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Effect of particle contact bond on shear modulus
80A 932069 Effect of particle contact bond on shear modulus Chang, T S; Woods, R D
J Geotech Engng Div ASCE Vl18, NS, Aug 1992, P12161233 Improvement of sand by cementation is widely practised. The most significant factors affecting the low strain shear modulus of sands cemented with various cementitious or chemical grouting agents have been studied in resonant column tests. The number of contact points between particles at which bonds are developed is the most important paraineter. This is controlled by effective grain size and coefficient of conformity. Cementation level and the properties of the cementing agent are also influential. An empirical relation is presented for qualitatively estimating the low strain shear modulus of cemented sands. 932070 Constitutive behaviour of stress-induced anisotropic cohesive soil Budiman, J S; Sture, S; Ko, H Y
J Geotech Engng Div ASCE Vl18, N9, Sept 1992, P13481359 Experiments carried out in a directional shear cell, capable of applying independently controlled normal and shear stresses on four vertical faces of a cubical specimen under plane strain conditions, are described. Fabric anisotropy was introduced into an artificial cohesive soil by preloading. In subsequent tests, initial reloading direction coincided with the material principal axes, then reloading principal stresses were applied in discrete jumps at specific orientations to the direction of initial load. Pronounced effects of stress-induced anisotropy are indicated by significant variation in stress strain behaviour. Increase in maximum strain and volume strain and decrease in stiffness moduli with increasing rotation angle of stress direction are observed. 932071 Determination of unconfined compressive strength of coal for pillar design Hirt, A M; Shakoor, A
Min Engug I'44, N8, Aug 1992, P1037-1041 Compressive strengths were determined on cubes of coal from 12 mines in 4 Pennsylvania coal seams. Results were used to compute coal pillar strength. Using values of pillar stress according to tributary area theory, safety factors against pillar crushing were calculated. Although compressive strength values show variability within and between seams, adequate safety factors were found in all cases, indicating pillar design may IX overconservative. No strong correlations could be found between coal compressive strength and various physical and chemical properties. 932072 Material strength of sandstones of the Sherwood Sandstone Group of north Staffordshire with reference to microfabric Yates, P G J
Q J Engng Geol V25, N2, 1992, P107-113 The Sherwood Sandstone Group rocks are of Triassic age. They exhibit variable engineering properties, from sands to moderately weak rock. In north Staffordshire they range from argillaceous fine grained sandstone to sandy conglomerate. They are moisture sensitive and are generally assessed in the saturated state. Strength variability has been investigated and
its relation to microfabric and petrofabric features examined. Depositionai and diagenetic factors are equally important as weathering for influence on strength. A method is proposed for estimating shear strength of the weakest rocks. 932073 Sensitivity of sandstone strength and deformability to changes in moisture content Hawkins, A B; McConnel, B J
Q J Engng Geol V25, N2, 1992, Pl15-130 The relation between dry and saturated uniaxiai compressive strengths for 35 British sandstones has been examined. The difference between the two ranges from 78% for clay-rich Cretaceous Greensand to only 8% for Siliceous Sandstone. Sensitivity to moisture content is primarily controlled by proportions of clay minerals and quartz and to a smaller extent by microfabric. Changes in moisture content of as little as 1% from the dry state can have significant effects on strength and deformability properties. 932074 Limestone to dolomite to dedolomite conversion and its effect on rock strength: a case study Williams, D M; McNamara, K
Q J Engng Geol V25, N2, 1992, P131-135 Cores taken from Carboniferous rocks beneath the Cliff Dam in County Donegal, Ireland, show the presence of limestone, dolomite, and dedolomite. Probable events leading to the limestone to dolomite to dedolomite conversion are described. Laboratory testing showed compressive strength drop of about 20% for the limestone/dolomite conversion followed by a further 75% drop for dolomite/dedoiomite. Thin section examination may IX required to distinguish dedolomite from its country rock, as both react with acid. 932075 Technique for moulding cylindrical discontinuous models. Technical note Meyers, A G; Priest, S D
Rock Mech Rock Engng V25, N3, July-Sept 1992, P207-214 A technique is described for the repeatable production of cylindrical specimens, for example for triaxial testing, composed of distinct blocks of a virtually unlimited number of possible geometries. A styrofoam cylinder hot-wire machined from a block is held in a jig and the required discontinuities cut by hot-wire. The blocks formed are used to make silicone rubber negatives in which model materials can be cast. These cast blocks are reassembled to replicate the original specimen geometry. 932076 Some observations on the kinematic nature of soil stiffness Jardine, R J
Soils Found V32, N2, June 1992, Pl11-124 Some kinematic and nonlinear aspects of small strain soil stiffness seen in laboratory tests are discussed. Many can be described by defining in normalised stress space on outer Bounding Surface and two mobile zone boundaries, Kinematic Sub-Yield Surfaces, which subdivide the permissable interior region. Types of behaviour within each zone are illustrated using experimental data. The KSYSs can IX repositioned and modified by moving the current stress point. The scheme is used to explore stiffness aspects of a high OCR London Clay and a glacio-marine clay, Magnus till.
© 1993 Pergamon Press Ltd. Reproduction not permitted
J Geotech Engng Div ASCE Vl18, NS, Aug 1992, P12161233 Improvement of sand by cementation is widely practised. The most significant factors affecting the low strain shear modulus of sands cemented with various cementitious or chemical grouting agents have been studied in resonant column tests. The number of contact points between particles at which bonds are developed is the most important paraineter. This is controlled by effective grain size and coefficient of conformity. Cementation level and the properties of the cementing agent are also influential. An empirical relation is presented for qualitatively estimating the low strain shear modulus of cemented sands. 932070 Constitutive behaviour of stress-induced anisotropic cohesive soil Budiman, J S; Sture, S; Ko, H Y
J Geotech Engng Div ASCE Vl18, N9, Sept 1992, P13481359 Experiments carried out in a directional shear cell, capable of applying independently controlled normal and shear stresses on four vertical faces of a cubical specimen under plane strain conditions, are described. Fabric anisotropy was introduced into an artificial cohesive soil by preloading. In subsequent tests, initial reloading direction coincided with the material principal axes, then reloading principal stresses were applied in discrete jumps at specific orientations to the direction of initial load. Pronounced effects of stress-induced anisotropy are indicated by significant variation in stress strain behaviour. Increase in maximum strain and volume strain and decrease in stiffness moduli with increasing rotation angle of stress direction are observed. 932071 Determination of unconfined compressive strength of coal for pillar design Hirt, A M; Shakoor, A
Min Engug I'44, N8, Aug 1992, P1037-1041 Compressive strengths were determined on cubes of coal from 12 mines in 4 Pennsylvania coal seams. Results were used to compute coal pillar strength. Using values of pillar stress according to tributary area theory, safety factors against pillar crushing were calculated. Although compressive strength values show variability within and between seams, adequate safety factors were found in all cases, indicating pillar design may IX overconservative. No strong correlations could be found between coal compressive strength and various physical and chemical properties. 932072 Material strength of sandstones of the Sherwood Sandstone Group of north Staffordshire with reference to microfabric Yates, P G J
Q J Engng Geol V25, N2, 1992, P107-113 The Sherwood Sandstone Group rocks are of Triassic age. They exhibit variable engineering properties, from sands to moderately weak rock. In north Staffordshire they range from argillaceous fine grained sandstone to sandy conglomerate. They are moisture sensitive and are generally assessed in the saturated state. Strength variability has been investigated and
its relation to microfabric and petrofabric features examined. Depositionai and diagenetic factors are equally important as weathering for influence on strength. A method is proposed for estimating shear strength of the weakest rocks. 932073 Sensitivity of sandstone strength and deformability to changes in moisture content Hawkins, A B; McConnel, B J
Q J Engng Geol V25, N2, 1992, Pl15-130 The relation between dry and saturated uniaxiai compressive strengths for 35 British sandstones has been examined. The difference between the two ranges from 78% for clay-rich Cretaceous Greensand to only 8% for Siliceous Sandstone. Sensitivity to moisture content is primarily controlled by proportions of clay minerals and quartz and to a smaller extent by microfabric. Changes in moisture content of as little as 1% from the dry state can have significant effects on strength and deformability properties. 932074 Limestone to dolomite to dedolomite conversion and its effect on rock strength: a case study Williams, D M; McNamara, K
Q J Engng Geol V25, N2, 1992, P131-135 Cores taken from Carboniferous rocks beneath the Cliff Dam in County Donegal, Ireland, show the presence of limestone, dolomite, and dedolomite. Probable events leading to the limestone to dolomite to dedolomite conversion are described. Laboratory testing showed compressive strength drop of about 20% for the limestone/dolomite conversion followed by a further 75% drop for dolomite/dedoiomite. Thin section examination may IX required to distinguish dedolomite from its country rock, as both react with acid. 932075 Technique for moulding cylindrical discontinuous models. Technical note Meyers, A G; Priest, S D
Rock Mech Rock Engng V25, N3, July-Sept 1992, P207-214 A technique is described for the repeatable production of cylindrical specimens, for example for triaxial testing, composed of distinct blocks of a virtually unlimited number of possible geometries. A styrofoam cylinder hot-wire machined from a block is held in a jig and the required discontinuities cut by hot-wire. The blocks formed are used to make silicone rubber negatives in which model materials can be cast. These cast blocks are reassembled to replicate the original specimen geometry. 932076 Some observations on the kinematic nature of soil stiffness Jardine, R J
Soils Found V32, N2, June 1992, Pl11-124 Some kinematic and nonlinear aspects of small strain soil stiffness seen in laboratory tests are discussed. Many can be described by defining in normalised stress space on outer Bounding Surface and two mobile zone boundaries, Kinematic Sub-Yield Surfaces, which subdivide the permissable interior region. Types of behaviour within each zone are illustrated using experimental data. The KSYSs can IX repositioned and modified by moving the current stress point. The scheme is used to explore stiffness aspects of a high OCR London Clay and a glacio-marine clay, Magnus till.
© 1993 Pergamon Press Ltd. Reproduction not permitted