排序方式： 共有9条查询结果，搜索用时 15 毫秒
1
1.
Physical modelling of gelifluction and frost creep: Some results of a large-scale laboratory experiment 总被引：1，自引：0，他引：1
An experimental slope was constructed in a 5 m × 5 m square refrigerated tank. The slope was formed of four sections, each consisting of regolith (soil) collected from a distinct bedrock lithology. The four lithologies utilized were granite, limestone, mudstone and slate. The slope was subjected to freezing and thawing from the surface downwards. Water was supplied at the base of the soil during freezing. Frost heaving and surface downslope soil movement were determined after each of 15 freezing cycles, and the profiles of soil movement with depth for each soil type were measured at the end of the 15th cycle. The experimental soils were non-cohesive; those derived from granite and limestone were respectively sandy and gravelly in texture, while those derived from mudstone and slate were silt-rich. Mass movement in the granite and limestone soils was due mainly to frost creep and was associated with the growth of needle ice. In the mudstone and slate soils, gelifluction was dominant as a result of high moisture contents caused by the melting of segregation ice. Mean per cycle rates of downslope soil transport for the granite, limestone, mudstone and slate soils were 5·8 cm3 cm?1, 6·9 cm3 cm?1, 21·2 cm3 cm?1 and 31·2 cm3 cm?1 respectively, units referring to the volume of soil passing a unit width of slope per cycle. Mass movement rates were shown to be strongly related to the silt content of the soils. 相似文献
2.
Laboratory and numerical investigation of flow and transport near a seepage-face boundary 总被引：3，自引：0，他引：3
Laboratory and numerical modeling investigations were completed to study the unconfined ground water flow and transport processes near a seepage-face boundary. The laboratory observations were made in a radial sand tank and included measurements of the height of the seepage face, flow velocity near the seepage face, travel time distribution of multiple tracer slugs, and streamlines. All the observations were reliably reproduced with a three-dimensional, axi-symmetric, variably saturated ground water flow model. Physical data presented in this work demonstrate and quantify the importance of three-dimensional transport patterns within a seepage-face zone. The results imply that vertically averaged flow models that employ Dupuit approximations might introduce error in the analysis of localized solute transport near a seepage-face boundary. The experimental dataset reported in this work will also be of interest for those who are attempting to validate a numerical algorithm for solving ground water and contaminant discharge patterns near a surface-water boundary. 相似文献
3.
4.
Shari L. Gallop Ana Vila-Concejo Thomas E. Fellowes Mitchell D. Harley Maryam Rahbani John L. Largier 《地球表面变化过程与地形》2020,45(15):3854-3868
Many estuaries contain sandy beaches that provide habitats and offer protective buffers for wetlands and infrastructure, alongside cultural and recreational resources. Research underpinning coastal management tends to focus on tide- and swell-dominated sandy beaches, but little attention is given to beaches in estuaries and bays (BEBs) that exist along a continuum of wind/swell wave, tide and riverine influence. BEBs are subject to less wave energy than open coast locations because of the generally narrow window of directions for which ocean waves can propagate through the entrance. However, when storm wave direction coincides with the orientation of the estuary or bay entrance, waves can penetrate several kilometres inside. Here we focus on eight BEBs in two major bays/estuaries in Sydney, Australia and present observations from before and after a major extratropical storm with waves from an atypical direction in June 2016. We quantify magnitudes of beach erosion and recovery rates for 3 years post-storm. We show that when high-energy storm waves penetrate bays and estuaries, BEBs can undergo up to 100% of subaerial beach erosion. Three years after the storm, only 5 of the 29 (17%) eroded subaerial beach profiles had recovered to their pre-storm volume. This is likely due to the lack of low-frequency, beach-building waves at BEBs under modal weather conditions in between storms, in contrast to open coast beaches. We also show that the recovery of BEBs may be limited by the absence of adjacent sediment reservoirs due to the dominance of tidal processes mid-channel. Our study highlights the unique behaviour of BEBs relative to beaches on the open coast, and that shifting wave direction needs to be considered in long-term beach resilience under climate change. © 2020 John Wiley & Sons, Ltd. 相似文献
5.
Differential compaction has long been used by seismic interpreters to infer subsurface geology using knowledge of the relative compaction of different types of sediments. We outline a method to infer the gross fraction of shale in an interval between two seismic horizons using sandstone and shale compaction laws. A key component of the method involves reconstruction of a smooth depositional horizon by interpolating decompacted thicknesses from well control. We derive analytic formulae for decompaction calculations using known porosity–stress relations and do not employ discrete layer iterative methods; these formulae were found to depend not only upon the gross fraction of shale but also on the clay content of the shales and the thickness of the interval. The relative merits of several interpolation options were explored, and found to depend upon the structural setting. The method was successfully applied to an oil sands project in Alberta, Canada. 相似文献
6.
Fabrice G. Renaud Jörn Birkmann Marion Damm Gilberto C. Gallopín 《Natural Hazards》2010,55(3):749-763
External suffusion, as selective erosion of fine particles through the contact with a coarser layer and moving away, is an
important phenomenon in dams which may lead to their failure. To study the initiation of external suffusion, caused by water
level increase upstream the dam, a series of experimental investigations were conducted on laboratory-scale model, in the
hydrodynamic laboratory of école polytechnique de Montreal. On the built model, clay/moraine formed the core, sand was used
as a filter and gravel performed the role of the pervious layer. Several different models (in geometry and constituent materials)
were built and subjected to the water level increase upstream, which resulted in changes in the hydraulic gradient. The results
showed no evidence of considerable suffusion on the clay/moraine and sand interface, while the visual and quantitative data
show the presence of suffusion on the sand and gravel interface. The results of the experiments show that, when focusing on
the critical hydraulic gradient that initiates the movement of the clay/moraine particles, it can be concluded that despite
the differences in test conditions, the critical hydraulic gradient has approximately the same value in all cases. It was
also shown that increasing the length of the filter layer or applying stair-like slopes does not have great impacts on the
initiation of suffusion, whereas the gravel-size distribution has a great impact on the erosion rate. 相似文献
7.
8.
In southwest Western Australia, strong and persistent sea breezes are common between September and February. We hypothesized
that on the inner continental shelf, in the absence of tidal forcing, the depth, magnitude, and lag times of the current speed
and direction responses to sea breezes would vary though the water column as a function of the sea breeze intensity. To test
this hypothesis, field data were used from four sites were that were in water depths of up to 13 m. Sites were located on
the inner continental shelf and were on the open coast and in a semi-enclosed coastal embayment. The dominant spectral peak
in currents at all sites indicated that the majority of the spectral energy contained in the currents was due to forcing by
sea breezes. Currents were aligned with the local orientation of the shoreline. On a daily basis, the sea breezes resulted
in increased current speeds and also changed the current directions through the water column. The correlation between wind–current
speeds and directions with depth, and the lag time between the onset of the sea breeze and the response of currents, were
dependent on the intensity of the sea breezes. A higher correlation between wind and current speeds occurred during strong
sea breezes and was associated with shorter lag times for the response of the bottom currents. The lag times were validated
with estimates of the vertical eddy viscosity. Solar heating caused the water column to stratify in summer and the sea breezes
overcame this stratification. Sea breezes caused the mixed layer to deepen and the intensity of the stratification was correlated
to the strength of the sea breezes. Weak sea breezes of <5 m s−1 were associated with the strongest thermal stratification of the water column, up to 1°C between the surface and bottom layers
(6 and 10 m below the surface). In comparison, strong sea breezes of >14 m s−1 caused only slight thermal stratification up to 0.5°C. Apart from these effects on the vertical structure of water column,
the sea breezes also influenced transport and mixing in the horizontal dimension. The sea breezes in southwest Western Australia
rotated in an anticlockwise direction each day and this rotation was translated into the currents. This current rotation was
more prominent in surface currents and in the coastal embayment compared to the open coast. 相似文献
9.
Integration of all available data in reservoir characterization is critically important. 2D mapping is a reliable and robust technique that allows integration of multiple secondary data, including geological and geophysical surfaces and maps, to generate realistic summaries of reservoir quality at each location in an area of interest with an associated measure of uncertainty. This is achieved in 2D mapping with a more straightforward implementation, requiring significantly less time and fewer resources than three-dimensional modelling. In this paper, we propose an approach for the empirical calculation and optimization of differential compaction maps by leveraging existing well control for the use in 2D mapping. Success of the proposal is demonstrated through tests of accuracy, precision and fairness of the local uncertainty distributions for 100 new stratigraphical wells drilled in the Christina Lake and Kirby East area. 相似文献
1