Characteristic Stress Levels and Brittle Fracturing of Hard Rocks Subjected to True Triaxial Compression with Low Minimum Principal Stress

2018 ◽  
Vol 51 (12) ◽  
pp. 3681-3697 ◽  
Author(s):  
Yao-Hui Gao ◽  
Xia-Ting Feng ◽  
Xi-Wei Zhang ◽  
Guang-Liang Feng ◽  
Quan Jiang ◽  
...  
Keyword(s):  
Principal Stress ◽  
Triaxial Compression ◽  
True Triaxial ◽  
Hard Rocks ◽  
Minimum Principal Stress ◽  
Stress Levels ◽  
True Triaxial Compression ◽  
Characteristic Stress

A Three-Dimensional Failure Criterion for Hard Rocks Under True Triaxial Compression

2019 ◽  
Vol 53 (1) ◽  
pp. 103-111 ◽  
Author(s):  
Xia-Ting Feng ◽  
Rui Kong ◽  
Chengxiang Yang ◽  
Xiwei Zhang ◽  
Zhaofeng Wang ◽  
...  
Keyword(s):  
Failure Criterion ◽  
Triaxial Compression ◽  
Three Dimensional ◽  
True Triaxial ◽  
Hard Rocks ◽  
True Triaxial Compression

Effect of high differential stress and mineral properties on deformation and failure mechanism of hard rocks

2020 ◽  
Author(s):  
Xia-Ting Feng ◽  
Jun Zhao ◽  
Zhaofeng Wang ◽  
Cheng-Xiang Yang ◽  
Qiang Han ◽  
...  
Keyword(s):  
Triaxial Compression ◽  
Strain Curve ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Differential Stress ◽  
Deformation And Failure ◽  
True Triaxial ◽  
Elastic Plastic ◽  
Hard Rocks ◽  
True Triaxial Compression

In order to study the deformation and failure mechanism of hard rocks, true triaxial compression tests were conducted on four type of hard rocks to obtain the complete stress-strain curve and failure modes. Under true triaxial compression condition, the shape of the complete stress-strain curve can be divided into three types: elastic-brittle (EB), elastic-plastic-brittle (EPB), and elastic-plastic-ductile (EPD) types. According to the different post-peak deformation behaviours, the stress-strain curves of elastic-plastic-brittle (EPB) type can be subdivided into three sub-categories: post-peak instantaneous brittle (EPB-I) type, post-peak multi-stage brittle (EPB-M) type, and post-peak delayed brittle (EPB-D) type. The stress-strain curves change from EPD to EPB-D to EPB-M to EPB-I to EB with increasing differential stress (σ2-σ3). The deformation characteristics are dependent on the σ2, σ3, mineral composition and mineral texture to the rock sample. An increase in σ3 leads to an increased ductility, while an increase in σ2 leads to an increased brittleness. Moreover, rocks with regular mineral texture and low mineral hardness are more prone to ductility. When the deformation curve is transformed from EPD to EPB to EB, the tensile crack is gradually dominant, and the macroscopic failure angle is gradually steeper.

Strain energy evolution characteristics and mechanisms of hard rocks under true triaxial compression

2019 ◽  
Vol 260 ◽  
pp. 105222 ◽  
Author(s):  
Yan Zhang ◽  
Xia-Ting Feng ◽  
Xiwei Zhang ◽  
Zhaofeng Wang ◽  
Mostafa Sharifzadeh ◽  
...  
Keyword(s):  
Strain Energy ◽  
Triaxial Compression ◽  
Energy Evolution ◽  
True Triaxial ◽  
Hard Rocks ◽  
Evolution Characteristics ◽  
True Triaxial Compression

scholarly journals Influence of end effect on rock strength in true triaxial compression test

2017 ◽  
Vol 54 (6) ◽  
pp. 862-880 ◽  
Author(s):  
Y.H. Xu ◽  
M. Cai ◽  
X.W. Zhang ◽  
X.T. Feng
Keyword(s):  
Principal Stress ◽  
Failure Criterion ◽  
Rock Strength ◽  
Triaxial Compression ◽  
Numerical Approach ◽  
Compression Testing ◽  
End Effect ◽  
True Triaxial ◽  
The Coefficient Of Friction ◽  
True Triaxial Compression

The influence of the end effect on rock strength in true triaxial compression testing was studied using a numerical approach. The influence of the intermediate principal stress (σ2) on rock strength was isolated by using the two-dimensional Mohr–Coulomb failure criterion that depends only on the major principal stress (σ1) and minor principal stress (σ3). Thus, any enhancement to the rock strength with the increase of σ2 can be attributed to the end effect. It was shown that the end effect can result in an apparent σ2 effect, as long as the coefficient of friction (μ) at the rock specimen – steel platen contacts is not zero and the specimen in the σ2 loading direction is squat. When the strengthening due to the increase of σ2 predicted by a theoretical failure criterion was added to the strengthening due to the end effect, the results were in good agreement with the observed σ2 effect from some previous laboratory tests, indicating that the observed σ2 effect in true triaxial compression testing could be partially influenced by the end effect, particularly when σ3 was low. It is suggested to decrease the end effect to a level where the apparent σ2 effect is very small so that the obtained test results are more meaningful to characterize the actual σ2 effect.

Generalized crack damage stress thresholds of hard rocks under true triaxial compression

2019 ◽  
Vol 15 (3) ◽  
pp. 565-580 ◽  
Author(s):  
Yaohui Gao ◽  
Xia-Ting Feng ◽  
Xiwei Zhang ◽  
Yangyi Zhou ◽  
Yan Zhang
Keyword(s):  
Triaxial Compression ◽  
True Triaxial ◽  
Hard Rocks ◽  
Crack Damage Stress ◽  
True Triaxial Compression
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