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11.
Some observations on the prediction of the dynamic parameters of debris flows in pyroclastic deposits in the Campania region of Italy 总被引：1，自引：0，他引：1
Over the last 20 years, many tools have been developed for the prediction of the post-failure behaviour of rapid landslides.
However, as pointed out by several researchers, knowledge may be improved by the performance of back-analyses using different
models and the evaluation of their reliability. This paper reports the back-analysis, conducted using numerical models, of
57 rapid landslides that have occurred in the Campania region. The back-analysis has been performed using the 2-D DAN_W code
(version 2003) with two different rheological models: the Voellmy and the frictional models. The latter has been immediately
discarded because it did not match the observed data. Instead, using the Voellmy model, the best-fit values of the parameters
(friction μ and turbulence ξ) for different types of flow (channelled, un-channelled and mixed flows) have been researched.
With these values a parametric study has been carried out on four representative slope profiles of the Campania region, enabling
the prediction of runout, velocity and depth of flow (dynamic parameters) of potential debris flows.
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| Anna Scotto di SantoloEmail: |
12.
Summary In saturated rocks and soils it is possible to define different coefficients of thermal expansion depending on the drainage conditions. This topic is first examined from the theoretical point of view with regard to an ideal isotropic thermo-elastic porous medium. Some special features of the behaviour of natural soils and rocks during thermal expansion tests are subsequently discussed. An experimental evaluation of some of these coefficients is presented in the second part of the paper. The material investigated is a pyroclastic rock, the so-called Neapolitan Yellow Tuff. Thermal expansion coefficient in drairend conditions has been evaluated, when this material is saturated with water. The e pressure increase induced by heating has been measured in undrained tes temperatures investigated range between room temperature up to 225°C.Different types of apparatus have been used and, when possible, a comparison between the results has been proposed. The results obtained in undrained thermal expansion tests are in agreement with theoretical predictions. This research is part of an on-going study of the complex phenomena known as Bradyseism, which is occurring in a volcanic area a few kilometers from Naples (Italy). Some considerations on this phenomenon are drawn in the last paragraph of the paper.List of Symbols
l
linear thermal expansion coefficient
-
s
volumetric thermal expansion coefficient of the solid phase
-
ss
volumetric drained thermal expansion coefficient of the solid skeleton
-
st
volumetric drained thermal expansion coefficient that takes into account variations of porosity induced by heating
-
t
volumetric drained thermal expansion coefficient of the whole system
-
u
volumetric undrained thermal expansion coefficient of the whole system
-
v
volumetric thermal expansion coefficient
-
w
volumetric thermal expansion coefficient of the water
-
l
*
volumetric thermal expansion coefficient of the distilled water
-
Biot's coefficient
-
d
dry specific gravity
-
s
specific gravity of the solid phase
-
r
'
uniaxial compressive strength
-
r
'
yield stress in isotropic compression
-
B
T
parameter relating undrained thermally generated pore pressure with temperature change
-
d
0
maximum uplift during Bradyseismic crises
-
d
f
residual uplift during Bradyseismic crises
-
K
s
compressibility modulus of the solid phase
-
K
ss
compressibility modulus of the solid skeleton
-
K
w
compressibility modulus of the water
-
n
porosity
-
T
temperature
-
T
0
initial temperature in thermal expansion, tests performed in thermal expansion cell
-
T
m
temperature at which the volume of waterV
Eexpelled from thermal expansion cell. is measured
-
V
volume of the solid skeleton
-
V
E
volume expelled from thermal expansion cell
-
V
0
volume of the expansion cell at temperatureT
0
-
V
s
volume of the solid phase 相似文献
13.
N.R. Rigozo M.P. Souza Echer H. Evangelista D.J.R. Nordemann E. Echer 《Journal of Atmospheric and Solar》2011,73(11-12):1294-1299
The prediction of solar activity strength for solar cycles 24 and 25 is made on the basis of extrapolation of sunspot number spectral components. Monthly sunspot number data during the 1850–2007 interval (solar cycles 9–23) are decomposed into several levels and searched for periodicities by iterative regression in each level. For solar cycle 24, the peak is predicted in November 2013 with a sunspot number of 113.3. The cycle is expected to be weak, with a length of 133 mo (months) or 11.1 yr. The sunspot number maximum in cycle 25 is predicted to occur in April 2023 with a sunspot number 132.1 and a solar cycle length of 118 mo or 9.8 yr. Thus, solar cycle 24 is predicted to have an intensity 23% lower than cycle 23, and cycle 25 will be 5% lower than cycle 23. 相似文献
14.
H. Evangelista D. Godiva A. Sifeddine Z. M. A. N. Leão N. R. Rigozo B. Segal T. Ambrizzi M. Kampel R. K. P. Kikuchi F. Le Cornec 《Climate Dynamics》2007,29(7-8):869-880
Physical and biological changes in the marine environment, induced by oceanic-atmospheric processes, can be imprinted in massive coral skeletons. Herein, we present an evidence of potential El Niño impacts at the Southwestern South Atlantic Ocean (SWSA) inferred from the sclerochronology of the reef coral Favia leptophylla. The application of spectral analysis (wavelet decomposition and the iterative regression) to coral growth length and to meteorological-oceanographic parameters (air temperature, sea surface temperature and precipitation) as well as to Southern Oscillation Index (SOI) and solar irradiation indicated a major significant inverse relationship between SOI and coral growth length at the 4–8 years frequency band. We propose here that coral growth length from the SWSA could be affected by El Niño Southern Oscillation (ENSO) events through an “atmospheric bridge”, in contrast to its direct effect at the Pacific Ocean, related to the increase in sea surface temperature. 相似文献
15.
In normal practice, the active earth pressure on cantilever retaining wall is evaluated with different procedures relating to an ideal vertical plane passing through the heel of the wall. If the wall presents a long heel, failure planes do not interfere with the vertical stem, so that the limit Rankine conditions can develop freely in the backfill. The inclination of lateral actions along the ideal plane is assumed to be constant and depends on the geometry of the ground level and on the friction angle φ. The Authors recently proposed a new method to evaluate the active earth pressure coefficient due to seismic loading with a pseudo-static stress plasticity solution. The present paper describes the application of this method to a retaining wall supporting a φ soil backfill with an irregular surface. For two different configurations of wall-soil system, the behaviour is also studied by continuum FDM dynamic analyses, utilising four Italian accelerometric time-histories scaled at the same peak ground acceleration. The comparison between different procedures is also analysed. 相似文献
16.
How will climate change spatially affect agriculture production in Ethiopia? Case studies of important cereal crops 总被引：2，自引：0，他引：2
Nearly all of Ethiopia’s agriculture is dependent on rainfall, particularly the amount and seasonal occurrence. Future climate change predictions agree that changes in rainfall, temperature, and seasonality will impact Ethiopia with dramatic consequences. When, where, and how these changes will transpire has not been adequately addressed. The objective of our study was to model how projected climate change scenarios will spatially and temporally impact cereal production, a dietary staple for millions of Ethiopians. We used Maxent software fit with crop data collected from household surveys and bioclimatic variables from the WorldClim database to develop spatially explicit models of crop production in Ethiopia. Our results were extrapolated to three climate change projections (i.e., Canadian Centre for Climate Modeling and Analysis, Hadley Centre Coupled Model v3, and Commonwealth Scientific and Industrial Research Organization), each having two emission scenarios. Model evaluations indicated that our results had strong predictability for all four cereal crops with area under the curve values of 0.79, 0.81, 0.79, and 0.83 for teff, maize, sorghum, and barley, respectively. As expected, bioclimatic variables related to rainfall were the greatest predictors for all four cereal crops. All models showed similar decreasing spatial trends in cereal production. In addition, there were geographic shifts in land suitability which need to be accounted for when assessing overall vulnerability to climate change. The ability to adapt to climate change will be critical for Ethiopia’s agricultural system and food security. Spatially explicit models will be vital for developing early warning systems, adaptive strategies, and policy to minimize the negative impacts of climate change on food production. 相似文献
17.
The Mechanical Behaviour of a Pyroclastic Rock: Yield Strength and “Destructuration” Effects 总被引：1，自引：0，他引：1
Summary
A research programme on the mechanical behaviour of a homogenous volcanic tuff found in the centre of the city of Naples (Italy)
was carried out at the University of Naples a few years ago. Isotropic and drained triaxial tests were performed in a very
wide range of confining pressures (up to 60 MPa). After presenting the stress-strain curve pattern and the mean stress influence
on the shear behaviour, the paper focuses on the definition of a strength criterion and of the yield surface for this material.
Some tuff samples were subjected to isotropic compression tests up to a confining pressure approximately twice as high as
the isotropic yield stress; they were subsequently unloaded and subjected to drained triaxial tests. Partial loosening of
the interparticle bonds (“destructuration”) was observed. The paper also compares the mechanical behaviour of intact and “destructured”
samples, emphasising the effects of the structure on strength and yield. 相似文献
18.
Danielly Godiva Heitor Evangelista Milton Kampel Marcus Vinicius Licinio Casimiro Munita 《Estuarine, Coastal and Shelf Science》2010
Coral and reef environments in shallow waters are negatively affected by human activities in several coastal areas worldwide. It has been demonstrated that sediment influx and macronutrient discharges induce decline of coral population structure and diversity. Therefore, efforts to quantify sediment flux, sources and the biological response to sedimentation were conducted by several marine researchers. Herein, we investigated the case study of Armação dos Búzios/Brazil/Western South Atlantic, where coral colonies (mostly Siderastrea stellata) are under stress due to sediment apportionment as a consequence of regional human occupation. Classification of potential sediment source regions was based on a high-resolution aerogammaspectrometry survey for 232Th, 238U and 40K in main land near shore, used as primarily tool, in combination with sediment geochemistry. This approach allowed distinguishing three hydrographic basins (Macaé river basin, São João river basin and Una river basin) as potential sources. Hierarchical cluster analysis applied to the set of parameters identified the Macaé River as the most probable sediment contributor to the coralline site. 相似文献
19.
20.
Lorenza Evangelista Luigi Landolfi Anna d’Onofrio Francesco Silvestri 《Bulletin of Earthquake Engineering》2016,14(12):3363-3387
During the Abruzzo earthquake (6.IV.2009, MW = 6.3), the village of Castelnuovo, lying on an elliptical hill about 60 m high, underwent an intensive damage (IMCS = 9–10), that could be partly ascribed to the topographic amplification and to the presence of an underground cavity network. To verify these hypotheses, the seismic response of the hill was carefully investigated adopting both 2D and 3D finite difference numerical models. Analyses were carried out using a detailed geotechnical model, defined on the basis of a comprehensive field investigation (boreholes, DH, HVSR, ERT) and accurate laboratory tests (RC-TS). The reference input motion was reproduced considering the time history of the mainshock recorded at an accelerometric station close to the epicenter, conveniently deconvoluted to the bedrock and scaled in amplitude to the site of Castelnuovo. The results of the numerical analyses, expressed in terms of distribution of the amplification factor of peak acceleration and Housner intensity, proved that the topographic effects significantly influenced the ground motion at surface, whereas the role of cavities seemed to be negligible. 相似文献