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Physical properties and indirect estimation of microfractures using Nigerian carbonate rocks as examples
145A can be systematically investigated in the laboratory. The effects of varying the chemical composition and physical properties of coal mine tailings on the theoretical moisture content calibration have been examined. These tailings were used as they exhibit most of the features undesirable in a material for use with the neutron moisture gauge and properties consistent with the limits of validity of the gauge. 933O46 Geostatisticai analysis and hierarchical modelling of a fracture network In a stratified rock mass Gervais, F; Chiles, J P; Gentier, S
Pro¢ Conference on FractHred a~l Jointed Rock Masses, Lake Takoe, 3-5 June 1992 P158-165. Publ California: Lawrence Berkeley Laboratory, 1992 A 2D hierarchical model of fracture networks in a stratified rock mass has been developed. It reflects the chronology of joint formation and the geometry of the fracture network. Input data on the statistical parameters describing each fracture set were obtained from a limestone quarry in France. A statistical characterisation and a geostatistical approach to the fracture system are used. The validity of the model is demonstrated by comparing the shape of the polygons observed on horizontal surfaces in the field with those bounded by the generated fracture traces.
Deformation and strength characteristics See also: 933256, 933257, 933258, 933275, 933282, 933288, 933292, 933047 Clay mineralogy mad residual shear strength of the Santa Clara Formation claystone, Saratoga foothills, California Nelson, J L
Bull Asso¢ Engng Geol V29, N3, Sept 1992, P299-310 Most landslides in the Saratoga foothills occur as a result of progressive shear failure on previously sheared surfaces in overconsolidated claystone units. Primary geologic factors controlling failure are degree of overconsolidation and presence of smectite. Effects of clay mineralogy on residual shear strength of a well developed landslide surface have been examined. Analysis of samples taken showed smectite composed 34-100% of the clay fraction and 13-37% of the total sample. Residual friction coefficient of disturbed samples ranged from 0.105 to 0.465 (average 0.210); that of the intact shear surface was 0.80. Correlations of friction angle with plasticity index, liquid limit, and clay fraction were established. 933O48 Detera, i n i ~ the unconfined eompreJve strength of indurated volcanic-ash materials. Technical note Cook, B J; Nimlos, T J, Olsen, D S
Assoe F~gmg Geoi V29, N3, Sept 1992, P335-339 Indurated volcanic ash soils are common wherever volcanism has occurred. Their nomenclature is vague because of local naming and the difficulty in identifying such materials as rock or soil. The method of excavation chosen where these materials are found depends largely on their strength. New techniques to determine the UCS are described which are simple, quantitative, and inexpensive. 25ram cubes are crushed using a modified jack. Block cutting, block forming, and adjustments for moisture content are described.
933O49 Interpcemtion of field vane strength of an anisotro#c soil Garga, V K; Khan, M A
Can Geoteek J V29, N4, Aug 1992, P627-637 Field vane tests and isotropically consolidated undrained triaxial tests on weathered crustal clays give contrasting results. This is related to the strength anisotropy arising from the in situ anisotropic state of stress and orientation of soil fabric produced during deposition. The stress state around the field vane has been evaluated and how vane shear strengths relate to those from a range of triaxial and shear tests is discussed. Suitable shear strength values for use in foundation design in these soils are suggested.
933050 Phys/cal properties and indirect estimation of microfractures using Nigerian carbonate rocks as examples Edet, A
Eng~g Geoi V33, N1, Sept 1992, P71-80 The performance of rocks as construction materials is essentially controlled by the mechanical and physical properties, many of which are related to microfracturing. In countries where laboratory facilities are not extensive, it is important to develop semi-quantitative methods to estimate the quality of construction materials. Using several carbonate rocks from Nigeria as test materials, relations between porosity index (ratio of effective to total porosity), swelling index, and uniaxiai compressive strength have been examined. These relations are then used as a basis to indirectly estimate degree of micro fracturing.
933051 Behavioer at the shrinkage limit of d a y undergoing drying Williams, D J; Sibley, J W
Geotecli Test J V15, N3, Sept 1992, P217-222 Significant changes occur in many properties for a clay undergoing drying in the vicinity of the shrinkage limit. Changes in linear shrinkage strain, volumetric air content, heat of wetting, tensile strength, and thermal properties with water content have been studied for Deagan clay from Brisbane, Australia. Possible explanations for these changes are discussed. Further data from different soils under different conditions are required to confirm these findings, but the shrinkage limit appears to mark a fundamental change in soil behaviour, and future research is warranted.
933052 Determination of deformation I~roperties of collapsible soils Reznick, Y M
Geotech Test J V15, N3, Sept 1992, 1'248-255 Results are presented from field and laboratory examination of loessial soils from sites near Odessa. The geological profiles are described. Plate loading tests were carded out in situ on soils at saturated and natural water contents. The technique of these tests is described. Undisturbed samples were retrieved for laboratory characterization. The geotechnical properties from the field and laboratory tests are compared. The many engineering advantages of using the plate load test are discussed, but its relative cost may prevent its use in many cases.
© 1993 Pergamon Press Ltd. Reproduction not permitted
Pro¢ Conference on FractHred a~l Jointed Rock Masses, Lake Takoe, 3-5 June 1992 P158-165. Publ California: Lawrence Berkeley Laboratory, 1992 A 2D hierarchical model of fracture networks in a stratified rock mass has been developed. It reflects the chronology of joint formation and the geometry of the fracture network. Input data on the statistical parameters describing each fracture set were obtained from a limestone quarry in France. A statistical characterisation and a geostatistical approach to the fracture system are used. The validity of the model is demonstrated by comparing the shape of the polygons observed on horizontal surfaces in the field with those bounded by the generated fracture traces.
Deformation and strength characteristics See also: 933256, 933257, 933258, 933275, 933282, 933288, 933292, 933047 Clay mineralogy mad residual shear strength of the Santa Clara Formation claystone, Saratoga foothills, California Nelson, J L
Bull Asso¢ Engng Geol V29, N3, Sept 1992, P299-310 Most landslides in the Saratoga foothills occur as a result of progressive shear failure on previously sheared surfaces in overconsolidated claystone units. Primary geologic factors controlling failure are degree of overconsolidation and presence of smectite. Effects of clay mineralogy on residual shear strength of a well developed landslide surface have been examined. Analysis of samples taken showed smectite composed 34-100% of the clay fraction and 13-37% of the total sample. Residual friction coefficient of disturbed samples ranged from 0.105 to 0.465 (average 0.210); that of the intact shear surface was 0.80. Correlations of friction angle with plasticity index, liquid limit, and clay fraction were established. 933O48 Detera, i n i ~ the unconfined eompreJve strength of indurated volcanic-ash materials. Technical note Cook, B J; Nimlos, T J, Olsen, D S
Assoe F~gmg Geoi V29, N3, Sept 1992, P335-339 Indurated volcanic ash soils are common wherever volcanism has occurred. Their nomenclature is vague because of local naming and the difficulty in identifying such materials as rock or soil. The method of excavation chosen where these materials are found depends largely on their strength. New techniques to determine the UCS are described which are simple, quantitative, and inexpensive. 25ram cubes are crushed using a modified jack. Block cutting, block forming, and adjustments for moisture content are described.
933O49 Interpcemtion of field vane strength of an anisotro#c soil Garga, V K; Khan, M A
Can Geoteek J V29, N4, Aug 1992, P627-637 Field vane tests and isotropically consolidated undrained triaxial tests on weathered crustal clays give contrasting results. This is related to the strength anisotropy arising from the in situ anisotropic state of stress and orientation of soil fabric produced during deposition. The stress state around the field vane has been evaluated and how vane shear strengths relate to those from a range of triaxial and shear tests is discussed. Suitable shear strength values for use in foundation design in these soils are suggested.
933050 Phys/cal properties and indirect estimation of microfractures using Nigerian carbonate rocks as examples Edet, A
Eng~g Geoi V33, N1, Sept 1992, P71-80 The performance of rocks as construction materials is essentially controlled by the mechanical and physical properties, many of which are related to microfracturing. In countries where laboratory facilities are not extensive, it is important to develop semi-quantitative methods to estimate the quality of construction materials. Using several carbonate rocks from Nigeria as test materials, relations between porosity index (ratio of effective to total porosity), swelling index, and uniaxiai compressive strength have been examined. These relations are then used as a basis to indirectly estimate degree of micro fracturing.
933051 Behavioer at the shrinkage limit of d a y undergoing drying Williams, D J; Sibley, J W
Geotecli Test J V15, N3, Sept 1992, P217-222 Significant changes occur in many properties for a clay undergoing drying in the vicinity of the shrinkage limit. Changes in linear shrinkage strain, volumetric air content, heat of wetting, tensile strength, and thermal properties with water content have been studied for Deagan clay from Brisbane, Australia. Possible explanations for these changes are discussed. Further data from different soils under different conditions are required to confirm these findings, but the shrinkage limit appears to mark a fundamental change in soil behaviour, and future research is warranted.
933052 Determination of deformation I~roperties of collapsible soils Reznick, Y M
Geotech Test J V15, N3, Sept 1992, 1'248-255 Results are presented from field and laboratory examination of loessial soils from sites near Odessa. The geological profiles are described. Plate loading tests were carded out in situ on soils at saturated and natural water contents. The technique of these tests is described. Undisturbed samples were retrieved for laboratory characterization. The geotechnical properties from the field and laboratory tests are compared. The many engineering advantages of using the plate load test are discussed, but its relative cost may prevent its use in many cases.
© 1993 Pergamon Press Ltd. Reproduction not permitted