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Underground cavities and terrain instability in Mbuji-Mayi town (Zaire) (In French)
210A 924036 Sinkhole collapse resulting from pumping of karst groundwater: a problem and its solution Chen, J; Xiang, S Proc 4th International Conference on Land Subsidence, Houston, 12-17 May 1991 P313-322. Publ IAHS Press. Walling,ford, 1991 Collapse of karstic structures following groundwater pumping is becoming a serious problem in many areas. Prediction of karst prone areas is the first step in the program to minimise damage. This requires knowledge of the geological environment, investigation of sinkhole collapse sites, and prediction using geostatistical and empirical methods. Management of the pumping program can reduce the potential for collapse. Backfilling, spanning, grouting or deep foundations can help repair damage or prevent further problems. 924037 Underground cavities and terrain instability in Mbuji-Mayi town (Zaire) (In French) Mupande, K M; Kazadi, N; Mukonki, M Proc 6th International Congress international Association o f Engineering Geology, Amsterdam, 6-10 August 1990 I/3, PI929-1933. Publ Rotterdam: A A Balkema. 1990 Photogeologic studies reveal karst related collapse and depressions in calcareous formations of the Mbuji-Mayi plateau. Many affect infrastructure. The alignment of these karstic forms correlates with major regional trends revealed by satellite photography, suggesting local fracture systems are important to karstification. An effect-cause relation is indicated between intense surface erosion and karst formation.
Properties of Rocks and Soils Composition, structure texture and density See also: 924259
924038 Evaluation of methods for inferring air and water properties of soils from field morphology McKenzie, N J; Smettem, K R J; Ringrose-Voase, A J ;lust J Soil Res I"29, N5, 1991, P587-602 It is frequently not possible to accurately characterise soil properties during survey because of logistic or financial constraints. Four procedures to infer air-filled porosity, available water capacity, and saturated hydraulic conductivity on the basis of field determined soil morphological features have been evaluated against a limited data set from Australia. None predicted statistically significant values of available water capacity and values for air-filled porosity were only moderate. One method gave a reasonable prediction of saturated hydraulic conductivity. Possible improvements are discussed. 924039 Micromorphology of soil structure: description, quantification, application Ringrose-Voase, A J Aust J Soil Res V29, N6, 1991. P777,813 Considerable insight into the behaviour of a soil can be gained from examination of its microstructure. Undisturbed field samples are impregnated, thin sections prepared, and microstructures examined over a range of scales. Pore space, soil fabric characteristics, and associated structures can be
examined. Micromorphological observations can be parameterised by image analysis. Digitized images can be manipulated to show pore space and solids and to provide 3D parameters from 1D and 2D measurements. Examples of important features of soil microstructure are illustrated. 924040 Uniformity tests in calibration chamber samples by the thermal probe method Bellotti, R; Ghionna, V N; Morabito, P Geotech Test J VI4, N2, June 1991, P195-205 Calibration chambers must contain soil samples whose density is both uniform and repeatable. A test method to evaluate relative density of such large samples without removing the soil is presented. It is based on experimental correlations between density and thermal conductivity of dry sand. Conductivity is measured using 70mm long, Imm diameter probes installed in the chamber before pluviation of the sand, A calibration for the probe, including effects of stresses, is proposed. Results are presented for density of the ENEL-CRIS and ISMES chambers. 924041 Factors controlling properties and durability of concretionary laterite gravel aggregates Akpokodje, E G; Hudec, P P J Mater Civ Engng I/4. NI. Feb 1992, P58-70 Concretionary laterite gravels are common road materials in the tropics. Samples from 39 profiles in Nigeria were examined in the laboratory, with studies of absorption, bulk dry density, vacuum saturation, slake durability, adsorption, porosity, aggregate impact value, Iowa index pore test, weight loss on wetting and drying, specific gravity and chemical composition. Relations between these tests and major factors influencing tests were determined by factor (R-mode) analysis. Four principal component factors controlling material properties were seen: degree of laterization, porosity and pore size distribution, micropores, and adsorbed water. 924042 Application of back-scattered electron microscopy to the quantification of clay mineral microporosity in sandstones Nadeau, P H; Hurst, A J Sediment Petrol V61, /76, Not' 1991, P921-925 Clay minerals in sandstones may have diagenetic or detrital origin. Clay mineral microporosity can have significant influence on reservoir quality,water saturation, and electrical characteristics. A high resolution petrographic method using backscattered SEM images is proposed for quantifying this microporosity. Preliminary results for different clay minerals are presented, and limitations of the method discussed. 924043 Effect of mechanical interactions on the development of shape preferred orientations: a two-dimensional experimental approach Ildefonse, B; Launeau, P; Bouchez, J L; Fernandez, A J Struct Geol VI4, NI, 1992. P73-83 Samples were prepared with a viscous matrix containing rigid particles homogeneously distributed and oriented on the surface of the matrix. After deformation in pure shear and simple shear, shape preferred orientations were calculated from digitised photographs of the samples using an automatic process (Launeau et al, 1990). At high particle concentrations, collisions and disturbance of particles affect fabric development. Fabric intensity is weakened and is no longer cyclic in coaxial flow. Finite strains based on fabric orientation should thus be treated as a minimum value.
© 1992 Pergamon Press Ltd. Reproduction not permitted
Properties of Rocks and Soils Composition, structure texture and density See also: 924259
924038 Evaluation of methods for inferring air and water properties of soils from field morphology McKenzie, N J; Smettem, K R J; Ringrose-Voase, A J ;lust J Soil Res I"29, N5, 1991, P587-602 It is frequently not possible to accurately characterise soil properties during survey because of logistic or financial constraints. Four procedures to infer air-filled porosity, available water capacity, and saturated hydraulic conductivity on the basis of field determined soil morphological features have been evaluated against a limited data set from Australia. None predicted statistically significant values of available water capacity and values for air-filled porosity were only moderate. One method gave a reasonable prediction of saturated hydraulic conductivity. Possible improvements are discussed. 924039 Micromorphology of soil structure: description, quantification, application Ringrose-Voase, A J Aust J Soil Res V29, N6, 1991. P777,813 Considerable insight into the behaviour of a soil can be gained from examination of its microstructure. Undisturbed field samples are impregnated, thin sections prepared, and microstructures examined over a range of scales. Pore space, soil fabric characteristics, and associated structures can be
examined. Micromorphological observations can be parameterised by image analysis. Digitized images can be manipulated to show pore space and solids and to provide 3D parameters from 1D and 2D measurements. Examples of important features of soil microstructure are illustrated. 924040 Uniformity tests in calibration chamber samples by the thermal probe method Bellotti, R; Ghionna, V N; Morabito, P Geotech Test J VI4, N2, June 1991, P195-205 Calibration chambers must contain soil samples whose density is both uniform and repeatable. A test method to evaluate relative density of such large samples without removing the soil is presented. It is based on experimental correlations between density and thermal conductivity of dry sand. Conductivity is measured using 70mm long, Imm diameter probes installed in the chamber before pluviation of the sand, A calibration for the probe, including effects of stresses, is proposed. Results are presented for density of the ENEL-CRIS and ISMES chambers. 924041 Factors controlling properties and durability of concretionary laterite gravel aggregates Akpokodje, E G; Hudec, P P J Mater Civ Engng I/4. NI. Feb 1992, P58-70 Concretionary laterite gravels are common road materials in the tropics. Samples from 39 profiles in Nigeria were examined in the laboratory, with studies of absorption, bulk dry density, vacuum saturation, slake durability, adsorption, porosity, aggregate impact value, Iowa index pore test, weight loss on wetting and drying, specific gravity and chemical composition. Relations between these tests and major factors influencing tests were determined by factor (R-mode) analysis. Four principal component factors controlling material properties were seen: degree of laterization, porosity and pore size distribution, micropores, and adsorbed water. 924042 Application of back-scattered electron microscopy to the quantification of clay mineral microporosity in sandstones Nadeau, P H; Hurst, A J Sediment Petrol V61, /76, Not' 1991, P921-925 Clay minerals in sandstones may have diagenetic or detrital origin. Clay mineral microporosity can have significant influence on reservoir quality,water saturation, and electrical characteristics. A high resolution petrographic method using backscattered SEM images is proposed for quantifying this microporosity. Preliminary results for different clay minerals are presented, and limitations of the method discussed. 924043 Effect of mechanical interactions on the development of shape preferred orientations: a two-dimensional experimental approach Ildefonse, B; Launeau, P; Bouchez, J L; Fernandez, A J Struct Geol VI4, NI, 1992. P73-83 Samples were prepared with a viscous matrix containing rigid particles homogeneously distributed and oriented on the surface of the matrix. After deformation in pure shear and simple shear, shape preferred orientations were calculated from digitised photographs of the samples using an automatic process (Launeau et al, 1990). At high particle concentrations, collisions and disturbance of particles affect fabric development. Fabric intensity is weakened and is no longer cyclic in coaxial flow. Finite strains based on fabric orientation should thus be treated as a minimum value.
© 1992 Pergamon Press Ltd. Reproduction not permitted