Multi-beam bathymetry and seismic sequence surveys in the northern slope of the South China Sea reveal detailed geomorphology and seismic stratigraphy characteristics of canyons, gullies, and mass movements. Modern ca...Multi-beam bathymetry and seismic sequence surveys in the northern slope of the South China Sea reveal detailed geomorphology and seismic stratigraphy characteristics of canyons, gullies, and mass movements. Modern canyons and gullies are roughly elongated NNW–SSW with U-shaped cross sections at water depths of 400–1000 m. Mass movements include slide complexes, slide scars, and debris/turbidity flows. Slide complexes and slide scars are oriented in the NE–SW direction and cover an area of about 1790 and 926 km^2, respectively. The debris/turbidity flows developed along the lower slope. A detailed facies analysis suggests that four seismic facies exist, and the late Cenozoic stratigraphy above the acoustic basement can be roughly subdivided into three sequences separated by regional unconformities in the study area. The occurrence of gas hydrates is marked by seismic velocity anomalies, bottom-simulating reflectors, gas chimneys, and pockmarks in the study area. Seismic observations suggest that modern canyons and mass movements formed around the transition between the last glacial period and the current interglacial period. The possible existence and dissociation of gas hydrates and the regional tectonic setting may trigger instability and mass movements on the seafloor. Canyons may be the final result of gas hydrate dissociation. Our study aims to contribute new information that is applicable to engineering construction required for deep-water petroleum exploration and gas hydrate surveys along any marginal sea.展开更多
The mechanical behavior of sliding zone soils plays a significant role in landslide. In general, the sliding zone soils are basically in unsaturated state due to rainfall infiltration and reservoir water level fluctua...The mechanical behavior of sliding zone soils plays a significant role in landslide. In general, the sliding zone soils are basically in unsaturated state due to rainfall infiltration and reservoir water level fluctuation. Meanwhile, a large number of examples show that the deformation processes of landslides always take a long period of time, indicating that landslides exhibit a time-dependent property. Therefore, the deforma- tion of unsaturated soils of landslide involves creep behaviors. In this paper, the Burgers creep model for unsaturated soils under triaxial stress state is considered based on the unsaturated soil mechanics. Then, by curve fitting using the least squares method, creep parameters in different matric suction states are obtained based on the creep test data of unsaturated soils in the sliding zones of Qianjiangping landslide. Results show that the predicted results are in good agreement with the experimental data, Finally, to fur- ther explore the creep characteristics of the unsaturated soils in sliding zones, the relationships between parameters of the model and matric suction are analyzed and a revised Burgers creep model is developed correspondingly. Simulations on another group of test data are performed by using the modified Burgers creep model and reasonable results are observed,展开更多
This research shows a noticeable comparison between slide zones produced with the results using the Nilsen method with active tectonic hazard zonation map. A determination landform of geometry or morphometry factors i...This research shows a noticeable comparison between slide zones produced with the results using the Nilsen method with active tectonic hazard zonation map. A determination landform of geometry or morphometry factors is one of the best methods for study and evaluation active tectonics. The first image provided is a Dem maps from GIS software showing topography, geology and tectonic maps participant with field activities. The second image provided shows an active tectonic map also generated by the same above mentioned factors into three classes A, B, C, D and a landslide hazard zonation map which shows five classes: Stable zone, generally stable zone, stable moderately stable zone, moderately stable zone and talented to liquefaction zone. The study and comparison and conformity landslide hazard zonation map with hazard zonations into active tectonic hazard zonation map showed about 79 percent (56,880 hectare) moderately unstable zone and talented for liquefaction zone settled in A zone (very high tectonic activity) and B zone (high tectonic activity) active tectonic map and 21 percent (15,130 hectare) remain unsettled sequential 12 percent (8640 hectare) and 9 percent (6480 hectare) in C (moderate tectonic activity), D (lowest tectonic activity) zone of active tectonic hazard zonation produced from above mentioned factors. This research showed a relationship between slide zones produced in landslide hazard zonations using the Nilsen method to measure active tectonic hazard zonation in the study region.展开更多
The diffusion behavior of Zn/Al interfaces in their powders sintering was investigated with SEM. The results show that Zn-Al eutectoid microstructure can be achieved through their powders sintering, and the diffusion ...The diffusion behavior of Zn/Al interfaces in their powders sintering was investigated with SEM. The results show that Zn-Al eutectoid microstructure can be achieved through their powders sintering, and the diffusion characteristic between Zn and Al is just a demonstration of Kirkendall effect, by which Zn can dissolve into Al and contrarily Al cannot dissolve into Zn. During sintering, a diffusion-solution zone α′ has formed and subsequently transforms into eutectoid microstructure in cooling process. The superplastic deformation mechanism of Zn-Al eutectic alloy is phase boundary sliding which is controlled by diffusion-solution zone α′. If diffusion-solution zone α′ is unsaturated, it will have much more crystal defects and the combination between α′ and β phase is weak, thus the process of phase boundary sliding becomes easily; on the contrary, if the diffusion-solution zone α′ becomes thick and saturated, the sliding will be difficult.展开更多
A design scheme of adaptive fuzzy controller for a class of uncertain MIMO nonlinear systems with unknown dead-zones and a triangular control structure is proposed in this pa-per. The design is based on the principle ...A design scheme of adaptive fuzzy controller for a class of uncertain MIMO nonlinear systems with unknown dead-zones and a triangular control structure is proposed in this pa-per. The design is based on the principle of sliding mode control and the property of Nussbaum function. The approach does not require a priori knowledge of the signs of the control gains and the upper bounds and lower bounds of dead-zone parameters to be known a priori. By introducing the integral-type Lyapunov function and adopting the adaptive compensation term of the upper bound of the optimal approximation error and the dead-zone disturbance, the closed-loop control system is proved to be semi-globally stable in the sense that all signals involved are bounded, with tracking errors converging to zero.展开更多
A large number of laboratory investigations related to the permeability have been conducted on the sliding zones.Yet little attention has been paid to the particular sliding zones of the slideprone Badong Formation.He...A large number of laboratory investigations related to the permeability have been conducted on the sliding zones.Yet little attention has been paid to the particular sliding zones of the slideprone Badong Formation.Here,we experimentally investigate the permeability nature and the mechanism of seepage in the viscous sliding zone of the Huangtupo Landslide.Saturated seepage tests have been performed first with consideration of six dry densities and thirteen hydraulic gradients,in conjunction with the mercury intrusion porosimetry test and scanning electron microscopy test for the microstructure analysis after seepage.The results show that seepage in the sliding zone soil does not follow Darcy’s Law,since there is a threshold hydraulic gradient(i0)below which no flow is observed and a critical hydraulic gradient(icr)over which the hydraulic conductivity(K)tends to be stable.The percentage of bound water could be responsible for the occurrence of i0 and icr.Furthermore,pore size distributions(PSD)less than 0.6µm and between 10 and 90µm exhibit positive and negative correlations with the i0,respectively,indicating that the i0 is related to the PSD.The mechanism accounting for this result is that pore water pressure forces fine clay particles into the surrounding large pores and converts arranged particles to discretely distributed ones,thereby weakening the connectivity of pores.The seepages in the sliding zones behave differently from that in the sliding mass and sliding bed in response to the permeability.展开更多
基金funded by the China Geological Survey Project (Nos. GZH201500207 1212010611302 DD20160 138)
文摘Multi-beam bathymetry and seismic sequence surveys in the northern slope of the South China Sea reveal detailed geomorphology and seismic stratigraphy characteristics of canyons, gullies, and mass movements. Modern canyons and gullies are roughly elongated NNW–SSW with U-shaped cross sections at water depths of 400–1000 m. Mass movements include slide complexes, slide scars, and debris/turbidity flows. Slide complexes and slide scars are oriented in the NE–SW direction and cover an area of about 1790 and 926 km^2, respectively. The debris/turbidity flows developed along the lower slope. A detailed facies analysis suggests that four seismic facies exist, and the late Cenozoic stratigraphy above the acoustic basement can be roughly subdivided into three sequences separated by regional unconformities in the study area. The occurrence of gas hydrates is marked by seismic velocity anomalies, bottom-simulating reflectors, gas chimneys, and pockmarks in the study area. Seismic observations suggest that modern canyons and mass movements formed around the transition between the last glacial period and the current interglacial period. The possible existence and dissociation of gas hydrates and the regional tectonic setting may trigger instability and mass movements on the seafloor. Canyons may be the final result of gas hydrate dissociation. Our study aims to contribute new information that is applicable to engineering construction required for deep-water petroleum exploration and gas hydrate surveys along any marginal sea.
基金Supported by the National Natural Science Foundation of China (50879044)Master's Degree Thesis Excellent Training Funds of Three Gorges University(2011PY008)
文摘The mechanical behavior of sliding zone soils plays a significant role in landslide. In general, the sliding zone soils are basically in unsaturated state due to rainfall infiltration and reservoir water level fluctuation. Meanwhile, a large number of examples show that the deformation processes of landslides always take a long period of time, indicating that landslides exhibit a time-dependent property. Therefore, the deforma- tion of unsaturated soils of landslide involves creep behaviors. In this paper, the Burgers creep model for unsaturated soils under triaxial stress state is considered based on the unsaturated soil mechanics. Then, by curve fitting using the least squares method, creep parameters in different matric suction states are obtained based on the creep test data of unsaturated soils in the sliding zones of Qianjiangping landslide. Results show that the predicted results are in good agreement with the experimental data, Finally, to fur- ther explore the creep characteristics of the unsaturated soils in sliding zones, the relationships between parameters of the model and matric suction are analyzed and a revised Burgers creep model is developed correspondingly. Simulations on another group of test data are performed by using the modified Burgers creep model and reasonable results are observed,
文摘This research shows a noticeable comparison between slide zones produced with the results using the Nilsen method with active tectonic hazard zonation map. A determination landform of geometry or morphometry factors is one of the best methods for study and evaluation active tectonics. The first image provided is a Dem maps from GIS software showing topography, geology and tectonic maps participant with field activities. The second image provided shows an active tectonic map also generated by the same above mentioned factors into three classes A, B, C, D and a landslide hazard zonation map which shows five classes: Stable zone, generally stable zone, stable moderately stable zone, moderately stable zone and talented to liquefaction zone. The study and comparison and conformity landslide hazard zonation map with hazard zonations into active tectonic hazard zonation map showed about 79 percent (56,880 hectare) moderately unstable zone and talented for liquefaction zone settled in A zone (very high tectonic activity) and B zone (high tectonic activity) active tectonic map and 21 percent (15,130 hectare) remain unsettled sequential 12 percent (8640 hectare) and 9 percent (6480 hectare) in C (moderate tectonic activity), D (lowest tectonic activity) zone of active tectonic hazard zonation produced from above mentioned factors. This research showed a relationship between slide zones produced in landslide hazard zonations using the Nilsen method to measure active tectonic hazard zonation in the study region.
文摘The diffusion behavior of Zn/Al interfaces in their powders sintering was investigated with SEM. The results show that Zn-Al eutectoid microstructure can be achieved through their powders sintering, and the diffusion characteristic between Zn and Al is just a demonstration of Kirkendall effect, by which Zn can dissolve into Al and contrarily Al cannot dissolve into Zn. During sintering, a diffusion-solution zone α′ has formed and subsequently transforms into eutectoid microstructure in cooling process. The superplastic deformation mechanism of Zn-Al eutectic alloy is phase boundary sliding which is controlled by diffusion-solution zone α′. If diffusion-solution zone α′ is unsaturated, it will have much more crystal defects and the combination between α′ and β phase is weak, thus the process of phase boundary sliding becomes easily; on the contrary, if the diffusion-solution zone α′ becomes thick and saturated, the sliding will be difficult.
基金Supported by National Natural Science Foundation of P.R.China(60074013), the Foundation of the Education Bureau of JiangsuProvince (KK0310067&05KJB520152), and the Foundation of Infor-mation Science Subject Group of Yangzhou University (ISG 030606).
文摘A design scheme of adaptive fuzzy controller for a class of uncertain MIMO nonlinear systems with unknown dead-zones and a triangular control structure is proposed in this pa-per. The design is based on the principle of sliding mode control and the property of Nussbaum function. The approach does not require a priori knowledge of the signs of the control gains and the upper bounds and lower bounds of dead-zone parameters to be known a priori. By introducing the integral-type Lyapunov function and adopting the adaptive compensation term of the upper bound of the optimal approximation error and the dead-zone disturbance, the closed-loop control system is proved to be semi-globally stable in the sense that all signals involved are bounded, with tracking errors converging to zero.
基金supported by the National Key Scientific Instrument and Equipment Development Project of China(No.41827808)the Major Program of National Natural Science Foundation of China(No.42090055)the National Natural Science Foundation of China(Nos.42107180,42207212,42007268,42162023,and 42162025).
文摘A large number of laboratory investigations related to the permeability have been conducted on the sliding zones.Yet little attention has been paid to the particular sliding zones of the slideprone Badong Formation.Here,we experimentally investigate the permeability nature and the mechanism of seepage in the viscous sliding zone of the Huangtupo Landslide.Saturated seepage tests have been performed first with consideration of six dry densities and thirteen hydraulic gradients,in conjunction with the mercury intrusion porosimetry test and scanning electron microscopy test for the microstructure analysis after seepage.The results show that seepage in the sliding zone soil does not follow Darcy’s Law,since there is a threshold hydraulic gradient(i0)below which no flow is observed and a critical hydraulic gradient(icr)over which the hydraulic conductivity(K)tends to be stable.The percentage of bound water could be responsible for the occurrence of i0 and icr.Furthermore,pore size distributions(PSD)less than 0.6µm and between 10 and 90µm exhibit positive and negative correlations with the i0,respectively,indicating that the i0 is related to the PSD.The mechanism accounting for this result is that pore water pressure forces fine clay particles into the surrounding large pores and converts arranged particles to discretely distributed ones,thereby weakening the connectivity of pores.The seepages in the sliding zones behave differently from that in the sliding mass and sliding bed in response to the permeability.
