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61.
徐新辉 《广东海洋大学学报》2008,28(5)
实现人和自然和谐相处、共生同荣的美好理想,是弗罗斯特诗歌中重要的母题之一。从生态批评的角度,对弗罗斯特名诗《一堆木柴》进行细致分析,揭示了这堆木柴是一个生生不息、循环往复的生态体系,既是生态失衡、断裂的象征,又是生态再生、和谐的缩影。 相似文献
62.
徐新辉 《广东海洋大学学报》2006,26(5):100-104
作为“交替性诗人”的弗罗斯特熟谙古希腊文化,善于从古希腊文学中吸取创作素材。从弗罗斯特诗歌中最基本的意象“泉水”出发,力图展现弗罗斯特对古希腊神话的艺术主题再现和超越,揭示弗罗斯特诗歌艺术的不朽意义:实现真正的现代性和谐。 相似文献
63.
J. P. McGreevy 《地球表面变化过程与地形》1982,7(5):475-488
A laboratory experiment has been conducted to examine the effects of ‘frost and salt’ weathering (i.e. physical breakdown by the freezing of salt solutions) on a limestone. Results show that the presence of certain salts in solution can inhibit frost damage. These findings are in direct conflict with those presented by Goudie (1974) and, more recently, Williams and Robinson (1981). Comparison of the experimental methods used in each of these three studies suggests that opposing results can be explained in terms of the different experimental procedures which were employed. If salt supply is frequent and plentiful then it seems likely that rock breakdown will be enhanced-this is the case represented by the experiment of Williams and Robinson. Conversely if the salt supply is limited and the amounts of salt remain more or less constant then rock breakdown will be inhibited-the case of the present experimental study. Caution is therefore advocated when attempting to extrapolate laboratory-derived results to infer on the behaviour of rocks under natural conditions. Several environmental situations in which ‘frost and salt’ weathering may be a possibility are dsiscussed, but it is concluded that further field data, especially concerning temperature regimes and salt availability at and below rock surfaces in cold regions, would be necessary before more definite statements could be made about the efficacy of this process. 相似文献
64.
Frost action and hydration as rock weathering mechanisms on schist: A laboratory study 总被引:1,自引:0,他引:1
Barry D. Fahey 《地球表面变化过程与地形》1983,8(6):535-545
Recently it has been proposed that stress generated by the adsorption of water to clay surfaces in argillaceous rocks may be an important agent of mechanical weathering in polar and alpine environments, implying that long-held views on the status of frost action in these areas may be in need of revision. This study documents the response, under controlled experimental conditions, of aggregates of fresh and partlyweathered schist and fresh pre-cut schist blocks to 500 accelerated (12 hour) freeze-thaw and hydration-dehydration cycles. Aggregate samples subjected to freezing cycles produced the largest amounts of material in the less than 2 mm size range (an average of 8 per cent and 16 per cent for the fresh and partly-weathered aggregates respectively), whereas humidity cycles above and below freezing yielded lesser amounts (3 per cent and 4 per cent respectively). The fresh schist blocks were found to be highly resistant to both mechanisms; only those experiencing freeze-thaw oscillations produced measurable amounts of detritus. Although hydration effects were not as effective as frost action in causing particle size reduction in aggregates, the two mechanisms may well reinforce one another in periglacial environments, enhancing the ability of these areas to serve as source regions for loess. 相似文献
65.
中国冻胀研究进展 总被引:14,自引:0,他引:14
中国的冻胀研究从50年代末期开始,经科研单位、勘察设计院和大专院校冻土工作者近40年的努力,通过现场观察、原位测试、室内试验和计算机模拟等多种手段,开展了冻胀量、冻胀力、冻胀机理、冻胀预报和各类工程防冻胀措施研究,取得了丰硕成果。提出了冻土工程分类、冻胀量和冻胀力的设计值和估算方法,以及各类工程防冻胀破坏的行之有效的方法。目前,研究工作正朝着从表象到机理、从宏观到微观的方向深化。进一步研究多孔介质中热质迁移的物理过程,特别是水分迁移的驱动力与温度或温度梯度间的相互关系,提出能反映过程物理本质且简便的冻胀预报模式及研制出对冻胀不敏感的新材料应成为今后工作的重点。 相似文献
66.
Enno Steindlberger 《Environmental Geology》2004,46(3-4):378-390
In the Hessian region of Germany numerous deposits of tuffs are known from which natural building stones were extracted. Many buildings show examples of the use of this material in the past. In contrast to their attractive appearance and ease of extraction from quarries, tuffs are liable to destruction by weathering. Most common damages are disintegration, crumbling, cracking, scaling and flaking. In this paper, the causes of damage of selected varieties have been analysed using petrographical and petrophysical methods. The measured values are disadvantageous in comparison to other natural building stones. Large amounts of swellable clay minerals, mostly forming the cementing material, cause scaling due to repeated humidification. High porosity including negative pore structures and high adsorption effects results in structural damages while freezing. Consequently, most varieties of the described tuffs possess a limited usage as an outdoor building material. 相似文献
67.
Stephen H. Watts 《地球表面变化过程与地形》1985,10(2):161-172
Surface specimens obtained from highly-weathered upland plateau outcrops at three localities in high Arctic Canada have been studied using the scanning electron microscope. Observations are given on factors influencing bedrock surface microfracturing processes. Evidence for the concentration of both salts and organic material in surface cracks which could enhance microfracturing is presented. The importance of lithological parameters including: mineralogy, texture, and structures present in influencing the actual processes of disintegration is reiterated. Under cold, dry high Arctic conditions the combined and apparently inseparable affects of frost action, salt crystallization, and organic activity may have contributed to microfracturing largely responsible for widely scattered examples of highly weathered bedrock terrain. 相似文献
68.
We propose a conceptual model to interpret AM/PM high albedo events (HAEs) in crater interiors at the Martian seasonal polar caps. This model consists of two components: (1) a relatively permanent high-albedo water–ice body exposed in a crater interior and (2) a variable crater albedo in response to aerosol optical depth, dust contamination, and H2O/CO2 frost deposits or sublimes in four phases, based on temperature and solar longitude changes. Two craters (Korolev crater of fully exposed water–ice layer and ‘Louth’ crater of partially exposed water–ice layer) are used to demonstrate the model. This model explains the HAEs and their seasonal changes and suggests that many crater-like features formed in the last episodic advance of the polar ice cap in the last high obliquity period should have water–ice exposed or covered. For the AM-only HAEs craters, there seems no need of a water–ice layer to be fully exposed, but a subsurface water–ice layer (or ice-rich regolith) is a necessary condition. 相似文献
69.
In the Southern Alps, New Zealand, large gradients in precipitation (< 1 to 12 m year− 1) and rock uplift (< 1 to 10 mm year− 1) produce distinct post-glacial geomorphic domains in which landslide-driven sediment production dominates in the wet, rapid-uplift western region, and rockfall controls erosion in the drier, low-uplift eastern region. Because the western region accounts for < 25% of the active orogen, the dynamics of erosion in the extensive eastern region are of equal importance in estimating the relative balance of uplift and erosion across the Southern Alps. Here, we assess the efficacy of frost cracking as the primary rockfall mechanism in the eastern Southern Alps using air photo and topographic analysis of scree slopes, cosmogenic radionuclide dating of headwalls, paleo-climate data, and a numerical model of headwall temperature. Currently, active scree slopes occur at a relatively uniform mean elevation ( 1450 m) and their distribution is independent of hillslope aspect and rock type, consistent with the notion that frost cracking (which is maximized between − 3 and − 8 °C) may control rockfall erosion. Headwall erosion rates of 0.3 to 0.9 mm year− 1, measured using in-situ 10Be and 26Al in the Cragieburn Range, confirm that rockfall erosion is active in the late Holocene at rates that roughly balance rock uplift. Models of the predicted depth of frost activity are consistent with the scale of fractures and scree blocks in our field sites. Also, vegetated, paleo-scree slopes are ubiquitous at elevations lower than active scree slopes, consistent with the notion that lower temperatures during the last glacial advance induced pervasive rockfall erosion due to frost cracking. Our modeling suggests temporally-averaged peak frost cracking intensity occurs at 2300 m a.s.l., the approximate elevation of the highest peaks in the central Southern Alps, suggesting that the height of these peaks may be limited by a “frost buzzsaw.” 相似文献
70.
Frost weathering and rockwall erosion in the southeastern Swiss Alps: Long-term (1994–2006) observations 总被引:1,自引:1,他引:0
Rates and processes of frost weathering in the Alps were investigated by visual observations of intensively shattered rocks, continuous monitoring of frost wedging and rock temperatures in bedrock and measurements of rockfall activity. Rapid frost weathering of hard-intact rocks occurs along lakes and streams where seasonal freezing promotes ice segregation in the rock. Otherwise, rocks require pre-existing weakness or a long exposure period for intensively shattered. Automated monitoring shows that crack opening occurs at three scales, including small opening accompanying short-term frost cycles, slightly larger movements during seasonal freezing and occasional large opening originating from refreezing of snow-melt water during seasonal thawing. The opening events require at least partial water saturation in the crack. The repetition of crack opening (frost wedging) results in permanent opening and finally debris dislocation. Debris collections below fractured rockwalls show that pebble falls occur at an average rate of about 0.1 mm a− 1 with significant spatial and inter-annual variations. Occasional large boulder falls significantly raise the rockwall erosion rates, controlled by such factors as the joint distribution in the bedrock, repetition of annual freeze–thaw cycles and extraordinary summer thaw. 相似文献