Bused on the wave equations established by the authors, the characteristics of propagation velocities of elastic vaves in saturated soils arc analyzed and verified by ultrasonic test in laboratory and seismic survey i...Bused on the wave equations established by the authors, the characteristics of propagation velocities of elastic vaves in saturated soils arc analyzed and verified by ultrasonic test in laboratory and seismic survey in the field. The results provide theoretical basis for the determination of physical and mechanical parameters of saturated soils using propagation velocities of elastic waves. especially P-wave Velocity.展开更多
The saturation of the compacted bentonite buffer in the deep geological repository can cause bentonite swelling,intrusion into rock fractures,and erosion.Inevitably,erosion and subsequent bentonite mass loss due to gr...The saturation of the compacted bentonite buffer in the deep geological repository can cause bentonite swelling,intrusion into rock fractures,and erosion.Inevitably,erosion and subsequent bentonite mass loss due to groundwater inflow can aggravate the overall integrity of the engineered barrier system.Therefore,the coupled hydro-mechanical interaction between the buffer and rock during groundwater inflow and bentonite intrusion should be evaluated to guarantee the long-term safety of deep geological disposal.This study investigated the effect of bentonite erosion and intrusion on the elastic wave propagation characteristics in jointed rocks using a quasi-static resonant column test.Jointed rock specimens with different joint conditions(i.e.joint surface saturation and bentonite filling)were prepared using granite rock discs sampled from the Korea Underground Research Tunnel(KURT)and Gyeongju bentonite.The long-wavelength longitudinal and shear wave velocities were measured under different normal stress levels.A Hertzian-type power model was used to fit the wave velocities,and the relationship between the two fitted parameters provided the trend of joint conditions.Numerical simulations using three-dimensional distinct element code(3DEC)were conducted to better understand how the long-wavelength wave propagates through wet bentonite-filled rock joints.展开更多
Increased knowledge of the elastic and geomechnical properties of rocks is important for numerous engineering and geoscience applications(e.g. petroleum geoscience, underground waste repositories,geothermal energy, ea...Increased knowledge of the elastic and geomechnical properties of rocks is important for numerous engineering and geoscience applications(e.g. petroleum geoscience, underground waste repositories,geothermal energy, earthquake studies, and hydrocarbon exploration). To assess the effect of pressure and temperature on seismic velocities and their anisotropy, laboratory experiments were conducted on metamorphic rocks. P-(Vp) and S-wave(Vs) velocities were determined on cubic samples of granulites and eclogites with an edge length of 43 mm in a triaxial multianvil apparatus using the ultrasonic pulse emission technique in dependence of changes in pressure and temperature. At successive isotropic pressure states up to 600 MPa and temperatures up to 600 ℃, measurements were performed related to the sample coordinates given by the three principal fabric directions(x, y, z) representing the foliation(xy-plane), the normal to the foliation(z-direction), and the lineation direction(x-direction). Progressive volumetric strain was logged by the discrete piston displacements. Cumulative errors in Vpand Vsare estimated to be <1%. Microcrack closure significantly contributes to the increase in seismic velocities and decrease in anisotropies for pressures up to 200-250 MPa. Characteristic P-wave anisotropies of about 10% are obtained for eclogite and 3-4% in a strongly retrogressed eclogite as well as granulites. The wave velocities were used to calculate the geomechanical properties(e.g. density, Poisson’s ratio, volumetric strain, and elastic moduli) at different pressure and temperature conditions. These results contribute to the reliable estimate of geomechanical properties of rocks.展开更多
With the development of seismic engineering and seismic exploration of energy, the underground media that westudy are more and more complicated. Conventional anisotropy theory or two-phase isotropy theory is difficult...With the development of seismic engineering and seismic exploration of energy, the underground media that westudy are more and more complicated. Conventional anisotropy theory or two-phase isotropy theory is difficult todescribe anisotropic media containing fluid, such as fractures containing gas, shales containing water Based onBlot theory about two-phase anisotropy, with the use of elastic plane wave equations, we get Christoffel equations.We calculate and analyze the effects of frequency on phase velocity, attenuation, amplitude ratio and polarizationdirection of elastic waves of two-phase, transversely isotropic media. Results show that frequency affects slow Pwave the greatest among the four kinds of waves, i.e., fast P wave, slow P wave, fast S wave and slow S wave.Fluid phase amplitude to solid phase amplitude ratio of fast P wave, fast S wave and slow S wave approaches unitfor large dissipation coefficients. Polarization analysis shows that polarization direction of fluid phase displacement is different from, not parallel to or reverse to, that of solid phase displacement in two-phase anisotropic media.展开更多
The dynamic elasticity modulus(Ed)is the most commonly used indexes for nondestructive testing to represent the internal damage of hydraulic concrete.Samples with a specific size is required when the transverse resona...The dynamic elasticity modulus(Ed)is the most commonly used indexes for nondestructive testing to represent the internal damage of hydraulic concrete.Samples with a specific size is required when the transverse resonance method was used to detect the Ed,resulting in a limitation for field tests.The impact-echo method can make up defects of traditional detection methods for frost-resistance testing,such as the evaluation via the loss of mass or strength.The feasibility of the impact-echo method to obtain the relative Ed is explored to detect the frost-resistance property of large-volume hydraulic concretes on site.Results show that the impact-echo method can replace the traditional resonance frequency method to evaluate the frost resistance of concrete,and has advantages of high accuracy,easy to operate,and not affecting by the aggregate size and size effect of samples.The dynamic elastic modulus of concrete detected by the impact-echo method has little difference with that obtained by the traditional resonance method.The one-dimensional elastic wave velocity of concrete has a good linear correlation with the transverse resonance frequency.The freeze-thaw damage occurred from the surface to the inner layer,and the surface is expected to be the most vulnerable part for the freeze-thaw damage.It is expected to monitor and track the degradation of the frost resistance of an actual structure by frequently detecting the P-wave velocity on site,which avoids coring again.展开更多
Deep shale layer in the Lower Silurian Longmaxi Formation,southern Sichuan Basin is the major replacement target of shale gas exploration in China.However,the prediction of"sweet-spots"in deep shale gas rese...Deep shale layer in the Lower Silurian Longmaxi Formation,southern Sichuan Basin is the major replacement target of shale gas exploration in China.However,the prediction of"sweet-spots"in deep shale gas reservoirs lacks physical basis due to the short of systematic experimental research on the physical properties of the deep shale.Based on petrological,acoustic and hardness measurements,variation law and control factors of dynamic and static elastic properties of the deep shale samples are investigated.The study results show that the deep shale samples are similar to the middle-shallow shale in terms of mineral composition and pore type.Geochemical characteristics of organic-rich shale samples(TOC>2%)indicate that these shale samples have a framework of microcrystalline quartz grains;the intergranular pores in these shale samples are between rigid quartz grains and have mechanical property of hard pore.The lean-organic shale samples(TOC<2%),with quartz primarily coming from terrigenous debris,feature plastic clay mineral particles as the support frame in rock texture.Intergranular pores in these samples are between clay particles,and show features of soft pores in mechanical property.The difference in microtexture of the deep shale samples results in an asymmetrical inverted V-type change in velocity with quartz content,and the organic-rich shale samples have a smaller variation rate in velocity-porosity and velocity-organic matter content.Also due to the difference in microtexture,the organic-rich shale and organic-lean shale can be clearly discriminated in the cross plots of P-wave impedance versus Poisson’s ratio as well as elasticity modulus versus Poisson’s ratio.The shale samples with quartz mainly coming from biogenic silica show higher hardness and brittleness,while the shale samples with quartz from terrigenous debris have hardness and brittleness less affected by quartz content.The study results can provide a basis for well-logging interpretation and"sweet spot"prediction of Longmaxi Formation shale gas reservoirs.展开更多
Based on the Wyllie time-average relation and sonic velocity-log conditions, by introducing three basic assumptions and applying conventional elastic wave dynamic method , both P-wave and S-wave velocities for fluid-s...Based on the Wyllie time-average relation and sonic velocity-log conditions, by introducing three basic assumptions and applying conventional elastic wave dynamic method , both P-wave and S-wave velocities for fluid-saturated sandstones are derived theoretically in this paper . And Wyllie 's kinematic model for computing P-wave velocity is developed into a dynamic model for computing P-wave and S-wave velocities . The results are consistent with the data on P-wave and S-wave velocities for air-saturated sandstones measured by Wyllie et al.展开更多
The polycrystalline colossal magnetoresistive double-layered manganite samples R1.2Sr1.8Mn2O7(R = La Pr, Nd, Sm) were prepared by the sol–gel method and their room temperature elastic behavior was investigated by u...The polycrystalline colossal magnetoresistive double-layered manganite samples R1.2Sr1.8Mn2O7(R = La Pr, Nd, Sm) were prepared by the sol–gel method and their room temperature elastic behavior was investigated by ultrasonic pulse transmission technique at 1 MHz. The values of elastic constants were calculated from longitudinal and shear velocities and they were corrected to zero porosity using Hasselman and Fulrath's formulae. The elastic constants of the samples were also estimated by Modi's heterogeneous metal-mixture rule which is based on the metal ions present in the samples. The measured,corrected, and estimated values of elastic moduli are found to increase with decreasing rare earth ion size. The variation of elastic moduli with the size of the rare earth ion is interpreted in terms of strength of interatomic bonding.展开更多
In this study,for the first time,we investigate the nonlocality superimposed to the size effects on the nonlinear dynamics of an electrically actuated single-walled carbon-nanotube-based resonator.We undertake two mod...In this study,for the first time,we investigate the nonlocality superimposed to the size effects on the nonlinear dynamics of an electrically actuated single-walled carbon-nanotube-based resonator.We undertake two models to capture the nanostructure nonlocal size effects:the strain and the velocity gradient theories.We use a reduced-order model based on the differential quadrature method(DQM)to discretize the goverming nonlinear equation of motion and acquire a discretized-parameter nonlinear model of the system.The structural nonlinear behavior of the system assuming both strain and velocity gradient theories is investigated using the discretized model.The results suggest that nonlocal and size effects should not be neglected because they improve the prediction of corresponding dynamic amplitudes and,most importantly,the critical resonant frequencies of such nanoresonators.Neglcting these effects may impose a considerable source of error,which can be amended using more accurate modeling techniques.展开更多
The stress wave propagation law and dynamic buckling critical velocity are formulated and solved by considering a general axial connecting boundary for a slender elastic straight rod impacted by a rigid body. The infl...The stress wave propagation law and dynamic buckling critical velocity are formulated and solved by considering a general axial connecting boundary for a slender elastic straight rod impacted by a rigid body. The influence of connecting stiffness on the critical velocity is investigated with varied impactor mass and buckling time. The influences of rod length and rod mass on the critical velocity are also discussed. It is found that greater connecting stiffness leads to larger stress amplitude, and further results in lower critical velocity. It is particularly noteworthy that when the connecting stiffness is less than a certain value, dynamic buckling only occurs before stress wave reflects off the connecting end. It is also shown that longer rod with larger slenderness ratio is easier to buckle, and the critical velocity for a larger-mass rod is higher than that for a lighter rod with the same geometry.展开更多
A measurement scheme carried out in a tank is designed to obtain the compressionaland shear-wave velocities of a large elastic material.A hydrophone is used to receive the high frequency acoustic signals which penetra...A measurement scheme carried out in a tank is designed to obtain the compressionaland shear-wave velocities of a large elastic material.A hydrophone is used to receive the high frequency acoustic signals which penetrate the tested material,in order to determine the transmission time from the source to the hydrophone,the transmission time is also calculated according to the ray acoustic theory in layered media.A cost function is built based on the measured and the calculated transmission time,then the compressional- and shear-wave velocities can be obtained using the optimization algorithm.Compared with the traditional measurement scheme,this approach can not only get the 2 kinds of sound velocities in the tested material at the same time,but also keep the integrality of the tested material.With the proposed measurement system,the uncertainty of measurement results is less than 3.5%.展开更多
文摘Bused on the wave equations established by the authors, the characteristics of propagation velocities of elastic vaves in saturated soils arc analyzed and verified by ultrasonic test in laboratory and seismic survey in the field. The results provide theoretical basis for the determination of physical and mechanical parameters of saturated soils using propagation velocities of elastic waves. especially P-wave Velocity.
基金funding support from the Nuclear Research and Development Program of the National Research Foundation of Korea(Grant Nos.2021M2E1A1085193 and 2020M2C9A1062949).
文摘The saturation of the compacted bentonite buffer in the deep geological repository can cause bentonite swelling,intrusion into rock fractures,and erosion.Inevitably,erosion and subsequent bentonite mass loss due to groundwater inflow can aggravate the overall integrity of the engineered barrier system.Therefore,the coupled hydro-mechanical interaction between the buffer and rock during groundwater inflow and bentonite intrusion should be evaluated to guarantee the long-term safety of deep geological disposal.This study investigated the effect of bentonite erosion and intrusion on the elastic wave propagation characteristics in jointed rocks using a quasi-static resonant column test.Jointed rock specimens with different joint conditions(i.e.joint surface saturation and bentonite filling)were prepared using granite rock discs sampled from the Korea Underground Research Tunnel(KURT)and Gyeongju bentonite.The long-wavelength longitudinal and shear wave velocities were measured under different normal stress levels.A Hertzian-type power model was used to fit the wave velocities,and the relationship between the two fitted parameters provided the trend of joint conditions.Numerical simulations using three-dimensional distinct element code(3DEC)were conducted to better understand how the long-wavelength wave propagates through wet bentonite-filled rock joints.
文摘Increased knowledge of the elastic and geomechnical properties of rocks is important for numerous engineering and geoscience applications(e.g. petroleum geoscience, underground waste repositories,geothermal energy, earthquake studies, and hydrocarbon exploration). To assess the effect of pressure and temperature on seismic velocities and their anisotropy, laboratory experiments were conducted on metamorphic rocks. P-(Vp) and S-wave(Vs) velocities were determined on cubic samples of granulites and eclogites with an edge length of 43 mm in a triaxial multianvil apparatus using the ultrasonic pulse emission technique in dependence of changes in pressure and temperature. At successive isotropic pressure states up to 600 MPa and temperatures up to 600 ℃, measurements were performed related to the sample coordinates given by the three principal fabric directions(x, y, z) representing the foliation(xy-plane), the normal to the foliation(z-direction), and the lineation direction(x-direction). Progressive volumetric strain was logged by the discrete piston displacements. Cumulative errors in Vpand Vsare estimated to be <1%. Microcrack closure significantly contributes to the increase in seismic velocities and decrease in anisotropies for pressures up to 200-250 MPa. Characteristic P-wave anisotropies of about 10% are obtained for eclogite and 3-4% in a strongly retrogressed eclogite as well as granulites. The wave velocities were used to calculate the geomechanical properties(e.g. density, Poisson’s ratio, volumetric strain, and elastic moduli) at different pressure and temperature conditions. These results contribute to the reliable estimate of geomechanical properties of rocks.
文摘With the development of seismic engineering and seismic exploration of energy, the underground media that westudy are more and more complicated. Conventional anisotropy theory or two-phase isotropy theory is difficult todescribe anisotropic media containing fluid, such as fractures containing gas, shales containing water Based onBlot theory about two-phase anisotropy, with the use of elastic plane wave equations, we get Christoffel equations.We calculate and analyze the effects of frequency on phase velocity, attenuation, amplitude ratio and polarizationdirection of elastic waves of two-phase, transversely isotropic media. Results show that frequency affects slow Pwave the greatest among the four kinds of waves, i.e., fast P wave, slow P wave, fast S wave and slow S wave.Fluid phase amplitude to solid phase amplitude ratio of fast P wave, fast S wave and slow S wave approaches unitfor large dissipation coefficients. Polarization analysis shows that polarization direction of fluid phase displacement is different from, not parallel to or reverse to, that of solid phase displacement in two-phase anisotropic media.
基金Hainan Provincial Natural Science Foundation of China(522QN279)Research Lab Construction of Hainan University(ZY2019HN0904).
文摘The dynamic elasticity modulus(Ed)is the most commonly used indexes for nondestructive testing to represent the internal damage of hydraulic concrete.Samples with a specific size is required when the transverse resonance method was used to detect the Ed,resulting in a limitation for field tests.The impact-echo method can make up defects of traditional detection methods for frost-resistance testing,such as the evaluation via the loss of mass or strength.The feasibility of the impact-echo method to obtain the relative Ed is explored to detect the frost-resistance property of large-volume hydraulic concretes on site.Results show that the impact-echo method can replace the traditional resonance frequency method to evaluate the frost resistance of concrete,and has advantages of high accuracy,easy to operate,and not affecting by the aggregate size and size effect of samples.The dynamic elastic modulus of concrete detected by the impact-echo method has little difference with that obtained by the traditional resonance method.The one-dimensional elastic wave velocity of concrete has a good linear correlation with the transverse resonance frequency.The freeze-thaw damage occurred from the surface to the inner layer,and the surface is expected to be the most vulnerable part for the freeze-thaw damage.It is expected to monitor and track the degradation of the frost resistance of an actual structure by frequently detecting the P-wave velocity on site,which avoids coring again.
基金Supported by the National Natural Science Foundation of China(41774136)China National Science and Technology Major Project(2017ZX05035004)
文摘Deep shale layer in the Lower Silurian Longmaxi Formation,southern Sichuan Basin is the major replacement target of shale gas exploration in China.However,the prediction of"sweet-spots"in deep shale gas reservoirs lacks physical basis due to the short of systematic experimental research on the physical properties of the deep shale.Based on petrological,acoustic and hardness measurements,variation law and control factors of dynamic and static elastic properties of the deep shale samples are investigated.The study results show that the deep shale samples are similar to the middle-shallow shale in terms of mineral composition and pore type.Geochemical characteristics of organic-rich shale samples(TOC>2%)indicate that these shale samples have a framework of microcrystalline quartz grains;the intergranular pores in these shale samples are between rigid quartz grains and have mechanical property of hard pore.The lean-organic shale samples(TOC<2%),with quartz primarily coming from terrigenous debris,feature plastic clay mineral particles as the support frame in rock texture.Intergranular pores in these samples are between clay particles,and show features of soft pores in mechanical property.The difference in microtexture of the deep shale samples results in an asymmetrical inverted V-type change in velocity with quartz content,and the organic-rich shale samples have a smaller variation rate in velocity-porosity and velocity-organic matter content.Also due to the difference in microtexture,the organic-rich shale and organic-lean shale can be clearly discriminated in the cross plots of P-wave impedance versus Poisson’s ratio as well as elasticity modulus versus Poisson’s ratio.The shale samples with quartz mainly coming from biogenic silica show higher hardness and brittleness,while the shale samples with quartz from terrigenous debris have hardness and brittleness less affected by quartz content.The study results can provide a basis for well-logging interpretation and"sweet spot"prediction of Longmaxi Formation shale gas reservoirs.
文摘Based on the Wyllie time-average relation and sonic velocity-log conditions, by introducing three basic assumptions and applying conventional elastic wave dynamic method , both P-wave and S-wave velocities for fluid-saturated sandstones are derived theoretically in this paper . And Wyllie 's kinematic model for computing P-wave velocity is developed into a dynamic model for computing P-wave and S-wave velocities . The results are consistent with the data on P-wave and S-wave velocities for air-saturated sandstones measured by Wyllie et al.
文摘The polycrystalline colossal magnetoresistive double-layered manganite samples R1.2Sr1.8Mn2O7(R = La Pr, Nd, Sm) were prepared by the sol–gel method and their room temperature elastic behavior was investigated by ultrasonic pulse transmission technique at 1 MHz. The values of elastic constants were calculated from longitudinal and shear velocities and they were corrected to zero porosity using Hasselman and Fulrath's formulae. The elastic constants of the samples were also estimated by Modi's heterogeneous metal-mixture rule which is based on the metal ions present in the samples. The measured,corrected, and estimated values of elastic moduli are found to increase with decreasing rare earth ion size. The variation of elastic moduli with the size of the rare earth ion is interpreted in terms of strength of interatomic bonding.
基金H.M.Sedighi is grateful to the Research Council of Shahid Chamran University of Ahvaz for its financial support(Grant No.SCU.EM99.98).
文摘In this study,for the first time,we investigate the nonlocality superimposed to the size effects on the nonlinear dynamics of an electrically actuated single-walled carbon-nanotube-based resonator.We undertake two models to capture the nanostructure nonlocal size effects:the strain and the velocity gradient theories.We use a reduced-order model based on the differential quadrature method(DQM)to discretize the goverming nonlinear equation of motion and acquire a discretized-parameter nonlinear model of the system.The structural nonlinear behavior of the system assuming both strain and velocity gradient theories is investigated using the discretized model.The results suggest that nonlocal and size effects should not be neglected because they improve the prediction of corresponding dynamic amplitudes and,most importantly,the critical resonant frequencies of such nanoresonators.Neglcting these effects may impose a considerable source of error,which can be amended using more accurate modeling techniques.
文摘The stress wave propagation law and dynamic buckling critical velocity are formulated and solved by considering a general axial connecting boundary for a slender elastic straight rod impacted by a rigid body. The influence of connecting stiffness on the critical velocity is investigated with varied impactor mass and buckling time. The influences of rod length and rod mass on the critical velocity are also discussed. It is found that greater connecting stiffness leads to larger stress amplitude, and further results in lower critical velocity. It is particularly noteworthy that when the connecting stiffness is less than a certain value, dynamic buckling only occurs before stress wave reflects off the connecting end. It is also shown that longer rod with larger slenderness ratio is easier to buckle, and the critical velocity for a larger-mass rod is higher than that for a lighter rod with the same geometry.
基金supported by the National Natural Science Foundation of China(11104044)Science and Technology Foundation of State Key Laboratory(9140C200103110C20)the Key Project of NationalNatural Science Foundation(11234002)
文摘A measurement scheme carried out in a tank is designed to obtain the compressionaland shear-wave velocities of a large elastic material.A hydrophone is used to receive the high frequency acoustic signals which penetrate the tested material,in order to determine the transmission time from the source to the hydrophone,the transmission time is also calculated according to the ray acoustic theory in layered media.A cost function is built based on the measured and the calculated transmission time,then the compressional- and shear-wave velocities can be obtained using the optimization algorithm.Compared with the traditional measurement scheme,this approach can not only get the 2 kinds of sound velocities in the tested material at the same time,but also keep the integrality of the tested material.With the proposed measurement system,the uncertainty of measurement results is less than 3.5%.