ISRM Suggested Method: Determining Deformation and Failure Characteristics of Rocks Subjected to 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.

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Influence of Loading and Unloading Stress Paths on the Deformation and Failure Features of Jinping Marble Under True Triaxial Compression

Rock Mechanics and Rock Engineering ◽

10.1007/s00603-020-02104-4 ◽

2020 ◽

Vol 53 (7) ◽

pp. 3287-3301

Author(s):

Xia-Ting Feng ◽

Hong Xu ◽

Chengxiang Yang ◽

Xiwei Zhang ◽

Yaohui Gao

Keyword(s):

Triaxial Compression ◽

Deformation And Failure ◽

True Triaxial ◽

Loading And Unloading ◽

True Triaxial Compression ◽

Jinping Marble

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RETRACTED ARTICLE: ISRM Suggested Method for Determining Stress–Strain Curves for Rocks Under True Triaxial Compression

Rock Mechanics and Rock Engineering ◽

10.1007/s00603-017-1282-3 ◽

2017 ◽

Vol 50 (10) ◽

pp. 2847-2847 ◽

Cited By ~ 1

Author(s):

Xiwei Zhang ◽

Xia-Ting Feng ◽

Xiaochun Li ◽

Bezalel Haimson ◽

Kenichiro Suzuki

Keyword(s):

Triaxial Compression ◽

Suggested Method ◽

Stress Strain ◽

True Triaxial ◽

Retracted Article ◽

True Triaxial Compression

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Experimental Study of Size Effects on the Deformation Strength and Failure Characteristics of Hard Rocks under True Triaxial Compression

Advances in Civil Engineering ◽

10.1155/2021/6832775 ◽

2021 ◽

Vol 2021 ◽

pp. 1-15

Author(s):

Qiang Han ◽

Yaohui Gao ◽

Yan Zhang

Keyword(s):

Size Effect ◽

Sample Size ◽

Triaxial Compression ◽

Peak Strength ◽

Failure Characteristics ◽

True Triaxial ◽

Rock Samples ◽

True Triaxial Compression ◽

The Relationship ◽

Rock Size

Size effect has always been the focus of rock mechanics as a bridge between laboratory test and engineering site. Previously, the research conditions and objects of the rock size effect have mostly focused on cylindrical rock samples with different height-to-diameter ratios (H/Ds) under uniaxial or conventional triaxial compression, while there has been little research on the rock size effect under true triaxial compression (TTC), especially rectangular rock samples with different sizes and the same length-to-width-to-height ratio. Based on this, the deformation, strength, and failure characteristics of Beishan (BS) granite and Baihetan (BHT) basalt with different sample sizes under TTC were studied by a comparative analysis method. The size effect of deformation and failure characteristics under TTC are not obvious, including stress-strain curves, Young’s modulus, peak strains, failure angles, and macrofailure mode. However, the damage stress (σcd) and peak strength (σp) have obvious size effect; that is, the smaller the sample size is, the higher the strength is. Additionally, the relationship among the peak strength, sample size, and intermediate principal stress (σ2) is power function. In addition, by comparing the peak strength increment caused by the sample size of the two types of rocks, the σp of the fine-grained BHT basalt is more sensitive to sample size than that of the coarse-grained BS granite. Finally, by analyzing the relationship between the size of the mineral grains or clusters in the two types of hard rocks and the complexity of crack propagation in the fracture surface under TTC, it is suggested that the minimum side length of rock samples should not be less than 10 times the maximum mineral clusters (such as feldspar phenocrysts in BHT basalt). In addition, the method of estimating elastic strain is established by analyzing the relationship between the size of the rock sample σ2 and the elastic strain under TTC.

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