scholarly journals The Effect of Confining Pressure on the Mechanical Properties of Sand–Ice Materials

1973 ◽  
Vol 12 (66) ◽  
pp. 469-481 ◽  
Author(s):  
Bernard D. Alkire ◽  
Orlando B. Andersland
Keyword(s):  
Axial Strain ◽  
Triaxial Compression ◽  
Confining Pressure ◽  
Silica Sand ◽  
Creep Tests ◽  
Ice Volume ◽  
Coulomb Failure ◽  
Confining Pressures ◽  
Sand Material ◽  
Cylindrical Samples

Cylindrical samples containing 0.59 mm to 0.84 mm diameter silica sand at about 97% and 55% ice saturation (the ratio of ice volume to sand pore volume) were tested at a temperature of −12° C in triaxial compression. Both constant axial strain-rate tests and step-stress creep tests provide information on the influence of confining pressure on the shear strength and creep behavior of the sand–ice material. Changes in the degree of ice saturation help show the influence of the ice matrix versus the sand material on the mechanical behavior. Data are discussed in terms of the Mohr–Coulomb failure law and creep theories. It is shown that the cohesive component of strength depends on response of the ice matrix, whereas the frictional component of strength responds in a manner very similar to unfrozen sand tested at high confining pressures. Experimental data show that creep rates decrease exponentially and creep strength increases with an increase in confining pressure.

scholarly journals The Effect of Confining Pressure on the Mechanical Properties of Sand–Ice Materials

1973 ◽  
Vol 12 (66) ◽  
pp. 469-481 ◽  
Author(s):  
Bernard D. Alkire ◽  
Orlando B. Andersland
Keyword(s):  
Axial Strain ◽  
Triaxial Compression ◽  
Confining Pressure ◽  
Silica Sand ◽  
Creep Tests ◽  
Ice Volume ◽  
Coulomb Failure ◽  
Confining Pressures ◽  
Sand Material ◽  
Cylindrical Samples

Cylindrical samples containing 0.59 mm to 0.84 mm diameter silica sand at about 97% and 55% ice saturation (the ratio of ice volume to sand pore volume) were tested at a temperature of −12° C in triaxial compression. Both constant axial strain-rate tests and step-stress creep tests provide information on the influence of confining pressure on the shear strength and creep behavior of the sand–ice material. Changes in the degree of ice saturation help show the influence of the ice matrix versus the sand material on the mechanical behavior. Data are discussed in terms of the Mohr–Coulomb failure law and creep theories. It is shown that the cohesive component of strength depends on response of the ice matrix, whereas the frictional component of strength responds in a manner very similar to unfrozen sand tested at high confining pressures. Experimental data show that creep rates decrease exponentially and creep strength increases with an increase in confining pressure.

scholarly journals Experimental Research into the Evolution of Permeability of Sandstone under Triaxial Compression

Energies ◽  
2020 ◽  
Vol 13 (19) ◽  
pp. 5065
Author(s):  
Liming Zhang ◽  
Shengqun Jiang ◽  
Jin Yu
Keyword(s):  
Axial Strain ◽  
Triaxial Compression ◽  
Testing Machine ◽  
Volumetric Strain ◽  
Confining Pressure ◽  
Rate Of Change ◽  
Peak Strength ◽  
Sudden Increase ◽  
Seepage Pressure ◽  
Confining Pressures

Failure tests on sandstone specimens were conducted under different confining pressures and seepage pressures by using an MTS triaxial rock testing machine to elucidate the corresponding correlations of permeability and characteristic stress with confining pressure and pore pressure during deformation. The results indicate that permeability first decreases and presents two trends, i.e., a V-shaped increase and an S-shaped trend during the non-linear deformation stage. The greater the seepage pressure, the greater the initial permeability and the more obvious the V-shaped trend in the permeability. As the confining pressure was increased, the trend in the permeability gradually changed from V- to S-shaped. Compared with the case at a high confining pressure, the decrease of permeability occurred more quickly, the rate of change becomes greater, and the sudden increase observed in the permeability happened earlier under lower confining pressures. Within the range tested, confining pressure exerted a greater effect on the permeability than the seepage pressure. In comparison with the axial strain, volumetric strain better reflected changes in permeability during compaction and dilation of sandstone. The ratio of crack initiation stress to peak strength ranged from 0.37 to 0.50, while the ratio of dilation stress to peak strength changed from 0.58 to 0.72. Permeabilities calculated based on Darcy and non-Darcy flow changed within the same interval, while the change in permeability was different.

scholarly journals An Experimental Investigation of the Progressive Failure of Sandstone and Its Energy Evolution Characteristics

2018 ◽  
Vol 2018 ◽  
pp. 1-12
Author(s):  
Yan Chen ◽  
Baohua Guo
Keyword(s):  
Crack Propagation ◽  
Crack Closure ◽  
Progressive Failure ◽  
Axial Strain ◽  
Triaxial Compression ◽  
Confining Pressure ◽  
Energy Evolution ◽  
Evolution Characteristics ◽  
Confining Pressures ◽  
The Relationship

In this research study, the progressive failure and energy evolution characteristics of sandstone samples with different sizes were explored under uniaxial and triaxial compression conditions. The characteristic stresses and strains were captured using the crack axial strain levels and dissipative energy. The results showed that, with the increase in the ratios of the height to diameter (H/D), the crack closure stresses increased, while the crack damage stresses decreased. However, the levels of both the crack closure stresses and crack damages were observed to increase with the H/D. With increase in the confining pressure, it was found that the crack closure and crack damage stresses increased, while their levels decreased. The strains of the crack closures, peak crack axial, and crack propagation were observed to decrease with the H/D, while the crack closure strain levels increased. Also, the crack propagation strains were observed to increase with the confining pressures, while the crack closure, peak crack axial, and crack closure strain levels decreased. The progress failure of the sandstone samples was also obtained based on the evolution characteristics of the dissipative energy. The relationship between the energy densities during each phase and the H/D was also analyzed. It was determined that, with the increasing of the H/D, the input, elastic, and dissipative energy densities displayed different evolution characteristics. Furthermore, with the increases in the characteristic stresses, the input and elastic energy densities were found to increase. The dissipative energy density displayed a slight increase with the increases in the peak strength, which resulted in variations with regard to the crack closures and crack damage stresses.

Research on Post-Peak Characteristics of Elastic-Plastic Strain-Softening Model Based on Mohr-Coulomb Strength Criterions

2011 ◽  
Vol 261-263 ◽  
pp. 1439-1443
Author(s):  
Shao Qing Niu ◽  
Shuang Suo Yang ◽  
Lei Cui
Keyword(s):  
Rock Mass ◽  
Strain Softening ◽  
Triaxial Compression ◽  
Dynamic Change ◽  
Confining Pressure ◽  
Strength Parameters ◽  
Underground Engineering ◽  
Coulomb Failure ◽  
Confining Pressures ◽  
Damage Extent

Considering the characteristic that rock mass can transform from brittleness to plasticity and the dynamic change of post-peak strength parameters of the rock mass, the invariability of elastic modulus and poisson's ratio, constitutive model of rock mass could be described with the characteristic that strength parameters obey different Mohr-Coulomb failure criterions under different plastic strains. This model may reflect the post-peak subsequent characteristics of rock mass and the fact that rock mass can transform from brittleness to plasticity with the increase of confining pressure. Numerical calculation is applied to simulate the triaxial compression test under different confining pressures and underground engineering example, which proves that this model has the characteristic of reflecting the damage extent of surrounding rock.

scholarly journals Study of statistical damage constitutive model of layered composite rock under triaxial compression

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Yong-Sheng Liu ◽  
Zhuan-Zhuan Qiu ◽  
Xue-Cai Zhan ◽  
Hui-Nan Liu ◽  
Hai-Nan Gong
Keyword(s):  
Constitutive Model ◽  
Axial Strain ◽  
Triaxial Compression ◽  
Confining Pressure ◽  
Layered Composite ◽  
Model Parameters ◽  
Compression Tests ◽  
Fitting Method ◽  
Confining Pressures ◽  
Curve Fitting Method

Abstract The layered composite rock was subjected to triaxial compression tests under constant confining pressure and the stress–strain curves under different confining pressures were obtained. Based on the continuous damage theory and statistical strength theory, it is assumed that the strength of rock microelements obeys Weibull distribution by taking the defects such as random micro-cracks in the rock into account. The statistical constitutive model of layered composite rock with damage correction is established by taking the axial strain of rock as a random distribution variable of microelement strength. The model parameters were determined by the curve fitting method and referring to some test parameters. By comparing the experimental data and the constitutive model curve, the rationality and feasibility of the model are verified.

scholarly journals Deformation and Acoustic Emission Characteristics of Cracked Granite during Creep

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Chunping Wang ◽  
Jingli Xie ◽  
Jian Liu
Keyword(s):  
Acoustic Emission ◽  
Axial Strain ◽  
Failure Process ◽  
Deformation Characteristic ◽  
Temporal Distribution ◽  
Confining Pressure ◽  
High Energy ◽  
Lateral Strain ◽  
Creep Tests ◽  
Confining Pressures

A series of multistage creep tests under different confining pressures with acoustic emission monitoring have been performed to investigate the deformation characteristic and failure process of cracked granite during creep. The critical axial strain of cracked sample showed an increasing tendency with the increase of confining pressure. In contrast, critical lateral strain experienced a process of descending first at low confinement and then remaining nearly constant at high confinement. Compared with loading-cracked specimen, smaller critical axial strain, greater critical lateral strain, and higher lateral creep strain rate were found for unloading-cracked specimen. Based on the spatial and temporal distribution of acoustic emission events, the cracking process during creep was analysed. The AE events with high energy are mainly concentrated at the final fracture area of the specimen. The higher the confining pressure, the more the AE events with low energy. Compared with the loading-cracked specimen, the percentage of AE events with high energy is relatively small for the unloading-cracked specimen.

Mechanical behaviour of powders using a medium pressure flexible boundary cubical triaxial tester

2003 ◽  
Vol 217 (3) ◽  
pp. 233-241 ◽  
Author(s):  
F Li ◽  
V M Puri
Keyword(s):  
Shear Modulus ◽  
Mechanical Behaviour ◽  
Triaxial Compression ◽  
Three Dimensional ◽  
Volumetric Strain ◽  
Confining Pressure ◽  
Alumina Powder ◽  
Medium Pressure ◽  
Mean Pressure ◽  
Confining Pressures

A medium pressure (<21 MPa) flexible boundary cubical triaxial tester was designed to measure the true three-dimensional response of powders. In this study, compression behaviour and strength of a microcrystalline cellulose powder (Avicel® PH102), a spray-dried alumina powder (A16SG), and a fluid-bed-granulated silicon nitride based powder (KY3500) were measured. To characterize the mechanical behaviour, three types of triaxial stress paths, that is, the hydrostatic triaxial compression (HTC), the conventional triaxial compression (CTC), and the constant mean pressure triaxial compression (CMPTC) tests were performed. The HTC test measured the volumetric response of the test powders under isostatic pressure from 0 to 13.79MPa, during which the three powders underwent a maximum volumetric strain of 40.8 per cent for Avicel® PH102, 30.5 per cent for A16SG, and 33.0 per cent for KY3500. The bulk modulus values increased 6.4-fold from 57 to 367MPa for Avicel® PH102, 3.7-fold from 174 to 637 MPa for A16SG, and 8.1-fold from 74 to 597MPa for KY3500, when the isotropic stress increased from 0.69 to 13.79 MPa. The CTC and CMPTC tests measured the shear response of the three powders. From 0.035 to 3.45MPa confining pressure, the shear modulus increased 28.7-fold from 1.6 to 45.9MPa for Avicel® PH102, 35-fold from 1.7 to 60.5MPa for A16SG, and 28.5-fold from 1.5 to 42.8MPa for KY3500. In addition, the failure stresses of the three powders increased from 0.129 to 4.41 MPa for Avicel® PH102, 0.082 to 3.62 MPa for A16SG, and 0.090 to 4.66MPa for KY3500, respectively, when consolidation pressure increased from 0.035 to 3.45MPa. In addition, the shear modulus and failure stress values determined from the CTC test at 2.07, 2.76, and 3.45MPa confining pressures are consistently greater than those from the CMPTC test at the same constant mean pressures. This observation demonstrates the influence of stress paths on material properties. The CTT is a useful tool for characterizing the three-dimensional response of powders and powder mixtures.

scholarly journals Energy Evolution Law of Marble Failure Process Under Different Confining Pressures Based on Particle Discrete Element Method

2021 ◽  
Vol 8 ◽  
Author(s):  
Yan-Shuang Yang ◽  
Wei Cheng ◽  
Zhan-Rong Zhang ◽  
Hao-Yuan Tian ◽  
Kai-Yue Li ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Energy Dissipation ◽  
Axial Strain ◽  
Triaxial Compression ◽  
Failure Process ◽  
Rock Failure ◽  
Biaxial Compression ◽  
Energy Evolution ◽  
Confining Pressures ◽  
Energy Dissipated

The energy dissipation usually occurs during rock failure, which can demonstrate the meso failure process of rock in a relatively accurate way. Based on the results of conventional triaxial compression experiments on the Jinping marble, a numerical biaxial compression model was established by PFC2D to observe the development of the micro-cracks and energy evolution during the test, and then the laws of crack propagation, energy dissipation and damage evolution were analyzed. The numerical simulation results indicate that both the crack number and the total energy dissipated during the loading process increase with confining pressures, which is basically consistent with the experiment results. Two damage variables were presented in terms of the density from other researchers’ results and energy dissipation from numerical simulation, respectively. The energy-based damage variable varies with axial strain in the shape of “S,” and approaches one more closely than that based on density at the final failure period. The research in the rock failure from the perspective of energy may further understand the mechanical behavior of rocks.

Small-strain behavior of frozen sand in triaxial compression

1995 ◽  
Vol 32 (3) ◽  
pp. 428-451 ◽  
Author(s):  
Glen R. Andersen ◽  
Christopher W. Swan ◽  
Charles C. Ladd ◽  
John T. Germaine
Keyword(s):  
High Pressure ◽  
Strain Rate ◽  
Yield Stress ◽  
Axial Strain ◽  
Triaxial Compression ◽  
Strain Curve ◽  
Confining Pressure ◽  
Stress Strain ◽  
Strain Behavior ◽  
Frozen Sand

The stress–strain behavior of frozen Manchester fine sand has been measured in a high-pressure low-temperature triaxial compression testing system developed for this purpose. This system incorporates DC servomotor technology, lubricated end platens, and on-specimen axial strain devices. A parametric study has investigated the effects of changes in strain rate, confining pressure, sand density, and temperature on behavior for very small strains (0.001%) to very large (> 20%) axial strains. This paper presents constitutive behavior for strain levels up to 1%. On-specimen axial strain measurements enabled the identification of a distinct upper yield stress (knee on the stress–strain curve) and a study of the behavior in this region with a degree of precision not previously reported in the literature. The Young's modulus is independent of strain rate and temperature, increases slightly with sand density in a manner consistent with Counto's model for composite materials, and decreases slightly with confining pressure. In contrast, the upper yield stress is independent of sand density, slightly dependent on confining pressure (considered a second order effect), but is strongly dependent on strain rate and temperature in a fashion similar to that for polycrystalline ice. Key words : frozen sand, high-pressure triaxial compression, strain rate, temperature, modulus, yield stress.

scholarly journals Ice triaxial deformation and fracture

1994 ◽  
Vol 40 (135) ◽  
pp. 305-318 ◽  
Author(s):  
M.A. Rist ◽  
S.A.F Murrell
Keyword(s):  
Shear Fracture ◽  
Triaxial Compression ◽  
Confining Pressure ◽  
Maximum Principal Stress ◽  
Brittle Strength ◽  
Independent Evidence ◽  
Polycrystalline Ice ◽  
Confining Pressures ◽  
Pressure Independent ◽  
Ice Failure

AbstractAn experimental investigation into the mechanical behaviour of polycrystalline ice in triaxial compression has been conducted using conditions generally favourable to brittle fracture and microcracking. Under triaxial stresses at high strain rate, ice failure occurs by abrupt shear fracturing, generally inclined at about 45° to the maximum principal stress. At −20°C, such failure is suppressed by the imposition of a small confining pressure, allowing a transition to ductile-type flow accompanied by distributed microcracking, but at —40°C shear fracture persists under confinement of up to at least 50 MPa. For low confining pressures (< 10 MPa), brittle strength is strongly pressure-dependent; above this it is pressure-independent. Evidence is presented that suggests this may reflect a change from a fracture process influenced by friction to fracture initiated by localized yielding. Ductile yield strength is found to be little influenced by confining pressure despite the inhibition of cracking that leads to greatly contrasting observed crack densities. Flow conforms to the well-known power law for ice withQ= 69 J mol−1andn= 4.2 over the temperature range −20° to −4-5° C Under these conditions, microcracking in ice appears to remain remarkably stable and non-interacting.

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