Mechanism of rigid overlaying of carboniferous strata failure in face mining in the case of a multiseams deposit

The technique of assessing the failure of rigid overlying strata is applicable to deep mining with thick coal seams (a thickness of more than 1 m in the Ostrava–Karvina Coalfield), and in one case to longwall mining with controlled caving. The assessment of failure of rigid overlying strata makes it possible to distinguish whether the rigid overlying strata of rocks has been deformed or whether a strutting arch has been formed over the goaf below which is an area that is free from stress. Good knowledge of the mining, technical and geological conditions of a given site is a prerequisite for successful evaluation. There are advantages to utilising surface measurements for interpreting the effects of changes in rock mass, especially in areas of high overlying strata. The practical importance of failure assessment of overlying strata consists in determining the size of the mined-out area where the deformation of the rigid overlying strata occurred, which is dependent on the character of the rock mass. This paper is set in the context of the expected width of the goaf during deformation of rigid overlying strata within parameters that describe the mining and geological conditions of the locality. Changes in the area of the goaf, based the results of tensometric measurements, will also be placed in context.Web of Science10219518

Zkušenosti a poznatky z měření napětí horského masivu v podmínkách OKR

Příspěvek pojednává o metodách a hlavních výsledcích měření napěťových stavů in situ realizované na lokalitách české části hornoslezské pánve Ústavem geoniky. Jsou diskutovány metody hydraulického štěpení stěn vrtu a nově zaváděná metoda měření tenzoru napětí, či napěťových změn pomocí kuželové tenzometrické sondy. Jsou popsány první výsledky dlouhodobého měření změn napětí in situ. Jsou popsány a analyzovány výsledky měření napětí metodou hydrofracturing

Measurements of stress changes in the rock mass around the exploratory gallery site Skalka using tenzometric bolts in 2017

The subject of the report is to continue the monitoring and measurement of stress changes in the rock mass following previous measurements from 1997-2016 in the vicinity of the reconnaissance galley using tenzometric bolts mounted in the ceiling and hips of the reconnaissance and access galleries. Measurements took place during 2017

Horizontal stress in Czech part of Upper Silesian Basin

The results of measurement by hydrofracturing method in the area of Czech part of USB are discussed. The measurements proved some general direction of the primary stress impact: high anisotrophy of horizontal stress, relatively high ratio of horizontal to vertical stresses ((SH+Sh)/Sv÷2). Horizontal stresses in the zones intensely disturbed by mining activity indicate magnitudes corresponding only to effect of overburden load in elastic model of rock mass. Orientation of horizontal stress either corresponds direction of presumed effect of superposition of Carpathian nappes or copiers direction of vicinity tectonic faults usually near of them

Using of a conical gauge probe to long term monitoring of the stress changes

In frame of development of new device to full stress tensor measurement a simplified variant of gauge probe was completed. This variant, which is connected to datalogger by cable, is very good for long term monitoring of the stress changes. Functionality of that was verified not only on laboratory also in-situ in carboniferous rock mass during detection of the stress changes in relation to long wall progress

Determination of physical-mechanical properties of rock for the purpose of rock mass stress calculation based on CCBO probes measurements

To measure the primary stress of the rock mass, the overcoring method was used using a compact conical probe CCBO. A total of four stress measurements were performed in a metamorphic rock mass formed by biotite gneiss, in a horizontal borehole marked VRT-H. For the purposes of calculating the size of the main rock mass stress components, it is necessary to know the basic physico-mechanical properties of the rock mass at the measurement site. For this reason, test specimens were prepared from the drill core, which were subsequently tested on the ZWICK 1494 mechanical press. The research report describes the samples, methodological procedures and results of physico-mechanical properties

3D laser scanning of underground workings in various conditions

3D laser scanning of mining workings were implemented at three locations with different conditions. The roadways in volcanic rocks at a depth ca 50 m below the surface at the Experimental gallery Josef, selected part of the Z3-XX roadway located in a metamorphic rock mass at a depth about 950 m below the surface at the Rožná mine and the closed slate mine Modrá štola in sedimentary rock mass located just below the surface, were scanned and interpreted in detail. 3D scans of mining workings were mainly used as input data to the GENIE software for processing geophysical measurements in the 3D dimension. This software tool was developed by the staff of the Technical University of Liberec and Geotest a.s

Research of geotechnical methods – Stage research report – Stage C

The main goal of project No. FV20294 (GEOSTAB) was the verification of measured geophysical quantities with data obtained by various geotechnical methods. For this reason, stage C - Research of geotechnical methods was solved in parallel and in close cooperation with stage B - Research of geophysical methods. The geotechnical experiments in situ were carried out in the same localities where geophysical methods were applied. For this purpose, several underground mining workings located in different lithological and geomechanical conditions were selected. Experimental gallery Josef was selected in volcanic rocks, the metamorphic rock mass was represented by underground workings of the former deep uranium mine Rožná and the sedimentary environment was examined in the old slate mine Modrá štola. The stage research report summarizes the results of geotechnical, laboratory and numerical methods from all the mentioned localities