The material constants do not participate equally in developing the stress-, strain- and displacement stage generated when installing the support in underground openings, and excavations. The paper describes a method taking into calculation also the uncertainty of surrounding rocks with assigning the standard deviation of the different data of the final result to the standard deviation of the initial data.
Die Materialkonstanten beteiligen sich nicht mit gleichem Gewicht in der Ausbildung der Spannungs-, Verformungs- und Verschiebungszustande. Der Vortrag gibt eine Methode, die auch die Ungewissheit der Gebirgsumgebung ln Betracht zieht, die Standarddeviation der einzigen Daten des Endergebnisses der Standarddeviation den Ausgangsdaten zuordnend.
Les constantes du material ne participent pas egalement au developpement de la situation des tensions, deformations et deplacements qui se forment quand Ie soutenement des galeries et des cavites des mines est effectue. L''auteur donne la description d''une methode prenant en calculation aussi l''incertitude du terrain enveloppe, assignant la deviation des differents donnees a la deviation des donnees initiales.
When designing the support of underground roadways and openings there occurs generally an oversizing not to be determined that can not be justified by aiming at safety. This results on one hand from the fact that there is an uncertainty in the number of the nature parameters used for design, in the way of mea- suring them and in the reliability of the data obtained. On the other hand the design methods used do not adequately describe the behaviour of support with unduly idealizing the environment and using algorithms excessively simplifying and without Considering exactly all boundary conditions. In order to increase reliability and economic efficiency some processes correct the support parameters based on the high number of measurements and investigations carried out during execution with extrapolating the subsequent construction phases not known primarily.
The rock mechanical parameters can be detected by investigation results obtained by means of borings and samplings. These characteristics can show significant dispersion. In developing the arising stress, strain and displacement condition the material properties do not participate equally. We show a method which by taking into calculation also the uncertainty of the surrounding rocks tries to represent the environment in the most adequate way with illustrating the support method enabling the coaction of rock and support. Based on the parameter testing by the finite element method /FEM/ there can be established which data prove to be important from the point of view of the support design.
In the practice spatial problems are encountered both in mining and tunelling. The three dimensional testings of a given range requires one order higher computer capacity, calculating time /cpu/ and very sophisticated data preparation also a Hookean elasticity model compared to the plain /two dimensional/ testing. Therefore where it is not absolutely necessary using spatial programs is generlly avoided.
For the overwhelming majority of the cases occuring in pactice the plain testings are sufficient. However for special cases, e.g. the immediate surrounding of junctions, longwalls, parts near the face and very frequently changing soil and ground conditions, the three dimensional calculations prove to be indispensable.
The real situation can be well approximated by plain strain and therfore this model gives a good solution at an approximate distance of one and half road diameter from the face.
In order to investigate into the plain problems arising in our Institute isoparametric elements are used. The corresponding spatial element is the isoparametric hexahedron with 10 junctions applied for our spatial programs. Thus a high calculation accuracy can be reached with a relatively small number of elements andjunctions. For their employing we have well composed and proved programs. The FEM computation is based on continuum mechanical approach and therefore our loadings and boundary conditions have to be fixed in compliance with it.
