Study on Shear Strength of Artificial Methane Hydrate

2010 ◽  
Author(s):  
Feng Yu ◽  
Yongchen Song ◽  
Weiguo Liu ◽  
Yanghui Li ◽  
Jiafei Zhao
Keyword(s):  
Mechanical Properties ◽  
High Pressure ◽  
Shear Strength ◽  
Strain Rate ◽  
Methane Hydrate ◽  
Confining Pressure ◽  
Test System ◽  
Secant Modulus ◽  
Shear Tests ◽  
Hydrate Reservoir

The production of methane from hydrate reservoir may induce deformation of the hydrate-bearing strata. The research on mechanical properties of methane hydrate and establishing an efficient methane exploitation technology appear very important. In this paper, a low-temperature high-pressure triaxial test system including pressure crystal device (sample preparation system) was developed. A series of triaxial shear tests were carried out on artificial methane hydrate samples. The mechanical behavior was analyzed. The preliminary results show that the shear strength of methane hydrate increases with the increase of confining pressure and strain rate. While it increases with the decrease of temperature. Moreover, the secant modulus increases with the enhancement of strain rate and the decrease of confining pressure.

Damage evolution and recrystallization enhancement of frozen loess

2017 ◽  
Vol 27 (8) ◽  
pp. 1131-1155 ◽  
Author(s):  
Zhiwei Zhou ◽  
Wei Ma ◽  
Shujuan Zhang ◽  
Cong Cai ◽  
Yanhu Mu ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Strain Rate ◽  
Damage Evolution ◽  
Deformation Process ◽  
Triaxial Compression ◽  
Confining Pressure ◽  
Recrystallization Process ◽  
Frozen Soils ◽  
Time Deformation ◽  
Pressure Melting

A series of multistage triaxial compression, creep, and stress relaxation tests were conducted on frozen loess at the temperature of −6℃ in order to study the damage evolution and recrystallization enhancement of mechanical properties during deformation process. The effect of strain rate, confining pressure, and hydrostatic stress history in the degradation laws of mechanical properties is investigated further. The strain rate has a significant influence on the stress–strain curve which dominates the evolution trend of mechanical properties. The mechanical behaviors (strength, stiffness, and viscosity) of frozen loess all exhibit evident response for the consolidation and pressure melting phenomenon caused by the confining pressure. The multistage loading tests under different hydrostatic stresses are capable of differentiating the development characteristics of mechanical properties during axial loading and hydrostatic compression process, respectively. The testing results indicated that the recrystallization of the ice particle in the frozen soils is an important microscopic factor for enhancement behaviors of mechanical parameters during the deformation process. This strengthening degree of mechanical properties is determined by temperature, duration time, deformation degree, and stress state during the recrystallization process. The phase transformation led by pressure melting and ice recrystallization is a nonnegligible changing pattern of frozen soils microstructure, which has apparent role in the damage evolution of mechanical properties.

Triaxial Characterization of Minnesota Road Research Project Granular Materials

1997 ◽  
Vol 1577 (1) ◽  
pp. 27-36 ◽  
Author(s):  
Navneet Garg ◽  
Marshall R. Thompson
Keyword(s):  
Shear Strength ◽  
Granular Materials ◽  
Resilient Modulus ◽  
Axial Strain ◽  
Confining Pressure ◽  
Engineering Properties ◽  
Shear Tests ◽  
Road Project ◽  
Load Tests ◽  
Repeated Load

Six granular materials were used as base and subbase materials in the flexible pavement test sections for the Minnesota Road Research (Mn/ROAD) project. Crushed/fractured particles are not allowed in aggregate classes CL-1Fsp, CL-1Csp, CL-3sp, and CL-4sp. Ten to 15 percent crushed/fractured particles are required for CL-5sp. One hundred percent crushed/ fractured particles are required for CL-6sp. A comprehensive laboratory testing program was established to determine pertinent engineering properties of the granular materials. Rapid shear tests and repeated-load tests were conducted to determine the shear strength parameters (friction angle and cohesion), resilient modulus, rutting potential, stress history effects on shear strength, and moisture susceptibility. The results from the rapid shear tests and permanent deformation tests show that the rutting potential of a granular material can be characterized from rapid shear test at a confining pressure of 15 psi (103.35 kPa). The rutting parameter A was a function of the shear strength of the granular materials. The shear strength results obtained from rapid shear tests performed at a confining pressure of 15 psi reflect the rutting trends observed in the low-volume road test sections at the Mn/ROAD project. Results from repeated-load tests were used to develop the parameters for K-θ, UT-Austin, and Uzan’s models for evaluating the resilient modulus of granular materials. The axial strain values calculated from the resilient modulus models appear to be in good agreement with the measured axial strain values, except for the very low shear strength material CL-1Csp.

Effect of fibre content and structure on anisotropic elastic stiffness and shear strength of peat

2012 ◽  
Vol 49 (4) ◽  
pp. 403-415 ◽  
Author(s):  
Michael T. Hendry ◽  
Jitendra S. Sharma ◽  
C. Derek Martin ◽  
S. Lee Barbour
Keyword(s):  
Shear Strength ◽  
Confining Pressure ◽  
Deviatoric Stress ◽  
Direct Shear ◽  
Shear Tests ◽  
Direct Shear Tests ◽  
A Value ◽  
Frictional Strength ◽  
Fibrous Peat ◽  
Interparticle Friction

This paper presents the results of a laboratory testing program involving consolidated undrained triaxial tests and direct shear tests on remoulded peat, remoulded peat fibre, and Shelby specimens of peat obtained from a field site located in the Edson subdivision of the Canadian National railway in Alberta, Canada. These results were analyzed within the frameworks of elastic behaviour of cross-anisotropic materials and shear strength of fibre-reinforced soil. Shelby specimens were found to be inherently cross-anisotropic, whereas the remoulded peat and peat fibre specimens showed a transition from isotropic to cross-anisotropic with increasing vertical strain and effective confining pressure. The horizontal stiffness of Shelby specimens was found to be 2.6 to 2.9 times their vertical stiffness. The shear strength of intact peat is made up of interparticle friction as well as tension in the peat fibres. A novel procedure for estimating the interparticle frictional strength of fibrous peat from CU triaxial test results is proposed. It involves extrapolating the linear strain-hardening portion of the stress–strain curve to obtain the deviatoric stress at zero axial strain and plotting the deviatoric stress values thus obtained against initial mean effective confining pressure to obtain the frictional strength. Using this procedure, a value of 31° was obtained for the interparticle friction, which compares favourably with a value of 31° obtained from direct shear tests. It is recommended that further studies be undertaken to assess if interparticle frictional strength is an appropriate strength parameter for evaluation of the stability of structures founded on fibrous peat.

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.

Experimental Analysis of Mechanical Properties of High Organic Soft Clay at Different Depths

2014 ◽  
Vol 1056 ◽  
pp. 52-57
Author(s):  
Fei Liu ◽  
Jun Song Chen ◽  
Kai Wen Li
Keyword(s):  
Mechanical Properties ◽  
Northeast China ◽  
Soft Clay ◽  
Confining Pressure ◽  
Test Results ◽  
Shear Tests ◽  
Formation Stage ◽  
Good Guide ◽  
Different Depths ◽  
Clay Layers

In this study, with regard to the differences of formation stage and physicochemical properties for different high organic soft clay layers, a series of laboratory tests have been carried out to evaluate the mechanical properties of high organic soft clay in Northeast China. The conventional high-pressure consolidation and strain-controlled triaxial shear tests have been carried out to measure the compression and shear strength of high organic soft clay which formed in different ages. Furthermore, the comparisons of stress-strain relations between undisturbed and remoulded high organic soft clay samples under the confining pressure of 300kPa reveal the significant differences in compression and shear strengths of high organic soft clay at different depths, which can be interpreted by the differences in the degree of decomposition of the soil. The test results show that the degree of decomposition of high organic soft clay greatly depend on its formation stage at different depths, which is deemed to determine the mechanical properties. This study will provide a good guide to civil engineers on the constructions of the foundation.

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 Mechanical and structural properties of weak snow layers measured in situ

1998 ◽  
Vol 26 ◽  
pp. 1-6 ◽  
Author(s):  
Paul M. B. Föhn ◽  
Christian Camponovo ◽  
Georges Krüsi
Keyword(s):  
Mechanical Properties ◽  
Shear Strength ◽  
Strain Rate ◽  
Structural Properties ◽  
Strain Rate Range ◽  
Displacement Sensor ◽  
Dynamic Force ◽  
Rate Dependency ◽  
Snow Samples

Weak layers such as buried surface hoar or depth hoar frequently form the failure plane of slab avalanches. Therefore, the mechanical properties of such layers in relation to their snow structure have been investigated. Since it is difficult to transport samples containing a weak layer into cold rooms, the mechanical measurements have to be made in situ.We investigate strain-rate dependency of shear strength by measuring concurrently strength, deformation and acceleration, using a digital force gauge attached to a 0.05 m2 shear frame to which an accelerometer and a displacement sensor are fixed. In doing so, a dynamic force comparable to a driving skier is applied. The measurements cover a strain-rate range 10-2 to 1 s-1. The samples fail in a brittle manner. The shear-strength values cover the range 0.2–2.8 kPa. The dataset is also used to approximate the coefficient G, the shear modulus, for different weak layers.The snow structure has been analysed macroscopically in the field and for some layers representative snow samples have been extracted in order to prepare, in the cold laboratory, single-sided serial planes with cuts every 0.1 mm recorded by video. The analysis of these snow samples should have given the relation between some mechanical properties (strength, strain) and the structural properties. Due to basic problems in defining the connection between complex snow grains (e.g. surface hoar), we were unable to complete this part in due time. Only preliminary results on this aspect are presented here. Based on our long-term database, containing macroscopic structural and strength data of weak layers, a relationship between snow type and shear strength has been established.

scholarly journals SHPB Testing and Analysis of Bedded Shale under Active Confining Pressure

2020 ◽  
Vol 2020 ◽  
pp. 1-8
Author(s):  
Guoliang Yang ◽  
Jingjiu Bi ◽  
Xuguang Li ◽  
Jie Liu ◽  
Yanjie Feng
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Strain Rate ◽  
Peak Stress ◽  
Confining Pressure ◽  
Dynamic Mechanical Properties ◽  
Dynamic Elastic Modulus ◽  
Peak Strain ◽  
Dynamic Mechanical ◽  
Bedding Angle

Shale gas is the most important new energy source in the field of energy, and its exploitation is very important. The research on the dynamic mechanical properties of shale is the premise of exploitation. To study the dynamic mechanical properties of shale from the Changning-Weiyuan area of Sichuan Province, China, under confining pressure, we used a split Hopkinson pressure bar (SHPB) test system with an active containment device to carry out dynamic compression tests on shale with different bedding angles. (1) With active confining pressure, the shale experiences a high strain rate, and its stress-strain curve exhibits obvious plastic deformation. (2) For the same impact pressure, the peak stress of shale describes a U-shaped curve with an increasing bedding angle; besides, the peak stress of shale with different bedding angles increases linearly with rising confining pressure. The strain rate shows a significant confining pressure enhancement effect. With active confining pressure, the peak strain gradually decreases as the bedding angle increases. (3) As a result of the influence of different bedding angles, the dynamic elastic modulus of shale has obvious anisotropic characteristics. Shale with different bedding angles exhibits different rates of increase in the dynamic elastic modulus with rising confining pressure, which may be related to differences in the development of planes of weakness in the shale. The results of this study improve our understanding of the behavior of bedded shale under stress.

scholarly journals Effect of Confining Pressure on Mechanical Properties of Sediment Containing Synthetic Methane Hydrate

2010 ◽  
Vol 126 (7) ◽  
pp. 408-417 ◽  
Author(s):  
Kuniyuki MIYAZAKI ◽  
Tsutomu YAMAGUCHI ◽  
Yasuhide SAKAMOTO ◽  
Norio TENMA ◽  
Yuji OGATA ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Methane Hydrate ◽  
Confining Pressure

Mechanical Properties of Fly Ash-Slag-Dredged Silt System Stimulated by Alkali

2013 ◽  
Vol 807-809 ◽  
pp. 1140-1146 ◽  
Author(s):  
Yi Xuan Chen ◽  
Xiu Li Sun ◽  
Zhi Hua Li
Keyword(s):  
Mechanical Properties ◽  
Shear Strength ◽  
Fly Ash ◽  
Construction Materials ◽  
Xrd Analysis ◽  
Test Results ◽  
X Ray Diffraction ◽  
Shear Tests ◽  
X Ray ◽  
Direct Shear Tests

The objective of this work is to investigate the stimulation effect of the addition of alkali on the fly ash and slag for stabilizing dredged silt. Based on the test results, a viable alternative for the final disposal of dredged silt as subgrade construction materials were proposed. For this purpose, several mixtures of dredged silt-fly ash-slag and alkali were prepared and stabilized/solidified. In this system, fly ash and slag were used as hardening agents (solidified materials) of dredged silt and alkali was used as activator of fly ash and slag. The shear strength of the mixture was tested by several direct shear tests. Furthermore, X-Ray Diffraction (XRD) analysis was used to determine the hydration products of the system. The specimens were tested in order to determine the shear strength changes versus hydration time and the alkali content. It is indicated that mechanical properties of solidified silt are improved significantly by addition of fly ash and slag stimulated by alkali.

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