followed by an explosive phase (Fig. ۲). This development is mostly typical for induced seismic events, recorded during mining but not for destress blasting. These seismic events were recorded during longwall mining in the Czech part of the USCB, where destress blasting techniques have been used as active rockburst measures for some time now [2–۶]. Kine- matic source processes in the focal areas of selected seismic events were analyzed by the seismic moment tensor (SMT) inversion method, as well as by studying geomechanical rock mass condi- tions at the localities of the seismic events. The main goal of this analysis was to attempt to identify reasons for the non-typical development of volumetric changes in these cases.
One of the methods developed to ensure mine safety which was used is seismic monitoring to analyse the geomechanical activity of the rock mass. As such, non-destructive methods are very popular because of the large amount of information that can be gathered regarding the seismic activity taking place during mining operations, such as the number and energy levels of tremors in the area. Seismic monitoring is a part of rockburst prevention in many mining regions with high level of rockburst risk [۷–۹]. Seis- mic moment tensor inversion (SMT) analysis as a part of evaluation of seismic activity is a useful tool for determining focal mecha- nisms, especially the mine tremor focus [10–۱۴]. SMT analysis is used mainly in global seismology in evaluation of earthquakes [15–۱۸]. Similar outputs of the evaluation of mining induced seis- mic events correspond to destress blasting have not been pub- lished in the literature.
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