Towards a general model of quick clay development     

I. J. SMALLEY  C. J. FORDHAM  P. F. CALLANDER 《Sedimentology》1984,31(4):595-598

Torrance (1983) has recently reviewed factors producing high sensitivity in clayey sediments and proposed a general model for quick clay development. He suggested that the mineralogical requirement for quick clay behaviour to develop is that low activity minerals must predominate in the sediment. This is also the essential mineralogical requirement of the inactive-particle, short-range-bond hypothesis of high sensitivity (Smalley, 1971, 1972a, 1976; Cabrera & Smalley 1973; Smalley, Ross & Whitton, 1980). The predominance of low activity minerals causes most of the interparticle bonds to be of the short-range variety which allow/promote the'quick' behaviour—the transition from solid to liquid. In Canadian or Scandinavian quick clays the short-range bond requirement is largely met by the abundance of finegrained primary mineral particles. The very sensitive clays involved in the Tauranga landslide in New Zealand (Smalley et al ., 1980) owed their sensitivities to their content of inactive spheroidal halloysite particles. By many definitions the Tauranga material is a quick clay and its existence provides us with another window through which to view the quick clay problem. Torrance observed that for a quick clay to develop the sediment must have an open structure with a high void ratio. In a classic Canadian quick clay this structure is obtained by the slow sedimentation of fine particles in the salty Champlain Sea; in the Tauranga soil an open structure is obtained by air-fall sedimentation of the initial volcanic particles.  相似文献   

Attenuation of coda waves and Q_c value beneath the Chengdu telemetered seismic network     

曾健  陈天长  韩渭宾  范军  郑斯华  长谷川昭  堀内茂木  松本聪 《地震学报(英文版)》1997,(3)

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AN ANALYTICAL HYSTERESIS MODEL FOR ELASTOMERIC SEISMIC ISOLATION BEARINGS     

MASARU KIKUCHI  IAN D. AIKEN 《地震工程与结构动力学》1997,26(2):215-231

For the purpose of accurately predicting the seismic response of base-isolated structures, an analytical hysteresis model for elastomeric seismic isolation bearings is proposed. An extensive series of experimental tests of four types of seismic isolation bearings—two types of high-damping rubber bearings, one type of lead-rubber bearing and one type of silicon rubber bearing—was carried out with the objective of fully identifying their mechanical characteristics. The proposed model is capable of well-predicting the mechanical properties of each type of elastomeric bearing into the large strain range. Earthquake simulator tests were also conducted after the loading tests of the individual bearings. In order to show the validity of the proposed model, non-linear dynamic analyses were conducted to simulate the earthquake simulator test results. Good agreement between the experimental and analytical results shows that the model can be an effective numerical tool to predict not only the peak response value but also the force–displacement relationship of the isolators and floor response spectra for isolated structures. © 1997 by John Wiley & Sons, Ltd.  相似文献   

BOOK REVIEW: PHYSICAL ADJUSTMENTS IN A CHANGING LANDSCAPE: THE SINGAPORE STORY edited by A. Gupta and J. Pitts,Singapore University Press,Singapore, 1992. No. of pages: xviii + 423. ISBN 9971-69-172-8.     

IAN DOUGLAS 《地球表面变化过程与地形》1996,21(5):488-489

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LAMOST子镜镀膜研究进展          下载免费PDF全文

李凤云  韩智洁  刘明旭  淳于波  徐亚军  陈余  李双虎  闫秋浩  包铁威  郭王伟  李义成  李新南  王晋峰  田杰  乔撩云  陈亮  吕金虎  陈超  刘承  张勇  侯永辉  王跃飞  葛群  左恒  姜方华  李烨平  陆启帅  胡守伟  王佑  李爱华  倪季君  张超  倪小康  许静  李浩  李晓飞  张昊彤  白仲瑞  胡天柱  王丹  崔向群  赵永恒  李国平 《天文学报》2022,63(1):12-126

对大口径光学/红外天文望远镜而言,为保障其稳定高效运行,镜面镀膜是重要的维护环节之一.镀膜质量的好坏直接影响镜面光学反射率的高低,也严重影响到天文望远镜的成像质量、观测效率.国家重大科技基础设施—大天区面积多目标光纤光谱天文望远镜(Large Sky Area Multi-Object Fiber Spectroscopic Telescope, LAMOST,又名郭守敬望远镜)自2009年6月通过国家竣工验收并逐步投入巡天观测,目前已进入第2个5 yr巡天计划阶段,取得近两千万的光谱产出和大批高显示度的科学成果. LAMOST共拥有24块施密特改正镜子镜和37块球面主镜子镜,为了确保在野外恶劣观测环境下镜面反射率维持在较高水平,每年要对大批子镜进行镀膜.主要介绍了镀膜需求、镀膜设备,并基于大量实验和多年的完善探索出一套可行的镀膜工艺流程,确保了LAMOST子镜极高的镀膜质量.镀膜后子镜平均反射率高达90%以上,满足了LAMOST光谱巡天的镜面反射率要求.  相似文献   

Late Devensian river and floodplain dynamics and related environmental change in northwest Europe,with particular reference to a site at Woolhampton,Berkshire, England     

PHILIP E. F. COLLINS  IAN M. FENWICK  D. MICHAEL KEITH-LUCAS  PETER WORSLEY 《第四纪科学杂志》1996,11(5):357-375

Marked fluctuations in Late-glacial climate are correlated with significant changes in river behaviour and floodplain environment across much of northwest Europe. Evidence from a new site in the Kennet Valley provides a rare comprehensive picture of varying fluvial regime and local vegetation during this interval. Chronological control for the site is provided by biostratigraphical and morphostratigraphical correlations with other sites in the region, and by radiocarbon dating of carefully selected material. Preservation of the sedimentary sequence was facilitated by its occurrence within a large depression in the underlying bedrock. The origin of this depression is uncertain, perhaps reflecting subsidence or scour. Following the Last Glacial Maximum, a nival regime braided river dominated by floods deposited sandy gravels under stadial conditions. A large channel infilled by fine sediments during the latter part of the Windermere Interstadial indicates a fall in flow competence at a time of increased floodplain vegetation, most notably the appearance of tree birch. Variations in sediments and vegetation suggest fluctuations in the floodplain environment, reflecting complex vegetation dynamics and possibly climate forcing. During the Loch Lomond/Younger Dryas Stadial, a nival, braided regime was re-established, accompanied by the disappearance of tree birch.  相似文献   

LINKS BETWEEN PROGLACIAL STREAM SUSPENDED SEDIMENT DYNAMICS,GLACIER HYDROLOGY AND GLACIER MOTION AT MIDTDALSBREEN,NORWAY     

IAN C. WILLIS  KEITH S. RICHARDS  MARTIN J. SHARP 《水文研究》1996,10(4):629-648

Two-hourly suspended sediment concentration variations observed during the summer of 1987 in the proglacial stream draining Midtdalsbreen, Norway are modelled using multiple regression and time series techniques. Suspended sediment fluctuations are influenced by stream discharge variations, diurnal hysteresis effects, medium-term sediment supply and transport variations and the recent suspended sediment concentration history of the stream. They do not appear to be influenced by seasonal exhaustion or rainfall variations. Possible reasons for this are discussed. Large positive residuals from the fitted models are major pulses of suspended sediment unrelated to discharge variations; these sediment flushes correlate with periods of enhanced glacier motion. They cannot be explained by enhanced sediment production by subglacial erosion, but are probably due to the tapping of subglacially stored sediment during sudden changes in the hydraulics and/or configuration of the subglacial hydrological system. Seasonal changes in the lag between glacier motion peaks and suspended sediment flushes suggest that the subglacial hydrological system evolves over the summer from a distributed to a more channelized configuration.  相似文献   

HYDROGRAPHIES*     

IAN BAUCOM 《Geographical review》1999,89(2):301-313

ABSTRACT. Drawing on the work of the theoretical biologist Humberto Maturana, I offer in this essay a way of conceptualizing the forms of identity that survive the various death pronouncements of our postidentitarian moment. I associate the work of imagining those strange new forms of identity with what Frederic Jameson calls “cognitive mapping,” arguing that these “afteridentities” can emerge from a “hydrographic” charting of the fluid cultural territories of the modern and the postmodern. In conclusion, I indicate how this approach may be of use in contemporary attempts to “map” the diasporic territories of the Black Atlantic.  相似文献   

FLUCTUATIONS OF CRILLON GLACIER SYSTEM,SOUTHEAST ALASKA     

RICHARD P. GOLDTHWAIT  IAN C. Mc KELLAR  CASPAR CRONK 《水文科学杂志》2013,58(1):62-74

Abstract

Crillon Glacier system (Lat. 58° 37′ N, Long. 137° 23′w) consisting of two long feeding arms and a common T-shaped ending along the Fairweather Fault, with two cliffed termini, has been advancing. La Perouse's sketch map in 1786 suggests that North and South Crillon Glaciers were back far enough to have separate termini in Lituya Bay, so they must have advanced at about 30 m/yr for 150 years. More detailed maps and photos show that North Crillon terminus did advance 28 m/yr into open water positions from 1894 to 1933. Some of this 4.5 km advance may well be just the result of consolidation of two long calving ice cliffs into one deep water front.

South Crillon front in the other arm of the “T”, where no junction of fronts is involved, also advanced into Crillon Lake 10 m/yr between 1929 and 1961. This implies that the basic cause was some increased snowfall on the high mountains. At the same time glaciers from lower peaks just to the east of Glacier Bay lost nearly all accumulation by a rising snowline and receded 5 to 11 km.

Since 1926 the Lituya Bay terminus has been more or less stable where it lies in water; however, the land portion has advanced 25 m/yr since 1948. Between about 1920 and 1961 a large gravel delta appeared and grew to 145 × 10⁶ m³, so this slow ice advance on one side of the front may be due to ice shearing over the new land of the fan where ablation is slower than watercliff calving.

Prehistoric advances of Crillon Glacier system are recorded in stratigraphic deposits dated by C-14. Trees buried in the prominent extensive outer moraine system around Crillon Lake and Lituya Bay were annihilated in the maximal push of the Little Ice Age 400 to 1000 years ago. The first advance came 1500 to 1800 years ago when logs became buried in glacial outwash, now under Little Ice Age till. Because it is regional, this was a climatic event involving a lowering snowline due to cooler summers.

Still further back, in hypsithermal time, these Crillon Glacier termini were probably as retracted as today, because many outcrops of buried forest 3000 to 9000 years old occur in alluvial deposits in Lituya Bay. Underneath all these is outwash gravel and till recording the last push of Wisconsin ice, ending at least 9000 years ago. Still earlier Wisconsin advances of North Crillon Glacier carried the Lituya Bay ice tongue a little further to sea, yet all through the pleistocene, unglaciated refugia endured between the ice streams.  相似文献   

Late Holocene paleoseismology of a site in the region of maximum subsidence during the 1964 Mw 9.2 Alaska earthquake          下载免费PDF全文

IAN SHENNAN  NATASHA BARLOW  ROD COMBELLICK  KLARA PIERRE  OLIVIA STUART‐TAYLOR 《第四纪科学杂志》2014,29(4):343-350

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