scholarly journals The anisotropic mechanical characteristics of layered rocks under numerical simulation

2021 ◽  
Author(s):  
Xiao Zhuo ◽  
Xiangjun Liu ◽  
Xiangchao Shi ◽  
Lixi Liang ◽  
Jian Xiong
Keyword(s):  
Numerical Simulation ◽  
Triaxial Compression ◽  
Strength Properties ◽  
Wellbore Stability ◽  
Formation Condition ◽  
Compression Tests ◽  
Rock Matrix ◽  
True Triaxial ◽  
Anisotropic Mechanical Properties ◽  
Weak Plane

AbstractLayered rocks pose the challenge of wellbore stability in drilling engineering because of the anisotropic mechanical properties caused by the distinct weak planes. To understand the significant anisotropy of layered rocks in real formation condition, true triaxial compression tests are conducted by numerical simulation in this study. It is revealed that the mechanical responses of layered rocks are either controlled by the rock matrix or dominated by the weak plane and exhibit three different types associated with the orientations of the weak plane (including the dip direction α and dip angle β). When the orientations of the weak plane are α = 0°–90° and β = 0°, 60°–90°, the failure and strength properties of layered rocks depend entirely on the rock matrix, classified to the first type. Whereas the layered rocks with angle α ≤ 45° and β = 15°–45° fail by slipping failure along the weak plane, the relationship curves of rock strength versus the intermediate principal stress (σ2) are downward convex parabolas. In the last type, the mechanical behaviors of layered rocks with α > 45° and β = 15°–45°, involved in the changes of failure mode and the strength curve, are complex. Besides, the limitation of the simulation is discussed, and further studies on layered rocks are essential.

Anisotropic shear strength of a residual soil of sandstone

2008 ◽  
Vol 45 (3) ◽  
pp. 367-376 ◽  
Author(s):  
Adriano Virgilio Damiani Bica ◽  
Luiz Antônio Bressani ◽  
Diego Vendramin ◽  
Flávia Burmeister Martins ◽  
Pedro Miguel Vaz Ferreira ◽  
...  
Keyword(s):  
Shear Strength ◽  
Effective Stress ◽  
Yield Surface ◽  
Triaxial Compression ◽  
Strength Properties ◽  
Triaxial Tests ◽  
Residual Soil ◽  
Compression Tests ◽  
Soil Stiffness ◽  
Particle Bonding

This paper discusses results of laboratory tests carried out with a residual soil originated from the weathering of eolian sandstone from southern Brazil. Parent rock features, like microfabric and particle bonding, are remarkably well preserved within this residual soil. Stiffness and shear strength properties were evaluated with consolidated drained (CID) and consolidated undrained (CIU) triaxial compression tests. Undisturbed specimens were tested with two different orientations between the specimen axis and bedding surfaces (i.e., parallel (δ = 0°) or perpendicular (δ = 90°)) to investigate the effect of anisotropy. When CID triaxial tests were performed with δ = 0°, the yield surface associated with the structure was much larger than when tests were performed with δ = 90°. Coincidently, CIU tests with δ = 0° showed peak shear strengths much greater than for δ = 90° at comparable test conditions. Once the peak shear strength was surpassed, CIU tests followed collapse-type effective stress paths not shown by corresponding tests with remolded specimens. A near coincidence was observed between the yield surface determined with CID tests and the envelope of collapse-type effective stress paths for δ = 0° and δ = 90°.

Mechanical Properties of Bentonite-Sand Mixtures Under Triaxial Stress Condition

1994 ◽  
Vol 353 ◽  
Author(s):  
M. Umedera ◽  
A. Fujiwara ◽  
N. Yasufuku ◽  
M. Hyodo ◽  
H. Murata
Keyword(s):  
Mechanical Properties ◽  
Shear Strength ◽  
Water Content ◽  
Triaxial Compression ◽  
Confining Pressure ◽  
Strength Properties ◽  
Compression Tests ◽  
Optimum Water Content ◽  
Triaxial Compression Tests ◽  
Optimum Water

AbstractA series of triaxial compression tests is being conducted under the drained condition on bentonite and sand mixtures, known as buffer, in saturated and optimum water content states to clarify the mechanical properties of the buffer.It was found that the mechanical properties of bentonite and sand mixtures are strongly influenced by water and bentonite contents: shear strength in a saturated state is less than that in an optimum water content state; shear strength decreases rapidly with increasing bentonite content. Strength properties are much dependent on confining pressure.

scholarly journals Leaching Impact on Compressibility and Shear Strength of Undisturbed and Cement-treated Champlain Sea Clay

2021 ◽  
Author(s):  
Mohammad Afroz
Keyword(s):  
Shear Strength ◽  
Triaxial Compression ◽  
Strength Properties ◽  
Experimental Results ◽  
Salinity Level ◽  
Compression Tests ◽  
Treated Sample ◽  
Salinity Levels ◽  
Geotechnical Tests ◽  
The Impact

This research investigated the impact of leaching on the compressibility and shear strength properties of undisturbed and cement-treated Champlain Sea clay. A total of five undisturbed clay samples were leached with distilled water in the laboratory to reduce the salinity from initial values ranging from 9.5 to 15 g/L to the salinity values of 2.75, 1.45, 1.03, 0.55, and 0.35 g/L. A series of geotechnical tests were conducted on these samples at different salinity levels, including constant rate of strain consolidation tests, consolidated isotropic undrained triaxial compression tests, and vane shear tests. The experimental results showed that leaching leads to an increase in the compressibility and a reduction in shear strength of undisturbed Champlain Sea clay. The experimental results revealed that cement, mixed at a dosage of 50 kg/m3 , can significantly decrease the compressibility and increase the shear strength of Champlain Sea clay. A leached cement-treated sample exhibits a relatively higher compressibility than that of unleached cementtreated one. An increase in compressibility was also observed as salinity declines for the cementtreated samples. Moreover, a cement-treated sample at a lower salinity level displays slightly a higher shear strength compared to that of a cement-treated sample at the original salinity level.

INFLUENCE OF BALLAST GRAIN SHAPE ON ITS STRENGTH PROPERTIES

2017 ◽  
pp. 148-160
Author(s):  
Alexey Kolos ◽  
Pavel Chistyakov ◽  
Alexey Leus ◽  
Yevgeniy Shekhtman ◽  
Valeriy Shtykov
Keyword(s):  
Internal Friction ◽  
Grain Shape ◽  
Triaxial Compression ◽  
Practical Importance ◽  
Major Effect ◽  
Strength Properties ◽  
Compression Tests ◽  
Dynamic Impact ◽  
Angle Of Internal Friction ◽  
Different Shapes

Objective: To assess the influence of grain shape in railroad ballast, taking dynamic impact of moving trains, on its strength properties – unit bite and the angle of internal friction. Methods: Laboratory compression tests of 25–60 mm fracture ballast stone were carried out with different shapes of grains in a triaxial compression tool by the method of consolidated R-tests. Results: The values of ballast stone unit bite and the angle of internal friction with a different degree of grain rounding were obtained. Test findings demonstrate major effect of ballast stone grain shape on its unit bite, which reduced up to 60–70 % in certain trials depending on the degree of grain rounding. Practical importance: New results were obtained which make it possible to specify the amount of reclaimed ballast, returned to track after fine cleaning, depending on the degree of grain rounding.

Behavior of EPS geofoam in true triaxial compression tests

2008 ◽  
Vol 26 (2) ◽  
pp. 175-180 ◽  
Author(s):  
Chin Jian Leo ◽  
M Kumruzzaman ◽  
Henry Wong ◽  
Jin H Yin
Keyword(s):  
Triaxial Compression ◽  
Compression Tests ◽  
Eps Geofoam ◽  
True Triaxial ◽  
True Triaxial Compression ◽  
Triaxial Compression Tests

scholarly journals Experimental Investigation on the Deformation, Strength, and Acoustic Emission Characteristics of Sandstone under True Triaxial Compression

2018 ◽  
Vol 2018 ◽  
pp. 1-16 ◽  
Author(s):  
Zhaolin Li ◽  
Lianguo Wang ◽  
Yinlong Lu ◽  
Wenshuai Li ◽  
Kai Wang
Keyword(s):  
Acoustic Emission ◽  
Axial Strain ◽  
Triaxial Compression ◽  
Confining Pressure ◽  
Lateral Strain ◽  
Compression Tests ◽  
True Triaxial ◽  
Shear Slip ◽  
True Triaxial Compression ◽  
Triaxial Compression Tests

The study of deformation, strength, and other mechanical characteristics of sandstone under true triaxial compression is significant for understanding failure mechanisms in rock and evaluating the stability of underground structures. Conventional and true triaxial compression tests for sandstone are conducted for different stress states in this study using the self-developed true triaxial electrohydraulic servo test system combined with acoustic emission (AE) testing. This study presents an in-depth and systematic investigation of deformation, strength, and AE characteristics. The results show significant differences in deformation, strength, and acoustic emission characteristics for the rock under conventional triaxial and true triaxial compression tests, respectively. The peak strength, axial strain, lateral strain, and incremental strain (in unstable crack growth stage) increase with increasing confining pressure under conventional triaxial compression, and the AE count gradually decreases while shear crack proportion gradually increases, indicating that increasing confining pressure gradually inhibits the shear slip effect along fractures, delays perforation of the rock shear fracture surface, and enhances the ability of the rock to withstand deformation and load. Under true triaxial compression, the peak strength increases and then decreases with increasing intermediate principal stress σ2 and the axial strain ε1 and lateral strain ε2 gradually decrease; besides, the lateral strain (expansion) of the rock is mainly in the minimum principal stress σ3 direction, and lateral expansion tends to decrease before increasing. AE events first weaken and then enhance with increasing σ2, and the proportion of shear cracks increases first and then decreases, indicating that the confining pressure gradually changes from the shear slip effect that controls crack offset to the damage effect that promotes crack tension with increasing σ2. In addition, the protective effect of confining pressure improves when σ3 increases.

Study of Constitutive Model of the Schist under Natural and Saturated Condition

2013 ◽  
Vol 444-445 ◽  
pp. 1326-1334
Author(s):  
Xi Xi Zhu ◽  
Cong Xin Chen ◽  
Yun Zheng ◽  
Guan Wen Cheng ◽  
Yi Chao Zhou
Keyword(s):  
Rock Mass ◽  
Constitutive Model ◽  
Rock Slope ◽  
Triaxial Compression ◽  
Guangdong Province ◽  
Strength Properties ◽  
Deformation Characteristics ◽  
Compression Tests ◽  
Micro Cracks ◽  
Triaxial Compression Tests

Taking the schist as investigative subject, which is the weak layer widely distributed in Yun Fu pyrite, Guangdong province, the deformation characteristics and strength properties of the schist rock mass are analyzed through laboratory uniaxial and triaxial compression tests. Based on the tests on natural and saturated schist, the elastic constitutive equations of the schist, considering the closing of micro cracks, are established; and the deformation characteristics and strength properties of water-weakening influence is analyzed. Through the tests, the deformation characteristics and strength properties of the schist are further understood, which can give some advices to the design of rock slope containing weak layers of the schist.

scholarly journals Effect of drainage and saturation on undrained shear strength for compacted sandy soils

2019 ◽  
Vol 92 ◽  
pp. 07003
Author(s):  
Yukio Nakata ◽  
Tetsuya Tashita ◽  
Hiromu Chibana ◽  
Kenji Matsukata
Keyword(s):  
Triaxial Compression ◽  
Strength Properties ◽  
Undrained Shear Strength ◽  
Degree Of Saturation ◽  
Compression Tests ◽  
Compacted Soils ◽  
Partially Saturated ◽  
Saturated Condition ◽  
Undrained Strength ◽  
Triaxial Compression Tests

Collapses of embankments have occurred due to heavy rainfall. It is very important to understand the strength properties under various unsaturated, partially saturated and fully saturated conditions of compacted materials. So, a series of unsaturated and saturated triaxial compression tests for compacted soils have been conducted to understand the effects of drainage and saturation on undrained strength. Soil samples were collected from several road embankments to carry out the experiments. The undrained (CU) strength of compacted material decreased with increase in the degree of saturation. Especially, the strength decreased from partially saturated condition to fully saturated condition was remarkable. The decrease of the materials with volume contractive behaviour was appeared clearly.

scholarly journals Determination of Holmquist–Johnson–Cook Constitutive Parameters of Coal: Laboratory Study and Numerical Simulation

Processes ◽  
2019 ◽  
Vol 7 (6) ◽  
pp. 386 ◽  
Author(s):  
Beijing Xie ◽  
Zheng Yan ◽  
Yujing Du ◽  
Zeming Zhao ◽  
Xiaoqian Zhang
Keyword(s):  
Numerical Simulation ◽  
Constitutive Model ◽  
Split Hopkinson Pressure Bar ◽  
Impact Damage ◽  
Triaxial Compression ◽  
Model Parameters ◽  
Compression Tests ◽  
Hopkinson Pressure Bar ◽  
The Impact ◽  
Constitutive Parameters

The main sensitivity parameters of the Holmquist–Johnson–Cook constitutive model for coal were obtained from a variety of tests such as uniaxial compression, uniaxial cyclic loading, splitting and triaxial compression tests, as well as the indirect derivation equation of a briquette. The mechanical properties of briquettes under dynamic impact were investigated using a split Hopkinson pressure bar experiment. Based on the experimental measurement of the Holmquist–Johnson–Cook constitutive model, the numerical simulation of briquette was performed using ANSYS/LS-DYNA software. A comparison between experimental and simulation results verified the correctness of simulation parameters. This research concluded that the failure of briquette at different impact velocities started from an axial crack in the middle of the coal body, and the sample was swollen to some extent. By the increase of impact velocity, the severity of damage in the coal body was increased, while the size of the coal block was decreased. Moreover, there was good compliance between experimental and simulated stress wave curves in terms of coal sample failure and fracture morphology at different speeds. Finally, the parameters of the validated Holmquist–Johnson–Cook constitutive model were applied to the numerical simulation model of the impact damage of heading face and the process of coal seam damage in the roadway was visually displayed. The obtained results showed that the Holmquist–Johnson–Cook constitutive model parameters suitable for the prominent coal body were of great significance for the improvement and exploration of the occurrence mechanism of coal and rock dynamic disasters.

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