The Central Mining Institute is taking in Polish collieries measurements of stresses in rocks by means of following methods: - surface measurements: - spot drilling (strain measurements of the border) - coring (strain measurements of the core) - two-component compensation (strains of the border) - inner measurements: -coring, - isotopic methods. On account of the aim at facilitating the testing techniques the majority of methods is adapted to measurements in drill holes of 42 mm dia. However, each of the above methods has a limited range of applicability and the own difficulties of interpretation. Experiments resulting from the use of individual methods and trends to their further development are discussed. Rheological properties of carboniferous rocks in which stress measurements are taken are presented. In destressing methods the technique of a simultaneous determination of modulus of elasticity of the solid rock by surface pressure method and with the use of Schmidt test hammer is discussed. Experimental bases and a further development of isotopic method are given.
L'Institut Central des Mines poursuit dans les mines de charbon des mesures des contraintes dans les roches par les methodes suivantes: - mesurages de surface: - forage superficiel (mesurage des deformations du rebord), - carottage (mesurage des deformations de la carotte), - compensation de deux composants (deformation du rebord), - mesurages internes: - carottage, - methode d'isotopes. En egard à la tendance à la facilitation de la technique des essais la majorite des methodes est adaptee au mesurage dans les trous de sonde de 42 mm de diameter. Pourtant, chacune des methodes sus-dites possède une etendue limitee d'applicabilite et ses propres difficultes d'interpretation. On a discute des experiences resultant de l'application des methodes individuelles et les directions de leur developpement. On a presente les proprietes rheologiques des roches du carbonifere dans lesquelles les mesurages sont effectues. En discutant les methodes de detente on a presente la technique de determination du module d'elasticite du massif par la methode de pression superficielle et avec l'emploi du marteau de Schmidt. On a discute les bases experimentales et le developpement ulterieur de la methode radiologique.
Das Glówny Instytut Górnictwa (Bergbauhauptinstitut) fuert in den polnischen Steinkohlengruben Gesteinsspannungsmessungen mittels folgender Methoden durch: - Oberflachenmessungen: - Anbohrungen (Messung der Verformungen der Bohrlochumgebung). - Kernbohrungen (Messung der Verformungen des Gesteinskernes). - Zweikomponentenmessung (der Verformungen der Bohrlochumgebung). - Eindringmessungen: - Kernbohrungen - Isotopenmethode. Mit dem Ziel die Untersuchungstechnik zu vereinfachen sind die Messmethoden ueberwiegend auf Messungen in Bohrlöchern von 42 mm Durchmesser abgestimmt. Jedoch besitzt jede der oben angefuehrten Messmethoden einen begrenzten Anwendungsbereich und eigene Interpretationsschwierigkeiten. Die aus der Anwendung der einzelnen Messmethoden gewonnenen. Erfahrungen wie auch Entwicklungstendenzen dieser Messmethoden wurden besprochen. Rheologische Eigenschaften des Karbongesteines in welchem die Spannungsmessungen angestellt wurden, konnten angefuehrt werden. Bei den Entspannungsmethoden berichtete man ueber die Technik gleichzeitiger Bestimmung des Elastizitatsmodul des Anstehenden mit der Oberflachendruckmethode und unter Anwendung des Prallharnmers von Schmidt. Die Untersuchungsgrundlagen und die weitere Entwicklung der radiologischen Methode wurden besprochen.
The stress measurements taken in Polish collieries aim at making possible signalling of the state of effort of the solid coal at spots of a concentration of stresses (barrier pillars, rests of ungotten seams etc.) mainly on account of a possibility of rock bursts and outbursts of rocks. In connection with a gradual exhaustion of coal reserves in shallower parts of deposits, the average working depth of all mines in the Upper Silesian Coalfield increases by some tens of meters every year, the deepest workable levels reaching actually about 1000 m. This brings about that the problem of a steady control of rock effort of a suitable siting of main workings and the adaptation of mining methods to conditions of an increased rock pressure leave the field of research and experimental work and become a field of everyday engineering practice. Therefore the measuring methods should be possibly simple and adapted to technical possibilities of measurements at an average face in mine. The tests carried out for several years by the Central Mining Institute covered three groups of measuring methods, namely: - destressing methods, - compensation methods, - isotopic methods. They will be characterized successively from the view point of experiments resulting from their practical use, advantages and disadvantages of individual methods. Destressing methods The destressing methods, as it is well known consist in measuring the recovery of a part of rock affected by a full or partial trepanation. In such a case, only recoverable (elastic) strains can be covered by measurement. For determination of the accuracy of measurement taken by this method it is necessary to know rheological properties of rocks and proportions of individual kinds of strains (elastic and meta-elastic) resulting from. As it was shown by laboratory tests carried out by the Central Institute the main rocks of Carboniferous (sandstone, mudstone and coal) show complicated, non-linear rheological properties.
