Effect of volume changes on complete deformation behavior of rocks

Abstract

For the purpose of describing the deformation characteristics of rocks, the effect of volume changes on mechanical properties of rocks should be taken into account with relation to the development of constitutive model. Firstly, rocks are divided into three parts, i.e., voids, a damaged part and an undamaged part in the course of loading. The void ratio was applied to describing the changes of voids or pores during the deformation process. Then, using statistical damage theory, a constitutive model was developed for rocks to describe their strain softening and hardening on the basis of investigating the relationship between the net stress and apparent stress, in which the influence of volume changes on rock behavior was correctly taken into account, such as the initial phase of compaction and the latter stage of dilation. Thirdly, a method of determining model parameters was also presented. Finally, this model was used to compare the theoretical results with those observed from experiments under conventional triaxial loading conditions.

Keywords

rock mechanics / constitutive model / statistical damage theory / volume change / void ratio

References

[1] KawamotoT., IchikawaY., KyoyaT.. Deformation and fracturing behavior of discontinuous rock mass and damage mechanics theory [J]. International Journal for Numerical and Analytical Methods in Geomechanics, 1988, 12(1): 1-30

[2] KaiserP. K., TangC. A.. Numerical simulation of damage accumulation and seismic energy release during brittle rock failure: Part II. Rib pillar collapse [J]. International Journal of Rock Mechanics and Mining Sciences, 1998, 35(2): 123-134

[3] BlairS. C., CookN. G. W.. Analysis of compressive fracture in rock using statistical techniques: Part II. Effect of microscale heterogeneity on macroscopic deformation [J]. International Journal of Rock Mechanics and Mining Sciences, 1998, 35(7): 849-861

[4] AubertinM., LiL., SimonR., KhalifS.. Formulation and application of a short term strength criterion for isotropic rocks [J]. International Journal of Rock Mechanics and Mining Sciences, 2000, 37(8): 1169-1193

[5] PanY. W., WenB. H.. Constitutive model for the continuous damage of brittle rock [J]. Geotechnique, 2001, 51(2): 155-159

[6] ColmenaresL. B., ZobackM. D.. A statistical evaluation of intact rock failure criteria constrained by polyaxial test data for five different rocks [J]. International Journal of Rock Mechanics and Mining Sciences, 2002, 39(6): 695-729

[7] LiuH. Y., KouS. Q., LindqvistP. A., TangC. A.. Numerical studies on the failure process and associated micro-seismicity in rock under triaxial compression [J]. Tectonophysics, 2004, 38(4): 149-174

[8] BazantZ. P., PangS. D.. Activation energy based extreme value statistical and size effect in brittle and quasibrittle fracture [J]. Journal of Mechanics and Physics of Solids, 2007, 55(1): 91-131

[9] LemaitreJ.. A continuous damage mechanics model for ductile materials [J]. Journal of Engineering Materials and Technology, 1985, 107(1): 83-89

[10] CAO Wen-gui, ZHANG Sheng. Study on random statistical method of damage for softening hardening constitutive model of rock [C]// Proceedings of the 2nd China-Japan Geotechnical Symposium. Shanghai, 2005: 269–273.

[11] ShenZ.-jiang.. Breakage mechanics for geological materials: an ideal brittle-elasto-plastic model [J]. Chinese Journal of Geotechnical Engineering, 2003, 25(3): 253-257

[12] CaoW.-g., ZhaoH., ZhangL., ZhangY.-jie.. Damage statistical softening constitutive model for rock with consideration about damage threshold value and its parameter determination method [J]. Chinese Journal of Rock Mechanics and Engineering, 2008, 27(6): 1148-1154

[13] TangC.-an.Catastrophe in rock unstable failure [M], 1993, Beijing, The Coal Industry Press

[14] CaoW.-g., LiX., LiuFeng.. Discussion on strain softening damage constitutive model for fissured rock mass [J]. Chinese Journal of Rock Mechanics and Engineering, 2007, 26(12): 2488-2494

[15] CaoW.-g., LiX., ZhaoHeng.. Damage constitutive model for strain-softening rock based on normal distribution and its parameter determination [J]. Journal of Central South University of Technology, 2007, 14(5): 719-724

[16] LinZ.-y., WuY.-s., GuanL.-li.. Research on the brittle-ductile transition property of rocks under triaxial compression [J]. Chinese Journal of Rock and Soil Mechanics, 1992, 13(2): 45-51