To explore the variation of permeability and deformation behaviors of a fractured rock mass in high water pressure,a high pressure permeability test(HPPT),including measuring sensors of pore water pressure and displ...To explore the variation of permeability and deformation behaviors of a fractured rock mass in high water pressure,a high pressure permeability test(HPPT),including measuring sensors of pore water pressure and displacement of the rock mass,was designed according to the hydrogeological condition of Heimifeng pumped storage power station.With the assumption of radial water flow pattern in the rock mass during the HPPT,a theoretical formula was presented to estimate the coefficient of permeability of the rock mass using water pressures in injection and measuring boreholes.The variation in permeability of the rock mass with the injected water pressure was studied according to the suggested formula.By fitting the relationship between the coefficient of permeability and the injected water pressure,a mathematical expression was obtained and used in the numerical simulations.For a better understanding of the relationship between the pore water pressure and the displacement of the rock mass,a 3D numerical method based on a coupled hydro-mechanical theory was employed to simulate the response of the rock mass during the test.By comparison of the calculated and measured data of pore water pressure and displacement,the deformation behaviors of the rock mass were analyzed.It is shown that the variation of displacement in the fractured rock mass is caused by water flow passing through it under high water pressure,and the rock deformation during the test could be calculated by using the coupled hydro-mechanical model.展开更多
We report robust superconducting state and gap symmetry of Nb5Ir3O via electrical transport and specific heat measurements. The analysis of specific heat manifests that Nb5Ir3O is a strongly coupled superconductor wi...We report robust superconducting state and gap symmetry of Nb5Ir3O via electrical transport and specific heat measurements. The analysis of specific heat manifests that Nb5Ir3O is a strongly coupled superconductor with ΔC/γnTc ~ 1.91 and double s-wave superconducting gaps of 2ΔL(0)/kBTc ~ 6.56 and 2ΔS(0)/kBTc ~ 2.36 accounting for 90% and 10%,respectively. The(Cp-γnT)/T^3 vs. T plot shows a broad peak at ~ 23 K, indicating phonon softening and the appearance of low-lying phonon mode associated with the interstitial oxygen. This behavior explains the monotonic increase of Tc in Nb5Ir3O(1-δ)by strengthening the electron-phonon coupling and enlarging the density of states at Fermi level. The Hall coefficient is temperature independent below 200 K, and changes its sign from positive to negative above 250 K, suggesting that carrier is across the hole-to electron-dominant regions and the multi-band electronic structures. On warming, the resistivity shows a gradual crossover from T^2-to T^3-dependence at a critical temperature T^*, and a broad peak at a temperature Tp. The reduced Tc under pressure is linearly correlated with lattice parameters c/a ratio and Tp, suggesting the important phonon contributions in Nb5Ir3O as a phonon-medicated superconductor. Possible physical mechanisms are proposed.展开更多
This paper is directed to study the isotope effects of some superconducting materials that have a strong coupling coefficient <i>λ</i> > 1.5, and focuses on new superconducting materials whose critical...This paper is directed to study the isotope effects of some superconducting materials that have a strong coupling coefficient <i>λ</i> > 1.5, and focuses on new superconducting materials whose critical temperature is close to room temperature, specifically LaH<sub>10</sub>-LaD<sub>10</sub> and H<sub>3</sub>S-D<sub>3</sub>S systems. The Eliashberg-McMillan (EM) model and the recent Gor’kov-Kresin (GK) model for evaluating the isotope effects coefficient α were examined for these systems. The predicted values of α as a function of pressure, as compared to experimental values led to inference that these two models, despite their importance and simplicity, cannot be considered complete. These models can be used to calculate isotope effect of most superconducting materials with strong coupling coefficients but with critical reliability. The significance of studying the isotope effect lies in the possibility of identifying the interatomic forces that control the properties of superconducting materials such as electrons-mediated phonons and Coulomb interactions.展开更多
文摘To explore the variation of permeability and deformation behaviors of a fractured rock mass in high water pressure,a high pressure permeability test(HPPT),including measuring sensors of pore water pressure and displacement of the rock mass,was designed according to the hydrogeological condition of Heimifeng pumped storage power station.With the assumption of radial water flow pattern in the rock mass during the HPPT,a theoretical formula was presented to estimate the coefficient of permeability of the rock mass using water pressures in injection and measuring boreholes.The variation in permeability of the rock mass with the injected water pressure was studied according to the suggested formula.By fitting the relationship between the coefficient of permeability and the injected water pressure,a mathematical expression was obtained and used in the numerical simulations.For a better understanding of the relationship between the pore water pressure and the displacement of the rock mass,a 3D numerical method based on a coupled hydro-mechanical theory was employed to simulate the response of the rock mass during the test.By comparison of the calculated and measured data of pore water pressure and displacement,the deformation behaviors of the rock mass were analyzed.It is shown that the variation of displacement in the fractured rock mass is caused by water flow passing through it under high water pressure,and the rock deformation during the test could be calculated by using the coupled hydro-mechanical model.
基金Project supported by the National Key Research and Development Program of China(Grant Nos.2018YFA0305700 and 2018YFA0305800)JSPS Kakenhi(Grant No.17H06153)+4 种基金the Strategic Priority Research Program and Key Research Program of Frontier Sciences of the Chinese Academy of Sciences(Grant Nos.XDB25000000 and QYZDB-SSW-SLH013)the National Natural Science Foundation of China(Grant No.11574377)Beijing Natural Science Foundation,China(Grant No.Z190008)IOP Hundred-Talent Program,China(Grant No.Y7K5031×61)the Youth Promotion Association,Chinese Academy of Sciences(Grant No.2018010)
文摘We report robust superconducting state and gap symmetry of Nb5Ir3O via electrical transport and specific heat measurements. The analysis of specific heat manifests that Nb5Ir3O is a strongly coupled superconductor with ΔC/γnTc ~ 1.91 and double s-wave superconducting gaps of 2ΔL(0)/kBTc ~ 6.56 and 2ΔS(0)/kBTc ~ 2.36 accounting for 90% and 10%,respectively. The(Cp-γnT)/T^3 vs. T plot shows a broad peak at ~ 23 K, indicating phonon softening and the appearance of low-lying phonon mode associated with the interstitial oxygen. This behavior explains the monotonic increase of Tc in Nb5Ir3O(1-δ)by strengthening the electron-phonon coupling and enlarging the density of states at Fermi level. The Hall coefficient is temperature independent below 200 K, and changes its sign from positive to negative above 250 K, suggesting that carrier is across the hole-to electron-dominant regions and the multi-band electronic structures. On warming, the resistivity shows a gradual crossover from T^2-to T^3-dependence at a critical temperature T^*, and a broad peak at a temperature Tp. The reduced Tc under pressure is linearly correlated with lattice parameters c/a ratio and Tp, suggesting the important phonon contributions in Nb5Ir3O as a phonon-medicated superconductor. Possible physical mechanisms are proposed.
文摘This paper is directed to study the isotope effects of some superconducting materials that have a strong coupling coefficient <i>λ</i> > 1.5, and focuses on new superconducting materials whose critical temperature is close to room temperature, specifically LaH<sub>10</sub>-LaD<sub>10</sub> and H<sub>3</sub>S-D<sub>3</sub>S systems. The Eliashberg-McMillan (EM) model and the recent Gor’kov-Kresin (GK) model for evaluating the isotope effects coefficient α were examined for these systems. The predicted values of α as a function of pressure, as compared to experimental values led to inference that these two models, despite their importance and simplicity, cannot be considered complete. These models can be used to calculate isotope effect of most superconducting materials with strong coupling coefficients but with critical reliability. The significance of studying the isotope effect lies in the possibility of identifying the interatomic forces that control the properties of superconducting materials such as electrons-mediated phonons and Coulomb interactions.