Fluid permeability of sedimentary rocks in a complete stress–strain process

The permeability of sedimentary rocks during triaxial compression tests was investigated to relate it to the complete strain–stress process. It was found that the permeability was not constant, but varied with the stress and strain states in the rocks. Prior to the peak strength, the permeability decreases with increasing load. A dramatic increase in permeability occurs during the strain softening period. In the present study, in situ measurements of fluid flow and pressure in floor strata was carried out in a double longwall mining face in the Yangzhuang colliery. These measurements show that both the strata pressure and the position with respect to the mining face influence the hydrogeologic properties. The permeability increased in the floor strata behind the mining face because those mining induced fractures opened as the strata pressure decreased. To better understand this change in hydraulic behavior around the mining faces, 3-D numerical modeling was carried out. The model provides the general picture of the stress distribution and failure zone both in the floor and roof strata. The field and model results demonstrate the importance of changes in the stress and strain states on the hydrogeology of a site.     

Dissolved silica budget in the North basin of Lake Lugano

We studied the dissolved silica cycle in the water column of the North basin of Lake Lugano, Switzerland/Italy. Lake Lugano is a meromictic, eutrophic lake, permanently stratified below 100-m depth. A one-box model was used to calculate a silica mass-balance over 1993, based on various lake measurements, such as sediment traps, sediment cores, water analysis and biota countings. We found that the North basin of Lake Lugano is at steady state as far as dissolved silica is concerned. The primary source of dissolved silica in the lake is river input (about 80%), with diffusion from bottom sediments and groundwater input also playing a role. Atmospheric input is negligible. The main export of dissolved silica occurs via biogenic uptake by diatoms and final burial of their frustules in the bottom sediment. Loss of dissolved silica through the lake outflow only represents 15% of the total output. Of the total amount of Si exported to the lake bottom through diatom sinking, less than 20% is re-supplied to the surface water by diffusion. Thus, the lake acts as an important permanent sink for silica. The long residence time of dissolved silica in the lake (7 years) is related to the strong physical stratification of the lake. Only about 10% of the standing stock are available to phytoplankton uptake.     

地质图空间数据库建设中的拓扑关系处理

拓扑关系是空间数据库的核心。主要阐述拓扑关系的基本概念，详细介绍MAPGIS和ARC/INFO两大模块中，拓扑关系具体表现形式、处理方法及处理过程中的注意事项，形成了一套较为完善的工作流程，提高了工作效率，为今后的信息化提供了行之有效的工作方法。     

A Comparison of Two-Phase Dynamic Upscaling Methods Based on Fluid Potentials

Although a number of methods for calculating dynamic pseudo-functions have been developed over the years, there is still a lack of understanding as to why a certain method will succeed in some cases but fail in others. In this paper, we describe the results of an assessment of several upscaling methods, namely the Kyte and Berry (KB) method, the Stone method, the Hewett and Archer (HA) method and the Transmissibility-Weighted (TW) method. We have analyzed the equations for deriving the methods and investigated the results of numerical simulations of gas displacing oil, in a variety of models to enable us to gain new insights into these, and related, upscaling methods. In particular, some novel observations on methods based on fluid potential are presented and the issue of using predicted fluid mobilities as a criterion of accuracy of an upscaling method is clarified.     

Experimental Study on Mine Spoils During Superficial Geochemistry Processes

Based on the mineral and chemical compositions of spoils taken from the Shilu Cu-Mo deposit and Hetai gold deposit, the leaching and batch experiments were made on spoils taken from these two deposits using the leaching column designed by the authors. The experimental results showed that it is not always true that the mine drainage is acidic. Its acidity depends on acid-buffering capacity of gangue, host rock and its alteration mineral assemblage. The composition of the drainage water is related with the interaction between superficial or underground water and solid materials in the spoils, including minerals, hydroxides and amorphous substances. The leaching extent of the element is related with its occurrence form in the deposit. The preferential flow results in leaching-out of heavy metals in large amounts. So it is important to prevent the generating of preferential flow in the system. The results will provide very important grounds for the comprehensive management of land and ecological rehabilitation of the mine site.     

MODELING THE FATE AND TRANSPORT OF HYDROPHOBIC ORGANIC COMPOUNDS IN AN UNSTEADY RIVER-ESTUARINE SYSTEM

1 INTRODUCTION Extensive literature (Brown et al., 1985; Sawhney et al., 1981; Bierman and Swain, 1982; Connolly, 1980; Lopez-Avila and Hites, 1980; O扖onnor, 1988) described lots of sorbed pollutants or toxic substances in bed sediments of rivers, even after the effluent was halted for a long time. This is particularly true for hydrophobic organic compounds that can be sorbed on the particles and accumulated in the river bed sediments (Karickhoff et al., 1979). Pollution events of…     

Crystal-rich mass flow deposits related to the eruption of a sublacustrine silicic cryptodome (Early Permian Collio Basin, Italian Alps)

Sedimentological, granulometric and petrographic data are presented from a detailed study on a crystal-rich mass flow deposit, which is presumably related to the eruption of a sublacustrine cryptodome. The deposit forms a prominent intercalation in the Lower Permian Collio Formation in the Italian Alps north of Brescia. Outcrops of the 10–20-m-thick volcaniclastic deposit (Dasdana I Beds, DB) can be traced over 12 km from east to west. The DB consists of a thick, crystal-rich, sandy–gravelly lower subunit representing a sequence of amalgamated Bouma-a(b) divisions overlain by a thin, well-bedded, sandy–muddy subunit that is rich in outsize porphyritic silicic fragments. Modal and computer-aided image analyses reveal that the crystal-rich lower subunit contains up to 80% of volcanogenic crystals. Some samples contain up to 60% of porphyritic fragments, which have a phenocryst content of about 20%. The wide textural range from cryptocrystalline, poikilomosaic, to rarer medium-grained granophyric groundmass, the irregular to lensoid shapes of the porphyritic fragments, and the presence of basement and sedimentary clasts suggest that the DB originated from a sublacustrine eruption of a partially extrusive cryptodome (ca. 1.6 km³). Two other porphyritic felsic cryptodomes (Dosso dei Lupi, Dosso del Bue), described briefly here, emplaced into the Collio Formation sometime after the DB event, and expose flat bases and tilted sediments at their sides. Textures observed in these domes are comparable to those found in the DB porphyritic fragments.     

A model of equilibrium bed topography for meander bends with erodible banks

Channel curvature produces secondary currents and a transverse sloping channel bed, along which the depth increases towards the outer bank. As a result deep pools tend to form adjacent to the outer bank, promoting bank collapse. The interaction of sediment grains with the primary and secondary flow and the transverse sloping bed also causes meanders to move different grain sizes in different proportions and directions, resulting in a consistent sorting pattern. Several models have been developed to describe this process, but they all have the potential to over‐predict pool depth because they cannot account for the influence of erodible banks. In reality, bank collapse might lead to the development of a wider, shallower cross‐section and any resulting flow depth discrepancy can bias associated predictions of flow, sediment transport, and grain‐size sorting. While bed topography, sediment transport and grain sorting in bends will partly be controlled by the sedimentary characteristics of the bank materials, the magnitude of this effect has not previously been explored. This paper reports the development of a model of flow, sediment transport, grain‐size sorting, and bed topography for river bends with erodible banks. The model is tested via intercomparison of predicted and observed bed topography in one low‐energy (5·3 W m^?2 specific stream power) and one high‐energy (43·4 W m^?2) study reach, namely the River South Esk in Scotland and Goodwin Creek in Mississippi, respectively. Model predictions of bed topography are found to be satisfactory, at least close to the apices of bends. Finally, the model is used in sensitivity analyses that provide insight into the influence of bank erodibility on equilibrium meander morphology and associated patterns of grain‐size sorting. The sensitivity of meander response to bank cohesion is found to increase as a function of the available stream power within the two study bends. Copyright © 2002 John Wiley & Sons, Ltd.     

流动成像测井研究进展

流动成像测井属于对非均匀介质动态的非线性测量，通过对油气井内多相流体信息的投影扫描和反演处理，实时成像显示流体分布及流动状况，国外研制的电导法，电容法仪器采用电导探针或电容元件构成阵列测量探头，分别利用油气与水的导电特性和介电特性差异辨识井内流体，对流动截面的测量局限于个别点上，已在水平井中见到应用效果，但对物场信息投影测量的数据量和分辨率未能满足成像要求。我国提出的电磁法采用环状阵列电极构成测量探头，综合利用油气与水的导电和介电特性差异辨识井内流体，可以测量获得多相流体流动截面的清晰图像，为研究开发全新的流动成像测井系统奠定了良好基础。     

Efficient methods for solving water flow in variably saturated soils under prescribed flux infiltration

The non-linear solvers in numerical solutions of water flow in variably saturated soils are prone to convergence difficulties. Many aspects can give rise to such difficulties and in this paper we address the gravity term and the prescribed-flux boundary in the Picard iteration. The problem of the gravity term in the Picard iteration is iteration-to-iteration oscillation as the gravity term is treated, by analogy with the time-step advance technique, ‘explicitly’ in the iteration. The proposed method for the gravity term is an improvement of the ‘implicit’ approach of Zhang and Ewen [Water Resour. Res. 36 (2000) 2777] by extending it to heterogeneous soil and approximating the inter-nodal hydraulic conductivity in the diffusive term and the gravity term with the same scheme. The prescribed-flux boundary in traditional methods also gives rise to iteration-to-iteration oscillation because there is no feedback to the flux in the solution at the new iteration. To reduce such oscillation, a new method is proposed to provide such a feedback to the flux. Comparison with traditional Picard and Newton iteration methods for a wide range of problems show that a combination of these two proposed methods greatly improves the stability and consequently the computational efficiency, making the use of small time step and/or under-relaxation solely for convergence unnecessary.