Grain crushing plays an important role in one-dimensional (1D) compression and creep behaviors of granular materials under high stress. It is clear that the macro-properties of granular materials are closely related t...Grain crushing plays an important role in one-dimensional (1D) compression and creep behaviors of granular materials under high stress. It is clear that the macro-properties of granular materials are closely related to the micro-fracture properties of grains in 1D compression and creep tests. In this paper, a series of 1D compression and creep tests were performed on Ottawa sand to investigate the deformation and grain crushing properties of granular materials, and it shows that the void ratio is correlated to the grain crushing amount (the quantity of crushed grains) for granular materials subjected to grain crushing. The test results, combining with the existing test data related to grain crushing of granular materials, were used to verify the relation. Moreover, the implications of these relations on the yield of granular material, and the equivalent effect of stress and time in changing soil fabric are presented.展开更多
A new evanescently-coupled uni-traveling-carrier photodiode （EC-UTC PD） based on a multimode diluted waveguide （MDW） structure is fabricated, analysed and characterized. Optical and electrical characteristics of t...A new evanescently-coupled uni-traveling-carrier photodiode （EC-UTC PD） based on a multimode diluted waveguide （MDW） structure is fabricated, analysed and characterized. Optical and electrical characteristics of the device are investigated. The excellent characteristics are demonstrated such as a responsivity of 0.36 A/W, a bandwidth of 11.5 GHz and a small-signal 1-dB compression current greater than 18 mA at 10 GHz. The saturation current is significantly improved compared with those of similar evanescently-coupled pin photodiodes. The radio frequency （RF） bandwidth can be further improved by eliminating RF losses induced by the cables, the probe and the bias tee between the photodiode and the spectrum analyzer.展开更多
Polycrystalline rock salt’s compression is a function of applied stresses,exposure duration to the applied stresses,ambient temperature,and water content.Rock salt’s compressional behavior under different conditions...Polycrystalline rock salt’s compression is a function of applied stresses,exposure duration to the applied stresses,ambient temperature,and water content.Rock salt’s compressional behavior under different conditions and its effects on the specimens’mechanical properties have been investigated in the literature.However,the one-dimensional(1D)compression behavior of polycrystalline rock salt at various water contents and how the specimen’s compression at different water contents further affects its physical and mechanical properties are not fully understood yet.In this study,polycrystalline rock salt specimens were prepared under nominally dry and wet conditions and some of the dry and wet specimens were annealed after the preparation.The relationship between the porosity of the specimens and the logarithm of the applied axial stresses during the 1D compression was found to follow a linear relationship after reaching unique critical porosities of 32%and 37%for the dry and wet specimens,respectively.Unloading and reloading the specimens did not result in any major changes in the porosity of the specimens.The specimens compressed under wet condition showed an average final porosity of 2.6%compared to 6.9%for the dry specimens.The dry and wet specimens that were annealed after the compression exhibited a lower porosity in comparison to the dry and wet specimens,respectively.Unconfined compression experiments on the specimens showed dry and wet specimens possess averaged unconfined compressive strengths(σ_(u))of 64.3 and 16.2 MPa,respectively.Annealing decreased σ_(u)of the dry specimens to 39.6 MPa and increased σ_(u)of the wet specimens to 41 MPa.展开更多
The stiffness has a large influence on the behavior of soils. Its value is affected by some of the soils properties, such as the over consolidated ratio(OCR), the effective normal stress, and the plasticity index etc....The stiffness has a large influence on the behavior of soils. Its value is affected by some of the soils properties, such as the over consolidated ratio(OCR), the effective normal stress, and the plasticity index etc. In this paper, the numerical modeling of soft soils was carried out using an improved elasto-plastic S-clay1 model accounting for degradation of stiffness. The relation between the stiffness and the shear strain was established based on a large number of experimental data. The effects of strain-dependent stiffness of normally consolidated soils and over consolidated soils on the stress-strain behavior were studied through a comparison of the simulations with the experimental results of undrained triaxial compression tests. The results show that the behaviors of soils can be well predicted with the improved constitutive model, particularly before the peak stress.展开更多
基金Supported by Natural Sciences and Engineering Research Council of Canada, Alberta Energy Research Institute and the Department of Civil Engineering at University of Calgary
文摘Grain crushing plays an important role in one-dimensional (1D) compression and creep behaviors of granular materials under high stress. It is clear that the macro-properties of granular materials are closely related to the micro-fracture properties of grains in 1D compression and creep tests. In this paper, a series of 1D compression and creep tests were performed on Ottawa sand to investigate the deformation and grain crushing properties of granular materials, and it shows that the void ratio is correlated to the grain crushing amount (the quantity of crushed grains) for granular materials subjected to grain crushing. The test results, combining with the existing test data related to grain crushing of granular materials, were used to verify the relation. Moreover, the implications of these relations on the yield of granular material, and the equivalent effect of stress and time in changing soil fabric are presented.
基金Project supported by the National High Technology Research and Development of China (Grant Nos 2006AA01Z256,2007AA03Z419 and 2007AA03Z417)the State Key Development Program for Basic Research of China (Grant Nos 2006CB604901 and 2006CB604902)the National Natural Science Foundation of China (Grant Nos 90401025,60736036,60706009 and60777021)
文摘A new evanescently-coupled uni-traveling-carrier photodiode （EC-UTC PD） based on a multimode diluted waveguide （MDW） structure is fabricated, analysed and characterized. Optical and electrical characteristics of the device are investigated. The excellent characteristics are demonstrated such as a responsivity of 0.36 A/W, a bandwidth of 11.5 GHz and a small-signal 1-dB compression current greater than 18 mA at 10 GHz. The saturation current is significantly improved compared with those of similar evanescently-coupled pin photodiodes. The radio frequency （RF） bandwidth can be further improved by eliminating RF losses induced by the cables, the probe and the bias tee between the photodiode and the spectrum analyzer.
基金This material is based on work supported by the National Science Foundation under Grant No.CMMI-1641054.
文摘Polycrystalline rock salt’s compression is a function of applied stresses,exposure duration to the applied stresses,ambient temperature,and water content.Rock salt’s compressional behavior under different conditions and its effects on the specimens’mechanical properties have been investigated in the literature.However,the one-dimensional(1D)compression behavior of polycrystalline rock salt at various water contents and how the specimen’s compression at different water contents further affects its physical and mechanical properties are not fully understood yet.In this study,polycrystalline rock salt specimens were prepared under nominally dry and wet conditions and some of the dry and wet specimens were annealed after the preparation.The relationship between the porosity of the specimens and the logarithm of the applied axial stresses during the 1D compression was found to follow a linear relationship after reaching unique critical porosities of 32%and 37%for the dry and wet specimens,respectively.Unloading and reloading the specimens did not result in any major changes in the porosity of the specimens.The specimens compressed under wet condition showed an average final porosity of 2.6%compared to 6.9%for the dry specimens.The dry and wet specimens that were annealed after the compression exhibited a lower porosity in comparison to the dry and wet specimens,respectively.Unconfined compression experiments on the specimens showed dry and wet specimens possess averaged unconfined compressive strengths(σ_(u))of 64.3 and 16.2 MPa,respectively.Annealing decreased σ_(u)of the dry specimens to 39.6 MPa and increased σ_(u)of the wet specimens to 41 MPa.
文摘The stiffness has a large influence on the behavior of soils. Its value is affected by some of the soils properties, such as the over consolidated ratio(OCR), the effective normal stress, and the plasticity index etc. In this paper, the numerical modeling of soft soils was carried out using an improved elasto-plastic S-clay1 model accounting for degradation of stiffness. The relation between the stiffness and the shear strain was established based on a large number of experimental data. The effects of strain-dependent stiffness of normally consolidated soils and over consolidated soils on the stress-strain behavior were studied through a comparison of the simulations with the experimental results of undrained triaxial compression tests. The results show that the behaviors of soils can be well predicted with the improved constitutive model, particularly before the peak stress.
