Transient foundation solution of saturated soil to impulsive concentrated loading     

X. L. Zhou  J. H. Wang  J. F. Lu 《Soil Dynamics and Earthquake Engineering》2002,22(4)

The transient dynamic response of saturated soil under suddenly applied normal and horizontal concentrated loading is studied in this paper. The behavior of saturated soil is governed by Biot's consolidation theory. The general solutions for Biot equations of equilibrium are derived in terms of displacements and variations of fluid volume, using Laplace–Hankel integral transforms. The solutions in the time domain can be evaluated by numerical inverse Laplace–Hankel transforms. Selected numerical results for displacements, stresses, and pore pressures are presented. Comparisons with existing closed-form solutions for the elastic half-space are made to confirm the accuracy of the present solutions. The solutions can be used to study a variety of transient wave propagation problems and dynamical interactions between saturated soil and structures.  相似文献   

Modelling of meteorological conditions at an urban scale for the PUMA winter campaign     

X.-M Cai  Y Zheng  G.R McGregor 《Physics and Chemistry of the Earth》2002,27(35):1479-1485

For the winter 2000 campaign of the Pollution of Urban Midlands Atmosphere project, observation and numerical modelling of meteorological conditions over the West Midlands conurbation, UK, was undertaken. Modelling was performed using the regional atmospheric meteorological system (RAMS). This paper presents a comparison of modelled and observed wind and temperature for 25 and 26 January 2000. The RAMS model uses two nested grids with a mesh size of 2 km for the inner grid which is embedded in the outer grid with a mesh size of 8 km. Statistical evaluation of the model results against the observational data of wind speed, direction and temperature at 10 m was conducted. In general, the modelling results are in a reasonable agreement with observation. The statistical evaluation suggests that model performance is poorer for the inner grid than the outer grid as the model uncertainties (mainly mean bias) transfer from the outer to inner one. The low indices of agreement of temperature and wind are mainly associated with the systematic root-mean-square-difference values. For temperature, the systematic bias may also be affected by representation of cloud amount by the model. For wind, the model tends to have a poor performance for calm conditions, as under a stable anti-cyclonic situation local wind patterns associated with topography may develop, although the topography of the region is relatively flat. The results for the inner grid reveal some subtle spatial patterns at a scale smaller than 10 km near hills and valleys with differences in elevation of a few hundred metres.  相似文献   

Identification of Mining Blasts at Mid- to Far-regional Distances Using Low Frequency Seismic Signals     

M. A. H. Hedlin  B. W. Stump  D. C. Pearson  X. Yang 《Pure and Applied Geophysics》2002,159(4):831-863

—?This paper reports results from two recent monitoring experiments in Wyoming. Broadband seismic recordings of kiloton class delay-fired cast blasts and instantaneous calibration shots in the Black Thunder coal mine were made at four azimuths at ranges from 1° to 2°. The primary focus of this experiment was to observe and to explain low-frequency signals that can be seen at all azimuths and should routinely propagate above noise to mid-regional distances where most events will be recorded by International Monitoring System (IMS) stations.¶The recordings clearly demonstrate that large millisecond delay-fired cast blasts routinely produce seismic signals that have significant spectral modulations below 10?Hz. These modulations are independent of time, the azimuth from the source and the orientation of the sensor. Low-frequency modulations below 5?Hz are seen beyond 9°. The modulations are not due to resonance as they are not produced by the calibration shots. Linear elastic modeling of the blasts that is guided by mine-blast reports fails to reproduce the fine detail of these modulations but clearly indicates that the enhanced “spectral roughness” is due to long interrow delays and source finiteness. The mismatch between the data and the synthetics is likely due to source processes, such as nonlinear interactions between shots, that are poorly understood and to other effects, such as variations of shot time and yield from planned values, that are known to be omnipresent but cannot be described accurately. A variant of the Automated Time-Frequency Discriminant (Hedlin, 1998b), which uses low-frequency spectral modulations, effectively separates these events from the calibration shots.¶The experiment also provided evidence that kiloton class cast blasts consistently yield energetic 2–10 second surface waves. The surface waves are strongly dependent on azimuth but are seen beyond 9°. Physical modeling of these events indicates that the surface waves are due mainly to the extended source duration and to a lesser extent to the slap-down of spalled material. The directionality is largely a path effect. A discriminant that is based on the partitioning of energy between surface and body waves routinely separates these events from the calibration shots.¶The Powder River Basin has essentially no natural seismic activity. How these mining events compare to earthquake observations remains to be determined.  相似文献   

山西北部至晋冀蒙交界地区几次中强地震前4.0级地震活动的研究     

薛丁  徐建德  阎海滨  张晁军  朱学健 《山西地震》2002,(4):17-21

对山西北部至晋冀蒙交界地区中强地震前的 4 .0级地震进行了研究 ,得出其特征为异常增强—异常平静—信号地震的结论 ,认为该区某些 4 .0级地震活动似可作为某些中强地震的前兆地震而进行进一步的研究。  相似文献   

Modelling the drainage evolution of a river–shelf system forced by Quaternary glacio-eustasy     

X. D. Meijer 《Basin Research》2002,14(3):361-377

The Quaternary glaciations had a profound impact on the geomorphology and stratigraphy of passive continental margins. The challenge is to resolve the contributions of the main forcing controls relative sea‐level change and sediment flux. The key to answer this question is to understand the interaction between the marine and terrestrial environments, where river dynamics play an essential role. A comprehensible three‐dimensional numerical model is presented in order to investigate quantitatively the behaviour of river–shelf sedimentary systems under glacio‐eustatic conditions. Distinctive features observed in the model results include river avulsion, delta‐lobe switching, incision and knickpoint migration. An important event in the development of the modelled river–shelf system is the establishment of a direct and inextricable link between the drainage basin and the depocentre on the shelf edge, thereby bypassing the exposed shelf. This is termed as ‘drainage connection’. In the model, the timing of drainage connection occurs over a broad interval when the model run is repeated many times with small differences in the initial topography, reflecting the sensitivity of the system to its initial state. It demonstrates the inherent variability in the evolution of a sedimentary system as a consequence of non‐linear behaviour. A statistical approach to modelling is suggested in order to deal with this problem.  相似文献   

Receiver function study of the Hellenic subduction zone: imaging crustal thickness variations and the oceanic Moho of the descending African lithosphere   总被引：3，自引：0，他引：3  

X. Li  G. Bock  A. Vafidis  R. Kind  H.-P. Harjes  W. Hanka  K. Wylegalla  M. van der Meijde  X. Yuan 《Geophysical Journal International》2003,155(2):733-748

  相似文献   

中国煤炭地质钻探技术发展五十年   总被引：1，自引：1，他引：1  

李生红  丁祥发 《中国煤田地质》2003,15(6):77-80

概要介绍了煤田钻探技术五十年来的发展状况，提出了今后的设想。  相似文献   

马来西亚沙捞越邦达、什兰江控矿角砾岩筒构造对比研究及其找矿意义     

赵财胜  孙丰月  李碧乐  丁清峰  吴尚昆 《世界地质》2003,22(4):366-372

马来西亚沙捞越邦达、什兰江控矿角砾岩筒构造均为典型的浅成—半浅成角砾岩筒构造，角砾岩及控矿类型具有明显的垂向分带特点。邦达控矿角砾岩筒构造发育角砾岩筒上段的塌陷角砾岩，角砾岩筒剥蚀深度较浅，控制典型的高硫化型浅成低温金铜矿床，且其深部具有较大的找矿潜力。什兰江控矿角砾岩筒构造发育角砾岩筒下段的爆发角砾岩和中段的流化角砾岩，分别控制斑岩型金矿化和低硫化型浅成低温热液型金矿化，角砾岩筒剥蚀深度较大，对矿床的保存和找矿极为不利。  相似文献   

利用粉煤灰合成沸石及其去除水中重金属的实验研究   总被引：8，自引：0，他引：8  

王焰新  郭永龙  杨志华  蔡鹤生  X.Querol 《中国科学D辑》2003,33(7):636-643

在水热条件下直接对粉煤灰进行晶化, 合成反应结束后得到的产物有NaP1沸石、方沸石、菱沸石三种沸石. 粉煤灰转化为单种沸石的最大转化率为40% ~ 75%左右, 总转化率达60% ~ 80%左右. 实验结果表明, 合成体系中的涡流、粘度以及温度、时间、NaOH浓度等参数对合成沸石品种及转化率影响较大. 利用合成沸石去除水中Cu²⁺, Pb²⁺和Cd²⁺分批实验表明, 合成沸石对重金属的吸附容量比粉煤灰的高.  相似文献   

DEVELOPMENT OF A DECISION SUPPORT SYSTEM FOR MANAGING PESTICIDE LOSSES IN AGRICULTURAL WATERSHEDS     

Y.-F.LI  Y.R.LI  G.H.HUANG  J.STRUGER  J.D.FISCHER  B.CHEN  J.B.LI  X.H.NIE 《国际泥沙研究》2003,18(1)

1 INTRODUCTION Agricultural use of pesticides has been recognized as one of the important non-point pollution sources in the world, and the pesticide application to agricultural lands has led to large amounts of residues discharged into surface water through runoff (Leonard, 1990). There have been growing concerns about the fate and transport of pesticides in agricultural lands, due to the associated adverse impacts on water environment and human health (Agassi et al., 1995; Ng and Clegg…  相似文献