25 resultados para Automatic water level recorder (AWLR)
Resumo:
本文以具有典型特征的苏北淤泥质潮滩海岸作为研究区,利用1975-2003年间14景覆盖该地区的Landsat和SPOT卫星影像作为主要数据源,结合地面调查和验证工作,在遥感影像处理和地理信息系统分析技术的支持下,对区内潮滩、岸线、水边线和盐沼植被等进行遥感解译,分析苏北辐射沙脊群和沿岸地貌的空间分布特征和动态演变趋势。研究结果表明:苏北辐射沙脊群海域的潮汐水位过程的不同步现象普遍存在,限制了常规遥感数据在苏北潮滩地貌研究中的适用范围和解译精度;在人工判别的辅助下,多光谱遥感的非监督分类方法可以有效解译淤泥质潮滩的水边线;利用修改型土壤调整植被指数(MSAVI)可以较好地提取潮滩上的盐沼植被信息;苏北沿岸潮滩的快速淤长促进了盐沼植被带向海侧快速扩展,近年来持续的潮滩围垦工程则不断从陆侧侵占盐沼植被带,使盐沼植被带宽度减小乃至消失;在大规模人类活动和自然条件的共同影响下,苏北辐射沙脊群海岸的岸线发育趋于平直化,无序的潮滩围垦项目使得可垦滩地资源被过度消耗;1975~2002年间,研究区北部和南部沿岸的高潮滩整体上处于淤长状态,中部沿岸潮滩和离岸沙洲高潮滩则被大面积侵蚀;1999年以来,研究区内低潮滩部位开始形成有序排列的滩面地物,并表现出逐年大面积蔓延的趋势,可能是滩涂紫菜养殖区扩展的结果。
Resumo:
The Indian monsoon, an integral part of the global climate system, has been extensively investigated during the past decades. Most of the proxy records are derived from marine sediments and focused on time periods of the late Miocene and Pleistocene. The Pliocene represents a period when Earth’s boundary conditions underwent dramatic changes. However, variations of the Indian monsoon during the Pliocene and its forcing mechanisms have remained unclear. The Yuanmou Basin, located in the region of the Indian monsoon, provides an ideal target for understanding the Pliocene history of Indian monsoon variations. Detailed investigations on the lithostratigraphy, magnetostratigraphy and limnology of a 650-m-thick fluvio-lacustrine sedimentary sequence from the basin are carried out in the present study. The clay and clay-plus-fine-silt fractions of the sediments are referred to the midlake-facies components, and changes in the percentages of both fractions generally reflect changes in the water level of the lakes developed in the basin closely related to variations in the intensity of the Indian monsoon. Whereas the greenish-gray lacustrine mud beds represent the environment of deep-water lakes, and the frequency of individual lacustrine mud beds is considered to indicate the frequency of the deep-water lakes developed in the basin associated with the variability of the Indian monsoon. The proxy data suggest that the Indian monsoon experienced abrupt shifts at 3.53, 3.14, 2.78 and 2.42 Ma, respectivey. 1) Since 3.53 Ma, the midlake-facies components displayed a general trend of increase in the concentrations, accompanied by an increase in the sedimentation rate from an average ~10 to 25 cm ka–1. The data suggest that high stands of the lakes in the basin rose progressively, implying a gradual intensification of the Indian monsoon since that time. This shift occurred coeval with the accelerated uplift of the northern Tibetan Plateau, denoting a close link between the Indian monsoon strengthening and the Tibetan Plateau uplifting. 2) 2.78 Ma ago, the concentrations of the midlake-facies components decreased abruptly and the dominant fraction of the sediments turned to fluvial sands. The data indicate that lakes in the basin disappeared, reflecting a dramatic decline in the intensity of the Indian monsoon at that time. This shift coincided with the formation of extensive Northern Hemisphere ice sheets, implying a quick response of the low-latitude monsoon regime to the high-latitude glaciation. 3) At 3.14 Ma, the initial appearance of blackish-grey mud beds with long durations and occasional occurrences of lacustrine mud beds indicate that the basin was overall dominated by shallow lakes, implying a shift to decreased variability of the Indian monsoon at that time. At 2.42 Ma, an increase in the frequency and a decrease in the duration of the lacustrine mud beds suggest that deep-water lakes were frequently developed in the basin, denoting a shift to increased variability of the Indian monsoon at that time. The former shift coincides with the onset of large-scale glaciation in the circum Atlantic region and the latter corresponds to the inception of predominance of the 41 ka periodicity in Northern Hemisphere ice-sheet cover fluctuations, presumably suggesting a physical link between the Indian monsoon system and the high-latitude ice sheets in the Northern Hemisphere.
Resumo:
Based on field survey, laboratory testing and numerical modeling, engineering characteristics of undisturbed loess and the mechanism of long-runout loess landslides caused by underground water level rise, as well as the formation conditions and spatial distribution of landslides, are systematically studied and analyzed. Loess landslides at south Plateau of Jingyang County are mainly classified as flowslide, slide and fall. Flowslide is the main type characteristic of high velocity, long runout and multi-stages. The steep relief composed of loose structured loess-old aged soil serials and the rise of groundwater table are the predominant conditions for landslides in the study area. To study loess mechanic poperties and loess landslides mechanisims, isotropically and anisotropically consolidated undrained compression(ICU and ACU) tests and constant-deviator-drained compression (CQD) tests were carried out on undisturbed samples. The results of undrained compression tests performed at the in-situ stress level show that the soils are of consistently strain-softening in the stress-strain relations and cause high excess pore pressure. The steady-state line and the potential region of instability are obtained from ICU and ACU test results. A necessary condition for liquefaction is that the soil state initially lies in or is brought into the potential instability region. In addition, a strong strain-softening model is also formed. CQD tests demonstrate that the mobilized friction angle is far less than the steady-state angle and that the soil experiences undrained contractive failure suddenly at very small strains when its stress path during drained loading tries to cross the potential instability region,thus validates the proposed instability region. Based on the location of the region of potential instability and the stress state of slope soil, a method of static liquefaction analysis is proposed for loess landslides caused by rise in groundwater table. Compared with other liquefaction analysis methods, this method overcomes the limitations inherent in conventional slope stability method and undrained brittleness index method. Triaxial tests composed of constant water content (CW) and wetting tests at constant deviator stress are performed on undisturbed unsaturated samples. The stress-strain relation of CW tests takes on strain-hardening behavior; The results of wetting tests at constant deviator stress designed to study the mechanics of failure of unsaturated loess caused by an increase in the degree of saturation (wetting) shows that a contractive failure occurs in the undisturbed samples. On the basis of the above triaxial test results, the initiation of static liquefaction is presented for long-runout loess landslides caused by rise in groundwater table, that is, the loess slope soil gradually transfer from unsaturated to saturated state under the infiltration of irrigation. A contractive failure occurs in the local region at very small strain by increasing the pore-water pressure at constant deviator stresses under drained conditons. It is the contractive failrue resulting from rise of pore pressure that leads to high excess pore pressure in the neighbour soil which reduces shear resistance of soil. The neighbour soils also fail due to the rapid increase in pore-water pressure. Thus a connected failure surface is developed quickly and a flowslide occurs. Based on the saturated-unsaturated seepage theory, transient seepage is computed using the finite element method on loess slope under groundwater table rise. Pore-water pressure distribution for every time step after irrigation are obtained. The phreatic surface in the slope increases with the groundwater table. Pore-water pressure distribution within 8m above the phreatic surface changes very quickly,but the water content and pore water pressure in the region ranging from 8m above the phreatic surface up to ground surface is almost not affected and the matric suction usually is kept at 100~120 kPa. Based on the results of laboratory tests and seepage flow analysis, the development process of loess landslide is modeled considering groundwater table rise. The shearing plastic zone first occurs at the slope toe where the soil is soaked for long term during rise in groundwater table. As irrigation continues, the shearing plastic zone gradually extends to the interior soils, with the results that the tensile plastic zone occurs at the slope crown. As time goes on, both the shearing plastic zone and tensile plastic zone continue to extend. Then a connected plastic zone is formed and fowslide occurs. In comparision to laboratory test results, the results of numerical simulation quite well verify the presented mechanism of static liquefaction of long-runout loess landslides caused by rise in groundwater table.
Resumo:
The aim of this study is to increase the precision of groundwater modeling. The way is use the distributed model calculate the mountain basin groundwater lateral discharge and the river runoff. With appropriate technique help, the groundwater model can couple the distributed model results. This paper’s study object is makeing the distributed hydrological model HEC-HMS coupled to the popular groundwater model Visual MODFLOW. The application example is Jiyuan basin which is a typical basin of North China. HEC-HMS can calculate the surface runoff and subsurface runoff at mountain-pass. The subsurface runoff can turn to recharge well straightly. The water level - runoff course and Trial method is used to back analyze the parameters of surface runoff to Visual MODFLOW. So the distributed hydrological model can coupled to the groundwater model. The research proved that base on couple the distributed surface water model the groundwater model’s results are notability improved. The example is Jiyuan basin where use the distributed model coupled to the groundwater model. On the base of the coupled model applied to Jiyuan basin groundwater modeling. The paper estimates the groundwater change in the study area. Then, by use the water resources integrated planning results, the article calculate the basin groundwater can be development and utilization quantity and potential.
Resumo:
Soil-rock mixture (S-RM) refers to one extremely uneven loose rock and soil materials system with certain stone content. Its formation has started since Quaternary and it is composed of block stone, fine grained soil and pore with certain project scale and high strength. S-RM has extensive distribution in nature, especially in southwest China where the geotectonic background is complicated, the fracture activity is developed and the geomorphological characteristics of high mountain and steep gorge area are protuberant. This kind of complicated geologic body has developed wider in these areas. S-RM has obvious difference with the general soil or rock (rock mass) in physical and mechanical properties because its two components-“soil” and “rock-block” has extreme differences in physical and mechanical properties. The proposition of S-RM and its deep research are needed in the modern engineering construction. It is also the necessity in the modern development of rock and soil mechanics. The dissertation starts from the meso-structural characteristics of soil-rock and takes a systematic research on its meso-structural mechanics, deformation and failure mechanism and the stability of S-RM slope. In summary, it achieves the following innovative results and conclusions. There are various views on the conception of S-RM and its classification system. Based on the large number of field tests, the dissertation makes the conception and classification of S-RM more systematic. It systematically proposed the conception of meso-structural mechanics of S-RM. Thus the dissertation has laid a foundation for its deep study. With the fast development of the computer technology and digital image processing theory, digital image processing technology has been successfully applied in many fields and provided reliable technology support for the quantitative description of the structural characteristics of S-RM. Based on the digital image processing technology, the dissertation systematically proposes and developed the quantitative analysis method and quantitative index for the meso-structure of S-RM. The results indicate that the meso-structure such as its internal soil-rock granularity composition, the soil-rock shape and the orientability has obvious self-organization in the macro statistical level. The dissertation makes a systematic research on the physical mechanical properties, deformation and failure mechanism of S-RM based on large field test. It proposes the field test for the underwater S-RM and deduces the 3D data analysis method of in-situ horizontal push-shear test. The result indicates that S-RM has significant phenomenon of shear dilatancy in the shearing process, and its dilatancy will be more obvious with the increased proportion of rock or the decreased confining pressure. The proportion of rock has great effect on the strength of S-RM and rock-block, especially the spatial position of particles with comparatively big size has great effect on the shape and spatial position of the sample shear zone. The dissertation makes some improvements in the single ring infiltration test equipment and its application on the permeability of S-RM. The results indicate that the increasing of rock-block would make it more difficult for the soil to fill in the vacuity between the rock-block and the proportion would increase which would result in the increased permeability coefficient. The dissertation builds the real meso-structural model of S-RM based on the digital image processing technology. By using geometric reconstruction technology, it transfers the structural mode represented by Binary image into CAD format, which makes it possible to introduce the present finite element analysis software to take research on numerical experimental investigation. It systematically realizes leaping research from the image,geometric mode, to meso-structural mechanics numerical experiment. By using this method, the dissertation takes large scale numerical direct-shear test on the section of S-RM. From the mesoscopic perspective, it reveals three extended modes about the shear failure plane of S-RM. Based on the real meso-structural model and by using the numerical simulation test, the character and mechanics of seepage failure of S-RM are studied. At the same time, it builds the real structural mode of the slope based on the analysis about the slope crosssection of S-RM. By using the strength reduction method, it takes the research on the stability of S-RM and gets great achievements. The three dimensional geometric reconstruction technology of rock block is proposed, which provides technical support for the reconstruction of the 3D meso-structural model of S-RM. For the first time, the dissertation builds the stochastic structure model of two-dimensional and three-dimensional polygons or polyhedron based on the stochastic simulation technique of monte carlo method. It breaks the traditional research which restricted to the random generation method of regular polygon and develops the relevant software system (R-SRM2D/3D) which has great effect on meso-structural mechanics of S-RM. Based on the R-SRM software system which randomly generates the meso-structural mode of S-RM according to the different meso-structural characteristics, the dissertation takes a series of research on numerical test of dual axis and real three-axis, systematically analyses the meso destroy system, the effects of meso-structural characteristics such as on the stone content, size composition and block directionality on the macro mechanical behavior and macro-permeability. Then it proposes the expression of the upper and lower limit for the macro-permeability coefficient of the inhomogeneous geomaterials, such as S-RM. By using the strength reduction FEM, the dissertation takes the research on the stability of the slope structural mode of the randomly formed S-RM. The results indicate that generally, the stability coefficient of S-RM slope increases with the increasing of stone content; on the condition of the same stone content, the stability coefficient of slope will be different with different size composition and the space position of large block at the internal slop has great effect on the stability. It suggests that meso-structural characteristics, especially the space position of large block should be considered when analyzing the stability of this kind of slope and strengthening design. Taking Xiazanri S-RM slope as an example, the dissertation proposes the fine modeling of complicated geologic body based on reverse engineering and the generation method of FLAC3D mode. It resolves the bottleneck problem about building the fine structural mode of three-dimensional geological body. By using FLAC3D, the dissertation takes research on the seepage field and the displacement field of Xiazanri S-RM slope in the process of reservoir water level rising and decreasing. By using strength reduction method, it analyses the three-dimension stability in the process of reservoir water level rising and decreasing. The results indicate that the slope stability firstly show downward trend in the process of reservoir water level rising and then rebound to increase; the sudden drawdown of reservoir water level has great effect on the slope stability and this effect will increase with the sudden drawdown amplitude rising. Based on the result of the rock block size analysis of S-RM, and using R-SRM2D the stochastic structure model of Xiazanri S-RM slope is built. By using strength reduction method, the stability of the stochastic structure model is analysis, the results shows that the stability factor increases significantly after considering the block.
Resumo:
Gas condensate reservoir research involves not only structure sediment reservoir liquid properties characterization but also the change of the temperature field, the change of the pressure field, the change of liquid phase and the reservoir sensitivity. To develop the gas condensate reservoir effectively .we must depict the static properties of the oil and gas system ,build exact and comprehensive parameter field, predict the rule of dynamic change and do the necessary reservoir characterization development plan dynamic prediction direct production. The MoBei Oil and Gas Field is the first gas condensate reservoirs which is found by the Xinjiang Oil Field Company in ZhunGaEr basin belly.it has deserved some knowledge after prospect evaluation, the MoBei Oil and Gas Field start development ,it is one of the important development blocks of Xinjiang Oil Field Company productivity constuction. During its development , it gradually appears some problems, such as complex oil and gas phase, great change of reservoir stretch .uncertain reservoir type and scale, controling its development strategy and plan difficultly. To deserve the high efficient development and long-term stable production of the gas condensate reservoir, it is necessary to characterize it systematically and form a suit of scientific development strategy. This thesis take the MoBei zone SanGongHe sand group reservoir as research object, applied advanced log techniques ,such as the nulear magnetism log ,MDT testing .etc. After comprehensive research of loging geology information, set up a suit of methods to identify oil gas water layer .these methods can identify the gas-oil level and the oil-water level. On the basis of reasonable development object system, according fine structure interpretation and structure modeling. build any oil water column height of the reservoir accurately. Through carefully analysis of the basic theory and method of reservoir seism prediction. optimize a reservoir inversion method .technique. software fitting the research region aiming strata, set up the GR field, porosity field, Rt field, impedence field .permeability field and initial oil saturation field, generating the base of quantity reservoir characterization. Discussing the characteristic of reservoir fluid and the movement and reallocating of muti-phase fluid in reservoir. And according the material of 100 soviet gas condensate reservoir ,build the recognition method and mode of gas condensate reservoir. Building the 3D geology model ,carry on the static and production evaluation, propose the development strategy and improve plan , provide the base of increasing reserves and advancing production and enriching the prospect development theory of the gas condensate reservoi
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This paper presents a method for trace level analysis of microcystins in water using solid-phase extraction and high performance liquid chromatography. The optimized condition enabled the determination of common microcystins at levels as low as 0.02 similar to 0.05 mug/L, and the liner range is from 0.1 mug/L to 50 mug/L. The method has been applied to the analysis of field sample from Dianchi lake.
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This paper presents a new image segmentation method that applies an edge-based level set method in a relay fashion. The proposed method segments an image in a series of nested subregions that are automatically created by shrinking the stabilized curves in their previous subregions. The final result is obtained by combining all boundaries detected in these subregions. The proposed method has the following three advantages: 1) It can be automatically executed without human-computer interactions; 2) it applies the edge-based level set method with relay fashion to detect all boundaries; and 3) it automatically obtains a full segmentation without specifying the number of relays in advance. The comparison experiments illustrate that the proposed method performs better than the representative level set methods, and it can obtain similar or better results compared with other popular segmentation algorithms.