A fractal fragmentation model for rockfalls   总被引：1，自引：0，他引：1  

Roger Ruiz-Carulla  Jordi Corominas  Olga Mavrouli 《Landslides》2017,14(3):875-889

The impact-induced rock mass fragmentation in a rockfall is analyzed by comparing the in situ block size distribution (IBSD) of the rock mass detached from the cliff face and the resultant rockfall block size distribution (RBSD) of the rockfall fragments on the slope. The analysis of several inventoried rockfall events suggests that the volumes of the rockfall fragments can be characterized by a power law distribution. We propose the application of a three-parameter rockfall fractal fragmentation model (RFFM) for the transformation of the IBSD into the RBSD. A discrete fracture network model is used to simulate the discontinuity pattern of the detached rock mass and to generate the IBSD. Each block of the IBSD of the detached rock mass is an initiator. A survival rate is included to express the proportion of the unbroken blocks after the impact on the ground surface. The model was calibrated using the volume distribution of a rockfall event in Vilanova de Banat in the Cadí Sierra, Eastern Pyrenees, Spain. The RBSD was obtained directly in the field, by measuring the rock block fragments deposited on the slope. The IBSD and the RBSD were fitted by exponential and power law functions, respectively. The results show that the proposed fractal model can successfully generate the RBSD from the IBSD and indicate the model parameter values for the case study.  相似文献   

Near-inertial motions in and around the Palamós submarine canyon (NW Mediterranean) generated by a severe storm     

Antoni Jordi  Dong-Ping Wang 《Continental Shelf Research》2008,28(17):150-2534

During 9–16 November 2001 the western Mediterranean Sea was lashed by one of the most extreme storms of the last decades. Current meter data from seven moorings in the Palamós submarine canyon (northwestern Mediterranean) are analyzed to understand the vertical propagation of near-inertial energy generated by the storm. The daily inertial rotary components are examined for evidence of free and forced near-inertial oscillations. Free near-inertial motions are increased during the storm, although they are larger outside the canyon than inside. Conversely, forced near-inertial motions are relatively large inside the canyon but are almost negligible outside. Based on the results of a three-dimensional ocean circulation model, these differences are shown to be caused by the presence of a storm-generated alongshore front. The mechanisms by which near-inertial energy propagates are distinct at each side of the front. On the onshore side of the front (inside the canyon), free near-inertial motions are rapidly carried away by normal inertial waves, and wave reflection off canyon wall is responsible for the dissipation of free near-inertial motions and enhancement of forced near-inertial motions. On the offshore side of the front (outside the canyon), on the other hand, free near-inertial motions propagates first downward with anomalously low frequency internal waves and are then advected southward and offshore by the mean flow.  相似文献   

An operational forecasting system for physical processes in the Santos-Sao Vicente-Bertioga Estuarine System,Southeast Brazil     

Costa  Carine G. R.  Leite  José Roberto B.  Castro  Belmiro M.  Blumberg  Alan F.  Georgas  Nickitas  Dottori  Marcelo  Jordi  Antoni 《Ocean Dynamics》2020,70(2):257-271

Ocean Dynamics - We describe the design, implementation, and performance of a fully automated Santos Operational Forecasting System (SOFS), built to monitor and predict short-term (< 3 days)...  相似文献   

Estimates of Horizontal Groundwater Flow Velocities in Boreholes     

Martí Bayer-Raich  Anthony Credoz  Jordi Guimerà  Salvador Jordana  Diego Sampietro  Jordi Font-Capó  Nathalie Nief  Matthieu Grossemy 《Ground water》2019,57(4):525-533

Currently, monitoring tools can be deployed in observation boreholes to better assess groundwater flow, flux of dissolved contaminants and their mass discharge in an aquifer. The relationship between horizontal water velocity in observation boreholes and Darcy fluxes in the surrounding aquifer has been studied for natural flow conditions (i.e., no pumping). Interpretation of measurements taken with dilution tests, the colloidal borescope, the Heat Pulse Flowmeter, and other techniques require the conversion of observed borehole velocity u to aquifer Darcy flux q_∞ . This conversion is typically done through a proportionality factor α = u/q_∞ . In experimental studies as well as in theoretical developments, reported values of α vary almost three orders of magnitude (from 0.5 to 10). This large variability in reported values of α could be explained by: (1) unclear distinction between Darcy flux and water seepage velocity, (2) unclear definition of water velocity in the borehole, (3) effects of well screen and the presence of the measurement device itself on the observable velocities, and (4) hydraulic conditions in the borehole annulus. We address (1), (2) from a conceptual/theoretical perspective, and (3) by means of numerical simulations. We show that issue (1) in low porosity aquifers can yield to order-of-magnitude discrepancies in estimates of q_∞ ; (2) may result in discrepancies of up to 50%, and (3) can cause differences up to 20% of water velocity in the borehole void space compared to the theoretical case of an open borehole.  相似文献   

Particle fluxes dynamics in Blanes submarine canyon (Northwestern Mediterranean)     

Diana Zúñiga  M. Mar Flexas  Anna Sanchez-Vidal  Johan Coenjaerts  Antoni Calafat  Gabriel Jordà  Jordi García-Orellana  Joan Puigdefàbregas  Miquel Canals  Manuel Espino  Francesc Sardà  Joan B. Company 《Progress in Oceanography》2009,82(4):239-251

Within the framework of the multidisciplinary RECS project and with the aim of describing the particle flux transfer from the continental shelf to the deep basin, an array of five mooring lines equipped with a total of five pairs of PPS3/3 sequential-sampling sediment traps and RCM-7/8 current meters were deployed 30 m above the bottom from March 2003 to March 2004 inside and outside the Blanes Canyon. One mooring line was located in the upper canyon at 600 m depth, one in the canyon axis at 1700 m depth and other two close to the canyon walls at 900 m depth. A fifth mooring line was deployed in the continental open slope at 1500 m water depth.The highest near-bottom downward particle flux (14.50 g m⁻² d⁻¹) was recorded at the trap located in the upper canyon (M1), where continental inputs associated with the presence of the Tordera River are most relevant. On the other hand, the downward fluxes (4.35 g m⁻² d⁻¹) in the canyon axis (M2) were of the same order as those found in the western flank (M3) of the canyon. Both values were clearly higher than the value (1.95 g m⁻² d⁻¹) recorded at the eastern canyon wall (M4). The open slope (M5) mass flux (5.42 mg m⁻² d⁻¹) recorded by the sediment trap located outside the canyon system was three orders of magnitude lower than the other values registered by the inner canyon stations. The relevance of our data is that it explains how the transport pathway in the canyon occurs through its western flank, where a more active and persistent current toward the open ocean was recorded over the entire year of the experiment.Off-shelf sediment transport along the canyon axis showed clear differences during the period of the study, with some important events leading to strong intensifications of the current coupled with large transport of particle fluxes to the deepest parts of the canyon. Such events are primarily related to increases in river discharge and the occurrence of strong storms and cascading events during the winter.In summary, in this study it is shown that the dynamics of the water masses and the currents in the study area convert the sharp western flank of the Blanes Canyon in a more active region that favors erosion processes than the eastern flank, which has a smoother topography and where the absence of erosional conditions yields to steadier sedimentary processes.  相似文献   

Sediment entrainment in karst basins     

Jordi Colomer  John Alan Ross  Xavier Casamitjana 《Aquatic Sciences - Research Across Boundaries》1998,60(4):338-358

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Astrometry and Photometry of Open Clusters: NGC 1746, NGC 1750 and NGC 1758     

D. Galadí-Enríquez  C. Jordi  E. Trullols 《Astrophysics and Space Science》1998,263(1-4):307-310

We present an astrometric and photometric analysis of a 5 square degree region around NGC 1746, NGC 1750 and NGC 1758, close to the Galactic anti-center (l = 179°, b = -10°), in Taurus. We describe the acquisition, reduction and analysis of the observational data, including the development of innovative data analysis tools. The data comprise CCD UBVRI photometry, photographic BVR photometry and proper motions. The clusters NGC 1750 and 1758 are poor and loose. We determine several physical parameters (distance, age, colour excess, positions, density profiles). The mutual separation, their relative velocity and their age difference allows us to conclude that these two clusters are physically independent. No real object in the area can be identified as NGC 1746. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

GAIA: Fundamental Parameters from the Space     

J. Torra  X. Luri  F. Figueras  C. Jordi 《Astrophysics and Space Science》1998,263(1-4):315-318

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OSIRIS Imaging and Spectroscopy for the GTC     

Jordi Cepa 《Astrophysics and Space Science》1998,263(1-4):369-372

The characteristics of OSIRIS (Optical System for Imaging and low-Resolution Integrated Spectroscopy), an instrument for imaging and low resolution spectroscopy proposed for the GTC 10m telescope, are described. OSIRIS is a multi-purpose instrument that incorporates in a "classical design" several innovations, already tested in 4m-class telescopes, that will provide a powerful first light instrument for the GTC. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

General patterns of circulation, sediment fluxes and ecology of the Palamós (La Fonera) submarine canyon, northwestern Mediterranean     

Albert Palanques  Emilio García-Ladona  Dami Gomis  Jacobo Martín  Marta Marcos  Ananda Pascual  Pere Puig  Josep-Maria Gili  Mikhail Emelianov  Sebasti Monserrat  Jorge Guilln  Joaquín Tintor  Mariona Segura  Antoni Jordi  Simn Ruiz  Gotzon Basterretxea  Jordi Font  Dolors Blasco  Francesc Pags 《Progress in Oceanography》2005,66(2-4):89

Currents, particle fluxes and ecology were studied in the Palamós submarine canyon (also known as the Fonera canyon), located in the northwestern Mediterranean. Seven mooring arrays equipped with current meters and sediment traps were deployed along the main canyon axis, on the canyon walls and on the adjacent slope. Additionally, local and regional hydrographic cruises were carried out. Current data showed that mean near surface and mid-depth currents were oriented along the mean flow direction (NE–SW), although at 400 and 1200 m depth within the canyon current reversals were significant, indicating a more closed circulation inside the canyon. Mean near-bottom currents were constrained by the local bathymetry, especially at the canyon head. The most significant frequency at all levels was the inertial frequency. A second frequency of about three days, attributed to a topographic wave, was observed at all depths, suggesting that this wave was probably not trapped near the bottom. The current field observed during the most complete survey revealed a meandering pattern with cyclonic vorticity just upstream from and within the canyon. The associated vertical velocity ranged between 10 and 20 m/day and was constrained to the upper 300 m. This latter feature, together with other computations, suggests that during this survey the meander was not induced by the canyon but by some kind of instability of the mean flow.In the canyon, suspended sediment concentration, downward particle fluxes, chlorophyll and particulate C and N were significantly higher up-canyon from about 1200 m depth than offshore, defining, along with the different hydrodynamics, two canyon domains: one from the canyon head to about 1200 m depth more affected by the canyon confinement and the other deeper than 1200 m depth more controlled by the mean flow and the shelf-slope front. The higher near-bottom downward total mass fluxes were recorded in the canyon axis at 1200 m depth along with sharp turbidity increases and are related to sediment gravity flows. During the deployment period, the increase in downward particle fluxes occurred by mid-November, when a severe storm took place. On the canyon walls at 1200 m depth, suspended sediment concentrations, downward particle fluxes, chlorophyll and particulate C and N were higher on the southern wall than on the northern wall inversely to the current’s energy. This could be caused by an upward water supply on the southern canyon wall and/or the mean flow interacting with the canyon bathymetry. In the swimmers collected by the sediment traps, the dominant species was an elasipod holothurian, which has not been recorded in other canyons or elsewhere in the Mediterranean, indicating particular speciation.  相似文献