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821.
An almost 6,000 years old slide in marine clay at Fossmoen, Northern Norway is studied to: characterize the scar, the slide
deposits and the slide event; evaluate the role that stratigraphic variations played for failure; and view the slide event
within long-term landscape development. A geological model for the area is based on drilling, outcrops and ground-penetrating
radar with emphasis on the stratigraphic variations of fjord deposits. The slide’s age implies that the deposits were sensitive
already shortly after emergence above sea level, and layers are still sensitive. River incision was probably responsible for
the initial slide, whereas stratigraphy and groundwater movement controlled the location and shape of the scar. Laminated,
inclined and discontinuous bedding are suggested as playing different roles for ground-water flow and pore pressures, adding
to existing models on the development of soft and sensitive layers prone to sliding. 相似文献
822.
Landslide hazard mapping at Selangor, Malaysia using frequency ratio and logistic regression models 总被引:28,自引:9,他引:28
The aim of this study is to evaluate the landslide hazards at Selangor area, Malaysia, using Geographic Information System
(GIS) and Remote Sensing. Landslide locations of the study area were identified from aerial photograph interpretation and
field survey. Topographical maps, geological data, and satellite images were collected, processed, and constructed into a
spatial database in a GIS platform. The factors chosen that influence landslide occurrence were: slope, aspect, curvature,
distance from drainage, lithology, distance from lineaments, land cover, vegetation index, and precipitation distribution.
Landslide hazardous areas were analyzed and mapped using the landslide-occurrence factors by frequency ratio and logistic
regression models. The results of the analysis were verified using the landslide location data and compared with probability
model. The comparison results showed that the frequency ratio model (accuracy is 93.04%) is better in prediction than logistic
regression (accuracy is 90.34%) model. 相似文献
823.
Charles A. Stock Dennis J. McGillicuddy Jr Donald M. Anderson Andrew R. Solow Richard P. Signell 《Continental Shelf Research》2007
Blooms of the toxic dinoflagellate Alexandrium fundyense commonly occur in the western Gulf of Maine but the amount of toxin observed in coastal shellfish is highly variable. In this study, a coupled physical–biological model is used to investigate the dynamics underlying the observed A. fundyense abundance and shellfish toxicity in 1993 (a high toxicity year) and 1994 (low toxicity year). The physical model simulates the spring circulation, while the biological model estimates the germination and population dynamics of A. fundyense based on laboratory and field data. The model captures the large-scale aspects of the initiation and development of A. fundyense blooms during both years, but small-scale patchiness and the dynamics of bloom termination remain problematic. In both cases, the germination of resting cysts accounts for the magnitude of A. fundyense populations early in the spring. Simulations with low net A. fundyense growth rates capture the mean observed concentration during the bloom peak, which is of similar magnitude during both years. There is little evidence that large-scale changes in biological dynamics between 1993 and 1994 were a primary driver of the differences in shellfish toxicity. Results instead suggest that the persistent southwesterly flow of the western Maine Coastal Current led to A. fundyense populations of similar alongshore extent by late May of both years. This period coincides with peak cell abundance in the region. Variations in wind forcing (downwelling favorable in 1993, upwelling favorable in 1994) and subsequent cell transport (inshore in 1993, offshore in 1994) in early June then provides a plausible explanation for the dramatic mid-June differences in shellfish toxicity throughout the western Gulf of Maine. 相似文献
824.
The physical process of oxygen transfer or oxygen absorption from the atmosphere acts to replenish the used oxygen, a process termed re‐aeration or aeration. Aeration enhancement by macro‐roughness is well‐known in water treatment and one form is the aeration cascade. The macro‐roughness of the steps significantly reduces the flow velocities and leads to flow aeration along the stepped cascade. In this paper, the aeration efficiency in stepped cascade aerators was modeled by using the Adaptive Network Based Fuzzy Inference System (ANFIS). The obtained model was tested with experimental data. Test results showed that ANFIS can be used to estimate the aeration efficiency in stepped cascade aerators. 相似文献
825.
三维景观建模技术是地理信息系统的重要发展领域。本文以AUTOCAD格式的施工设计图为基础,利用三维可视地理信息系统软件Imagis2.3,通过数据的预处理、三维建模、纹理映射,建立了福建师范大学新校区理工楼群模型,并就有关技术问题进行了讨论。 相似文献
826.
滑坡支挡结构荷载取值问题研究 总被引:5,自引:1,他引:5
当前,在我国工程界,滑坡支挡结构上的荷载取值普遍以传递系数法的条间力(即剩余下滑力)为基础,本文对这种荷载取值方法存在的问题进行了分析,提出了以稳定性为基础确定滑坡支挡结构上荷载的方法,该方法能弥补现行荷载取值方法的不足。 相似文献
827.
828.
The literature review on discrete element (DEM) model analysis of jigging reveals that an idealized fluid behavior is assumed and the damping of the fluid motion across the mineral bed is generally ignored. A microscopic model based on the principles of Computational Fluid Dynamics (CFD) is used to simulate the liquid flow and stratification of coal particles with a wide size range and density distribution in jigging. Fluid motion is calculated by directly solving the Navier–Stokes equations. Coal particles are moved in a Lagrangian frame through the action of forces imposed by the fluid and gravity. Particle effects on fluid motion are fed back at each time step through calculating the velocity disturbance caused by the particle. Particle–particle and particle–wall collisions are also considered. The snapshots of particle configurations for the simulation of stratification in oscillating flow show that the model predicts the macroscopic behavior, such as segregation and stratification, of particles reasonably well. 相似文献
829.
A risk analysis is developed for a test site located in the area north of Lisbon using a scenario of a temporary interruption
of the motorway A9 due to a landslide of rotational or translational type. Landslide susceptibility is assessed at the regional
scale independently for rotational and translational slides, comparing the landslide distribution with a set of assumed independent
landslide predisposing factors. Susceptibility models are validated and classified through the computation of prediction rate
curves based on the temporal partition of the landslide data sets. Landslide hazard maps are based on a scenario of future
landslide occurrence for the next 27 years. These maps allow the definition of two critical areas on the motorway A9 with
regards to landslide susceptibility. Direct costs associated with both critical spots are assessed taking into account the
probable affected area of the motorway, and the reconstruction costs. Indirect costs derived from the traffic interruption
are evaluated considering the alternatives paths to the motorway, and include costs resulting from: (1) additional fuel consumption;
(2) decrease in tollgate income; and (3) loss of productive time. Results show that indirect costs may be 24 to 43 times higher
than direct costs, assuming a temporary interruption of the motorway for 6 months. 相似文献
830.
Distribution of landslides adjacent to the northern side of the Yarlu Tsangpo Grand Canyon in Tibet, China 总被引:2,自引:0,他引:2
This paper presents results of recent studies on distribution and category of landslides in one section of the Sichuan–Tibet
Highway, adjacent to the northern side of the Yarlu Tsangpo Grand Canyon, Tibet, Southwestern China. In the tectonic setting
predominated by compression and strike-slipping, active faults are dominant and result in the genesis of the great alpine
relief together with fluvial incision and unloading. In this section, with a distance of about 290 km between Ranwu and Lulang,
34 landslides occurred. Among them, the 12 large and super-large landslides comprise the most dangerous part of the highway
system to road users over the past 50 years. The landslides usually occurred in slopes comprised of moraine with a large thickness,
fluvio-pluvial and lacustrine deposits and fractured rocks. Based on the examination of the physical geography, structural
geology, Quaternary geology, stratigraphy and petrography, this paper presents the temporal-spatial distribution of landslides
along the section and classification of them into three types with respect to mechanism and composites of landslides.
Each of the three types is presented by distinctive case examples. Type 1 is Yigong Landslide; type 2 includes Dongjiu Landslide
group, 102 Landslide group, Suotong Landslide group, Songzong Landslide; and the type 3 is Layue Landslide. A binary landslide,
which is seldom seen in nature and which occurred in the outlet of one creek under the integrative function of fluvial incision
and road cut, is also presented. These are distributed in different parts of the area with characterized structural geology,
topography and composites (gneiss and Quaternary deposits) with accumulative quantity between Suotong and Dongjiu. The most
occurred with frequent and rapid translation, shallow shearing planes, various influential factors and unique triggering factors,
and a variable period of reoccurrence with a tendency of increasing magnitude. In this region, six influential factors greatly
contribute to their occurrence: (a) intensive neotectonic movements, (b) ongoing alpine canyon relief, (c) earthquakes, (d)
heavy precipitation, (e) stream erosion, and (f) human activities, to a certain extent. Mostly, the latter four factors play
major roles in triggering landslide occurrence. The earthquake causes the rock and soil to fracture and deform, and tends
to be unstable, or cause earth-induced landslides. The heavy rainfall in monsoon seasons which saturates the soil and lower
the shearing strength is mostly responsible for the occurrence of landslides. The stream erosion disturbs slope toes causing
progressive failure. Road construction and deforestation decrease the natural slope stability. Comments and suggestions on
the physical measures for remediation of landslides and safety of highways are also made. 相似文献
Type 1. | Landslide initiated at high elevation and transformed into a distal debris flow damming the river with a long reoccurrence interval |
Type 2. | Landslide at stream banks, in different ranks of mass movements in dissecting layers of moraines |
Type 3. | Landslide of fractured rock mass with quick translation movements. |