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71.
72.
Summary Left in place pillars of abandoned mines are subject to weathering (e.g action of water, bacteria) that degrades their mechanical
strength and eventually leads to collapse. A simple weathering model is proposed, that is governed by two parameters: the
rate of progression of weathered front and the rate of degradation of the compressive strength with time. Both plane strain
and axisymmetric analyses are performed and closed form solutions of the variation with time of the bearing capacity of the
pillar are given. Experimental data of the tests conducted on gypsum and anhydrite specimens attacked by water are presented.
It is shown that in order to fit the experimental data a third parameter must be introduced. New closed form solutions are
given and the data are used for estimating the time to failure of abandoned gypsum mines in Northern Italy.
Authors’ address: Dr. Riccardo Castellanza, Research Assistant, Department of Structural Engineering, Milan University of
Technology (Politecnico), Piazza Leonardo da Vinci 32, 20133 Milan, Italy 相似文献
73.
Historical space as narrative medium: on the configuration of spatial narratives of time at historical sites 总被引:1,自引:0,他引:1
This paper examines how narratives of history are organized spatially at historical sites and memorial spaces, especially
in urban settings and in places invested with a sense of collective memory. Much recent research has focused on landscape,
memory, and place and how relationships of political and social power influence the representation of historical events in
public spaces. Although the meaning of such sites may be hotly contested for long periods of time, we focus here on narrative
theory and the related, but unexplored, issue of how such historical stories are configured on the ground at actual historical
sites. We identify a number of narrative strategies which are frequently used to configure historical stories in space. Declamatory
strategies using markers presenting a snapshot of an event are common, but sequential and non-sequential linear strategies
are also used, as are thematic strategies that cross-cut space and time to present complex historical stories at various spatial
scales. Examples are drawn from a range of historical sites in North America, Europe and Israel. 相似文献
74.
M. Mejías J. Garcia-Orellana J. L. Plata M. Marina E. Garcia-Solsona B. Ballesteros P. Masqué J. López C. Fernández-Arrojo 《Environmental Geology》2008,54(3):521-536
A methodology for the characterization of deep carbonate aquifers has been developed and applied to El Maestrazgo Jurassic
aquifer in Castellón, Spain. Characterization of these aquifer formations, located at more than 300 m deep, consisted of a
previous phase of compilation, analysis and synthesis of the existing information about the area, followed by a coordinated
combination of different speciality studies: geology, stratigraphy, structural analysis, hydrogeology, hydrochemistry, geophysics
and remote sensing. Geological studies included geological mapping, definition of stratigraphical units and facies and structural
analysis. The aim of the hydrogeology study was to define aquifer formations, recharge area, aquifer points inventory and
groundwater flow directions for the establishment of piezometric and water quality observation nets. Special techniques were
applied, like thermal infrared aerial images and the evaluation of submarine groundwater discharge by means of natural radium
isotopes. Hydrochemical techniques, including majority elements characterization and stable isotopes (18O, 2H and 3H) determination, allowed classifying hydrochemical facies and establishing a renewal pattern for water within the system.
Geophysics was useful in determining the aquifer geometry, the features of the basement and the petrophysical characteristics
of the geological formations. Preliminary results show an important tectonic complexity and the possibilities for groundwater
uses in the area of study. 相似文献
75.
Using plane wave theory and assuming a given input wavelet the shape of the reflected (or transmitted) wavelet from a layered boundary is derived. Several types of boundaries are considered, among them the weathered layer and a wedge shaped intermediate layer. Different angles of incidence and all internal multiples are taken into account. The examples shown in the figures can be used for a direct comparison between theoretical and observed shapes of reflected (or transmitted) wavelets from special boundaries. 相似文献
76.
E. H. Thompson 《The Photogrammetric Record》1967,5(29):385-396
This paper discusses a simple method of computing independent strips under certain reasonable approximations. It is shown that, if the method is regarded as if it were computation by polynomials, the order of the polynomial is decided by the nature of the control provided and not by the number of controlled models. This conclusion should throw some light on the vexed (and perennial) problem of the choice of orders for polynomials. 相似文献
77.
78.
Adrian E. Scheidegger 《Pure and Applied Geophysics》1966,65(1):160-163
Summary Recently, a new theory of the subsidence of rock masses has been advanced byLitwiniszyn and coworkers, which is based on the notion that the individual rock particles perform random walks. It is shown in the present paper that the final equations of the random walk theory can be justified from general principles of statistical mechanics in which no specific theoretical model of particle behaviour has to be made. The theory appears to account appropriately for subsidence phenomena.The research reported in this paper was supported by the Petroleum Research Fund of the American Chemical Society. Acknowledgment is made to the donors of the Petroleum Research Fund administered by the American Chemical Society for support of this reseach. 相似文献
79.
80.
A new and inexpensive pop-up ocean-bottom hydrophone recorder has been developed for use in seismic refraction experiments. It is capable of operating in water depths of up to 4000 m and in very rugged topography, and uses an acoustic command system built by the U.K. Institute of Oceanographic Sciences for recovery. The instrument is mounted in an inexpensive cylindrical pressure case based on commercially available extruded aluminium alloy tubing, and uses glass spheres and syntactic foam for buoyancy. Hydrophone and clock signals are frequency modulated and recorded on tape cassettes, with a recording duration of three hours allowing up to 18 programmed shot windows. The prototype has made seven free descents on the Mid-Atlantic ridge and in the Gulf of Oman, and successfully recorded shots under operational conditions for the first time in September 1979. The total component cost of the prototype was £2740 (1979 prices).(Department of Earth Sciences, University of Cambridge Contribution No. ES135). 相似文献