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Analysis of an aquifer-water table aquitard system
325A explained by preferential reactivation of weak, shallow preexisting faults. Reduction of strength of the faults below that of the rock mass and enhanced pore pressure in the fault further enhance the likelihood of earthquakes. An analytical treatment examines the values of fault parameters which can account for shallow normal-slip earthquakes.
structure after freezing and formation of ice crystals at different temperature ranges have been studied using cryogenic SEM. An example of a current cold stage system in which ice crystallization features may be resolved through controlled sublimation is presented.
906016 Example of slip instability resulting from displacement-varying strength Lockner, D; Byerlee, J Pure Appl Geophys Vl13, N2, April 1990, P269-281
Hydrogeology
A cylinder of Westerly granite was prepared with a clay filled sawcut at 30 deg to the axis, with the sawcut surfaces machined to give regularly spaced ridges and grooves perpendicular to the direction of shear. The specimen was deformed at constant confining and pore pressures and strain rate. Sliding strength varied periodically with displacement. By varying effective machine stiffness, a range of stable and unstable slip behaviour was achieved. This experiment simulated fault slip behaviour dominated by displacement dependent strength.
Frost action, permafrost and frozen ground See also: 906039 906O17 Decay and preservation of stone in modern environments Gauri, K L Environ Geol Water Sci V15, N1, Jan~Feb 1990, P45-54 Acid attack by atmospheric sulphur dioxide, combined effects of salts in the stone and meteorological conditions in arid climates, and hydrolysis disruption of mineral structures in humid tropical environments are described with reference to famous landmarks. Careful cleaning and impregnation of the stone which maintains its breathability can protect against hostile environments, but cases are described where human activity has aggravated problems by altering the path of water through the stone. 906O18 Weathering of fimestone beds at the Great Sphinx Chowdhury, A N; Punuru, A R; Gauri, K L Environ Geol Water Sci V15, N3, May/June 1990, P217-223 Weathering of limestone strata exposed on the Giza Plateau is examined with reference to the pore system (ink bottle pores). The pore systems reflect depositional regime and diagenetic alteration of the rocks, and vary between strata. In lower micritic rocks, pores are connected by the fine capillary network of their narrow throats. In upper rocks, large as well as small throats provide interconnections. Relation between macro- and micro-porosity has a strong influence on weathering. 906019 Cryogenic scanning electron microscopy research applications in arctic and polar regions Lilly, M R; Sargent, J A Proc 9th International Conference on Offshore Mechanics and Arctic Engineering, Houston, 18-23 February 1990 I/4, P5160. Publ New York: ASME, 1990 The study of biological and physical systems in arctic and polar regions may be enhanced by cryogenic scanning electron microscopy (SEM). The reduction of SEM stage temperature to that of liquid nitrogen causes a stable environment in which ice and ice-rich components may be observed. Changes in soil
Groundwater See also: 906245 906020 Monitoring well into abandoned deep-well disposal formations at Sarnia, Ontario Raven, K G; Lafleur, D W; Sweezey, R A Can Geotech J V27, N1, Feb 1990, P105-118 A 300m deep monitoring well was sunk in the Detroit River Group of formations, to help assess potential near surface problems resulting from previous deep injection of waste. Conductivity and hydraulic head of the disposal and confining horizons were determined. Groundwater analyses indicated pollutants in a 10m thick layer in the Lucas dolomite at 192m depth, and in high permeability limestone layers in the confining Hamilton Group at 74m and 123m. Chemical analysis indicates this is not due to upward migration from deep disposal, and other potential sources are considered. 906021 Aquifer parameters from a one-dimensional steady-leaky type carve
Motz, L H Ground Water V28, N3, May-June 1990, P350-356 A drain function and a type curve are defined for the steady state case of a leaky aquifer, with vertical leaking through a confining bed, draining into a line sink. Using these, a match point procedure was developed to determine transmissivity and leakance. When applied to field data from a canal pumping test, results compared favourably with those from other methods. 906022 Analysis of an aquifer-water table aquitard system Sridharan, K; Sekhar, M; Mohan Kumar, M S J Hydrol Vl14, NI/2, March 1990, P175-189 Pumping from an aquifer system overlain by an aquitard containing the phreatic surface is studied. Elastic properties of the aquifer and aquitard and gravity drainage of the aquitard are taken into account, the water table being treated as an unknown boundary. The coupled differential equations are solved numerically. Three parameters related to system hydraulic properties control the problem. Type curves are generated and illustrated through a field application. 906023 Simulation of dispersion in layered coastal aquifer systems Reilly, T E J Hydrol VII4, N3/4, May 1990, P211-228 Groundwater flow in layered coastal aquifers is treated as a density-dependent miscible-solute-transport problem. This is analysed using the computer code SUTRA, which uses a two dimensional finite element approximation in space and an implicit finite difference approximation in time to solve the governing differential equations. The transition zone is not an impermeable sharp interface as for homogeneous aquifers.
© 1990 Pergamon Press plc. Reproduction not permitted
structure after freezing and formation of ice crystals at different temperature ranges have been studied using cryogenic SEM. An example of a current cold stage system in which ice crystallization features may be resolved through controlled sublimation is presented.
906016 Example of slip instability resulting from displacement-varying strength Lockner, D; Byerlee, J Pure Appl Geophys Vl13, N2, April 1990, P269-281
Hydrogeology
A cylinder of Westerly granite was prepared with a clay filled sawcut at 30 deg to the axis, with the sawcut surfaces machined to give regularly spaced ridges and grooves perpendicular to the direction of shear. The specimen was deformed at constant confining and pore pressures and strain rate. Sliding strength varied periodically with displacement. By varying effective machine stiffness, a range of stable and unstable slip behaviour was achieved. This experiment simulated fault slip behaviour dominated by displacement dependent strength.
Frost action, permafrost and frozen ground See also: 906039 906O17 Decay and preservation of stone in modern environments Gauri, K L Environ Geol Water Sci V15, N1, Jan~Feb 1990, P45-54 Acid attack by atmospheric sulphur dioxide, combined effects of salts in the stone and meteorological conditions in arid climates, and hydrolysis disruption of mineral structures in humid tropical environments are described with reference to famous landmarks. Careful cleaning and impregnation of the stone which maintains its breathability can protect against hostile environments, but cases are described where human activity has aggravated problems by altering the path of water through the stone. 906O18 Weathering of fimestone beds at the Great Sphinx Chowdhury, A N; Punuru, A R; Gauri, K L Environ Geol Water Sci V15, N3, May/June 1990, P217-223 Weathering of limestone strata exposed on the Giza Plateau is examined with reference to the pore system (ink bottle pores). The pore systems reflect depositional regime and diagenetic alteration of the rocks, and vary between strata. In lower micritic rocks, pores are connected by the fine capillary network of their narrow throats. In upper rocks, large as well as small throats provide interconnections. Relation between macro- and micro-porosity has a strong influence on weathering. 906019 Cryogenic scanning electron microscopy research applications in arctic and polar regions Lilly, M R; Sargent, J A Proc 9th International Conference on Offshore Mechanics and Arctic Engineering, Houston, 18-23 February 1990 I/4, P5160. Publ New York: ASME, 1990 The study of biological and physical systems in arctic and polar regions may be enhanced by cryogenic scanning electron microscopy (SEM). The reduction of SEM stage temperature to that of liquid nitrogen causes a stable environment in which ice and ice-rich components may be observed. Changes in soil
Groundwater See also: 906245 906020 Monitoring well into abandoned deep-well disposal formations at Sarnia, Ontario Raven, K G; Lafleur, D W; Sweezey, R A Can Geotech J V27, N1, Feb 1990, P105-118 A 300m deep monitoring well was sunk in the Detroit River Group of formations, to help assess potential near surface problems resulting from previous deep injection of waste. Conductivity and hydraulic head of the disposal and confining horizons were determined. Groundwater analyses indicated pollutants in a 10m thick layer in the Lucas dolomite at 192m depth, and in high permeability limestone layers in the confining Hamilton Group at 74m and 123m. Chemical analysis indicates this is not due to upward migration from deep disposal, and other potential sources are considered. 906021 Aquifer parameters from a one-dimensional steady-leaky type carve
Motz, L H Ground Water V28, N3, May-June 1990, P350-356 A drain function and a type curve are defined for the steady state case of a leaky aquifer, with vertical leaking through a confining bed, draining into a line sink. Using these, a match point procedure was developed to determine transmissivity and leakance. When applied to field data from a canal pumping test, results compared favourably with those from other methods. 906022 Analysis of an aquifer-water table aquitard system Sridharan, K; Sekhar, M; Mohan Kumar, M S J Hydrol Vl14, NI/2, March 1990, P175-189 Pumping from an aquifer system overlain by an aquitard containing the phreatic surface is studied. Elastic properties of the aquifer and aquitard and gravity drainage of the aquitard are taken into account, the water table being treated as an unknown boundary. The coupled differential equations are solved numerically. Three parameters related to system hydraulic properties control the problem. Type curves are generated and illustrated through a field application. 906023 Simulation of dispersion in layered coastal aquifer systems Reilly, T E J Hydrol VII4, N3/4, May 1990, P211-228 Groundwater flow in layered coastal aquifers is treated as a density-dependent miscible-solute-transport problem. This is analysed using the computer code SUTRA, which uses a two dimensional finite element approximation in space and an implicit finite difference approximation in time to solve the governing differential equations. The transition zone is not an impermeable sharp interface as for homogeneous aquifers.
© 1990 Pergamon Press plc. Reproduction not permitted