The validity of the cubic law for laminar flow of fluids through open fractures consisting of parallel planar plates has been established by others over a wide range of conditions with apertures ranging down to a minimum of 0.2 µm. The law may be given in simplified form by Q/Δh = C(2b)3, where Q is the flow rate, Δh is the difference in hydraulic head, C is a constant that depends on the flow geometry and fluid properties, and 2b is the fracture aperture. The validity of this law for flow in a closed fracture where the surfaces are in contact and the aperture is being decreased under stress has been investigated at room temperature by using homogeneous samples of granite, basalt, and marble. Tension fractures were artificially induced, and the laboratory setup used radial as well as straight flow geometries. Apertures ranged from 250 down to 4µm, which was the minimum size that could be attained under a normal stress of 20 MPa. The cubic law was found to be valid whether the fracture surfaces were held open or were being closed under stress, and the results are not dependent on rock type. Permeability was uniquely defined by fracture aperture and was independent of the stress history used in these investigations. The effects of deviations from the ideal parallel plate concept only cause an apparent reduction in flow and may be incorporated into the cubic law by replacing C by C/ƒ. The factor ƒ varied from 1.04 to 1.65 in these investigations. The model of a fracture that is being closed under normal stress is visualized as being controlled by the strength of the asperities that are in contact. These contact areas are able to withstand significant stresses while maintaining space for fluids to continue to flow as the fracture aperture decreases. The controlling factor is the magnitude of the aperture, and since flow depends on (2b)3, a slight change in aperture evidently can easily dominate any other change in the geometry of the flow field. Thus one does not see any noticeable shift in the correlations of our experimental results in passing from a condition where the fracture surfaces were held open to one where the surfaces were being closed under stress.

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VALIDITY OF CUBIC LAW FOR FLUID FLOW IN A DEFORMABLE ROCK FRACTURE - eScholarship

A numerical, field and laboratory study of flow in rocks with deformable fractures

Integration of remote sensing (RS), geographic information systems (GIS) and global positioning system (GPS) are emerging research areas in the field of groundwater hydrology, resource management, environmental monitoring and during emergency response. Recent advancements in the fields of RS, GIS, GPS and higher level of computation will help in providing and handling a range of data simultaneously in a time- and cost-efficient manner. This review paper deals with hydrological modeling, uses of remote sensing and GIS in hydrological modeling, models of integrations and their need and in last the conclusion. After dealing with these issues conceptually and technically, we can develop better methods and novel approaches to handle large data sets and in a better way to communicate information related with rapidly decreasing societal resources, i.e. groundwater.

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Integrating remote sensing, geographic information systems and global positioning system techniques with hydrological modeling

A combined electrical resistivity and Magnetic surveys was carried out to locate fissured zones and associated groundwater-bearing media at Baikin Area in Ondo State, Nigeria that is known to have acute groundwater supply shortage. One Hundred (100) Vertical Electrical Soundings were acquired along ten traverses using the Schlumberger array with maximum half current electrode spacing (AB/2) of 200 m. Magnetic data were acquired along the traverses at station interval of 10 m using the Proton Precession Magnetometer. Four geologic layers were delineated. These include the topsoil, weathered layer, fractured basement and fresh basement bedrock. The thickness of the topsoil ranged from 0.2 to 1.1 m while the resistivity values varied from 29 to 455 Ωm. The weathered layer thickness varied between 0.2 and 12.6 m while its resistivity ranged between 13 and 307 Ωm. The fractured basement delineated had resistivity value of 61 Ωm. The fresh basement resistivity ranged between 941 and α Ωm. The overburden thickness ranged between 1.1 and 12.9 m. The weathered and fractured aquifers constituted the main aquifer units. Aquifer thickness varied between 0.2 and 12.6 m. Quasi 3D magnetic models also showed that depth to bedrock in the study area was shallow. The study concluded that the groundwater potential of Baikin Area was generally low.

/pdf/evaluation-of-groundwater-potential-of-baikin-ondo-state-8wcckf1eij.pdf

Evaluation of Groundwater Potential of Baikin Ondo State Nigeria Using Resistivity and Magnetic Techniques: A Case Study

Surface geophysical methods were used to determine the locations of fracture zones in part of the hard rock area in Sonebhadra District of Uttar Pradesh, India. The survey comprises three DC resistivity profile using the gradient profiling technique and ten very low frequency electromagnetic (VLF-EM) traverses profiles. The methods were used over survey lines extending between 200 and 400 m; the results were correlated to locate fracture zones for the purpose of groundwater exploration. Qualitative interpretation of the VLF-EM was carried out using Fraser and Karous–Hjelt filters. The result of the interpretation revealed a number of subsurface zones with high real component current density that defines the potential subsurface features (probably fracture zones). The subsurface feature concurred with the low resistive zones indentified from the gradient resistivity profiling. The zones where further inferred quantitatively using data obtained from DC resistivity sounding at some selected anomalous points. The result obtained proves the efficiency of integrating both methods in detecting fractures zones in hard rock area.

Identifications of fractured zones in part of hard rock area of Sonebhadra District, U.P., India using integrated surface geophysical method for groundwater exploration

S.C. Teme

Papers

Detection of groundwater flow in fractured media through remote sensing techniques — some Nigerian cases