Lateral response of dams in semi-elliptical rigid canyons   总被引：2，自引：0，他引：2  

P. Dakoulas  C. Hsu 《Soil Dynamics and Earthquake Engineering》1993,12(8):497-507

An analytical closed-form solution is developed for the lateral response of earth and rockfill dams built in semi-elliptical canyons. The dam is idealized as a linearly hysteretic elastic body deforming only in shear, whereas the canyon is assumed to be rigid. The solution for the dam response is given in terms of prolate spheroidal radial and angular functions of the first kind and zero order. Results are presented for natural frequencies, modal displacement shapes, participation factors, and response to transient and steady-state harmonic base excitation for various dam length-to-height ratios. Comparisons are made of the effects of the length-to-height ratio and the canyon shape on the response of dams built in semi-elliptical and rectangular canyons. A subsequent study (Dakoulas, P. & Hsu, C.H., Response of earth dams in semi-elliptical flexible canyons to oblique SH waves, Report, Rice University, Houston, Texas, 1993) extends this model to a semi-elliptical canyon consisting of flexible elastic rock, subjected to obliquely incident harmonic SH waves.  相似文献   

Basic concepts in three-part quantitative assessments of undiscovered mineral resources   总被引：23，自引：0，他引：23  

Donald A. Singer 《Natural Resources Research》1993,2(2):69-81

Since 1975, mineral resource assessments have been made for over 27 areas covering 5×10⁶ km² at various scales using what is now called the three-part form of quantitative assessment. In these assessments, (1) areas are delineated according to the types of deposits permitted by the geology,(2) the amount of metal and some ore characteristics are estimated using grade and tonnage models, and (3) the number of undiscovered deposits of each type is estimated.Permissive boundaries are drawn for one or more deposit types such that the probability of a deposit lying outside the boundary is negligible, that is, less than 1 in 100,000 to 1,000,000.  相似文献   

“A world in a grain of sand”: towards a reconceptualisation of geographical scale     

Richard Howitt 《The Australian geographer》1993,24(1):33-44

Difficulties in relating local scale change to broader dynamics of social and economic restructuring continue to be reflected in much geographical research. This paper argues that inadequate conceptualisations of geographical scale restrict the relevance of much research to the agenda of an applied peoples' geography. A framework which conceptualises geographical scale as dialectically and internally related to the totality of social relations, is proposed and discussed with examples from remote mining regions in Australia.  相似文献   

Band-limited heterogeneous fractal structure of earthquakes and acoustic-emission events     

Xinglin Lei  Osamu Nishizawa  Kinichiro Kusunose 《Geophysical Journal International》1993,115(1):79-84

  相似文献   

Velocity model inversion using parametric curves     

Alberto Michelini 《Geophysical Journal International》1993,115(2):337-343

  相似文献   

广义扰动位公式     

申文斌  晁定波  金标仁 《武汉大学学报(信息科学版)》1994,(4)

在对δＭ和Ｕ０不作限制的条件下，给出了整个地球外部空间的广义扰动位公式，而ＳｔｏｋｅｓＰｉｚｚｅｔｔｉ公式以及ＳＰＨＭ公式均为其特例．  相似文献   

一个正压和斜压不稳定的充要条件   总被引：1，自引：0，他引：1  

陆维松 《南京气象学院学报》1994,17(2):135-140

提出一个新的李雅普诺夫函数，首次得到了正压和斜压不稳定的充要条件，大大改善了热知的Ｒａｙｌｅｉｇｈ－郭晓岚定理和Ｆｊｏｒｔｏｆｔ定理，解决了Ｒａｙｌｅｉｇｈ（１８８０）提出的无粘切变流正压稳定性问题。  相似文献   

Velocity weakening in a dynamical model of friction     

Dmitri Pisarenko  Peter Mora 《Pure and Applied Geophysics》1994,142(3-4):447-466

  相似文献   

Stochastic space transforms in subsurface hydrology — Part 2: Generalized spectral decompositions and plancherel representations     

G. Christakos  D. T. Hristopulos 《Stochastic Environmental Research and Risk Assessment (SERRA)》1994,8(2):117-138

In earlier publications, certain applications of space transformation operators in subsurface hydrology were considered. These operators reduce the original multi-dimensional problem to the one-dimensional space, and can be used to study stochastic partial differential equations governing groundwater flow and solute transport processes. In the present work we discuss developments in the theoretical formulation of flow models with space-dependent coefficients in terms of space transformations. The formulation is based on stochastic Radon operator representations of generalized functions. A generalized spectral decomposition of the flow parameters is introduced, which leads to analytically tractable expressions of the space transformed flow equation. A Plancherel representation of the space transformation product of the head potential and the log-conductivity is also obtained. A test problem is first considered in detail and the solutions obtained by means of the proposed approach are compared with the exact solutions obtained by standard partial differential equation methods. Then, solutions of three-dimensional groundwater flow are derived starting from solutions of a one-dimensional model along various directions in space. A step-by-step numerical formulation of the approach to the flow problem is also discussed, which is useful for practical applications. Finally, the space transformation solutions are compared with local solutions obtained by means of series expansions of the log-conductivity gradient.  相似文献   

A model for the three-dimensional evolution of continental rift basins,north-east Africa     

William Bosworth 《International Journal of Earth Sciences》1994,83(4):671-688

Large areas of north-east Africa were dominated by regional extension in the Late Phanerozoic. Widespread rifting occurred in the Late Jurassic, with regional extension culminating in the Cretaceous and resulting in the greatest areal extent and degree of interconnection of the west, central and north African rift systems. Basin reactivation continued in the Paleocene and Eocene and new rifts probably formed in the Red Sea and western Kenya. In the Oligocene and Early Miocene, rifts in Kenya, Ethiopia and the Red Sea linked and expanded to form the new east African rift system.This complex history of rifting resulted in failed rift basins with low to high strain geometries, a range of associated volcanism and varying degrees of interaction with older structures. One system, the Red Sea rift, has partially attained active seafloor spreading. From a comparison of these basins, a general model of three-dimensional rift evolution is proposed. Asymmetrical crustal geometries dominated the early phases of these basins, accompanied by low angle normal faulting that has been observed at least locally in outcrop. As rifting progressed, the original fault and basin forms were modified to produce larger, more through-going structures. Some basins were abandoned, others experienced reversals in regional dip and, in general, extension and subsidence became focused along narrower zones near the rift axes. The final transition to oceanic spreading was accomplished in the Red Sea by a change to high angle, planar normal faulting and diffuse dike injection, followed by the organization of an axial magma chamber.  相似文献