تاثير پارامترهاي هندسي و تنش بر تغيير شكل پذيري، مقاومت و رفتار پس از مقاومت نهايي توده سنگ هاي درزه دار با استفاده از روش DFN-DEM

چكيده انگليسي :

116 Effects of Geometrical Properties and stress on Deformability Strength and Post Peak Behavior of fractured Rock Masses Using DEM DFN Approach Alireza Khani a khani@mi iut ac ir March 15th 2011 Department of Mining Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language Farsi Supervisors Alireza Baghbanan E mail bagh110@cc iut ac ir Hamid Hashemalhoseini E mail hamidh@cc iut ac ir Abstract Knowledge of mechanical and strength parameters and also post peak behavior of rock masses are of considerable importance in designing and analyzing different rock engineering structures Determination of these parameters with the lowest degree of uncertainty is imperative in economic and safety of rock engineering projects In this thesis the effects of fracture intensity and stress on deformability elastic strength and post peak behavior of fractured rock masses are investigated The concepts applied in this research work are the fundamental principles of the general theory of elasticity Representative Elementary Volume REV the compliance tensor and the strength criteria of fractured rocks With inadequate and small scales of rock sample such investigations may not be possible to conduct in laboratory scale which necessitates the development of new approaches The effects of geometrical properties such as fracture densities on elastic properties strength post peak behavior and REV have not been investigated and reported in literature There exist different methods for calculating the mentioned parameters of rock masses Experimental analytical and numerical approaches One of the most effective methods is utilizing a hybrid numerical Discrete Fracture Network Distinct Element Method DFN DEM to study the effects of geometrical parameters and stress on deformation modulus Poisson s ratio strength and post peak behavior of fractured rock masses Numerous DFN models with variable fracture intensities and sizes were generated by means of Monte Carlo simulation method In order to determine the deformability parameters elastic strength and post peak behavior using the DFN DEM method and UDEC code the compliance tensors for DEM models with variable geometrical patterns were calculated and the stress strain curves for these models were studied Accordingly considering the scale and stress effects the REVs related to mechanical and stress parameters for DEM models with particular fracture intensities were determined The results show the significant effect of fracture intensity on deformation modulus Poisson s ratio and elastic strength of fractured rocks The results highlight a negative correlation between the fracture intensity up to 6 9 m2 the calculated values of E and decrease drastically about 50 compared to the models with and the values of strength and deformability parameters of the DEM models When fracture density is increased density of 2 3 m2 Moreover a twofold increase in the fracture intensity yields a decrease in the mentioned values over 30 An increase in the applied stress yields to the increase of deformation modulus and strength Compared with the Hoek Brown criterion the Mohr Coulomb strength stress envelope provides a better fit to the results of numerical tests The post peak behavior of fractured rock masses one of the subjects which have insufficiently been detected in the literature has been analyzed on the basis of DFN DEM concept in this paper In the situations that instability occurs in the DEM models the work hardening behavior proceeding failure is often observed Keywords Discrete Fracture Network Discrete Element Method Compliance Tensor Representative Elementary Volume Elastic Strength Fracture Intensity

خاني، عليرضا

تاثير پارامترهاي هندسي و تنش بر تغيير شكل پذيري، مقاومت و رفتار پس از مقاومت نهايي توده سنگ هاي درزه دار با استفاده از روش DFN-DEM

شبكه شكستگي هاي مجزا , روش المان هاي مجزا , ماتريس