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51.
Although studies on glacial isostatic adjustment usually assume a purely linear rheology, we have previously shown that mantle relaxation after the melting of Laurentide ice sheet is better described by a composite rheology including a non-linear term. This modelling is, however, based on axially symmetric geometry and glacial forcing derived from ICE-3G and suffers from a certain amount of arbitrariness in the definition of the ice load. In this work we apply adjusted spherical harmonics analysis to interpolate the ice thicknesses of ICE-3G and ICE-1 glaciological models. This filters out the non-axisymmetric components of the ice load by considering only the zonal terms in the spherical harmonics expansion. The resulting load function is used in finite-element simulation of postglacial rebound to compare composite versus purely linear rheology. Our results confirm that composite rheology can explain relative sea level (RSL) data in North America significantly better than a purely linear rheology. The performance of composite rheology suggests that in future investigations, it may be better to use this more physically realistic creep law for modelling mantle deformation induced by glacial forcing. 相似文献
52.
依据渤海海冰物理和力学特征值和国内水池实验室能力,以1:10~1:30比尺要求,发展了DUT-1合成模型冰.文中简介该模型冰的理想参数、成分和制备过程.就其弯曲强度和弹性模量进行系统的实验分析.通过500多次弯曲实验,获得该模型冰在不同加载速度下的破坏方式,各向同性证据和弯曲强度为35~65kPa和弹性模量平均53MPa的结果.并且得到弯曲强度和弹性模量在实测湿密度范围内呈递增关系,浸水模型冰性能稳定时间超过4h,弹性模量与弯曲强度之比82%超过2000. 相似文献
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利用9个国际纬度观测站的平纬长期变化序列,重新讨论并估计了平极的长期漂移,得到漂移的平均速率为(3.356“±0.142”)×l0-3/a,方向为西经78.7°±2.5°.进一步基于最新的ICE-4G冰期后地壳反弹模型,采用地球上8个冰盖的冰融参数,估计了理论的平极长期漂移方向为西经74.8°.由观测的平极长期漂移速率为约束,基于1066B地球模型,估计得到地球平均下地幔的黏性为vLM=(0.5-1.7)×1022Pa.s,表明vLM应具有近1022Pa.s量级,并认为地球平极的长期漂移很可能是由最近的21000年以来冰期后的地壳反弹所致. 相似文献
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56.
未来上海地区海平面上升将引起地下水位抬升,将会对土压缩模量E产生影响,Es是土的最重要的物理力学参数指标之一,尤其在地基沉降计算中具有重要意义。本文主要针对土压缩模量Es的预测分析工作,进行了地基变形的;探讨研究,供交流参考。 相似文献
57.
Geomorphology of a beach-ridge complex and adjacent lake basins along the northern shore of Lake Michigan records fluctuations in the level of Lake Michigan for the last 8000 to 10 000 14C yr B.P. (radiocarbon years Before Present). A storm berm at 204.7–206 m (671.6–675.9 ft) exposed in a sandpit provides evidence of a pre-Chippewa Low lake level that is correlated with dropping water levels of Glacial Lake Algonquin (c. 10 300–10 100 14C yr B.P.). Radiocarbon dates from organic material exposed in a river cutbank and basal sediments from Elbow Lake, Mackinac Co., Michigan, indicate a maximum age of a highstand of Lake Michigan at 6900 14C yr B.P., which reached as high as 196.7 m (645 ft), during the early-Nipissing transgression of Lake Michigan. Basal radiocarbon dates from beach swales and a second lake site (Beaverhouse Lake, Mackinac Co.) provide geomorphic evidence for a subsequent highstand which reached 192.6 m (632 ft) at 5390±70 14C yr B.P.Basal radiocarbon dates from a transect of sediment cores, along with tree-ring data, and General Land Office Surveyor notes of a shipwreck, c. A.D. 1846, reveal a late-Holocene rate for isostatic rebound of 22.6 cm/100 radiocarbon years (0.74 ft/100 radiocarbon years) for the northern shore of Lake Michigan, relative to the Lake Michigan-Lake Huron outlet at Port Huron, Michigan. Changes in sediment stratigraphy, inter-ridge distance, and sediment accumulation rates document a mid- to late-Holocene retreat of the shoreline due to isostatic rebound. This regression sequence was punctuated by brief, periodic highstands, resulting in progressive development over the past 5400 14C yr of 75 pairs of dune ridges and swales each formed over an interval of approximately 72 years. Times of lake-level fluctuation were identified at 3900, 3200, and 1000 14C yr B.P. based on changes in inter-ridge spacing, shifts in the course of Millecoquins River, and reorientation of beach-ridge lineation. Soil type, dune development, and selected pollen data provide supporting evidence for this chronology. Late-Holocene beach-ridge development and lake-level fluctuations are related to a retreat of the dominant Pacific airmass and the convergence of the Arctic and Tropical airmasses resulting in predominantly meridional rather than zonal air flow across the Great Lakes region.This is the 13th in a series of papers published in this special AMQUA issue. These papers were presented at the 1994 meeting of the American Quaternary Association held 19–22 June, 1994, at the University of Minnesota, Minneapolis, Minnesota, USA. Dr Linda C. K. Shane served as guest editor for these papers. 相似文献
58.
对《深圳地区建筑地基基础设计规程SJG1-88》中全、强风化花岗岩的划分和承载力值进行讨论,将全、强风化层各划出两个亚层,同时提出了各亚层的承载力及变形模量范围值。 相似文献
59.
通过研究地球对表面载荷的响应来反演确定地球深部的物理参数.采用分为4层的地球模型,各层的介质被看作Maxwell粘弹性体.将柴达木盆地沉降发育过程中积累的沉积物作为随时间变化的载荷加于地表,通过拟合柴达木盆地沉降中心附近地区的沉降过程来研究该地区地壳的厚度及剪切模量、岩石层地幔的粘性及软流层的粘性等物理参数.计算结果表明,该地区地壳的剪切模量不会超过全球平均值的60%,岩石层地幔的粘性系数不大于1.5×1023Pa·s.通过研究对该地区的深部物理参数得出了新的认识. 相似文献
60.