A new back analysis is proposed for identifying deformational mechanism of a jointed rock mass around a large cavern. Joint slip displacements are treated as the main unknown parameters to be determined from measured displacements. Results, obtained by considering Mohr - Coulomb failure criterion on joint planes, indicate that the method could be a promising tool for safety assessment of a monitored cavern.
On propose une nouvelle retroanalyse pour identifier le mecanisme de deformation d'un massif rocheux diaclase autour d'une grande caverne. On traite les deplacements par glissement de diaclases comme les principaux parametres inconnus a être determines a partit des deplacements mesures, Les resultats obtenus en considerant Ie critere de rupture de Mohr-Coulomb sur les plans de diaclases, indiquent que la methode pourrait être un outil prometteur pour l'evaluation de la securite d'une caverne auscultee.
Es wird eine neue Rueckrechnung vorgeschlagen, um den Verformungsmechanismus eines gekluefteten Gebirges um eine große Kaverne zu identifizieren. Kluftgleitverschiebungen werden als die hauptsachlichen unbekannten Parameter behandelt, die, mittels der gemessenen Verschiebungen bestimmt werden muessen. Ergebnisse, die unter Beruecksichtigung des Mohr-Coulombschen Bruchkriteriumsauf den Kluftebenen erhalten wurden, zeigen, daß die Methode ein vielversprechendes Hilfsmittel fuer die Sicherheitasabschatzung einer beobachteten Kaverne sein könnte.
Observational procedures are now employed commonly for most geotechnical engineering projects in recent years. Excavation of a large underground cavern is one such example, Information collected prior to excavation of a main cavern, such as geological data, in-situ stresses, rock mass deformability, etc., helps us form a representative model of the rock mass and compute deformational responses to excavation in a predictive manner. However, we all know that the prediction is just a prediction and the real behavior of the rock mass has to be monitored step by step to obtain an improved model of the rock mass in concern and to confirm the cavern stability based on observation. Of all types of data gathered for this purpose, displacement measured within rock masses is one of the most important data types that could be interpreted in many different ways but has to be interpreted with the best method possible to realize safety assessment of the highest quality.
In this paper, one possible alternative for interpretation of displacements measured within discontinuous rock masses is introduced. The concept and brief mathematical definition are presented, firstly, which is followed by an application example incorporating the latest modification of the back analysis procedure considering Mohr - Coulomb failure criterion on joint planes.
The method of back analysis introduced in this paper, views a rock mass as illustrated in Figure 1.
(Figure in full paper)
Of the six components comprising the total compliance, the two corresponding to nonelastic slip deformation for joint sets 1 and 2 are the most difficult to be defined compared to the other four, because of general complexities in geological conditions and inhomogeniety in strength and deformational characteristics of rock joints.
