From spatial-continuous electrical resistivity measurements to the soil hydraulic functioning at the field scale     

Isabelle Cousin  Arlène Besson  Hocine Bourennane  Catherine Pasquier  Bernard Nicoullaud  Dominique King  Guy Richard 《Comptes Rendus Geoscience》2009,341(10-11):859-867

The aim of this article is to present a strategy to interpret the hydraulic functioning of a small field area by using measurements of the soil electrical resistivity. The spatial soil electrical resistivity was recorded at a high resolution on a 2 ha area by the MultiContinous Electrical Profiling (MuCEP) device at two dates. These apparent electrical resistivity measurements were firstly interpreted in terms of local electrical resistivity by 1D inverse modelling to estimate the real resistivity of the soil. These interpreted electrical resistivity data were then transformed into soil water content values and soil water potential values by the use of independent punctual data of water content and the use of the water retention curve determined by laboratory data. Our analysis has permitted us to describe the spatial variability and temporal evolution of the hydraulic functioning at high resolution from electrical resistivity data. The interpretation of the water content and matric potential maps demonstrated that some soil hydraulic processes, such as lateral overland flow, can occur in the studied zone. They would never have been detected by local measurements of soil characteristics or by the use of the soil map.  相似文献   

Modeling of shear failure in fractured reservoirs with a porous matrix     

Rajdeep Deb  Patrick Jenny 《Computational Geosciences》2017,21(5-6):1119-1134

A finite volume-based numerical modeling framework using a hierarchical fracture representation (HFR) has been developed to compute flow-induced shear failure. To accurately capture the mechanics near fracture manifolds, discontinuous basis functions are employed which ensure continuity of the displacement gradient across fractures. With these special basis functions, traction and compressive forces on the fracture segment can be calculated without any additional constraints, which is extremely useful for estimating the irreversible displacement along the fracture (slip) based on a constitutive friction law. The method is further extended to include slip-dependent hydraulic aperture change and grid convergent results are obtained. Further, the change in hydraulic aperture is modeled using an asymptotic representation which respects the experimentally observed behavior of pore volume dilation due to shear slip. The model allows the initial rapid increase in hydraulic aperture due to shear slip and asymptotically approaches a finite value after repeated shearing of a fracture segment. This aperture increase is the only feedback for mechanics into the fluid flow for a linear elastic mechanics problem. The same model is also extended to include poroelastic relations between flow and mechanics solver. The grid convergence result in the case of poroelastic flow-mechanics coupling for flow-induced shear failure is also obtained. This proves the robustness of the numerical and analytical modeling of fracture and friction in the extended finite volume method (XFVM) set-up. Finally, a grid convergent result for seismic moment magnitude for single fracture and fracture network with random initial hydraulic and friction properties is also obtained. The b-value, which represents the slope of seismic moment occurrence frequency decay vs seismic moment magnitude, which is approximately constant in a semi-logarithmic plot, is estimated. The numerical method leads to converged b-values for both single fracture and fracture network simulations, as grid and time resolutions are increased. For the resulting linear system, a sequential approach is used, that is, first, the flow and then the mechanics problems are solved. The new modeling framework is very useful to predict seismicity, permeability, and flow evolution in geological reservoirs. This is demonstrated with numerical simulations of enhancing a geothermal system.  相似文献   

Coupled surface and subsurface flow modeling of natural hillslopes in the Aburrá Valley (Medellín,Colombia)     

Daniela Blessent  Janet Barco  André Guy Tranquille Temgoua  Oscar Echeverrri-Ramirez 《Hydrogeology Journal》2017,25(2):331-345

Numerical results are presented of surface-subsurface water modeling of a natural hillslope located in the Aburrá Valley, in the city of Medellín (Antioquia, Colombia). The integrated finite-element hydrogeological simulator HydroGeoSphere is used to conduct transient variably saturated simulations. The objective is to analyze pore-water pressure and saturation variation at shallow depths, as well as volumes of water infiltrated in the porous medium. These aspects are important in the region of study, which is highly affected by soil movements, especially during the high-rain seasons that occur twice a year. The modeling exercise considers rainfall events that occurred between October and December 2014 and a hillslope that is currently monitored because of soil instability problems. Simulation results show that rainfall temporal variability, mesh resolution, coupling length, and the conceptual model chosen to represent the heterogeneous soil, have a noticeable influence on results, particularly for high rainfall intensities. Results also indicate that surface-subsurface coupled modeling is required to avoid unrealistic increase in hydraulic heads when high rainfall intensities cause top-down saturation of soil. This work is a first effort towards fostering hydrogeological modeling expertise that may support the development of monitoring systems and early landslide warning in a country where the rainy season is often the cause of hydrogeological tragedies associated with landslides, mud flow or debris flow.  相似文献   

Tidal disruptions: II. A continuum theory for solid bodies with strength, with applications to the Solar System     

Keith A. Holsapple  Patrick Michel 《Icarus》2008,193(1):283-301

We present a comprehensive theory for the breakup conditions for ellipsoidal homogeneous secondary bodies subjected to the tidal forces from a nearby larger primary: for materials ranging from purely fluid ones, to granular rubble-pile gravel-like ones, and to those with either cohesive or granular strength including cohesive rocks and metals. The theory includes but greatly extends the classical analyses given by Roche in 1847, which dealt only with fluids, and also our previous analysis [Holsapple, K.A., Michel, P., 2006. Icarus 183, 331-348], which dealt only with solid but non-cohesive bodies. The results here give the distance inside of which breakup must occur, for both a steadily orbiting satellite and for a passing or impacting object. For the fluid bodies there is a single specific shape (a “Roche Ellipsoid”) that can be in equilibrium at any given distance from a primary, and especially only one shape that can exist at the overall minimum distance (d/R)(ρ/ρp)^1/3=2.455, the classical well-known “Roche limit.” In contrast, solid bodies can exist at a given distance from a primary with a range of shapes. Here we give multiple plots of the minimum distances for various important combinations of body shape, spin, mass density, and the strength parameters characterized by an angle of friction and cohesive strength. Such results can be used in different ways. They can be used to estimate limits on strengths and mass densities for orbiting bodies at a known distance and shape. They can be used to determine breakup distances for passing bodies with an assumed strength and shape. They can be used to constraint physical properties such as bulk density of bodies with a known shape that were known to breakup at a given distance. A collection of approximately 40 satellites of the Solar System is used for comparison to the theory. About half of those bodies are closer than the Roche fluid limit and must have some cohesion and/or friction angle to exist at their present orbital distance. The required solid strength for those states is determined. Finally, we apply the theory to the break up of the SL9 comet at close approach with Jupiter. Our results make clear that the literature estimates of its bulk density depend markedly on unknown parameters such as shape, orientation and spin, and most importantly, material strength characterization.  相似文献   

Runoff generation from logged and burnt convergent hillslopes: rainfall simulation and modelling     

Patrick N. J. Lane  Jacky C. Croke  Paul Dignan 《水文研究》2004,18(5):879-892

This paper reports results from field experiments and hydrological modelling on the dynamics of runoff generation in highly convergent parts of the landscape in a logged and burnt eucalypt forest in south‐eastern Victoria, Australia. Large‐scale rainfall simulation experiments were conducted to explore runoff generating mechanisms from harvested areas, and to assess the effectiveness of standard water quality protective measures, here a disturbed filter strip, in preventing accession of sediment to near‐stream areas. We then examined the likely effects of varying antecedent moisture conditions on surface and subsurface runoff generating mechanisms. Very small volumes of surface runoff were generated only at very high rainfall intensity rates that exceeded a 100 year recurrence interval event during the simulated experiments. There was little or no identifiable impact of either compaction from logging operations or fire‐induced hydrophobicity on surface infiltration or generation of surface runoff. Measured soil hydraulic properties and soil depths explained the paucity of surface runoff, and the dominance of subsurface storm flow as the prime runoff generating mechanism. Deep lateral subsurface flow was observed from the cut‐face of a fire access track and into a streamhead downslope of the experimental plots. Water balance modelling using Topog_Dynamic indicated the conditions under which saturated overland flow in this environment could be generated are rare, but that care should be taken in siting of roads and tracks in lower parts of convergent landscapes. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

The interaction of the spiral density wave and the Sun's galactic orbit     

K. A. Innanen  A. T. Patrick  W. W. Duley 《Astrophysics and Space Science》1978,57(2):511-515

The galactocentric radial motion of the Sun introduces another periodicity to the encounters between the Sun and the spiral density wave. We describe a model simulation of the effect and present the associated periods.  相似文献   

GIS-based hydrogeological databases and groundwater modelling   总被引：4，自引：2，他引：2  

Radu Gogu  Guy Carabin  Vincent Hallet  Valerie Peters  Alain Dassargues 《Hydrogeology Journal》2001,9(6):555-569

Reliability and validity of groundwater analysis strongly depend on the availability of large volumes of high-quality data. Putting all data into a coherent and logical structure supported by a computing environment helps ensure validity and availability and provides a powerful tool for hydrogeological studies. A hydrogeological geographic information system (GIS) database that offers facilities for groundwater-vulnerability analysis and hydrogeological modelling has been designed in Belgium for the Walloon region. Data from five river basins, chosen for their contrasting hydrogeological characteristics, have been included in the database, and a set of applications that have been developed now allow further advances. Interest is growing in the potential for integrating GIS technology and groundwater simulation models. A "loose-coupling" tool was created between the spatial-database scheme and the groundwater numerical model interface GMS (Groundwater Modelling System). Following time and spatial queries, the hydrogeological data stored in the database can be easily used within different groundwater numerical models. Electronic Publication  相似文献   

Long-term performance of permeable reactive barriers using zero-valent iron: geochemical and microbiological effects   总被引：15，自引：0，他引：15  

Wilkin RT  Puls RW  Sewell GW 《Ground water》2003,41(4):493-503

Geochemical and microbiological factors that control long-term performance of subsurface permeable reactive barriers were evaluated at the Elizabeth City, North Carolina, and the Denver Federal Center, Colorado, sites. These ground water treatment systems use zero-valent iron filings (Peerless Metal Powders Inc.) to intercept and remediate chlorinated hydrocarbon compounds at the Denver Federal Center (funnel-and-gate system) and overlapping plumes of hexavalent chromium and chlorinated hydrocarbons at Elizabeth City (continuous wall system). Zero-valent iron at both sites is a long-term sink for carbon, sulfur, calcium, silicon, nitrogen, and magnesium. After about four years of operation, the average rates of inorganic carbon (IC) and sulfur (S) accumulation are 0.09 and 0.02 kg/m2/year, respectively, at Elizabeth City where upgradient waters contain <400 mg/L of total dissolved solids (TDS). At the Denver Federal Center site, upgradient ground water contains 1000 to 1200 mg/L TDS and rates of IC and S accumulation are as high as 2.16 and 0.80 kg/m2/year, respectively. At both sites, consistent patterns of spatially variable mineral precipitation and microbial activity are observed. Mineral precipitates and microbial biomass accumulate the fastest near the upgradient aquifer-Fe0 interface. Maximum net reductions in porosity due to the accumulation of sulfur and inorganic carbon precipitates range from 0.032 at Elizabeth City to 0.062 at the Denver Federal Center (gate 2) after about four years. Although pore space has been lost due the accumulation of authigenic components, neither site shows evidence of pervasive pore clogging after four years of operation.  相似文献   

Instructions for Authors     

Patrick Blackburn 《Boundary-Layer Meteorology》2003,109(3):337-338

Instructions for Authors

Instructions for Authors  相似文献   

Experimental study and TEM characterization of dusty olivines in chondrites: Evidence for formation by in situ reduction     

Hugues Leroux  Guy Libourel  Laurence Lemelle  Fran&#x;ois Guyot 《Meteoritics & planetary science》2003,38(1):81-94

Abstract— An analytical transmission electron microscopy (ATEM) study was undertaken in order to better understand the formation conditions of dusty olivines (i.e., olivines containing abundant tiny inclusions of Fe‐Ni metal) in primitive meteorites. Dusty olivines from type I chondrules in the Bishunpur chondrite (LL3.1) and from synthetic samples obtained by reduction of San Carlos olivines were examined. In both natural and experimental samples, micron size metal blebs observed in the dusty region often show preferential alignments along crystallographic directions of the olivine grains, have low Ni contents (typically <2 wt%), and are frequently surrounded by a silica‐rich glass layer. These features suggest that dusty olivines are formed by a sub‐solidus reduction of initially fayalitic olivines according to the following reaction: Some volatilization of SiO_gas may account for the apparent excess of metal relative to silica‐rich glass observed in both experimental and natural samples. Comparison with experimentally produced dusty olivines suggests that time scales of the order of minutes usually inferred for chondrule formation are also adequate for the formation of dusty olivines. These observations are in agreement with the hypothesis that at least part of the metal phase in chondrites originated from reduction during chondrule formation.  相似文献