A full 3-D finite element method numerical modeling program is written based on the principle and technical specification of borehole electric image well logging tool. The response of well logging is computed in the f...A full 3-D finite element method numerical modeling program is written based on the principle and technical specification of borehole electric image well logging tool. The response of well logging is computed in the formation media model with a single fracture. The effect of changing fracture aperture and resistivity ratio to the logging response is discussed. The identification ability for two parallel fractures is also present. A quantitative evaluation formula of fracture aperture from borehole electric image logging data is set up. A case study of the model well is done to verify the accuracy of the for-mula. The result indicates that the formula is more accurate than the foreign one.展开更多
We have proposed a methodology to assess the robustness of underground tunnels against potential failure.This involves developing vulnerability functions for various qualities of rock mass and static loading intensiti...We have proposed a methodology to assess the robustness of underground tunnels against potential failure.This involves developing vulnerability functions for various qualities of rock mass and static loading intensities.To account for these variations,we utilized a Monte Carlo Simulation(MCS)technique coupled with the finite difference code FLAC^(3D),to conduct two thousand seven hundred numerical simulations of a horseshoe tunnel located within a rock mass with different geological strength index system(GSIs)and subjected to different states of static loading.To quantify the severity of damage within the rock mass,we selected one stress-based(brittle shear ratio(BSR))and one strain-based failure criterion(plastic damage index(PDI)).Based on these criteria,we then developed fragility curves.Additionally,we used mathematical approximation techniques to produce vulnerability functions that relate the probabilities of various damage states to loading intensities for different quality classes of blocky rock mass.The results indicated that the fragility curves we obtained could accurately depict the evolution of the inner and outer shell damage around the tunnel.Therefore,we have provided engineers with a tool that can predict levels of damages associated with different failure mechanisms based on variations in rock mass quality and in situ stress state.Our method is a numerically developed,multi-variate approach that can aid engineers in making informed decisions about the robustness of underground tunnels.展开更多
We investigated how density and quality of mesh around interest domain affect electromagnetic （EM） responses of 3D Earth layered media using finite element method （FEM）. Effect of different mesh shapes was also in...We investigated how density and quality of mesh around interest domain affect electromagnetic （EM） responses of 3D Earth layered media using finite element method （FEM）. Effect of different mesh shapes was also investigated using a method of mixing structured and unstructured mesh. As a case study, we estimated the effects of meshing on selectivity phenomenon of seismic electric signal （SES）. Our results suggest that the relative errors resulting from mesh effects may not be negligible, which may lead to some unconvincing explanation of the SES selectivity based on the numerical modeling results.展开更多
Various models exist to explain the formation of the Tibetan Plateau,including“tectonic escape”,“pure shear thickening”,“convective removal of the lithospheric mantle”,and“lower crustal flow”model.The first tw...Various models exist to explain the formation of the Tibetan Plateau,including“tectonic escape”,“pure shear thickening”,“convective removal of the lithospheric mantle”,and“lower crustal flow”model.The first two models are primarily constructed on pure mechanical models but are unable to reasonably explain the tension and shear phenomena inside the plateau.The latter two are rheological dynamic models based on deep geophysical observations.However,the spatial range of the lower crustal flow and its role in the plateau formation/uplift remain controversial.Five multi-terrane viscoplastic thermomechanical models were constructed to simulate the uplift and lithospheric structure change of the Tibetan Plateau during the post-collision stage(since 35 Ma)under the convergence of the Indian Plate.Results show that the plateau's formation begins with crustal thickening,blocked by strong terranes at the northern plateau,and expanded laterally to the east.The lithosphere thickens gradually and experiences delamination at its base,elevating temperature within the crust and forming partial melting layers in the central plateau.As convergence persists on the southern side,the northern plateau's lithosphere bends downward and undergoes delamination,further heating the crust and promoting the northward and eastward flow of partial melting layers,leading to secondary uplift around the plateau.展开更多
A 3-D numerical model is set up in a large domain covering the Hangzhou Bay and the Changjiang Estuary based on the ECOM model in orthogonal curvilinear coordinates.The numerical schemes for baroclinic pressure gradie...A 3-D numerical model is set up in a large domain covering the Hangzhou Bay and the Changjiang Estuary based on the ECOM model in orthogonal curvilinear coordinates.The numerical schemes for baroclinic pressure gradient (BPG)terms and convective terms are improved in the paper according to the characteristics of velocity field and mass transport in the area.The model is validated by the simulations of residual current and salinity transport in the Hangzhou Bay and the Changjiang Estuary.展开更多
Currently, numerical simulations of seismic channel waves for the advance detection of geological structures in coal mine roadways focus mainly on modeling two- dimensional wave fields and therefore cannot accurately ...Currently, numerical simulations of seismic channel waves for the advance detection of geological structures in coal mine roadways focus mainly on modeling two- dimensional wave fields and therefore cannot accurately simulate three-dimensional （3-D） full-wave fields or seismic records in a full-space observation system. In this study, we use the first-order velocity-stress staggered-grid finite difference algorithm to simulate 3-D full-wave fields with P-wave sources in front of coal mine roadways. We determine the three components of velocity Vx, Vy, and Vz for the same node in 3-D staggered-grid finite difference models by calculating the average value of Vy, and Vz of the nodes around the same node. We ascertain the wave patterns and their propagation characteristics in both symmetrical and asymmetric coal mine roadway models. Our simulation results indicate that the Rayleigh channel wave is stronger than the Love channel wave in front of the roadway face. The reflected Rayleigh waves from the roadway face are concentrated in the coal seam, release less energy to the roof and floor, and propagate for a longer distance. There are surface waves and refraction head waves around the roadway. In the seismic records, the Rayleigh wave energy is stronger than that of the Love channel wave along coal walls of the roadway, and the interference of the head waves and surface waves with the Rayleigh channel wave is weaker than with the Love channel wave. It is thus difficult to identify the Love channel wave in the seismic records. Increasing the depth of the receivers in the coal walls can effectively weaken the interference of surface waves with the Rayleigh channel wave, but cannot weaken the interference of surface waves with the Love channel wave. Our research results also suggest that the Love channel wave, which is often used to detect geological structures in coal mine stopes, is not suitable for detecting geological structures in front of coal mine roadways. Instead, the Rayleigh channel wave can be used for the advance detection of geological structures in coal mine roadways.展开更多
A coupled discrete-continuum simulation incorporating a 3D aspect and non-circular particles was performed to analyze soil-pile interactions during pile penetration in sand.A self-developed non-circular particle numer...A coupled discrete-continuum simulation incorporating a 3D aspect and non-circular particles was performed to analyze soil-pile interactions during pile penetration in sand.A self-developed non-circular particle numerical simulation program was used which considered sand near the pile as interacted particles using a discrete element method;the sand away from the pile was simulated as a continuous medium exhibiting linear elastic behaviors.The domain analyzed was divided into two zones.Contact forces at the interface between the two zones were obtained from a discrete zone and applied to the continuum boundaries as nodal forces,while the interface velocities were obtained from the continuum zone and applied to the discrete boundaries.We show that the coupled discrete-continuum simulation can give a microscopic description of the pile penetration process without losing the discrete nature of the zone concerned,and may significantly improve computational efficiency.展开更多
Numerical simulation modeling is a hotspot in the geological engineering computing field. Tak- ing a fast Langrangian analysis of continua in 3 dimensions （FLAC3D） numerical modeling on com- puting the geo-deformati...Numerical simulation modeling is a hotspot in the geological engineering computing field. Tak- ing a fast Langrangian analysis of continua in 3 dimensions （FLAC3D） numerical modeling on com- puting the geo-deformation information caused by the mining subsidence in a coalmine for example, a new GIS-Excel modeling method is proposed to build geologic strata within the simulation range combined with the coal-seam dip angle of the underground mining working-planes. First of all, the coal-seam model of the numerical computing is built by using the geographic information system （GIS） according to the stripe-through principle and the calculating formula on the size of the model blocks in the paper defined, then the FLAC3D numerical computing model of all geologic strata with- in the simulation range is also built based on the calculating formula of thickness of each stratum and the Excel fast computing advantages. The GIS-Excel method is good at the higher modeling accuracy, seldom making mistakes and consuming less time. The reliability and validity of the method is veri- fied well by its practical applications in the coalmine area.展开更多
Seismic hazard assessment based on urban active faults can provide scientific bases for city planning and project construction, while numerical simulation of strong ground motion is an important method for seismic haz...Seismic hazard assessment based on urban active faults can provide scientific bases for city planning and project construction, while numerical simulation of strong ground motion is an important method for seismic hazard prediction and assessment. A 3-D physical model in conformity with real strata configuration of （mainly） the Quaternary is a prerequisite to ensure the reliability of the simulation results. In this paper, we give a detailed account of the technical scheme and process for creating a 3-D physical model in Kunming basin. The data used are synthe- sized from seismogeological data, borehole data, topographic data, digital elevation mode （DEM） data, seismic exploration results and wave velocity measurements. Strafigraphic division is based mainly on shear wave velocity, with strata sequence taken into consideration. The model construction is finally accomplished with ArcGIS and many relevant programming techniques via layer-by-layer stacking （in depth direction） of the adjacent medium interfaces （meshes）. Meanwhile, a database of 3-D physical models is set up, which provides model data and parameters for strong ground motion simulation. Some processing methods and significant issues are also addressed in the paper in accordance with different types of exploration and experimental data.展开更多
A three-dimensional numerical model of sand wave dynamics,incorporating the interaction of currents and waves at various angles,has been developed using the Regional Ocean Modeling System(ROMS).This model accounts for...A three-dimensional numerical model of sand wave dynamics,incorporating the interaction of currents and waves at various angles,has been developed using the Regional Ocean Modeling System(ROMS).This model accounts for both bedload and suspended load sediment transport under combined waves and current conditions.The investigation examines the influence of several key parameters,including the rotation angle of sand waves relative to the main current,tidal current velocity amplitude,residual current,water depth,wave height,wave period,and wave direction,on sand wave evolution.The growth rate and migration rate of sand waves decrease as their rotation angle increases.For rotation angles smaller than 15°,sand wave evolution can be effectively simulated by a vertical 2D model with an error within 10%.The numerical results demonstrate that variations in tidal current velocity amplitude or residual current affect both vertical growth and horizontal migration of sand waves.As tidal current velocity amplitude and residual current increase,the growth rate initially rises to a maximum before decreasing.The migration rate shows a consistent increase with increasing tidal current amplitude and residual current.Under combined waves and current,both growth and migration rates decrease as water depth increases.With increasing wave height and period,the growth rate and migration rate initially rise to maximum values before declining,while showing a consistent increase with wave height and period.The change rate of sand waves reaches its maximum when wave propagation aligns parallel to tidal currents,and reaches its minimum when wave propagation is perpendicular to the currents.This phenomenon can be explained by the fluctuation of total bed shear stress relative to the angle of interaction between waves and current.展开更多
Atmospheric models are physical equations based on the ideal gas law. Applied to the atmosphere, this law yields equations for water, vapor (gas), ice, air, humidity, dryness, fire, and heat, thus defining the model o...Atmospheric models are physical equations based on the ideal gas law. Applied to the atmosphere, this law yields equations for water, vapor (gas), ice, air, humidity, dryness, fire, and heat, thus defining the model of key atmospheric parameters. The distribution of these parameters across the entire planet Earth is the origin of the formation of the climatic cycle, which is a normal climatic variation. To do this, the Earth is divided into eight (8) parts according to the number of key parameters to be defined in a physical representation of the model. Following this distribution, numerical models calculate the constants for the formation of water, vapor, ice, dryness, thermal energy (fire), heat, air, and humidity. These models vary in complexity depending on the indirect trigonometric direction and simplicity in the sum of neighboring models. Note that the constants obtained from the equations yield 275.156˚K (2.006˚C) for water, 273.1596˚K (0.00963˚C) for vapor, 273.1633˚K (0.0133˚C) for ice, 0.00365 in/s for atmospheric dryness, 1.996 in<sup>2</sup>/s for humidity, 2.993 in<sup>2</sup>/s for air, 1 J for thermal energy of fire, and 0.9963 J for heat. In summary, this study aims to define the main parameters and natural phenomena contributing to the modification of planetary climate. .展开更多
Three- dimension (3-D) wind-driven currents in the Bohai Sea in both winter and summer are calculated by using a 3- D barotropic steady model, and the results are consistent with observed flow char -acteristics. Based...Three- dimension (3-D) wind-driven currents in the Bohai Sea in both winter and summer are calculated by using a 3- D barotropic steady model, and the results are consistent with observed flow char -acteristics. Based on the results, 3- D characteristics of flow, currents at different depths, compensated flow in the lower layer , long and narrow alongshore current, the area of upwelling and downwelling, main circulation in vertical profile, and the current in Bohai Strait are discussed.展开更多
3-D geological modeling plays an increasingly important role in Petroleum Geology, Mining Geology and Engineering Geology. The complexity of geological conditions requires different modeling methods in different situa...3-D geological modeling plays an increasingly important role in Petroleum Geology, Mining Geology and Engineering Geology. The complexity of geological conditions requires different modeling methods in different situations. This paper summarizes the general concept of geological modeling; compares the characteristics of borehole-based modeling, cross-section based modeling and multi- source interactive modeling; analyses key techniques in 3-D geological modeling; and highlights the main difficulties and directions of future studies.展开更多
Applying new approaches, methods, and technologies for the estimation of reserves can effectively improve the efficiency and accuracy of assessments of solid mineral resources. After analyzing the development of 3-D g...Applying new approaches, methods, and technologies for the estimation of reserves can effectively improve the efficiency and accuracy of assessments of solid mineral resources. After analyzing the development of 3-D geoscience modeling technology （3-D GMT）, this paper discusses the application of 3-D GMT for the estimation of solid mineral reserves, emphatically introducing its workflow and two key technologies, 3-D orebody surface modeling, and property modeling. Moreover, the paper analyzes the limitations of traditional methods, such as the section method and geological block method, and points out the advantages of 3-D GMT： building more accurate 3-D orebody models, expressing the internal inhomogeneous attributes of an orebody, reducing the potential for errors in the estimation of reserves, and implementing dynamic estimations of reserves.展开更多
Underground coal mines use mechanical bolts in addition to other types of bolts to control the rib deformation and to stabilize the yielded coal ribs.Limited research has been conducted to understand the performance o...Underground coal mines use mechanical bolts in addition to other types of bolts to control the rib deformation and to stabilize the yielded coal ribs.Limited research has been conducted to understand the performance of the mechanical bolts in coal ribs.Researchers from the National Institute for Occupational Safety and Health(NIOSH)conducted this work to understand the loading characteristics of mechanical bolts(stiffness and capacity)installed in coal ribs at five underground coal mines.Standard pull-out tests were performed in this study to define the loading characteristics of mechanical rib bolts.Different installation torques were applied to the tested bolts based on the strength of the coal seam.A typical tri-linear load-deformation response for mechanical bolts was obtained from these tests.It was found that the anchorage capacity depended mainly on the coal strength.Guidelines for modeling mechanical bolts have been developed using the tri-linear load-deformation response.The outcome of this research provides essential data for rib support design.展开更多
Rockslides are one of the most common geological hazards in mountainous areas and can pose significant threats to the safety of human lives and infrastructures. Studying the dynamic fragmentation process, and fragment...Rockslides are one of the most common geological hazards in mountainous areas and can pose significant threats to the safety of human lives and infrastructures. Studying the dynamic fragmentation process, and fragment characteristics of rock blocks during rockslides is of great significance. In this study,the influences of the slope angle on the dynamic fragmentation process, damage and energy evolution,and the fragments’ flying velocity and flying angle were systematically investigated using a coupled 3D FEM-DEM method. An improved fragment search algorithm was first proposed to more effectively extract the information of the fragments after impacting. The input parameters in the numerical modeling were carefully calibrated based on the quasi-static uniaxial compression tests and the rockimpact tests. The complex fragmentation process of rock block sliding along an inclined slope was simulated. The results indicate that the fragmentation intensity gradually increases with increasing the slope angle, and the fragmentation intensity of the front region of the rock block is always higher than that of the rear region. Additionally, the slope angle can significantly affect the damage ratio, energy dissipation, and the ratio of tensile crack to shear crack during the rockslides. The number of the fragments having higher flying velocities and larger flying angles increases with increasing the slope angle,which contributes to a larger spreading distance and a wider deposition area.展开更多
In earthquake early warning systems, real-time shake prediction through wave propagation simulation is a promising approach. Compared with traditional methods, it does not suffer from the inaccurate estimation of sour...In earthquake early warning systems, real-time shake prediction through wave propagation simulation is a promising approach. Compared with traditional methods, it does not suffer from the inaccurate estimation of source parameters. For computation efficiency, wave direction is assumed to propagate on the 2-D surface of the earth in these methods. In fact, since the seismic wave propagates in the 3-D sphere of the earth, the 2-D space modeling of wave direction results in inaccurate wave estimation. In this paper, we propose a 3-D space numerical shake pre- diction method, which simulates the wave propagation in 3-D space using radiative transfer theory, and incorporate data assimilation technique to estimate the distribution of wave energy. 2011 Tohoku earthquake is studied as an example to show the validity of the proposed model. 2-D space model and 3-D space model are compared in this article, and the prediction results show that numerical shake prediction based on 3-D space model can estimate the real-time ground motion precisely, and overprediction is alleviated when using 3-D space model.展开更多
In the last 30 years,the scientific community has developed and proposed different models and numerical approaches for the study of vibrations induced by railway traffic.Most of them are formulated in the frequency/wa...In the last 30 years,the scientific community has developed and proposed different models and numerical approaches for the study of vibrations induced by railway traffic.Most of them are formulated in the frequency/wave number domain and with a 2.5D approach.Three-dimensional numerical models formulated in the time/space domain are less frequently used,mainly due to their high computational cost.Notwithstanding,these models present very attractive characteristics,such as the possibility of considering nonlinear behaviors or the modelling of excess pore pressure and non-homogeneous and non-periodic geometries in the longitudinal direction of the track.In this study,two 3D numerical approaches formulated in the time/space domain are compared and experimentally validated.The first one consists of a finite element approach and the second one of a finite difference approach.The experimental validation in an actual case situated in Carregado(Portugal)shows an acceptable fitting between the numerical results and the actual measurements for both models.However,there are some differences among them.This study therefore includes some recommendations for their use in practical soil dynamics and geotechnical engineering.展开更多
Flat subduction can significantly influence the distribution of volcanism,stress state,and surface topography of the overriding plate.However,the mechanisms for inducing flat subduction remain controversial.Previous t...Flat subduction can significantly influence the distribution of volcanism,stress state,and surface topography of the overriding plate.However,the mechanisms for inducing flat subduction remain controversial.Previous two-dimensional(2-D)numerical models and laboratory analogue models suggested that a buoyant impactor(aseismic ridge,oceanic plateau,or the like)may induce flat subduction.However,three-dimensional(3-D)systematic studies on the relationship between flat subduction and buoyant blocks are still lacking.Here,we use a 3-D numerical model to investigate the influence of the aseismic ridge,especially its width(which is difficult to consider in 2-D numerical models),on the formation of flat subduction.Our model results suggest that the aseismic ridge needs to be wide and thick enough to induce flat subduction,a condition that is difficult to satisfy on the Earth.We also find that the subduction of an aseismic ridge parallel to the trench or a double aseismic ridge normal to the trench has a similar effect on super-wide aseismic ridge subduction in terms of causing flat subduction,which can explain the flat subduction observed beneath regions such as Chile and Peru.展开更多
Fetr6 is an underground mine in which chromite is extracted using stope and pillar mining method. Despite of all improving works such as roof supporting and replacing of ore pillars with concrete pillars, pillar No. 1...Fetr6 is an underground mine in which chromite is extracted using stope and pillar mining method. Despite of all improving works such as roof supporting and replacing of ore pillars with concrete pillars, pillar No. 19 failed and other pillars failed progressively as a domino effect and 4000 m2 of mine collapsed within a few minutes, consequently. For detail investigation, two 3-D numerical models were developed by 3Dec. The first, a base model, was used for estimation of stress on pillars just before failure and the other for investigation of rock burst in pillar No. 19. The results show that discontinuity parameters such as friction angle and shear stiffness is critical parameters in this pillar failure. In addition, it indicates that W/H ratio equal 0.3, the lack of ore extraction strategy and inadequate roof support are the major reasons for this failure. In this paper, the procedure of study was described.展开更多
基金Supported by the National High-Tech Research & Development Program of China (Grant No.2006AA060102)
文摘A full 3-D finite element method numerical modeling program is written based on the principle and technical specification of borehole electric image well logging tool. The response of well logging is computed in the formation media model with a single fracture. The effect of changing fracture aperture and resistivity ratio to the logging response is discussed. The identification ability for two parallel fractures is also present. A quantitative evaluation formula of fracture aperture from borehole electric image logging data is set up. A case study of the model well is done to verify the accuracy of the for-mula. The result indicates that the formula is more accurate than the foreign one.
基金funding received by a grant from the Natural Sciences and Engineering Research Council of Canada(NSERC)(Grant No.CRDPJ 469057e14).
文摘We have proposed a methodology to assess the robustness of underground tunnels against potential failure.This involves developing vulnerability functions for various qualities of rock mass and static loading intensities.To account for these variations,we utilized a Monte Carlo Simulation(MCS)technique coupled with the finite difference code FLAC^(3D),to conduct two thousand seven hundred numerical simulations of a horseshoe tunnel located within a rock mass with different geological strength index system(GSIs)and subjected to different states of static loading.To quantify the severity of damage within the rock mass,we selected one stress-based(brittle shear ratio(BSR))and one strain-based failure criterion(plastic damage index(PDI)).Based on these criteria,we then developed fragility curves.Additionally,we used mathematical approximation techniques to produce vulnerability functions that relate the probabilities of various damage states to loading intensities for different quality classes of blocky rock mass.The results indicated that the fragility curves we obtained could accurately depict the evolution of the inner and outer shell damage around the tunnel.Therefore,we have provided engineers with a tool that can predict levels of damages associated with different failure mechanisms based on variations in rock mass quality and in situ stress state.Our method is a numerically developed,multi-variate approach that can aid engineers in making informed decisions about the robustness of underground tunnels.
基金partially supported by the National R & D Special Fund of Public Welfare Industry(No.200808069)National Natural Science Foundation of China(Nos.40974038 and 41025014)the Joint Research Collaboration Program by the Ministry of Science and Technology of China(No.2010DFA21570)
文摘We investigated how density and quality of mesh around interest domain affect electromagnetic （EM） responses of 3D Earth layered media using finite element method （FEM）. Effect of different mesh shapes was also investigated using a method of mixing structured and unstructured mesh. As a case study, we estimated the effects of meshing on selectivity phenomenon of seismic electric signal （SES）. Our results suggest that the relative errors resulting from mesh effects may not be negligible, which may lead to some unconvincing explanation of the SES selectivity based on the numerical modeling results.
基金sponsored by the National Key R&D Program of China(No.2021YFA0715100)the Shenzhen Fundamental Research Program,China(No.JCYJ20220818102601004)+1 种基金the National Natural Science Foundation of China(No.41774145)the Pre-research Project on Civil Aerospace Technologies(No.D020101)of CNSA。
文摘Various models exist to explain the formation of the Tibetan Plateau,including“tectonic escape”,“pure shear thickening”,“convective removal of the lithospheric mantle”,and“lower crustal flow”model.The first two models are primarily constructed on pure mechanical models but are unable to reasonably explain the tension and shear phenomena inside the plateau.The latter two are rheological dynamic models based on deep geophysical observations.However,the spatial range of the lower crustal flow and its role in the plateau formation/uplift remain controversial.Five multi-terrane viscoplastic thermomechanical models were constructed to simulate the uplift and lithospheric structure change of the Tibetan Plateau during the post-collision stage(since 35 Ma)under the convergence of the Indian Plate.Results show that the plateau's formation begins with crustal thickening,blocked by strong terranes at the northern plateau,and expanded laterally to the east.The lithosphere thickens gradually and experiences delamination at its base,elevating temperature within the crust and forming partial melting layers in the central plateau.As convergence persists on the southern side,the northern plateau's lithosphere bends downward and undergoes delamination,further heating the crust and promoting the northward and eastward flow of partial melting layers,leading to secondary uplift around the plateau.
文摘A 3-D numerical model is set up in a large domain covering the Hangzhou Bay and the Changjiang Estuary based on the ECOM model in orthogonal curvilinear coordinates.The numerical schemes for baroclinic pressure gradient (BPG)terms and convective terms are improved in the paper according to the characteristics of velocity field and mass transport in the area.The model is validated by the simulations of residual current and salinity transport in the Hangzhou Bay and the Changjiang Estuary.
基金supported by National Natural Science Foundation of China(Nos.41204077,41372290,41572244,51034003,51174210,and 51304126)natural science foundation of Shandong Province(Nos.ZR2011EEZ002 and ZR2013EEQ019)State Key Research Development Program of China(No.2016YFC0600708-3)
文摘Currently, numerical simulations of seismic channel waves for the advance detection of geological structures in coal mine roadways focus mainly on modeling two- dimensional wave fields and therefore cannot accurately simulate three-dimensional （3-D） full-wave fields or seismic records in a full-space observation system. In this study, we use the first-order velocity-stress staggered-grid finite difference algorithm to simulate 3-D full-wave fields with P-wave sources in front of coal mine roadways. We determine the three components of velocity Vx, Vy, and Vz for the same node in 3-D staggered-grid finite difference models by calculating the average value of Vy, and Vz of the nodes around the same node. We ascertain the wave patterns and their propagation characteristics in both symmetrical and asymmetric coal mine roadway models. Our simulation results indicate that the Rayleigh channel wave is stronger than the Love channel wave in front of the roadway face. The reflected Rayleigh waves from the roadway face are concentrated in the coal seam, release less energy to the roof and floor, and propagate for a longer distance. There are surface waves and refraction head waves around the roadway. In the seismic records, the Rayleigh wave energy is stronger than that of the Love channel wave along coal walls of the roadway, and the interference of the head waves and surface waves with the Rayleigh channel wave is weaker than with the Love channel wave. It is thus difficult to identify the Love channel wave in the seismic records. Increasing the depth of the receivers in the coal walls can effectively weaken the interference of surface waves with the Rayleigh channel wave, but cannot weaken the interference of surface waves with the Love channel wave. Our research results also suggest that the Love channel wave, which is often used to detect geological structures in coal mine stopes, is not suitable for detecting geological structures in front of coal mine roadways. Instead, the Rayleigh channel wave can be used for the advance detection of geological structures in coal mine roadways.
基金Project (No.90815008) supported by the National Natural Science Foundation of China
文摘A coupled discrete-continuum simulation incorporating a 3D aspect and non-circular particles was performed to analyze soil-pile interactions during pile penetration in sand.A self-developed non-circular particle numerical simulation program was used which considered sand near the pile as interacted particles using a discrete element method;the sand away from the pile was simulated as a continuous medium exhibiting linear elastic behaviors.The domain analyzed was divided into two zones.Contact forces at the interface between the two zones were obtained from a discrete zone and applied to the continuum boundaries as nodal forces,while the interface velocities were obtained from the continuum zone and applied to the discrete boundaries.We show that the coupled discrete-continuum simulation can give a microscopic description of the pile penetration process without losing the discrete nature of the zone concerned,and may significantly improve computational efficiency.
基金Supported by the National Natural Science Foundation of China(No.41271436)
文摘Numerical simulation modeling is a hotspot in the geological engineering computing field. Tak- ing a fast Langrangian analysis of continua in 3 dimensions （FLAC3D） numerical modeling on com- puting the geo-deformation information caused by the mining subsidence in a coalmine for example, a new GIS-Excel modeling method is proposed to build geologic strata within the simulation range combined with the coal-seam dip angle of the underground mining working-planes. First of all, the coal-seam model of the numerical computing is built by using the geographic information system （GIS） according to the stripe-through principle and the calculating formula on the size of the model blocks in the paper defined, then the FLAC3D numerical computing model of all geologic strata with- in the simulation range is also built based on the calculating formula of thickness of each stratum and the Excel fast computing advantages. The GIS-Excel method is good at the higher modeling accuracy, seldom making mistakes and consuming less time. The reliability and validity of the method is veri- fied well by its practical applications in the coalmine area.
基金Urban Active Fault Detection Project sponsored by the National Development andReform Commission of China(2004-1138)National Natural Science Foundation of China(40604005)+1 种基金Joint Seismological Science Foundation of China(A07027)Key Project during the 10th Five-year Plan Period from Earthquake Administration of China(J105B-16).
文摘Seismic hazard assessment based on urban active faults can provide scientific bases for city planning and project construction, while numerical simulation of strong ground motion is an important method for seismic hazard prediction and assessment. A 3-D physical model in conformity with real strata configuration of （mainly） the Quaternary is a prerequisite to ensure the reliability of the simulation results. In this paper, we give a detailed account of the technical scheme and process for creating a 3-D physical model in Kunming basin. The data used are synthe- sized from seismogeological data, borehole data, topographic data, digital elevation mode （DEM） data, seismic exploration results and wave velocity measurements. Strafigraphic division is based mainly on shear wave velocity, with strata sequence taken into consideration. The model construction is finally accomplished with ArcGIS and many relevant programming techniques via layer-by-layer stacking （in depth direction） of the adjacent medium interfaces （meshes）. Meanwhile, a database of 3-D physical models is set up, which provides model data and parameters for strong ground motion simulation. Some processing methods and significant issues are also addressed in the paper in accordance with different types of exploration and experimental data.
基金the National Natural Science Foundation of China(Grant Nos.52371289 and 51979192).
文摘A three-dimensional numerical model of sand wave dynamics,incorporating the interaction of currents and waves at various angles,has been developed using the Regional Ocean Modeling System(ROMS).This model accounts for both bedload and suspended load sediment transport under combined waves and current conditions.The investigation examines the influence of several key parameters,including the rotation angle of sand waves relative to the main current,tidal current velocity amplitude,residual current,water depth,wave height,wave period,and wave direction,on sand wave evolution.The growth rate and migration rate of sand waves decrease as their rotation angle increases.For rotation angles smaller than 15°,sand wave evolution can be effectively simulated by a vertical 2D model with an error within 10%.The numerical results demonstrate that variations in tidal current velocity amplitude or residual current affect both vertical growth and horizontal migration of sand waves.As tidal current velocity amplitude and residual current increase,the growth rate initially rises to a maximum before decreasing.The migration rate shows a consistent increase with increasing tidal current amplitude and residual current.Under combined waves and current,both growth and migration rates decrease as water depth increases.With increasing wave height and period,the growth rate and migration rate initially rise to maximum values before declining,while showing a consistent increase with wave height and period.The change rate of sand waves reaches its maximum when wave propagation aligns parallel to tidal currents,and reaches its minimum when wave propagation is perpendicular to the currents.This phenomenon can be explained by the fluctuation of total bed shear stress relative to the angle of interaction between waves and current.
文摘Atmospheric models are physical equations based on the ideal gas law. Applied to the atmosphere, this law yields equations for water, vapor (gas), ice, air, humidity, dryness, fire, and heat, thus defining the model of key atmospheric parameters. The distribution of these parameters across the entire planet Earth is the origin of the formation of the climatic cycle, which is a normal climatic variation. To do this, the Earth is divided into eight (8) parts according to the number of key parameters to be defined in a physical representation of the model. Following this distribution, numerical models calculate the constants for the formation of water, vapor, ice, dryness, thermal energy (fire), heat, air, and humidity. These models vary in complexity depending on the indirect trigonometric direction and simplicity in the sum of neighboring models. Note that the constants obtained from the equations yield 275.156˚K (2.006˚C) for water, 273.1596˚K (0.00963˚C) for vapor, 273.1633˚K (0.0133˚C) for ice, 0.00365 in/s for atmospheric dryness, 1.996 in<sup>2</sup>/s for humidity, 2.993 in<sup>2</sup>/s for air, 1 J for thermal energy of fire, and 0.9963 J for heat. In summary, this study aims to define the main parameters and natural phenomena contributing to the modification of planetary climate. .
基金Project supported by the National Natural science Foundation of China
文摘Three- dimension (3-D) wind-driven currents in the Bohai Sea in both winter and summer are calculated by using a 3- D barotropic steady model, and the results are consistent with observed flow char -acteristics. Based on the results, 3- D characteristics of flow, currents at different depths, compensated flow in the lower layer , long and narrow alongshore current, the area of upwelling and downwelling, main circulation in vertical profile, and the current in Bohai Strait are discussed.
文摘3-D geological modeling plays an increasingly important role in Petroleum Geology, Mining Geology and Engineering Geology. The complexity of geological conditions requires different modeling methods in different situations. This paper summarizes the general concept of geological modeling; compares the characteristics of borehole-based modeling, cross-section based modeling and multi- source interactive modeling; analyses key techniques in 3-D geological modeling; and highlights the main difficulties and directions of future studies.
文摘Applying new approaches, methods, and technologies for the estimation of reserves can effectively improve the efficiency and accuracy of assessments of solid mineral resources. After analyzing the development of 3-D geoscience modeling technology （3-D GMT）, this paper discusses the application of 3-D GMT for the estimation of solid mineral reserves, emphatically introducing its workflow and two key technologies, 3-D orebody surface modeling, and property modeling. Moreover, the paper analyzes the limitations of traditional methods, such as the section method and geological block method, and points out the advantages of 3-D GMT： building more accurate 3-D orebody models, expressing the internal inhomogeneous attributes of an orebody, reducing the potential for errors in the estimation of reserves, and implementing dynamic estimations of reserves.
文摘Underground coal mines use mechanical bolts in addition to other types of bolts to control the rib deformation and to stabilize the yielded coal ribs.Limited research has been conducted to understand the performance of the mechanical bolts in coal ribs.Researchers from the National Institute for Occupational Safety and Health(NIOSH)conducted this work to understand the loading characteristics of mechanical bolts(stiffness and capacity)installed in coal ribs at five underground coal mines.Standard pull-out tests were performed in this study to define the loading characteristics of mechanical rib bolts.Different installation torques were applied to the tested bolts based on the strength of the coal seam.A typical tri-linear load-deformation response for mechanical bolts was obtained from these tests.It was found that the anchorage capacity depended mainly on the coal strength.Guidelines for modeling mechanical bolts have been developed using the tri-linear load-deformation response.The outcome of this research provides essential data for rib support design.
基金supported by the National Natural Science Foundation of China (Grant Nos.52004182, 51908431)。
文摘Rockslides are one of the most common geological hazards in mountainous areas and can pose significant threats to the safety of human lives and infrastructures. Studying the dynamic fragmentation process, and fragment characteristics of rock blocks during rockslides is of great significance. In this study,the influences of the slope angle on the dynamic fragmentation process, damage and energy evolution,and the fragments’ flying velocity and flying angle were systematically investigated using a coupled 3D FEM-DEM method. An improved fragment search algorithm was first proposed to more effectively extract the information of the fragments after impacting. The input parameters in the numerical modeling were carefully calibrated based on the quasi-static uniaxial compression tests and the rockimpact tests. The complex fragmentation process of rock block sliding along an inclined slope was simulated. The results indicate that the fragmentation intensity gradually increases with increasing the slope angle, and the fragmentation intensity of the front region of the rock block is always higher than that of the rear region. Additionally, the slope angle can significantly affect the damage ratio, energy dissipation, and the ratio of tensile crack to shear crack during the rockslides. The number of the fragments having higher flying velocities and larger flying angles increases with increasing the slope angle,which contributes to a larger spreading distance and a wider deposition area.
基金supported by the National Key Technology Research and Development Program of the Ministry of Science and Technology of China(grant No.2014BAK03B02)Science for Earthquake Resilience(grant Nos XH16021 and XH16022Y)
文摘In earthquake early warning systems, real-time shake prediction through wave propagation simulation is a promising approach. Compared with traditional methods, it does not suffer from the inaccurate estimation of source parameters. For computation efficiency, wave direction is assumed to propagate on the 2-D surface of the earth in these methods. In fact, since the seismic wave propagates in the 3-D sphere of the earth, the 2-D space modeling of wave direction results in inaccurate wave estimation. In this paper, we propose a 3-D space numerical shake pre- diction method, which simulates the wave propagation in 3-D space using radiative transfer theory, and incorporate data assimilation technique to estimate the distribution of wave energy. 2011 Tohoku earthquake is studied as an example to show the validity of the proposed model. 2-D space model and 3-D space model are compared in this article, and the prediction results show that numerical shake prediction based on 3-D space model can estimate the real-time ground motion precisely, and overprediction is alleviated when using 3-D space model.
文摘In the last 30 years,the scientific community has developed and proposed different models and numerical approaches for the study of vibrations induced by railway traffic.Most of them are formulated in the frequency/wave number domain and with a 2.5D approach.Three-dimensional numerical models formulated in the time/space domain are less frequently used,mainly due to their high computational cost.Notwithstanding,these models present very attractive characteristics,such as the possibility of considering nonlinear behaviors or the modelling of excess pore pressure and non-homogeneous and non-periodic geometries in the longitudinal direction of the track.In this study,two 3D numerical approaches formulated in the time/space domain are compared and experimentally validated.The first one consists of a finite element approach and the second one of a finite difference approach.The experimental validation in an actual case situated in Carregado(Portugal)shows an acceptable fitting between the numerical results and the actual measurements for both models.However,there are some differences among them.This study therefore includes some recommendations for their use in practical soil dynamics and geotechnical engineering.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB 41000000)the National Natural Science Foundation of China(Grant No.41820104004)the Fundamental Research Funds for the Central Universities(Grant No.WK2080000144).
文摘Flat subduction can significantly influence the distribution of volcanism,stress state,and surface topography of the overriding plate.However,the mechanisms for inducing flat subduction remain controversial.Previous two-dimensional(2-D)numerical models and laboratory analogue models suggested that a buoyant impactor(aseismic ridge,oceanic plateau,or the like)may induce flat subduction.However,three-dimensional(3-D)systematic studies on the relationship between flat subduction and buoyant blocks are still lacking.Here,we use a 3-D numerical model to investigate the influence of the aseismic ridge,especially its width(which is difficult to consider in 2-D numerical models),on the formation of flat subduction.Our model results suggest that the aseismic ridge needs to be wide and thick enough to induce flat subduction,a condition that is difficult to satisfy on the Earth.We also find that the subduction of an aseismic ridge parallel to the trench or a double aseismic ridge normal to the trench has a similar effect on super-wide aseismic ridge subduction in terms of causing flat subduction,which can explain the flat subduction observed beneath regions such as Chile and Peru.
文摘Fetr6 is an underground mine in which chromite is extracted using stope and pillar mining method. Despite of all improving works such as roof supporting and replacing of ore pillars with concrete pillars, pillar No. 19 failed and other pillars failed progressively as a domino effect and 4000 m2 of mine collapsed within a few minutes, consequently. For detail investigation, two 3-D numerical models were developed by 3Dec. The first, a base model, was used for estimation of stress on pillars just before failure and the other for investigation of rock burst in pillar No. 19. The results show that discontinuity parameters such as friction angle and shear stiffness is critical parameters in this pillar failure. In addition, it indicates that W/H ratio equal 0.3, the lack of ore extraction strategy and inadequate roof support are the major reasons for this failure. In this paper, the procedure of study was described.
