The paper presented proposes methods for evaluating rock massif stability in constructing large underground openings. Two types of stability massif loss are discussed. First of all instability around large underground openings is conditioned by failure in some zones near the opening due to stress concentration. Secondly instability of rock massif may be conditioned by rockfalls. The geomechanical criterion characterizing the tendency of the jointed rock to spontaneous fall its own weight is proposed.


On propose les methodes de l'evaluation de la stabilite du massif au temps du traçage des galeries à grande section à l'expose. En premier lieu, on examine la perte de la stabilite des roches autour des ouvrages souterrains, conditionnee par l'attaque des roches dans les zones limitees près des ouvrages à cause de concentration des contraintes. En second lieu, la perte de la stabilite du massif peut être condition- nee par l'attaque des roches. On a propose le critère geomecanique caracterisant la capacite des roches fissurees à la chute brusque sous l'action du poids proper.


Im Vorschlag werden die Bewertungsmethoden der Gesternsstandfestigkeit im Laufe der Errichtung der Untertagebauten groβen Querschnitts vorgelegt. Zwei Typen des Verlusts der Gesternsstandfestigkeit werden besprochen. Erstens, der Verlust der Gesternsstandtestigkeit rings um den Groβuntertagebauten her durch die Gesternszerstorung..inner- halb der Grenzen unweit vom Untertagebau infolge der Spannungsanhaufung wird betrachtet. Zweitens, der Verlust der Gesteinsstandfestigkeit kann durch die Gesternszerstorung bedrungt werden. Das geomechanische Kriterium, das die Fahrgkeit klueftigen Gesterns zum unerharteten ergenmassekraftigen Bruch charakterisiert, wird vorgelegt.


Stability evaluation for proposed underground openings is an important stage in the design of those openings. The purpose of stability evaluation is preliminary identification of the category and degree of stability of underground openings during their construction according to table 1. Obviously that a technology of excavating and a type of support systems are depended on the above evaluation. We have identified two kinds of loss of unsupported underground openings stability, namely rocks failure near the excavations as a result of high stress to strength conditions, and spontaneous rock fall under its own weight due to faulting and jointing rock massive. The above mechanism and mode of instability take place most often in the practice. Physical nature of those phenomena being different, the evaluation criteria should also differ.


The estimation of rock behaviour resulting from failure at a great depth below surface or to a weak rocks is very important. In this case the H/6c ratio (where 6c is the compressive strength in the rock mass) is used for general estimation of rock stability (Stacey and Page, 1986). A more detailed picture of rock stability during excavation can be obtained from the information and sized of possible rock failure zone (nonelastic deformations) near the opening. There are methods of numerical analysis of the formation of the above zones. We have suggested the analytic approach to that problem. The proposed method consists of stress analysis around underground opening and of determining the boundary of the nonelastic deformations conditional zone. The stress analysis is based on solving the plane problem of the elasticity theory the design scheme of which is shown in Fig.1. There is the L opening of an arbitrary with one symmetry axis in the S elastic infinite plate simulating the underground excavation. This problem has been solved by the Kolosov-Muschelishvily method Using the analytical functions of Complex variables, conformal transformations and the Koshi integrals.

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