Strain Localization Simulation Of Rock Based On Strain-softening Model

In this paper, regarding the lateral deformation as the main observations and using uniaxial compression test and resistance strain monitoring to explore the relationship between starts and features of rock strain localization phenomena and characteristics of rock deformation and failure; Using numerical simulation method,based on strain softening constitutive, considering the changes of the strength parameters of rock after peak value, confining pressure and initial defect factors,combining rock failure characteristics and shear bands form, exploring rock the whole process of stress-strain strain localization, get the following conclusions:1) Experimentally derived the ratio of strain localization startup stress σB and peak stress σd were 0.42,0.44,0.58, test results of strain localization of rock start that began roughly in the middle and late stages of rock stable crack growth, startup of rock strain localization began roughly in the middle and late stages of rock stable crack growth, relatively obvious in stages of crack accelerated expansion; Three rock damage morphology from uniaxial compression test corresponding to specific strain localization process.2) Decay modes of shear strength parameters after the peak have a significant impact on the stress-strain relationship of rock samples and affect the average lateral strain characteristics relatively small. While considering the lateral strain of rock samples in different locations, the results from decay modes of shear strength parameters after the peak is significantly different, the final form of the rock sample is not the same and strain localization phenomena also have different performance.When the "X" type of shear zones and near-vertical shear zone, compared with shear zone concentrated in the local area, strain localization performance is not obvious,Strain localization performance is clearly and closely related to shear zones form.3) Strain localization phenomenon is fairly different when confining pressure is different. When lithologic conditions are consistent, under low and middle confining pressure, the rock sample strain localization phenomenon is quite obvious, with the increase of confining pressure, differences of rock samples lateral strain in different position decreases, strain localization phenomenon is gradually unconspicuous,deformation of various parts of the rock samples tended to the overall cooperative deformation.4) While rock samples exist initial defect, it has a relatively large impact ondeformation, strength and shear zone form. Shear zone form can be divided into single oblique shear plane and "V-type" wedge shear zone, shear zone were developed in the defect location. When the inclination and length of shear zone is maximal, it has the biggest peak strength and smallest residual strength, strain can concentrate near the shear zone, strain localization phenomenon is relatively evident.5) Using FLAC3 D software respectively base on Mohr-Coulomb model and strain softening model that considering strength degradation to analyse, when using the strain-softening model, rock exhibit more pronounced deformation phenomena after the peak, relief area has a wider range, pressure of bearing pressure zone is reduced, shear stress concentration area of overburden rock has a wider range, so that the scope of the destruction of overlying strata produce larger. Thus, it is dangerous for engineering when ignores rock strength decreases after peak to carry on numerical analysis.