Failures occuring with underground openings of large section without locking depend on stress field, its orientation, the physical characteristics of the rocky environment of openings, the geometry of openings and the character of discontinuity. In this case the quantity, orientation and quality of discontinuity is meant by the character of discontinuity. Rheological properties of rocks and discontinuity are mainly responsible for failures. Consequently, stress field, deformation field and displacement field after driving the opening should be determined by considering the rheological properties of rocks. As next step the assessed system of discontinuity should be drawn around the Opening and rock bloks tending to move off potentially should be subjected to stability investigation. It is made possible by test results that by considering the character of the surfaces of discontinuity and its frequency the sections of openings requiring locking can be indicated.
Die bei den Untergrundhöhlen mit grossem Profil ohne Sicherung eintretenden Einbrueche haugen vorn primaren Spannungsfeld, von dessen Orientierung, von den physikalischen Eigenschaften der Gesteinsumgebung der Anlage, der Geometrie der Höhle sowie vom Character der Klueft igkeit ab. Beim Eintreten der Einbrueche spielen rheologischen Eigenschaften des Gesteinkörpers und die Klueftigkeit die Hauptrolle. Dementsprechend muss das Spannungs- Deformations- und Verschiebungsfeld nach Strecken abbau mit Beruecksichtigung der rheologischen Eigenschaften des Gesteins bestimmt werden. Es ist der folgende Schritt, das bemcssene Kluef''tigkeitssystem um die Höhle zu zeichnen und diejenigen Gesteinblöcke, die potentiell zur Verschiebung geneigt sind, einer Stabilitatsuntersuchung zu unterwerfen. Als Ergebnis der Untersuchung können mit Beruecksichtigung des Charakters und des Haufigkeitswerts der Klueftigkeitsflachen diejenigcn Strecken angesetzt werden, an denen Versicherungsanlagen gebaut werden muessen.
Les ruptures de toit des cavites souterraines de grande dimensions dependent du champ de contraint primaire et de son orientation, des proprietes de I'' environnement rocheux, de la g eometric de la cavite ainsi que de la presence des discontinuites. La discontinuite doit être exprimee par les mesures, I'' orientation et la qualite. Ce sont le comportement rheologique et la discontinuite qui jouent le rôle plus important au cours des ruptures. Les champs de contraint et de mouvernent doivent être dêterminês en tenant compte des propriêtês rheologiques des roches. Le pas suivant doit être de projeter le systerne de disco ntinuite rnesure autours de la cavite, et executer une analyse de stabilite des blocs potenciellement prêts aux movements. Les sections, où un soutènernent doit être assure peuvent être determinees à I'' aide de caractère et de frequence des discontinuites comme le resultat de notre consideration.
The choice of safety system in case of underground openings, caves of large section is made possible by knowing the primary state of stress, the rock-physical characteristics, and the regularity of mechanical processes due to geological effects. In favourable conditions it is not necessary to ensure the safety of openings by the means of special built-in mechanism, because the developing state of stress does not cause any failure in the environment of the opening. Even in such cases local failure may occur in some sections.
The driving of openings is accompanied by failures expanded in time. This phenomenon can be explained by discontinuity dividing rock bodies into bloks, consequently mechanical regularities due to geological effects should be investigated.
Rocky environment before starting building activity is inactive and this state of stress is called primary state of stress (if rocky environment is disturbed e. g. by other mining caverns, then the state of stress before starting building is considered as quasi-primary state). This state at depth H is represented by stress tensor Fp (H) having as a rule general orientation instead of horizontalvertical one
