Degradation of rock fracture asperities in unloading,reloading, and reversal     

Pooyan Asadollahi  Fulvio Tonon 《国际地质力学数值与分析法杂志》2011,35(12):1334-1346

Among the constitutive models for rock fractures developed over the years, Barton's empirical model has been widely used. Although Barton's failure criterion predicts peak shear strength of rock fractures with acceptable precision, it has some limitations in estimating the peak shear displacement, post‐peak shear strength, dilation, and surface degradation. The first author modified Barton's original model in order to address these limitations. Barton proposed his model for degradation of fracture asperities in unloading, reloading, and shear displacement reversal based on just one cyclic direct shear test. In this study, a database of results of 18 cyclic direct shear tests available in the literature was collected and analyzed. Modifications were made to Barton's original model (in terms of fracture cyclic shearing) to make it consistent with the modified model proposed by the first author. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Manuscripts Using Numerical Discrete Element Methods     

Giovanni Barla  Herbert Einstein  Kalman Kovari 《Rock Mechanics and Rock Engineering》2013,46(4):655-655

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The Holocene tephrostratigraphic record of Lake Shkodra (Albania and Montenegro)     

Roberto Sulpizio  Aurelien Van Welden  Benoit Caron  Giovanni Zanchetta 《第四纪科学杂志》2010,25(5):633-650

Two cores were recovered in the southeastern part of Lake Shkodra (Montenegro and Albania) and sampled for identification of tephra layers. The first core (SK13, 7.8 m long) was recovered from a water depth of 7 m, while the second core (SK19, 5.8 m long) was recovered close to the present‐day shoreline (water depth of 2 m). Magnetic susceptibility investigations show generally low values with some peaks that in some cases are related to tephra layers. Naked‐eye inspection of the cores allowed the identification of four tephra layers in core SK13 and five tephra layers in core SK19. Major element analyses on glass shards and mineral phases allowed correlation of the tephra layers between the two cores, and their attribution to six different Holocene explosive eruptions of southern Italy volcanoes. Two tephra layers have under‐saturated composition of glass shards (foiditic and phonolitic) and were correlated to the AD 472 and the Avellino (ca. 3.9 cal. ka BP) eruptions of Somma‐Vesuvius. One tephra layer has benmoreitic composition and was correlated to the FL eruption of Mount Etna (ca. 3.4 cal. ka BP). The other three tephra layers have trachytic composition and were correlated to Astroni (ca. 4.2 cal. ka BP), Agnano Monte Spina (ca. 4.5 cal. ka BP) and Agnano Pomici Principali (ca. 12.3 cal. ka BP) eruptions of Campi Flegrei. The ages of tephra layers are in broad agreement with eight ¹⁴C accelerator mass spectrometric measurements carried out on plant remains and charcoal from the lake sediments at different depths along the two cores. The recognition of distal tephra layers from Italian volcanoes allowed the physical link of the Holocene archive of Lake Shkodra to other archives located in the central Mediterranean area and the Balkans (i.e. Lake Ohrid). Five of the recognised tephra layers were recognised for the first time in the Balkans area, and this has relevance for volcanic hazard assessment and for ash dispersal forecasting in case of renewed explosive activity from some of the southern Italy volcanoes. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Experimental and numerical study of soil-reinforcement effects on the low-strain stiffness and bearing capacity of shallow foundations     

Wilson Chung  Giovanni Cascante 《Geotechnical and Geological Engineering》2007,25(3):265-281

This paper presents results of meticulous laboratory testing and numerical simulations on the effect of reinforcement on the low-strain stiffness and bearing capacity of shallow foundations on dry sand. The effect of the location and the number of reinforcement layers is studied in the laboratory, whereas numerical simulations are used to study the reinforcement-foundation interaction. Laboratory tests show an increase of 100, 200, and 275% not only in bearing capacity but also in low-strain stiffness (linear load–displacement behaviour) of a square foundation when one, two, and three layers of reinforcement are used, respectively. The specimen preparation technique is found to be crucial for the repeatability and reliability of the laboratory results (less than 5% variability). Numerical simulations demonstrate that if reinforcements are placed up to a depth of one footing width (B) below the foundation, better re-distribution of the load to deeper layers is achieved, thus reducing the stresses and strains underneath the foundation. Numerical simulations and experimental results clearly identify a critical zone between 0.3 and 0.5B, where maximum benefits not only on the bearing capacity but also on the low-strain stiffness of the foundation are obtained. Therefore, soil reinforcement can also be used to reduce low-strain vibrations of foundations.  相似文献   

Capturing critical behaviour in soil moisture spatio-temporal dynamics     

Antonella Di Domenico  Giovanni Laguardia  Mauro Fiorentino 《Advances in water resources》2007

A physical system is subject to a phase transition process when it shows a discontinuous change of a macroscopic feature of the system under a continuous change of a system’s state variable.  相似文献   

The June 4th 1999 severe weather episode in San Quirino, Italy: a tornado event?     

Renzo Bechini  Dario Giaiotti  Agostino Manzato  Fulvio Stel  Stefano Micheletti 《Atmospheric Research》2001,56(1-4)

On the morning of June 4th 1999, a severe weather event took place in San Quirino, a small village of Friuli-Venezia Giulia in the northeast of Italy. This village is located near the piedmont of the Alps, 40 km west from Udine and 60 km north from Venice.Around 0900 UTC (1100 local time), a thunderstorm with an intense hail fall affected the area of San Quirino. A few minutes later (around 0920 UTC, source: a farmer), a funnel cloud from a cumulonimbus touched the ground, producing damages to houses, trees and sheds. The damaged area was quite narrow (about 300 m) and short (less than 10 km). No injuries to people were reported.In spite of the smallness of the area interested by the phenomenon, this storm is studied here starting from the synoptic scale, moving to the mesoscale and finishing with the storm scale, trying to underline its characteristics. These analyses, especially those coming from the Doppler radar images, bring us to the conclusion that the San Quirino episode was produced by a supercell storm.  相似文献   

Evolution of Pangea: paleomagnetic constraints from the Southern Alps, Italy     

Giovanni Muttoni  Dennis V. Kent  James E.T. Channell 《Earth and Planetary Science Letters》1996,140(1-4):97-112

A new early Late Triassic paleopole for Adria has been obtained from the Val Sabbia Sandstone in the Southern Alps. As Early Permian and Jurassic-Cretaceous paleomagnetic data from para-autochthonous regions of Adria such as the Southern Alps are consistent with ‘African’ APWPs[1–2], paleomagnetic data from this region can be used to bolster the West Gondwana APWP in the poorly known Late Permian-Triassic time interval. The Southern Alpine paleopoles are integrated with the West Gondwana and Laurussia APWPs of Van der Voo [1] and used to generate a tectonic model for the evolution of Pangea. The Early Permian overall mean paleopole for West Gondwana and Adria, in conjunction with the coeval Laurussia paleopole, support Pangea B of Morel and Irving [3]. The Late Permian/Early Triassic and the Middle/Late Triassic paleopoles from Adria and Laurussia support Pangea A-2 of Van der Voo and French [4]. The phase of transcurrent motion between Laurasia and Gondwana[5] that caused the Pangea B to A-2 transition occurred essentially in the Permian (at the end of Variscan orogeny) with an average relative velocity of approximately 10 cm/yr. Finally, the Late Triassic/Early Jurassic paleopoles from West Gondwana and Laurussia agree with Pangea A-1 of Bullard et al. [6], the widely accepted Pangea configuration at the time of the Jurassic breakup.  相似文献   

Seismotectonic models and CN algorithm: The case of Italy     

Giovanni Costa  Ivanka Orozova-Stanishkova  Giuliano Francesco Panza  Irina M. Rotwain 《Pure and Applied Geophysics》1996,147(1):119-130

The CN algorithm is utilized here both for the intermediate term earthquake prediction and to validate the seismotectonic model of the Italian territory. Using the results of the analysis, made through the CN algorithm and taking into account the seismotectonic model, three main areas, one for Northern Italy, one for Central Italy and one for Southern Italy, are defined. Two transition areas between the three main areas are delineated. The earthquakes which occurred in these two areas contribute to the precursor phenomena identified by the CN algorithm in each main area.  相似文献   

Map of the geoidal ondulations in Italy and the cross section Como-Otranto     

Prof. Dr. Giovanni Boaga 《Pure and Applied Geophysics》1955,30(1):8-12

Summary Astronomic and geodetic values of all observations made in Italy from 1868 to the present days are used to draw the geoidal ondulations-map in Italy.The geoidal ondulation along a cross section from Como to Otranto (for 1160 km length) is then traced.  相似文献   

New Minerals approved in 1998 by the Commission on New Minerals and Mineral Names International Mineralogical Association     

Joel D. Grice  Giovanni Ferraris 《Mineralogy and Petrology》1999,65(3-4):277-286

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