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Permeability and electrical conductivity changes due to hydrostatic stress cycling of Berea and Muddy J sandstone
137A
864091 Permeability and electrical conductivity changes due to hydrostatic stress cycling of Berea and Muddy J sandstone Dey, T N J Geophys Res V91, NB1. 10 Jan 1986, P763-766 Experiments described examine the irreversible permeability changes due to hydrostatic stress. The effective confining pressure on two sandstones was repeatedly raised and lowered between 3.5 and 31.5MPa. Permeabilities dropped by 30% for Berea sandstone and 90% for Muddy J sandstone after three cycles. Total pore volume always returned to its initial value after each cycle and water salinity had little effect on the results. However, electrical conductivity results depended strongly on the conductivity of the pore fluid and permeability changes were most likely changed by clay particle arrangement in the pores.
864092 Non-Darcian transmission of water in certain humified peats Waine, J; Brown, J M B; Ingram, H A P J Hydrol 1/82. N3/4, 30 Dec 1985, P327-339 Laboratory permeameter tests on a moderately humified peat confirmed field-measured nonlinear variation of seepage velocity with hydraulic gradient over a gradient range 1.5-17.5. Apparent hydraulic conductivity increases with gradient but at a decreasing rate. Two possible explanations are put forward. The first suggests a structuring of water in the pore spaces. The second invokes the mechanical effects of pressure difference on pore size. Experiments are planned to distinguish between these explanations.
864093 Heat mining Ledingham, P Min Mag March 1986, P241-251 Basics of geothermal energy extraction are discussed and preliminary development work at the Hot Dry Rock (HDR) site in Cornwall, UK, is described. The initial aims. drilling, fracturing, pumping, recovery and reservoir analysis are outlined. Microseismic mapping of the reservoir and further attempts at well stimulation by hydrofracturing with fluids more viscous than water are reported. The complex problem of modelling the interacting physical processes in the reservoir and calculating flow rates through a large number of narrow joints has not yet been overcome.
864094 Modelling and measurement of super-conducting rock joints Barton, N; Makurat, A; Vik, G; Loser, F In: Research and Engineering Applications in Rock Masses (paper to the 26th US Symposium on Rock Mechanics, Rapid City, 26-28 June 1985) V1. P487-495. Publ Rotterdam: A. A. Balkema, 1985 Joints with exceptionally high conductivity cause problems of water inflow in underground projects. They are often found in deeply weathered discontinuities where outwashing of the joint filling has occurred. A model of joint has been developed which couples shear displacement, dilation and conductivity, and predicts increases of 1-3 orders of magnitude in conductivity for the first few millimetres of sliding in the case of nonplanar joints. Laboratory tests have been carried out on jointed rock cores in a specially designed biaxial rig and have supported the theoretical predictions.
864O95 Coupled finite element/boundary element analysis for nonlinear fluid flow in rock fissures and fissure networks Elsworth, D In: Research and Engineering App~cations in Rock Masses (paper to the 26th US Symposium on Rock Mechanics, Rapid City, 26-28 June 1985) |'1. P633-641. Puhl Rotterdam. A. A. Balkema. 1985 A procedure has been formulated which couples finite element analysis and boundary element methods to model nonlinear potential flow. Nonlinear groundwater flo~ can be expected to result from the onset of turbulent flow conditions within a fissure. Quadrilateral finite elements discretisc the nonlinear portion of the domain and a boundary element is used to represent linear behaviour in the far field. The coupled expression is validated against analytical solutions. It is of importance in cases where significant hydraulic gradients occur in localised areas, in wells or underground constructions.
Compressibility, swelling and consolidation See also. 864152. 864158
864096 Prediction of the preconsolidation pressure and recompression index of soils. Technical note Nagaraj, T R; Srinivasa Murthy, B R Geotech Test J V8. N4. Dec 1985. P199-202 A procedure, based on the generalised compressibility equation, is presented which can be used to estimate the preconsolidation pressure and recompression index of stress and time dependent overconsolidated soils. It requires knowledge of the in situ void ratio, the liquid limit, in situ overburden pressure and specific gravity of the soil solids. Suitably accuratc estimates of these parameters can be obtained without carrying out consolidation tests. Estimated values for specific soils are compared to published data.
864097 Pattern of volume change development. Technical note Subba Rao. K S: Satyadas, G C J Geotech Engng Div A S C E V112, N2. Feb 19~¢6, P203-207 Field data for swelling, heave, rebound, settlement and shrinkage from a variety of sources and soils has been plotted against time using log-log plots. All cases showed a simple power law relationship, but with three separate rectilinear sections characterised by different power exponents. The value of exponent decreases with time, approaching zero in phase three. These graphs may be used to predict volume changes. No attempt is made to explain this phenomenon.
864O98 Building embankments with shale Oakland, M W; Lovell, C W In: Research and Engineering Applications in Rock Masses (paper to the 26th US Symposium on Rock Mechanics, Rapid City, 26-28 June 1985) VI, P305-312. Puhl Rotterdam: A. ,4. Balkema. 1985 Degradation of shales, mainly caused by slaking effects, with resultant volume change and loss of strength, necessitates careful material examination if they are to be used in the construction of embankments. Problem materials may be identified using index tests (Atterberg limits, point load, slakc durability or 5 cycle slaking index) and the Franklin rating system (1981). Compaction properties are complex because of degradation. The degradation tests of Oakland and Lovell (1982) have been developed to assess compaction behaviour.
~ 1986 Pergamon Journals Ltd. Reproduction not permitted
864091 Permeability and electrical conductivity changes due to hydrostatic stress cycling of Berea and Muddy J sandstone Dey, T N J Geophys Res V91, NB1. 10 Jan 1986, P763-766 Experiments described examine the irreversible permeability changes due to hydrostatic stress. The effective confining pressure on two sandstones was repeatedly raised and lowered between 3.5 and 31.5MPa. Permeabilities dropped by 30% for Berea sandstone and 90% for Muddy J sandstone after three cycles. Total pore volume always returned to its initial value after each cycle and water salinity had little effect on the results. However, electrical conductivity results depended strongly on the conductivity of the pore fluid and permeability changes were most likely changed by clay particle arrangement in the pores.
864092 Non-Darcian transmission of water in certain humified peats Waine, J; Brown, J M B; Ingram, H A P J Hydrol 1/82. N3/4, 30 Dec 1985, P327-339 Laboratory permeameter tests on a moderately humified peat confirmed field-measured nonlinear variation of seepage velocity with hydraulic gradient over a gradient range 1.5-17.5. Apparent hydraulic conductivity increases with gradient but at a decreasing rate. Two possible explanations are put forward. The first suggests a structuring of water in the pore spaces. The second invokes the mechanical effects of pressure difference on pore size. Experiments are planned to distinguish between these explanations.
864093 Heat mining Ledingham, P Min Mag March 1986, P241-251 Basics of geothermal energy extraction are discussed and preliminary development work at the Hot Dry Rock (HDR) site in Cornwall, UK, is described. The initial aims. drilling, fracturing, pumping, recovery and reservoir analysis are outlined. Microseismic mapping of the reservoir and further attempts at well stimulation by hydrofracturing with fluids more viscous than water are reported. The complex problem of modelling the interacting physical processes in the reservoir and calculating flow rates through a large number of narrow joints has not yet been overcome.
864094 Modelling and measurement of super-conducting rock joints Barton, N; Makurat, A; Vik, G; Loser, F In: Research and Engineering Applications in Rock Masses (paper to the 26th US Symposium on Rock Mechanics, Rapid City, 26-28 June 1985) V1. P487-495. Publ Rotterdam: A. A. Balkema, 1985 Joints with exceptionally high conductivity cause problems of water inflow in underground projects. They are often found in deeply weathered discontinuities where outwashing of the joint filling has occurred. A model of joint has been developed which couples shear displacement, dilation and conductivity, and predicts increases of 1-3 orders of magnitude in conductivity for the first few millimetres of sliding in the case of nonplanar joints. Laboratory tests have been carried out on jointed rock cores in a specially designed biaxial rig and have supported the theoretical predictions.
864O95 Coupled finite element/boundary element analysis for nonlinear fluid flow in rock fissures and fissure networks Elsworth, D In: Research and Engineering App~cations in Rock Masses (paper to the 26th US Symposium on Rock Mechanics, Rapid City, 26-28 June 1985) |'1. P633-641. Puhl Rotterdam. A. A. Balkema. 1985 A procedure has been formulated which couples finite element analysis and boundary element methods to model nonlinear potential flow. Nonlinear groundwater flo~ can be expected to result from the onset of turbulent flow conditions within a fissure. Quadrilateral finite elements discretisc the nonlinear portion of the domain and a boundary element is used to represent linear behaviour in the far field. The coupled expression is validated against analytical solutions. It is of importance in cases where significant hydraulic gradients occur in localised areas, in wells or underground constructions.
Compressibility, swelling and consolidation See also. 864152. 864158
864096 Prediction of the preconsolidation pressure and recompression index of soils. Technical note Nagaraj, T R; Srinivasa Murthy, B R Geotech Test J V8. N4. Dec 1985. P199-202 A procedure, based on the generalised compressibility equation, is presented which can be used to estimate the preconsolidation pressure and recompression index of stress and time dependent overconsolidated soils. It requires knowledge of the in situ void ratio, the liquid limit, in situ overburden pressure and specific gravity of the soil solids. Suitably accuratc estimates of these parameters can be obtained without carrying out consolidation tests. Estimated values for specific soils are compared to published data.
864097 Pattern of volume change development. Technical note Subba Rao. K S: Satyadas, G C J Geotech Engng Div A S C E V112, N2. Feb 19~¢6, P203-207 Field data for swelling, heave, rebound, settlement and shrinkage from a variety of sources and soils has been plotted against time using log-log plots. All cases showed a simple power law relationship, but with three separate rectilinear sections characterised by different power exponents. The value of exponent decreases with time, approaching zero in phase three. These graphs may be used to predict volume changes. No attempt is made to explain this phenomenon.
864O98 Building embankments with shale Oakland, M W; Lovell, C W In: Research and Engineering Applications in Rock Masses (paper to the 26th US Symposium on Rock Mechanics, Rapid City, 26-28 June 1985) VI, P305-312. Puhl Rotterdam: A. ,4. Balkema. 1985 Degradation of shales, mainly caused by slaking effects, with resultant volume change and loss of strength, necessitates careful material examination if they are to be used in the construction of embankments. Problem materials may be identified using index tests (Atterberg limits, point load, slakc durability or 5 cycle slaking index) and the Franklin rating system (1981). Compaction properties are complex because of degradation. The degradation tests of Oakland and Lovell (1982) have been developed to assess compaction behaviour.
~ 1986 Pergamon Journals Ltd. Reproduction not permitted