Effects of Confining Pressure on Gas and Water Permeabilities of Rocks

2000 ◽  
Vol 663 ◽  
Author(s):  
M. Zhang ◽  
M. Takeda ◽  
T. Esaki ◽  
M. Takahashi ◽  
H. Endo
Keyword(s):  
Rock Specimen ◽  
Pulse Method ◽  
Confining Pressure ◽  
Great Depth ◽  
Test System ◽  
Saturated Rock ◽  
Underground Disposal ◽  
High Confining Pressure ◽  
Confining Pressures ◽  
The Difference

ABSTRACTKnowledge of the permeability of hydraulically-tight rock at great depth is crucially important for the design and/or assessment of facilities associated with underground disposal of radioactive nuclear wastes. This paper presents a recently developed laboratory permeability test system capable of testing low permeability rocks either by using air as a permeant or by the transient-pulse method under high confining pressure conditions that simulate ground pressures at depths. The new system was used to test Shirahama sandstone and Inada granite, which are two types of rock widely available in Japan. To investigate the effects of heterogeneity on rock permeability, specimens cored parallel to and perpendicular to bedding for sandstone, and specimens cored in the direction perpendicular to Rift Plane, Grain Plane and Hardway Plane for granite, were used. The results of this study showed that: 1) gas permeabilities of a dried rock specimen tested by air permeation are almost the same values as water permeabilities of the same saturated rock specimen tested by the transient-pulse method; 2) the intrinsic permeabilities of Shirahama sandstone and Inada granite range from about 8.33E-16 to 7.38E-17 m2 and from 1.86E-17 to 6.94E-20 m2, respectively. They decrease monotonously with increase in effective confining pressure (defined as the difference between the confining and pore pressures), while the rate of decrease diminishes at higher confining pressures. The reduction in permeabilities is due to the closure of microcracks that control fluid flow at low confining pressures; and 3) Inada granite is a heterogeneous and isotropic material. Its hydraulic heterogeneity is more significant in Rift Plane than in Hardway and Grain Planes.

Study on Strength Properties and Crack Expansion Evolution Laws of Rock Containing Multiple Fissures

2013 ◽  
Vol 353-356 ◽  
pp. 608-613 ◽  
Author(s):  
Hong Hui Zhao ◽  
Hong Wen Jing ◽  
Hai Jian Su
Keyword(s):  
Failure Process ◽  
Confining Pressure ◽  
Strength Properties ◽  
Test System ◽  
Shear Cracks ◽  
High Confining Pressure ◽  
Confining Pressures ◽  
Hydraulic Servo ◽  
Evolution Laws ◽  
Tension Cracks

Through experiments that were carried out to study the rock-like specimens with nine fissures under uniaxial compression by YNS2000 electro-hydraulic servo test system, to reveal the mechanism about strength and mechanism about crack expansion evolution laws of rock containing multiple fissures. Applying numerical simulation (RFPA) for the whole failure process of rock containing multiple fissures with reasonable parameters, the results present the influence mechanism of different confining pressures for strength and crack expansion characteristics. The experimental results show: the peak strength of specimens with nine fissures degrades obviously compared with complete specimens; Specimens containing multiple fissures begin to crack with tension cracks, and break with shear cracks finally. With the increase of confining pressure, the compressive strength of rock containing multiple fissures increases gradually; And crack expansion generally occurs on the middle diagonal fissure-plane under high confining pressure.

scholarly journals Intragranular deformation mechanisms in calcite deformed by high-pressure torsion at room temperature

2020 ◽  
Vol 114 (2) ◽  
pp. 105-118
Author(s):  
Roman Schuster ◽  
Gerlinde Habler ◽  
Erhard Schafler ◽  
Rainer Abart
Keyword(s):  
High Pressure ◽  
Twin Boundary ◽  
Brittle Failure ◽  
Room Temperature ◽  
High Pressure Torsion ◽  
Confining Pressure ◽  
Temperature Deformation ◽  
Orientation Relationships ◽  
High Confining Pressure ◽  
Confining Pressures

AbstractPolycrystalline calcite was deformed to high strain at room-temperature and confining pressures of 1–4 GPa using high-pressure torsion. The high confining pressure suppresses brittle failure and allows for shear strains >100. The post-deformation microstructures show inter- and intragranular cataclastic deformation and a high density of mechanical e$$ \left\{01\overline{1}8\right\} $$011¯8 twins and deformation lamellae in highly strained porphyroclasts. The morphologies of the twins resemble twin morphologies that are typically associated with substantially higher deformation temperatures. Porphyroclasts oriented unfavorably for twinning frequently exhibit two types of deformation lamellae with characteristic crystallographic orientation relationships associated with calcite twins. The misorientation of the first deformation lamella type with respect to the host corresponds to the combination of one r$$ \left\{10\overline{1}4\right\} $$101¯4 twin operation and one specific f$$ \left\{01\overline{1}2\right\} $$011¯2 or e$$ \left\{01\overline{1}8\right\} $$011¯8 twin operation. Boundary sections of this lamella type often split into two separated segments, where one segment corresponds to an incoherent r$$ \left\{10\overline{1}4\right\} $$101¯4 twin boundary and the other to an f$$ \left\{01\overline{1}2\right\} $$011¯2 or e$$ \left\{01\overline{1}8\right\} $$011¯8 twin boundary. The misorientation of the second type of deformation lamellae corresponds to the combination of specific r$$ \left\{10\overline{1}4\right\} $$101¯4 and f$$ \left\{01\overline{1}2\right\} $$011¯2 twin operations. The boundary segments of this lamella type may also split into the constituent twin boundaries. Our results show that brittle failure can effectively be suppressed during room-temperature deformation of calcite to high strains if confining pressures in the GPa range are applied. At these conditions, the combination of successive twin operations produces hitherto unknown deformation lamellae.

scholarly journals Macroscopic and Mesoscopic Mechanical Properties of Mine Tailings with Different Dry Densities under Different Confining Pressures

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Zhi-jun Zhang ◽  
Yao-hui Guo ◽  
Ya-kun Tian ◽  
Lin Hu ◽  
Xi-xian Wang ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Coordination Number ◽  
Mine Tailings ◽  
Confining Pressure ◽  
Simulation Software ◽  
Particle Flow ◽  
Dry Density ◽  
Stress Strain ◽  
High Confining Pressure ◽  
Confining Pressures

Particle flow numerical simulation software (PFC3D) was utilized to establish the consolidated-undrained triaxial compression test numerical models of mine tailings with different dry densities to deeply investigate the macroscopic and microscopic characteristics of mine tailings in a tailing pond in Hunan Province. Comparing the results of the simulation and the laboratory experiment, the mesoscopic parameters of the particle flow numerical simulation were obtained through continuously adjusting the mesoscopic parameter with the higher degree of agreement between the stress-strain curve, the peak strength, and the elastic modulus as the determining standard. The macroscopic and microscopic characteristics of mine tailings were studied from the perspectives of stress-strain, axial strain-volume strain, coordination number, particle velocity vector, and contact force between particles. After numerous numerical tests, it was found that the PFC3D simulation results are consistent with experiment results of the dry density tailing samples under different confining pressures; compared with the high confining pressure, the simulation test results at lower confining pressures were more with that of the laboratory tests; low density and high confining pressure both have inhibitory effect on the dilatancy characteristics of triaxial samples; with the same confining pressure, the dilatancy tendency of low dry density samples is suppressed comparing with the high dry density samples. The initial coordination number of the numerical model is large, which proves that the contact degree of the model is good to some extent.

“Deformation of Rocks under High Confining Pressures. I. Experiments at Room Temperature.” Journal of Geology, Vol. xliv, no. 5, pp. 541–577. By David T. Griggs. (1936).

Geophysics ◽  
1936 ◽  
Vol 1 (3) ◽  
pp. 378-379
Author(s):  
M. Mott‐Smith
Keyword(s):  
High Pressure ◽  
Hydrostatic Pressure ◽  
Room Temperature ◽  
Confining Pressure ◽  
Earth’S Crust ◽  
Differential Stress ◽  
High Confining Pressure ◽  
Confining Pressures ◽  
Earth's Crust

This article describes experiments on the flow and rupture of rocks under compression, tension, and torsion, while at the same time subjected to a high confining pressure supplied through a liquid surrounding the specimen. The hydrostatic pressure of this liquid could be measured very accurately and could be maintained constant. In addition, a “differential” stress was applied to the specimen, and the deformation was measured directly. By using the high pressure technique of P. W. Bridgman the confining pressure was carried up to 13,000 atmospheres, equivalent to a depth in the earth’s crust of 28 miles, and four times that available to F. W. Adams in his pioneering experiments (1901–1917).

Biot coefficient is distinct from effective pressure coefficient

Geophysics ◽  
2016 ◽  
Vol 81 (4) ◽  
pp. L27-L33 ◽  
Author(s):  
Tobias M. Müller ◽  
Pratap N. Sahay
Keyword(s):  
Pressure Coefficient ◽  
Fluid Pressure ◽  
Confining Pressure ◽  
Effective Pressure ◽  
Pore Scale ◽  
Biot Coefficient ◽  
Saturated Rock ◽  
Bulk Volume ◽  
The Difference ◽  
Pressure Changes

Within the Biot poroelasticity theory, the effective pressure coefficient for the bulk volume of a fluid-saturated rock and the Biot coefficient are one and the same quantity. The effective pressure coefficient for the bulk volume is the change of confining pressure with respect to fluid-pressure changes when the bulk volume is held constant. The Biot coefficient is the fluid volume change induced by bulk volume changes in the drained condition. However, there is experimental evidence showing a difference between these two coefficients, arguably caused by microinhomogeneities, such as microcracks and other compliant pore-scale features. In these circumstances, we advocate using the generalized constitutive pressure equations recently developed by Sahay wherein the effective pressure coefficient and the Biot coefficient enter as distinct quantities. Therein, the difference is attributed to the porosity effective pressure coefficient that serves as a measure for the deviation from the Biot prediction and accounts for microinhomogeneities. We have concluded that these generalized constitutive pressure equations offer a meaningful alternative to model observed rock behavior.

scholarly journals Shaft Resistance of Long (Flexible) Piles Considering Strength Degradation

2021 ◽  
Vol 27 (3) ◽  
pp. 54-66
Author(s):  
Aysar Hassan Subair ◽  
Ala Nasir Aljorany
Keyword(s):  
Soil Structure ◽  
Frictional Resistance ◽  
Confining Pressure ◽  
Strength Degradation ◽  
Analysis Tool ◽  
Shaft Resistance ◽  
Model Pile ◽  
High Confining Pressure ◽  
Confining Pressures ◽  
Shear Strength Degradation

Soil-structure frictional resistance is an important parameter in the design of many foundation systems. The soil-structure interface area is responsible for load transferring from the structure to the surrounding soil. The mobilized shaft resistance of axially loaded, long slender pile embedded in dense, dry sand is experimentally and numerically analyzed when subjected to pullout force. Experimental setup including an instrumented model pile while the finite element method is used as a numerical analysis tool. The hypoplasticity model is used to model the soil adjacent to and surrounding the pile by using ABAQUS FEA (6.17.1). The soil-structure interface behavior depends on many factors, but mainly on the interface soil's tendency to contract or dilate under shearing conditions. To investigate this tendency, three piles with different surface roughness and under different confining pressures are used. A dilation behavior is observed in the relation of the average shaft resistance with the axial displacement for piles with rough and medium roughness surfaces, while contraction behavior is noticed when shearing piles with smooth surfaces. A large shear strength degradation of about (10%) reduction in the shaft resistance is observed under low confining pressure compared to a lesser reduction value of about (2%) under high confining pressure. Good agreement is obtained between the experimental and the numerical results.

scholarly journals Method Improvement and Effect Analysis of Triaxial Compression Acoustic Emission Test for Coal and Rock

2019 ◽  
Vol 2019 ◽  
pp. 1-10
Author(s):  
Yan Zhou ◽  
Chuanxiao Liu ◽  
Depeng Ma
Keyword(s):  
Acoustic Emission ◽  
Rock Mechanics ◽  
Triaxial Compression ◽  
Confining Pressure ◽  
Outer Wall ◽  
Test System ◽  
Test Method ◽  
Effect Analysis ◽  
High Confining Pressure ◽  
Ae Signals

In the study of the acoustic emission (AE) characteristics of rock samples or coal samples under triaxial compression conditions, most scholars carry out relevant experiments by placing the AE detector on the outer wall of the triaxial chamber of the rock mechanics test system. Owing to the continuous obstruction of AE signals by hydraulic oil in the triaxial chamber and the frequent interference of external noises, the final experimental data cannot objectively and truly reflect the essential characteristics of AE of rock or coal under triaxial compression conditions. It is difficult to scientifically guide and accurately predict precursory information of rock’s or coal’s rupture and instability. Based on this, a series of improvements and optimizations were made to the original triaxial compression AE test method, which is based on the modification of the communication interface of the rock mechanics test system, a test head which can put the AE detector into the triaxial chamber and withstands high confining pressure, in order to obtain the true, comprehensive, and reliable AE signals. It is of considerable significance to the scientific determination of the precursory characteristics of rock’s or coal’s rupture and instability.

Laboratory Measurement of Low-Permeability Rocks With a New Flow Pump System

1997 ◽  
Vol 506 ◽  
Author(s):  
Ming Zhang ◽  
Manabu Takahashi ◽  
Tetsuro Esaki
Keyword(s):  
Pore Pressure ◽  
Fluid Pressure ◽  
Confining Pressure ◽  
Test System ◽  
Low Permeability ◽  
Specific Storage ◽  
Pump System ◽  
The Difference ◽  
Host Rocks ◽  
Flow Pump

ABSTRACTNearly impermeable host rocks have been recognized as favorable media for many kinds of underground utilization such as radioactive nuclear waste disposal, storage of oil and LP gas, and CAES. To properly evaluate the ability of a geologic medium to retard transmission of fluids, it is necessary to accurately measure its hydraulic properties, most notably the permeability and specific storage. This paper presents a new flow pump permeability test system capable of testing low-permeability rocks under high confining and high pore pressure conditions, which simulate ground pressures at large depths. The new system was used to test the Inada Granite from Japan. The results of present study show that: 1) both permeability and specific storage of the rock are dependent not only on the confining pressure but also on the pore pressure. They decrease with the increment of the effective confining pressure, i.e., the difference between confining and pore pressures; 2) the permeability and specific storage of Inada Granite range from 10−11 to 10−12 cm/s and 10−6 to 10−7 1/cm, respectively. The flow pump technique with its rigorous theoretical analysis can be used to effectively obtain such low permeabilities within several tens of hours; 3) the storage capacity of flow pump system itself decreases with the increment of fluid pressure within the permeating system.

Prefabricated Structures Surface Marble Rheological Tests and Constitutive Model Analysis

2014 ◽  
Vol 501-504 ◽  
pp. 419-425
Author(s):  
Qing Xu ◽  
Jiang Da He ◽  
Hong Qiang Xie ◽  
Ming Li Xiao ◽  
Jian Feng Liu
Keyword(s):  
Mechanical Properties ◽  
Rheological Properties ◽  
Flow Rate ◽  
Axial Stress ◽  
Triaxial Compression ◽  
Confining Pressure ◽  
Rheological Parameters ◽  
Structural Plane ◽  
High Confining Pressure ◽  
Confining Pressures

The mechanical properties of intact rock and rock containing structural plane are very different. From the diversion tunnel of Jinping deep rock site to retrieve the complete block of marble, after a high confining pressure triaxial compression simulation tectonic movements, the formation of structural plane, it represents the mechanical properties of the original rock. On the surface of the marble structure containing triaxial compression creep tests, the results showed: at low confining pressure, the weak marble surface as micro-damage accumulation, the emergence of non-uniform partial destruction, while at high confining pressure, creep curve better continuity and integrity; different confining pressures, marble initial rheology and stability both appear rheological phase, accelerated phase rheological obvious; different confining pressures, the same stage of the axial stress steady flow rate compared with the confining pressure increases, the axial steady state flow rate becomes smaller; marble under test showed the rheological properties, the use of Nishihara model can better demonstrate the rheological properties and determine the rheological parameters for other practical engineering reference.

scholarly journals Sealing Performance of New Solidified Materials: Mechanical Properties and Stress Sensitivity Characterization of Pores

2020 ◽  
Vol 2020 ◽  
pp. 1-16
Author(s):  
Chao Zhang ◽  
Gaohan Jin ◽  
Chao Liu ◽  
Shugang Li ◽  
Junhua Xue ◽  
...  
Keyword(s):  
Coal Sample ◽  
Axial Strain ◽  
Triaxial Compression ◽  
Peak Stress ◽  
Confining Pressure ◽  
Stress Sensitivity ◽  
Test System ◽  
Sample Material ◽  
Sealing Material ◽  
The Difference

Borehole-sealing solidified material plays a significant role in improving sealing quality and enhancing gas drainage performance. In this study, the MTS815 electro-hydraulic triaxial servo test system and MR-60 NMR test system were adopted to conduct triaxial compression control experiment on the coal sample material, concrete material, and new solidified sealing material, respectively. This paper aims to analyze the difference of support effects, porosity, and stress sensitivity between those materials. Experimental results show that under the same stress condition, the stiffness of traditional concrete solidified material is the largest, while the new solidified material is the second, and the coal sample material is the smallest. Compared with the traditional concrete solidified material, the new solidified sealing material has better strain-bearing capacity and volumetric expansion capacity under each confining pressure in the experiment. The axial strain and volume increment of new solidified material is higher than those of the traditional concrete solidified material at the peak stress. Meanwhile, the confining pressure has a certain hysteresis effect on the postpeak stress attenuation. Fracture has the strongest stress sensitivity in three pore types, and its T2 map relaxation area has a larger compression than adsorption pore and seepage pore under the same pressure. The relative content of seepage pore and fracture in the new solidified material is less than that of coal and concrete samples, and the stress sensitivity of the new solidified materials is weaker than that of coal and concrete materials, thence, new solidified material will have better performance in borehole sealing. Outcomes of this study could provide guidance on the selection of the most effective sealing materials for sealing-quality improvement.

Sign in / Sign up

Export Citation Format

Share Document