Former sea-levels and ice limits in part of Wester Ross,northwest Scotland     

J.B. Sissons  A.G. Dawson 《Proceedings of the Geologists' Association. Geologists' Association》1981,92(2):115-124

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Influence of geocell reinforcement on uplift response of belled piles     

S. N. Moghaddas Tafreshi  S. Javadi  A. R. Dawson 《Acta Geotechnica》2014,9(3):513-528

Piles are frequently used to transfer the heavy compressive loads to strong soil layers located in the depth of bed. In addition, such piles may be subjected to combination of repeated compressive and tensile loads due to earthquake, wind, etc. This paper describes a series of laboratory model tests, at unit gravity, performed on belled pile, embedded in unreinforced and geocell-reinforced beds. The tests were performed to evaluate the beneficial effect of geocell in decreasing the downward and upward displacements and performance improvement of the uplift response of belled pile under repeated compressive and tensile loads. Pile displacements due to fifty load repetitions were recorded. The influence of the height of geocell above the bell of pile, an additional geocell layer at the base of belled pile, and the number of load cycles on pile displacements were investigated. The test results show that the geocell reinforcement reduces the magnitude of the final upward displacement. It also acts as a displacement retardant, and changes the behaviour of belled pile from unstable response condition due to excessive upward pile displacement in unreinforced bed to approximately steady response condition. Therefore, the geocell reinforcement permits higher tensile loads or increased cycling. The efficiency of reinforcement in reducing the maximum upward displacement of the pile (i.e. pull-out resistance) was increased by increasing the height of geocell above the bell of the pile. Furthermore, the comparison showed that a specific improvement in upward and downward displacement and the stability against uplift can be achieved using an additional geocell layer at the base. The geocell reinforcement may reduce the required length of pile shaft, consequently reducing required excavation, backfill, and pile’s material. Simple dimensional analysis showed the need for an increased stiffness of the geosynthetic components in order to match prototype-scale performance similitude.  相似文献   

A tracer‐based assessment of hydrological pathways at different spatial scales in a mesoscale Scottish catchment     

C. Soulsby  P. Rodgers  R. Smart  J. Dawson  S. Dunn 《水文研究》2003,17(4):759-777

Geochemically based hydrograph separation techniques were used in a preliminary assessment to infer how runoff processes change with landscape characteristics and spatial scale (1–233 km²) within a mesoscale catchment in upland Scotland. A two‐component end‐member mixing analysis (EMMA) used Gran alkalinity as an assumed conservative tracer. Analysis indicated that, at all scales investigated, acidic overland flow and shallow subsurface storm flows from the peaty soils covering the catchment headwaters dominated storm runoff generation. The estimated groundwater contribution to annual runoff varied from 30% in the smallest (ca 1 km²) peat‐dominated headwater catchment with limited groundwater storage, to >60% in larger catchments (>30 km²) with greater coverage of more freely draining soils and more extensive aquifers in alluvium and other drift. This simple approach offers a useful, integrated conceptualization of the hydrological functioning in a mesoscale catchment, which can be tested and further refined by focused modelling and process‐based research. However, even as it stands, the simple conceptualization of system behaviour will have significant utility as a tool for communicating hydrological issues in a range of planning and management decisions. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

Evidence for the detection of gamma-rays up to 150 TeV from the active galaxy centaurus A     

R. W. Clay  B. R. Dawson  R. Meyhandan 《Astroparticle Physics》1994,2(4):347-352

Evidence is presented for the observation of UHE gamma-rays from the direction of the active galaxy Centaurus A (NGC 5128). An excess of events from this direction is detected only for energies below the expected cosmic microwave background induced cut-off at around 150 TeV.  相似文献   

Visualizing uncertainties in a storm surge ensemble data assimilation and forecasting system   总被引：2，自引：1，他引：1  

Thomas Höllt  M. Umer Altaf  Kyle T. Mandli  Markus Hadwiger  Clint N. Dawson  Ibrahim Hoteit 《Natural Hazards》2015,77(1):317-336

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Variations in dissolved CO2 and CH4 in a first‐order stream and catchment: an investigation of soil–stream linkages     

Diane Hope  Sheila M. Palmer  Michael F. Billett  Julian J. C. Dawson 《水文研究》2004,18(17):3255-3275

Spatial and seasonal variations in CO₂ and CH₄ concentrations in streamwater and adjacent soils were studied at three sites on Brocky Burn, a headwater stream draining a peatland catchment in upland Britain. Concentrations of both gases in the soil atmosphere were significantly higher in peat and riparian soils than in mineral soils. Peat and riparian soil CO₂ concentrations varied seasonally, showing a positive correlation with air and soil temperature. Streamwater CO₂ concentrations at the upper sampling site, which mostly drained deep peats, varied from 2·8 to 9·8 mg l^?1 (2·5 to 11·9 times atmospheric saturation) and decreased markedly downstream. Temperature‐related seasonal variations in peat and riparian soil CO₂ were reflected in the stream at the upper site, where 77% of biweekly variation was explained by an autoregressive model based on: (i) a negative log‐linear relationship with stream flow; (ii) a positive linear relationship with soil CO₂ concentrations in the shallow riparian wells; and (iii) a negative linear relationship with soil CO₂ concentrations in the shallow peat wells, with a significant 2‐week lag term. These relationships changed markedly downstream, with an apparent decrease in the soil–stream linkage and a switch to a positive relationship between stream flow and stream CO₂. Streamwater CH₄ concentrations also declined sharply downstream, but were much lower (<0·01 to 0·12 mg l^?1) than those of CO₂ and showed no seasonal variation, nor any relationship with soil atmospheric CH₄ concentrations. However, stream CH₄ was significantly correlated with stream flow at the upper site, which explained 57% of biweekly variations in dissolved concentrations. We conclude that stream CO₂ can be a useful integrative measure of whole catchment respiration, but only at sites where the soil–stream linkage is strong. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

Tsunami. The underrated hazard,E. Bryant (ed.). Publisher Cambridge University Press,Cambridge, 2001 (320 pp) ISBN 0‐521‐77599‐X (PB) 0‐521‐77244‐3 (HB)     

Alastair G. Dawson 《第四纪科学杂志》2003,18(6):582-582

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H-polarization induction in two thin half-sheets     

T. W. Dawson  J. T. Weaver 《Geophysical Journal International》1979,56(3):419-438

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Late Quaternary sea-level correlation and applications. Edited by D. B. SCOTT,P. A. PIRAZZOLI and C. A. HONG. Publisher Kluwer Academic Publishers,Dordrecht, The Netherlands 1987 £42.00 (hardcover); US $69.00 or DFI 130.00 (229 pp) ISBN 0 7923 001 6 5     

Alastair G. Dawson 《第四纪科学杂志》1989,4(3):276-277

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Secular variation in North America during historical times     

L. R. Newitt  E. Dawson 《Geophysical Journal International》1984,78(1):277-289

Summary. The secular variation of the declination, inclination and total force of the geomagnetic field has been plotted for 74 locations in North America. A comparison of the occurrences of maxima and minima in the SV curves from different stations shows little evidence of drift in North America. Although a declination maximum exhibits westward drift up to 1915, all other extrema in declination, inclination and total intensity occur almost simultaneously over a wide area. The major feature of SV in North America appears to be a 4000 nT decrease in the total field since 1850, which may be due to a decrease in the dipole moment coupled with the decay of a large non-dipole anomaly situated under the continent. Short-period changes in the rate of decrease are possibly jerks of the magnetic field. Maximum entropy spectral analysis of all three components of the field indicates periods of 102 and 53 yr.  相似文献