This paper offers a new method for the definition of geotechnical sectors in open pit mines based on multivariate cluster analysis. A geological-geotechnical data set of a manganese open pit mine was used to demonstrate the methodology. The data set consists of a survey of geological and geotechnical parameters of the rock mass, measured directly in several points of the mine, structured initially in twenty-eight variables. After the preprocessing of the data set, the clustering technique was applied using the k-Prototype algorithm. The squared Euclidean distance was used to quantify the proximity between numerical variables, and the Jaccard's coefficient of similarity was used to quantify the proximity between the nominal variables. The different cluster results obtained were validated by the multivariate analysis of variance. The identification of cluster structures was achieved by plotting them on the mine map for spatial visualization and definition of geotechnical sectors. These sectors are spatially contiguous and relatively homogeneous regarding their geological–geotechnical properties, indicated by a high density of points of the same group. It was possible to observe a great adherence of the proposed sectors to the mine geology, demonstrating the practical representativeness of the clustering results and the proposed sectors.
The elastic and anelastic structure of the lithosphere and asthenosphere of the Iberian Peninsula is derived by means of tomographic
techniques applied to local phase and group velocities and local attenuation coefficients of Rayleigh wave fundamental mode.
The database consists of surface wavetrains recorded at the broadband stations located in the Iberian Peninsula on the occasion
of the ILIHA project. Path-averaged phase and group velocities and attenuation coefficients were previously obtained by standard
filtering techniques of surface wavetrains and, subsequently, local dispersion curves were computed according to the Yanovskaya-Ditmar
formulation. First, a principal component analysis (PCA) and the average linkage (AL) clustering algorithm are applied to
these local values in order to classify the Iberian Peninsula in several rather homogeneous domains from the viewpoint of
the similarity of the corresponding local dispersion curves, without previous seismotectonic constraints. Second, averaged
phase and group velocities and attenuation coefficients representing each homogeneous region are used to derive the respective
elastic and anelastic models of the lithosphere and asthenosphere. This purpose is achieved by using the uncoupled causal
inversion of phase and group velocities and attenuation coefficients. The main features of the homogeneous regions are discussed
by taking as reference the Hercynic, Alpine and Neogene domains of the Iberian Peninsula, and two questions affecting the
reliability of the elastic-anelastic models are revised. First, the coherence of the shear-velocity and Qβ−1 models obtained by causal uncoupled inversion for each region is analysed. Second, the influence of the causal phase and
group velocities on the shear-velocity models is evaluated by comparing elastic and anelastic models derived from causal uncoupled
inversion with those deduced from non-causal inversion. 相似文献
hydrological monitoring is essential for a proper decision-making process and modelling. Efforts have been made in Brazil to carry out field activities at the basin scale, but how complete and comprehensive are those studies? Where are they located? How long have they been carried out? What are the main findings? To answer these questions, an overview of experimental monitoring basins in Brazil is presented, listing their geographical locations, monitored variables, operational status, monitoring periods and main publications. We identified 60 monitored sites, spread across most Brazilian biomes, with an average monitoring period of 12 years. However, some publications from these monitoring studies are not fully accessible to the international community. Field hydrology activities in Brazil contribute to a better understanding of hydrological processes in humid and semi-arid regions and inform us about the impacts of land-use change on water quality and quantity. 相似文献
This paper deals with the geometry and kinematics of the active normal faults in northern Umbria, and their relationship with the seismicity observed in the area. In particular, we illustrate the contribution of seismic reflection data (a network of seismic profiles, NNW–SSE and WSW–ENE trending) in constraining at depth the geometry of the different active fault systems and their reciprocal spatial relationships. The main normal fault in the area is the Alto Tiberina fault, NNW trending and ENE dipping, producing a displacement of about 5 km, and generating a continental basin (Val Tiberina basin), infilled by up to 1500 m with Upper Pliocene–Quaternary deposits. The fault has a staircase trajectory, and can be traced on the seismic profiles to a depth of about 13 km. A set of WSW-dipping, antithetic faults can be recognised on the profiles, the most important of which is the Gubbio fault, bordering an extensional Quaternary basin and interpreted as an active fault based on geological, geomorphologic and seismological evidence. The epicentral distribution of the main historical earthquakes is strictly parallel to the general trend of the normal faults. The focal mechanisms of the major earthquakes show a strong similarity with the attitude of the extensional faults, mapped at the surface and recognised on the seismic profiles. These observations demonstrate the connection between seismicity in the area and the activity of the normal faults. Moreover, the distribution of the instrumental seismicity suggests the activity of the Alto Tiberina fault as the basal detachment for the extensional tectonics of the area. Finally, the action of the Alto Tiberina fault was simulated using two dimensional finite element modelling: a close correspondence between the concentration of shear stresses in the model and the distribution of the present earthquakes was obtained. 相似文献
Rayleigh wave group and phase velocities and attenuation coefficients are investigated in the 15–60-s period range for earthquakes occurring in the European area and registered at European stations. Observed group and phase velocities show clear differences in the period range 20–40 s, whereas attenuation coefficients are differentiated from 45 s to larger periods. From the shape of dispersion and attenuation curves, two broad zones have been isolated and designated as Western Europe and Southeastern Europe. Although some scatter is present, specially for attenuation, the data suggest that in general the shear velocity and Qβ values are higher for Southeastern Europe than for Western Europe. For Southeastern Europe there is a channel of low velocity and low Qβ, apparently correlated, located at the lower crust: in both regions there is a channel of low velocity and low Qβ values located at the uppermost mantle. In each case there also exists a channel of high Qβ values located at the lower crust but at slightly different depths. 相似文献
The principal stress axes and eigenvalue ratios of the stress tensors from two active seismic regions in Alaska (eastern Aleutian Arc and eastern Gulf of Alaska) are computed. These results are obtained using focal mechanisms of earthquakes with magnitudes ranging from 5.5 to 8.2 and show for both regions slightly different compressional states with an orientation of the pressure axis of N26°W for the eastern Gulf of Alaska and N27°W for the east Aleutian Arc. The eigenvalue ratios for the eastern Gulf of Alaska and east Aleutian Arc are 0.84 and 0.99, respectively. The algorithm used in computations allows us to detect some focal mechanisms which are incoherent with respect to the obtained stress tensors. These incoherences are explained in terms of some tectonic features of the region. The orientations of possible pre-existing fractures which would need an unrealistically high maximum shear stress to start a slip on their fault planes are also investigated. These critical orientations depend on a constitutive frictional law as well as on eigenvalue ratios and eigenvectors of the stress tensors. The orientation, which is given in our case by the angle between the normal vector to a fracture and the regional tensional axis, is approximately 59° for the eastern Aleutian Arc. This angle ranges from 49° to 59° for the eastern Gulf of Alaska. It must be pointed out that fractures which need unrealistically high shear stress to start slip on their fault planes are defined by a very narrow band of possible angles between tensional direction and the normal vector to fault plane. 相似文献
Summary Seven series of monthly pluviometric amounts, sometimes exceeding recording periods of 100 years and compiled by the Instituto Nacional de Meteorología (Spain), are used to study the irregularity of the pluviometric regime along the Spanish Mediterranean coast and nearby Atlantic
coast. First of all, three statistical functions (gamma, log-normal and a combination of Poisson and gamma distributions)
and moment-ratio diagrams are used to model the monthly and annual empirical distributions of precipitation amounts, each
distribution being tested by means of the Kolmogorov-Smirnov test. It is noteworthy that, whereas most of the monthly cases
require the gamma distribution, the pluviometric behaviour of the summer months is well described by the Poisson-gamma distribution.
Moreover, both the log-normal and the gamma distributions satisfactorily model empirical annual amounts. Consequently, rainfall
amounts are not identically distributed along a year for each gauge tested. Second, temporal trends deduced for annual and
seasonal amounts are computed and their statistical significance evaluated. The most notable fact is that, although some linear
trends are close to 1 mm/year, their significance levels exceed the assumed threshold value and, excepting the winter season
for Barcelona, they are considered non-significant from a statistical point of view. Finally, by again using monthly and annual
amounts, three temporal irregularity indexes are computed for each pluviometric series, the temporal disparity of the rainfall
patterns of the Mediterranean region being enhanced as a result. It addition to the temporal irregularity, a change with latitude
is observed both in the parameters of the statistical distributions and the temporal irregularity indexes for the rain gauges
analysed. The two most southerly rain gauges constitute a special case in comparison with the remaining stations, because
they also receive the Atlantic influences due to their proximity to this ocean.
Received February 25, 1999/Revised August 2, 1999 相似文献
Archaeological excavations at the Biblioteca Magliabechiana, which is part of the Uffizi gallery complex in Florence (Tuscany, central Italy), exposed Dark Earth deposits between alluvial sediments of the nearby Arno River. The term Dark Earth refers to thick, dark colored, and seemingly homogeneous deposits occurring in urban settings throughout Europe, broadly dated to the post‐Roman period. The stratigraphic sequence of the Biblioteca Magliabechiana was investigated by integrating geomorphological, chronological, and archaeological information with micromorphological and soil analytical data. This combination of approaches resulted in the identification of an early phase of Dark Earth formation (7th century A.D.) during which the area was characterized by the accumulation of manure or night soil in wet peri‐fluvial conditions. After a phase of abandonment, Dark Earth accretion resumed (10th to early 11th century A.D.), at this stage due primarily to the dumping of domestic waste. Subsequent progressive abandonment of the area was followed by the deposition of alluvium, probably during the major flood of November 4, 1177. The present study demonstrates that Dark Earth is the outcome of strong bioturbation and human reworking acting on anthropogenic deposits and possibly on alluvial sediments. 相似文献