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841.
Hugo A. Loaiciga Roy B. Leipnik Paul F. Hudak Miguel A. Marino 《Mathematical Geology》1996,28(5):563-584
Starting with a stochastic differential equation with random coefficients describing steady-state flow, the effective hydraulic conductivity of 1-, 2-, and 3-dimensional aquifers is derived. The natural logarithm of hydraulic conductivity (lnK) is assumed to be heterogeneous, with a spatial trend, and isotropic. The effective conductivity relates the mean specific discharge in an aquifer to the mean hydraulic gradient, thus its importance in predicting Darcian discharge when field data represent mean or average values of conductivity or hydraulic head. Effective conductivity results are presented in exact form in terms of elementary functions after the introduction of special sets of coordinate transformations in two and three dimensions. It was determined that in one, two, and three dimensions, for the type of aquifer heterogeneity considered, the effective hydraulic conductivity depends on: (i) the angle between the gradient of the trend of lnK and the mean hydraulic gradient (which is zero in the one-dimensional situation); (2) (inversely) on the product of the magnitude of the trend gradient of lnK, b, and the correlation scale of lnK, and (3) (proportionally) on the variance of lnK,
f
2
. The productb plays a central role in the stability of the results for effective hydraulic conductivity. 相似文献
842.
Hydraulic exponents and unit hydraulic exponents are unit-sum constrained, which requires that they be analyzed by statistical methods designed for compositional data. Though uncertainties remain regarding selection of the best constraining operation and method of handling departures from the unit-sum constraint, neither category of uncertainty should be an impediment to the selection of the appropriate statistical methodology. In a small sample study, the hydraulic geometry of different types of streams were compared: (1) semi-arid: perennial vs. ephemeral; (2) tropical: Puerto Rico vs. West Malaysia; and (3) semi-arid vs. tropical (by pooling the previous data sets). All three comparisons revealed statistically significant differences in either logratio mean vectorsor logratio covariance matrices but not both. All six categories of data had logistic normal distributions. Because the derivatives at a given discharge of curvilinear hydraulic geometry relationships and hydraulic exponents on either side of the breakpoints of piecewise linear relationships are unit-sum constrained, they also can be studied by compositional methods. However, the compositional approach is limited in cases where distributions have large departures from logistic normality and for streams that have negative hydraulic exponents. 相似文献
843.
岩溶区兴建水利工程可能产生的地质环境效应 总被引:1,自引:0,他引:1
葛龙进 《华东地质学院学报》1998,21(2):106-110
本文在陈述有概念,如地质环境、岩溶环境,地质环境系统。 相似文献
844.
845.
水力压裂法采盐对环境影响的环境地球化学研究 总被引:1,自引:0,他引:1
水力压裂法采盐对环境影响的环境地球化学研究向武鲍征宇(中国地质大学,武汉430074)关键词水采法盐渍环境盐矿污染我国现有矿山1万多座,为国家提供了80%的工业原料,同时也造成了较严重的环境危害。仅全国尾矿侵占和污染的土地就达667余万公顷,间接污... 相似文献
846.
In order to characterize the hydraulic properties of an aquifer in Finland comprising two subvertical fracture zones, observation-well
responses were matched with generalized radial flow (GRF) type curves. The responses in six wells out of seven are consistent
with the GRF model. The fractional flow dimensions (1–1.2 and 1.5) were determined by regression analysis of straight-line
slopes and type-curve matching. In each test, the flow dimensions in the neighboring fracture zone range from 2–2.25. Comparisons
of the late-time responses with the asymptotic GRF solution and the flow dimensions obtained by reversing the pumping and
observation points suggest homogeneous hydraulic properties. Deviations in responses can be explained by flow-path tortuosity.
After assessments of the extent of the flow and radial distances along the fracture system, hydraulic conductivities and storativities
were determined from the results of the type-curve matching procedure. The obtained hydraulic conductivities are 1.3×10–5 to 7.9×10–5 m/s and 5.0×10–6 to 2.5×10–5 m/s for the western and the eastern fracture zones, respectively. The results were verified by applying them to analytical
solutions for pumping wells. The calculated pumping-well responses are consistent with the observations. The analysis of flow
dimension also enhances qualitative interpretations on the hydrogeology of fracture zones.
Received, April 1997 · Revised, September 1997 · Accepted, May 1998 相似文献
847.
This study uses linear regression and composite analyses to identify a pronounced asymmetric connection of sea surface temperature (SST) in the Tasman Sea with the two opposite phases of El Ni?o-Southern Oscillation (ENSO) during austral summer. In El Ni?o years, the SST anomalies (SSTAs) in the Tasman Sea exhibit a dipolar pattern with weak warmth in the northwest and modest cooling in the southeast, while during La Ni?a years the SSTAs exhibit a basin-scale warmth with greater amplitude. Investigations into the underlying mechanism suggest that this asymmetry arises from a mechanism related to oceanic heat transport, specifically the anomalous Ekman meridional heat transport induced by the zonal wind stress anomalies, rather than the surface heat fluxes on the air-sea interface. Further analysis reveals that the asymmetry of oceanic heat transport between El Ni?o and La Ni?a years is driven by the asymmetric atmospheric circulation over the Tasman Sea stimulated by the asymmetric diabatic heating in the tropical Pacific between the two opposite ENSO phases. 相似文献
848.
Hydraulic conductivity is a dominant parameter in the design of engineered waste disposal facilities such as landfill liners and covers, lagoon liners and slurry walls. It is of interest to a geotechnical or geo-environmental engineer to develop a predictive method of determining the hydraulic conductivity of fine-grained soils, in order to assess its suitability as a liner material. To predict the hydraulic conductivity of soils, researchers and geotechnical engineers have attempted to correlate it with index properties of the soils, such as the liquid limit, void ratio and specific surface. Based on the present study a predictive method has been developed in this paper to predict the hydraulic conductivity in terms of void ratio and shrinkage index (Liquid limit – shrinkage limit) for remoulded fine-grained soils. Though the initial conditions for the soil will affect the hydraulic conductivity behaviour to some extent, both the void ratio and soil characteristics are primary factors in affecting the hydraulic conductivity. Therefore for predictive purpose, the study of hydraulic conductivity behaviour of remoulded fine-grained soils as presented in this paper can be found to be useful for compacted soils also. 相似文献
849.
J.?O.?AfolayanEmail author C.?M.?O.?Nwaiwu K.?J.?Osinubi 《Geotechnical and Geological Engineering》2005,23(5):561-581
A numerical investigation to determine the existence or otherwise of congruence between laboratory-based and field-based models for predicting hydraulic conductivity of compacted clay liners has been conducted. The comparisons here are based on values of the reliability index estimated with the use of the two models for cases when hydraulic conductivity is assumed to be normally and lognormally distributed. The laboratory reduced Proctor and modified Proctor compactive efforts were assumed to correspond to the lowest and highest compactor weights (165kN and 338kN for sheepsfoot rollers only from literature) respectively. The standard Proctor compactive effort was assumed to correspond to the mean compactor weight of 261.4kN. Reliability estimates from the laboratory-based model were consistently higher than the corresponding values from the field-based model for each of the variables common to the two models. As laboratory samples usually involve small samples which are often unrepresentative of field situations, it is considered that reliability levels estimated with the use of the field-based model provide more realistic assessment of compacted lateritic soils as hydraulic barriers. Compactor weight of 300kN and above may be needed for effective compaction of lateritic soil liners. Reliability-based designs of lateritic soil liners should incorporate appropriate probability distribution types for variables in the field-based model. 相似文献
850.
Peter Blümling 《Geotechnical and Geological Engineering》2005,23(6):843-858
Within the context of the phase IV (1994–1996) research and development activities at the Grimsel Test Site (GTS), Nagra developed, in collaboration with the Agence Nationale pour la Gestion des Déchets Radioactifs (Andra), an investigation project for the sealing of boreholes drilled from underground. The project had the following goals:
The new concept developed in this project was to use highly compacted bentonite pellets only. The two techniques tested were
Both techniques were tested in situ at the GTS to estimate their performance under realistic field conditions. The swelling pressures were monitored for 4 months after seal emplacement until an almost constant value was attained. Finally the hydraulic and mechanical performance of the seal was tested. It was found that the conductivities measured across the seal were equivalent to the matrix properties of the surrounding rock (2–5 × 10−12 m/s). The hydraulic testing also showed no linear preferential flow. 相似文献
| sealing of boreholes drilled from underground facilities with a length of up to 500 m, |
| sealing of boreholes with mainly irregular shape (e.g. breakouts of borehole wall), |
| ensuring a hydraulic conductivity of 10−11–10−12 m/s for the seal, |
| ensuring reliable quality control in routine production. |
(1) | pneumatic injection of pellets into a borehole using a grain size distribution of 4–10 mm, |
(2) | emplacement using a modified core barrel for transport and compaction of the pellets. |