Ground-penetrating radar (GPR) has been used predominantly for environments with low electrical conductivity like freshwater aquifers, glaciers, or dry sandy soils. The objective of the present study was to explore it...Ground-penetrating radar (GPR) has been used predominantly for environments with low electrical conductivity like freshwater aquifers, glaciers, or dry sandy soils. The objective of the present study was to explore its application for mapping in subsurface agricultural soils to a depth of several meters. For a loamy sand and a clayey site on the North China Plain, clay inclusions in the sand were detected; the thickness, inclination, and continuity of the confining clay and silt layers was assessed; and a local water table was mapped. Direct sampling (soil coring and profiling) in the top meter and independent measurement of the water table were utilized to confirm the findings. Also, effective estimates of the dielectric number for the site with the dielectric number of moist clayey soils depending strongly on frequency were obtained. Thus, important properties of soils, like the arrangement and type of layers and in particular their continuity and inclination, could be explored with moderate efforts for rather large areas to help find optimal locations for the time-consuming and expensive measurements which would be necessary to detail a model of the subsurface.展开更多
In the design of revetment engineering under wave action, to resist the wave action, the pattern of top layer-filter layer-core （subsoil） is often adopted. In general, the structure of top layer is usually single di...In the design of revetment engineering under wave action, to resist the wave action, the pattern of top layer-filter layer-core （subsoil） is often adopted. In general, the structure of top layer is usually single discrete blocks, typically accropode blocks, four-leg square hollow blocks and barrier boards, and also acropode, riprap, paved rock blocks or concrete slabs with smaller waves. Such top layer has been provided with many research findings on its stability and is widely used in engineering. Setting a filter layer between the top layer and the lower dike core mainly has two functions： （1） giving certain permeability, to minimize the hydrodynamic load directly acting on the lower foundation soil; （2） giving certain hydraulic tightness, to prevent fine sediment of the lower foundation soil from being washed out. This paper is focused on a special filter layer with geotextile as its upper structure and coarse aggregate as its lower structure. By simulating geotextile with different permeability and coarse aggregate with different size, the pressure of top of cover layer and the down side of the geotextile is tested under wave actions, and compared with theoretical analysis, in this way, how the permeability of geotextile impacts the stability of top layer is studied. The research shows that when the filter layer under the geotextile has high permeability and the geotextile＇s permeability gets poorer, the uplift force to geotextile and the top layer will be increased under wave action, which will cause damage to the top layer when it is greater than the vertical component of the underwater gravity along the slope surface.展开更多
Used numerical simulation method to study the floor water-inrush mechanism in working face which was influenced by fault structure, and set up many kinds of models and performs numerical calculation by fully using lar...Used numerical simulation method to study the floor water-inrush mechanism in working face which was influenced by fault structure, and set up many kinds of models and performs numerical calculation by fully using large finite element soft-ANSYS and element birth-death method. The results show that the more high the underground water pressure, the more big the floor displacement and possibility of water-inrush; the floor which has fault structure is more prone to water-inrush than the floor which not has fault structure, the floor which has multi-groups cracks is more prone to water-inrush than the floor which has single-group cracks. The numerical simulation result forecasts the water-inrush in working face preferably.展开更多
The structure of the South Asia High(SAH)in the stratosphere and the influence of ENSO on the SAH are systematically investigated with the long-term ECMWF reanalysis data.The results show that the SAH only exists in l...The structure of the South Asia High(SAH)in the stratosphere and the influence of ENSO on the SAH are systematically investigated with the long-term ECMWF reanalysis data.The results show that the SAH only exists in low levels of the stratosphere.The maximum intensity of the High is located at around 150 hPa and there is no obvious anti-cyclonic structure above 50 hPa.The axis of the SAH center tends to be northwest slanting from lower levels to higher levels.Further analyses show that the geopotential height and temperature fields of the SAH have dramatic anomalies during El Ni?o years and La Ni?a years. Corresponding to the ENSO,the SAH is weaker(stronger)at the warm(cold)phase.展开更多
Shear wave velocity is one of the important dynamic characteristics of soil layers and applied widely in aseismic engineering. In this paper, 500 drill logging data are used to make a linear interpolation based on 0. ...Shear wave velocity is one of the important dynamic characteristics of soil layers and applied widely in aseismic engineering. In this paper, 500 drill logging data are used to make a linear interpolation based on 0. 01° x 0. 01°x lm grid. A shallow 3-D shear wave velocity structure of Tianjin coastal area is obtained. According to the data and geological background, we selected two typical velocity profiles to try to introduce and explain its relationship to basement structure. The results show that the shear wave velocity structure clearly presents the characteristic of stratification and lateral inhomogeneity. Furthermore, the difference of the shear wave structure between tectonic elements is clear and the velocity structure between the two sides of the local or border fault in the Quaternary is disturbed or affected significantly. It intuitively shows that the basement structure and fault activity of this region had good control of sedimentation development and strata formation in the Quaternary period which would have an important effect on engineering seismic and geological condition evaluation.展开更多
The extensional model of the South China Sea(SCS)has been widely studied,but remains under debate.Based on the latest high-quality multi-channel seismic data,bathymetric data,and other obtained seismic profiles,the as...The extensional model of the South China Sea(SCS)has been widely studied,but remains under debate.Based on the latest high-quality multi-channel seismic data,bathymetric data,and other obtained seismic profiles,the asymmetric characteristics between the conjugate margins of the SCS are revealed and extensional model of the SCS margin is discussed further.Spatial variation of morphology,basement structure,and marginal faults are discovered among the SCS margin profiles.As for the NS-trending variation,the basement of northern margin displays in the shape of step downwards to the sea,while the basement of southern margin is composed of wide rotated and tilted blocks,without any obvious bathymetric change.The variation also exists in the development of marginal faults between the conjugate margins,and detachment fault system is identified on the southern margin.Along the southern margin from east to west,the Eastern and Southwestern Basins developed different structural units.Based on the tectonic contrast of the conjugate margins,differential extensional model is proposed to explain the spatial variation of the SCS structure,which introduces detachment faults controlling the evolution of the SCS.The upper crust above the detachment fault was deformed by simple shear,while the lower crust and upper mantle below the detachment fault was deformed by pure shear.Because of the different lateral transfer between the upper brittle faulting and the lower ductile extensional regions,there developed marginal plateau(Liyue basin)and outer rise(Zhenghe massif)on the lower plate margin of the Eastern Basin and the Southwestern Basin,respectively.The evolution of the present SCS may be influenced by the diachronous close of the paleo-SCS.展开更多
Ten years of SABER/TIMED temperature data are used to analyze the global structure and seasonal variations of the migrating 6-h tide from the stratosphere to the lower thermosphere. The amplitudes of the migrating 6-h...Ten years of SABER/TIMED temperature data are used to analyze the global structure and seasonal variations of the migrating 6-h tide from the stratosphere to the lower thermosphere. The amplitudes of the migrating 6-h tide increase with altitudes. In the stratosphere, the migrating 6-h tide peaks around 35°N/S. The climatologically annual mean of the migrating 6-h tide clearly shows the manifestation of the(4, 6) Hough mode between 70 and 90 km that peaks at the equator and near 35°N/S. Above 90 km, the 6-h tide shows more than one Hough mode with the(4, 6) mode being the dominant one. The migrating 6-h tide is stronger in the southern hemisphere. Annual, semiannual, 4-, and 3-month oscillations are the four dominant seasonal variations of the tidal amplitude. In the stratosphere and stratopause, the spring enhancement of the 6-h tide at middle latitudes is the most conspicuous feature. From the mesosphere to the lower thermosphere, the tidal amplitude at low latitudes is gradually in the scale of that at middle latitudes and exhibits different temporal variations at different altitudes and latitudes. Both ozone heating in the stratosphere and the background atmosphere probably affect the generation and the seasonal variations of the migrating 6-h tide. In addition, the non-linear interaction between different tidal harmonics is another possible mechanism.展开更多
基金Project supported in part by the Deutsche Forschungsgemeinschaft (DFG), Germany (No. RO 1080/8-1) jointly by Max-Planck Gesellschaft and the Chinese Academy of Sciences through a travel grant to the first author.
文摘Ground-penetrating radar (GPR) has been used predominantly for environments with low electrical conductivity like freshwater aquifers, glaciers, or dry sandy soils. The objective of the present study was to explore its application for mapping in subsurface agricultural soils to a depth of several meters. For a loamy sand and a clayey site on the North China Plain, clay inclusions in the sand were detected; the thickness, inclination, and continuity of the confining clay and silt layers was assessed; and a local water table was mapped. Direct sampling (soil coring and profiling) in the top meter and independent measurement of the water table were utilized to confirm the findings. Also, effective estimates of the dielectric number for the site with the dielectric number of moist clayey soils depending strongly on frequency were obtained. Thus, important properties of soils, like the arrangement and type of layers and in particular their continuity and inclination, could be explored with moderate efforts for rather large areas to help find optimal locations for the time-consuming and expensive measurements which would be necessary to detail a model of the subsurface.
文摘In the design of revetment engineering under wave action, to resist the wave action, the pattern of top layer-filter layer-core （subsoil） is often adopted. In general, the structure of top layer is usually single discrete blocks, typically accropode blocks, four-leg square hollow blocks and barrier boards, and also acropode, riprap, paved rock blocks or concrete slabs with smaller waves. Such top layer has been provided with many research findings on its stability and is widely used in engineering. Setting a filter layer between the top layer and the lower dike core mainly has two functions： （1） giving certain permeability, to minimize the hydrodynamic load directly acting on the lower foundation soil; （2） giving certain hydraulic tightness, to prevent fine sediment of the lower foundation soil from being washed out. This paper is focused on a special filter layer with geotextile as its upper structure and coarse aggregate as its lower structure. By simulating geotextile with different permeability and coarse aggregate with different size, the pressure of top of cover layer and the down side of the geotextile is tested under wave actions, and compared with theoretical analysis, in this way, how the permeability of geotextile impacts the stability of top layer is studied. The research shows that when the filter layer under the geotextile has high permeability and the geotextile＇s permeability gets poorer, the uplift force to geotextile and the top layer will be increased under wave action, which will cause damage to the top layer when it is greater than the vertical component of the underwater gravity along the slope surface.
文摘Used numerical simulation method to study the floor water-inrush mechanism in working face which was influenced by fault structure, and set up many kinds of models and performs numerical calculation by fully using large finite element soft-ANSYS and element birth-death method. The results show that the more high the underground water pressure, the more big the floor displacement and possibility of water-inrush; the floor which has fault structure is more prone to water-inrush than the floor which not has fault structure, the floor which has multi-groups cracks is more prone to water-inrush than the floor which has single-group cracks. The numerical simulation result forecasts the water-inrush in working face preferably.
基金Project of Program"973"(2006CB403600)Natural Foundamental Research and Development Project"973"Program(40675051)
文摘The structure of the South Asia High(SAH)in the stratosphere and the influence of ENSO on the SAH are systematically investigated with the long-term ECMWF reanalysis data.The results show that the SAH only exists in low levels of the stratosphere.The maximum intensity of the High is located at around 150 hPa and there is no obvious anti-cyclonic structure above 50 hPa.The axis of the SAH center tends to be northwest slanting from lower levels to higher levels.Further analyses show that the geopotential height and temperature fields of the SAH have dramatic anomalies during El Ni?o years and La Ni?a years. Corresponding to the ENSO,the SAH is weaker(stronger)at the warm(cold)phase.
基金jointly sponsored by the Special Program of Science and Technology Innovation of Tianjin Municipality ( 07FDZDSF02102 )the Geological Program of Mineral Resources Compensation of Tianjin Municipality,China
文摘Shear wave velocity is one of the important dynamic characteristics of soil layers and applied widely in aseismic engineering. In this paper, 500 drill logging data are used to make a linear interpolation based on 0. 01° x 0. 01°x lm grid. A shallow 3-D shear wave velocity structure of Tianjin coastal area is obtained. According to the data and geological background, we selected two typical velocity profiles to try to introduce and explain its relationship to basement structure. The results show that the shear wave velocity structure clearly presents the characteristic of stratification and lateral inhomogeneity. Furthermore, the difference of the shear wave structure between tectonic elements is clear and the velocity structure between the two sides of the local or border fault in the Quaternary is disturbed or affected significantly. It intuitively shows that the basement structure and fault activity of this region had good control of sedimentation development and strata formation in the Quaternary period which would have an important effect on engineering seismic and geological condition evaluation.
基金supported by the National Natural Science Foundation of China(Grant No.41006031)Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA11030102)the National High Technology Research and Development Program of China(Grant No.2009AA093401)
文摘The extensional model of the South China Sea(SCS)has been widely studied,but remains under debate.Based on the latest high-quality multi-channel seismic data,bathymetric data,and other obtained seismic profiles,the asymmetric characteristics between the conjugate margins of the SCS are revealed and extensional model of the SCS margin is discussed further.Spatial variation of morphology,basement structure,and marginal faults are discovered among the SCS margin profiles.As for the NS-trending variation,the basement of northern margin displays in the shape of step downwards to the sea,while the basement of southern margin is composed of wide rotated and tilted blocks,without any obvious bathymetric change.The variation also exists in the development of marginal faults between the conjugate margins,and detachment fault system is identified on the southern margin.Along the southern margin from east to west,the Eastern and Southwestern Basins developed different structural units.Based on the tectonic contrast of the conjugate margins,differential extensional model is proposed to explain the spatial variation of the SCS structure,which introduces detachment faults controlling the evolution of the SCS.The upper crust above the detachment fault was deformed by simple shear,while the lower crust and upper mantle below the detachment fault was deformed by pure shear.Because of the different lateral transfer between the upper brittle faulting and the lower ductile extensional regions,there developed marginal plateau(Liyue basin)and outer rise(Zhenghe massif)on the lower plate margin of the Eastern Basin and the Southwestern Basin,respectively.The evolution of the present SCS may be influenced by the diachronous close of the paleo-SCS.
基金supported by the Chinese Academy of Sciences(Grant No.KZZD-EW-01-2)the National Natural Science Foundation of China(Grant Nos.41331069,41274153)+2 种基金the National Basic Research Program of China(Grant No.2011CB811405)the Specialized Research Fund for State Key Laboratories of Chinaperformed by Numerical Forecast Modelling R&D and VR System of State Key Lab.of Space Weather and Special HPC workstand of Chinese Meridian Project
文摘Ten years of SABER/TIMED temperature data are used to analyze the global structure and seasonal variations of the migrating 6-h tide from the stratosphere to the lower thermosphere. The amplitudes of the migrating 6-h tide increase with altitudes. In the stratosphere, the migrating 6-h tide peaks around 35°N/S. The climatologically annual mean of the migrating 6-h tide clearly shows the manifestation of the(4, 6) Hough mode between 70 and 90 km that peaks at the equator and near 35°N/S. Above 90 km, the 6-h tide shows more than one Hough mode with the(4, 6) mode being the dominant one. The migrating 6-h tide is stronger in the southern hemisphere. Annual, semiannual, 4-, and 3-month oscillations are the four dominant seasonal variations of the tidal amplitude. In the stratosphere and stratopause, the spring enhancement of the 6-h tide at middle latitudes is the most conspicuous feature. From the mesosphere to the lower thermosphere, the tidal amplitude at low latitudes is gradually in the scale of that at middle latitudes and exhibits different temporal variations at different altitudes and latitudes. Both ozone heating in the stratosphere and the background atmosphere probably affect the generation and the seasonal variations of the migrating 6-h tide. In addition, the non-linear interaction between different tidal harmonics is another possible mechanism.
