Numerical evaluation of strength and deformability of fractured rocks
2013 (English)In: Journal of Rock Mechanics and Geotechnical Engineering, ISSN 1674-7755, Vol. 5, no 6, 419-430 p.Article in journal (Refereed) Published
Knowledge of the strength and deformability of fractured rocks is important for design, construction andstability evaluation of slopes, foundations and underground excavations in civil and mining engineering.However, laboratory tests of intact rock samples cannot provide information about the strength anddeformation behaviors of fractured rock masses that include many fractures of varying sizes, orientationsand locations. On the other hand, large-scale in situ tests of fractured rock masses are economically costlyand often not practical in reality at present. Therefore, numerical modeling becomes necessary. Numericalpredicting using discrete element methods (DEM) is a suitable approach for such modeling because of theiradvantages of explicit representations of both fractures system geometry and their constitutive behaviorsof fractures, besides that of intact rock matrix. In this study, to generically determine the compressivestrength of fractured rock masses, a series of numerical experiments were performed on two-dimensionaldiscrete fracture network models based on the realistic geometrical and mechanical data of fracturesystems from field mapping. We used the UDEC code and a numerical servo-controlled program forcontrolling the progressive compressive loading process to avoid sudden violent failure of the models.The two loading conditions applied are similar to the standard laboratory testing for intact rock samplesin order to check possible differences caused by such loading conditions. Numerical results show thatthe strength of fractured rocks increases with the increasing confining pressure, and that deformationbehavior of fractured rocks follows elasto-plastic model with a trend of strain hardening. The stresses andstrains obtained from these numerical experiments were used to fit the well-known Mohr-Coulomb (MC)and Hoek-Brown (H-B) failure criteria, represented by equivalent material properties defining thesetwo criteria. The results show that both criteria can provide fair estimates of the compressive strengthsfor all tested numerical models. Parameters of the elastic deformability of fractured models during elasticdeformation stages were also evaluated, and represented as equivalent Young’s modulus and Poisson’sratio as functions of lateral confining pressure. It is the first time that such systematic numerical predictingfor strength of fractured rocks was performed considering different loading conditions, with importantfindings for different behaviors of fractured rock masses, compared with testing intact rock samples undersimilar loading conditions.
Place, publisher, year, edition, pages
2013. Vol. 5, no 6, 419-430 p.
Strength, Deformability, Fractured rocks, Discrete element methods (DEM), Failure criteria
Engineering and Technology
IdentifiersURN: urn:nbn:se:kth:diva-155710DOI: 10.1016/j.jrmge.2013.09.002ScopusID: 2-s2.0-84901324491OAI: oai:DiVA.org:kth-155710DiVA: diva2:762150
QC 201411122014-11-102014-11-102014-11-11Bibliographically approved