Soil column drainage modelling using a geotechnical centrifuge. Technical note

291A difficulties in application of model test results. Preliminary results from tests in an unsaturated sand column at 50g and 100g are presented and compared to those of computer modelling. 925140 Soil column drainage modelling using a geotechnical centrifuge. Technical note Cooke, A B; Mitchell, R J Geotech Test J 1/14, N3, Sept 1991, P323-327 Equipment has been developed for study of one dimensional flow of water in unsaturated soils in the geotechnical centrifuge. It includes a cylindrical mould to contain the soil sample and a water tank assembly for supply and receipt of water. After completion of the modelling sequence, the soil column may be partitioned for moisture content or chemical analysis with minimum disruption to the moisture content profile. Initial results from its use are presented. 925141 Influence of pore pressure on apparent dispersivity of a fissured dolomitic aquifer Leap, D I; Belmonte, P M Ground Water 1/30, NI, Jan-Feb 1992, P86-95 Recirculating tracer tests at the Amargosa Tracer Calibration site, Nevada, using tritium, S-35, and tritium plus bromide tracers, gave apparent dispersivity values which differed considerably. The physical set-up of the tests was effectively the same, but recirculating rates and pore pressures were different. The differences in results are thought to be related to changes in fissure aperture width caused by changes in pore pressures amongst the tests. It is suggested that forced gradient tracer tests should not be used when the ambient and/or testing pressure is a significant proportion of overburden pressure, as test results will differ from those under unstressed natural conditions. 925142 Unsteady ground-water flow towards extended wells Sen, Z Ground Water V30, NI, Jan-Feb 1992, P61-67 Groundwater flow in naturally fractured rocks of low permeability cannot be described by classical radial flow techniques. Fractures increases conductivity but not storativity. The case of a dominant vertical fracture in hydraulic connection with a well (extended well) is considered. The fracture length is effectively infinite in most practical cases. A mixture of linear and radial flows is found. A simplified conceptual model of this situation is presented and an analytical solution with type curves developed, which can be used to determine aquifer parameters from drawdown data. 925143 Atmospheric pumping: a mechanism causing vertical transport of contaminated gases through fractured permeable media Nilson, R H; Peterson, E W; Lie, K H; Burkhard, N R; Hearst, J R J Geophys Res V96, NBI3, Dec 1991, P21933-21948 Changes in atmospheric pressure result in gas being drawn from the permeable earth to the atmosphere and vice versa. For a homogeneous permeable medium, the cyclical gas motions are piston-like and almost reversible. In a fractured medium, where flow is concentrated in the discontinuities, the effect can be amplified. Transport processes an order of magnitude greater than molecular diffusion are possible according to theoretical analysis. Effects are evaluated for idealised and

realistically fractured rock masses, considering potential enhanced escape of contaminated gases from waste repositories. 925144 Coupled hydromechanical-thermochemical processes in rock fractures Tsang, C F Rev Geophys V29, N4, No~, 1991, t'537-551 The response of rock fractures to various coupled processes is reviewed: hydromechanical; thermo-hydrologic; bydrochemical; thermohydromechanical; thermohydrochemical; hydromechanical-chemical; and thermomechanical-hydrochemical processes. Dilation, closure, shear, and joint propagation are considered, together with changes in fluid permeability, chemical sorption, and retardation. These phenomena are of importance to design of hazardous waste repositories. Coupled phenomena in systems with more than one fracture require further study. These coupled phenomena should be considered in interpretation of many field tests. 925145 Objectives and execution of hydraulic experiments in the KTB-Oberpfalz borehole with the long-term measurement and test program Kessels, W Sci Drilling V2, N6, 1991, P287-298 Hydraulic experiments in the KTB borehole have been carried out to examine the properties of the fracture zones and to recover formation fluids with minimum possible contamination. Following selection of zones for tests after log interpretation, a drawdown test, a pump test, and packer tests were run. Prominent inflows were found between 480m and 800m and in the deeper part of the hole. Low salinity/negligible gas content and high salinity/high gas content (including 30% methane) fluids were retrieved, respectively, from upper and deeper zones.

925146 Drill stem test analyses in the KTB-V-Weil. Part h fundamentals of hydraulic test analysis Pusch, G; Enachescu, C; Miehe, R; Ostrowski, L Sci Drilling V2. Nr, 1991. P299-305 Hydraulic properties of a rock mass must be known for interpretation of fluid movements through the formation and of anomalous geothermal gradients. Hydraulic pressures are changed by the presence of a wellbore and their monitoring provides data which can be analysed to evaluate initial pore pressure, transmissibility, and storativity of the formation. Analysis methods which take into account the different formation characteristics and effects of wellbore storage and skin effects are described. 925147 Drill stem test analyses in the KTB-V-WelI. Part 2: results of the drill stem test analyses Pusch, G; Enacbescu, C; Miehe, R; Ostrowski, L Sci Drilling V2, N6, 1991, P306-318 Four drill stem tests were carried out during the drilling phase of the KTB pilot bore, two in layered formations (depths 220257m and 348-385m) and two in gneiss (depths 813-839m and 3443-3487m). Two recovered sufficient fluid to analyse for its origin and three showed pressure response of the formation which allowed analysis as pulse or slug tests. Values returned for permeability, hydraulic conductivity, skin factor and storativity are given. Recommendations are made for improving experimental procedures.

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