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Estimation of rock strength: rapidly and reliably by the Schmidt hammer
345A by a continuous increasing function. This function is linear on a semilog scale up to shear strain around 25%, and is relatively unaffected by previous shear strain development on other planes. A similar relation was found for shear strain increment. The Masing model reasonably predicts the unloading portion of the stress strain curve and may be used to estimate plastic strains from monotonic loading tests. Mechanisms of shear strain development are discussed. 926045 Estimation of rock strength: rapidly and reliably by the Schmidt hammer Arioglu, E; Tokgoz, N J Min Metal Fuels 1/34, N9/lO, Sept-Oct 1991, P327-330 Schmidt hammer tests, which relate compressive strength solely to surface hardness, are widely used because of their ease, speed, and nondestructive nature. The accuracy has been questioned, because of sensitivity to surface conditions. Improvements by combining rebound value with ultrasonic pulse velocity or dry density have been recommended. Correlations between functions of rebound number alone and of rebound number and dry density with uniaxial compression strength are evaluated using regression analysis. 926046 Effect of cementation on the elastic properties of granular material Dvorkin, J; Mavke, G; Nur, A Mech Mater VI2, N3/4, Nov 1991, P207-217 Acoustic and mechanical properties of sedimentary rocks can be strongly affected by the characteristics of the intergranular bonding material. A simple analytical model is developed to describe the mechanics of such materials. The problem of 2D arbitrarily shaped cement layer deformation is reduced to an ordinary differential equation of the second order. A simple analytical solution is obtained for compression or shear of a cement layer between straight boundaries. It is shown that a cement layer under normal compression can be approximately treated as an elastic foundation between two grounds. Using this assumption, elastic mr dull of cemented granular materials are estimated. 926047 Size and shape effects in point load tests of irregular rock fragments Panck, L A; Fannon, T A Rock Mech Rock Engng 1/25, N2, April-June 1992, P109-140 Point load tests were carried out on over 500 irregular mine run samples of ironformation, metadiabase, and ophitic basalt, ranging up to 250ram in diameter. Multiple regression analysis was used to obtain a best expression of point load strength in terms of size and shape effects. Brazilian and unconfined compression tests were carried out on cores of three sizes of the basalt and metadiabase. Size effect was independent of rock type in the point load tests, but, as previously reported, was a variable characteristic of rock type in the other tests. 926048 Static and dynamic measurements of undrained stiffness on natural overconsolidated clays Georgiannou, V N; Rampello, S; Silvestri, F Proc lOth European Conference on Soil Mechanics and Foundation Engineering, Florence, 26-30 May 1991 V1, P9195. Publ Rotterdam. A A Balkema, 1991 A study was carried out to investigate the reliability and likely correlation of stiffness values for natural overconsolidated soils as measured by different testing techniques, static triaxial
compression and resonant column-torsional shear tests. Stiffness variation with strain was evaluated over a relatively wide strain range (0.01-0.1%). Three clays and a marl were tested. Fair agreement was found between static and dynamic stiffnesses for the clays, but not for the marl, possibly due to its cemented structure. Shear modulus decayed rapidly beyond a threshold strain for all these soils. 926049 Dynamic triaxiai tests on silt Gilles, P; Sine, B; Thimus, J F; Lousberg, E Proc lOth European Conference on Soil Mechanics and Foundation Engineering, Florence, 26-30 May 1991 V1, P97100. Publ Rotterdam: A A Balkema, 1991 A computer controlled dynamic triaxial testing machine for soils is illustrated. The theoretical basis of the test, to obtain a hysteresis loop from which Young's modulus and damping ratio can be evaluated, is outlined. A quaternary silt (a loess from the last glaciation) has been tested in the device. Effects of cyclic frequency, confining pressure, and water content on the two parameters are discussed. 926050 Laboratory tests on the soft clayey soil of an old city Goldscheider, M; Scherzinger, T Proc lOth European Conference on Soil Mechanics and Foundation Engineering, Florence, 26-30 May 1991 VI, P101106. Publ Rotterdam. A A Balkema, 1991 Undisturbed samples of soft clays were taken at the old city of Constance and stored in specially designed pressure cells under in situ conditions, to prevent ageing before laboratory study. Preconsolidation stress, coefficient of earth pressure at rest, and hydraulic stagnation gradient were evaluated using oedometer and triaxial tests. Undrained triaxial tests on uniaxially and isotropically consolidated samples show shear behaviour is dependent on consolidation history. These results are used to calculate the bearing capacity of medieval foundations and the earth pressure on a rigid excavation wall. 926051 Investigations of the stiffness of a glacial clay till Hird, C C; Powell, J J M; Yung, P C Y Proc lOth European Conference on Soil Mechanics and Foundation Engineering, Florence, 26-30 May 1991 V1. PI07110. Publ Rotterdam: A A Balkema, 1991 Comparison is made between stiffness of a glacial clay obtained from triaxial or large diameter plate tests. In the former case, high quality undisturbed samples were taken and stored under simulated in situ conditions before trimming to size and testing. The plate load tests used 865mm diameter plates in trenches and boreholes. Special strain measurement equipment was used in both cases. Good agreement is seen in stiffnesses, even at relatively low strain levels, supporting the view that high quality laboratory testing can produce realistic values of soil stiffness. 926052 Cyclic and permanent deformation of saturated sand with initial static shear stress during cyclic loading Hyodo, M; Murata, H; Yasufuku, N; Fujii, T Proc lOth European Conference on Soil Mechanics and Foundation Engineering, Florence, 26-30 May 1991 V1, P111114. Publ Rotterdam: A A Balkema, 1991 Cyclic triaxial compression tests were carried out on saturated samples of Toyoura sand with different levels of initial static shear stress and subsequent cyclic shear stress. Residual axial strains during undrained cyclic loading and post cyclic volume
© 1992 Pergamon Press Ltd. Reproduction not permitted
compression and resonant column-torsional shear tests. Stiffness variation with strain was evaluated over a relatively wide strain range (0.01-0.1%). Three clays and a marl were tested. Fair agreement was found between static and dynamic stiffnesses for the clays, but not for the marl, possibly due to its cemented structure. Shear modulus decayed rapidly beyond a threshold strain for all these soils. 926049 Dynamic triaxiai tests on silt Gilles, P; Sine, B; Thimus, J F; Lousberg, E Proc lOth European Conference on Soil Mechanics and Foundation Engineering, Florence, 26-30 May 1991 V1, P97100. Publ Rotterdam: A A Balkema, 1991 A computer controlled dynamic triaxial testing machine for soils is illustrated. The theoretical basis of the test, to obtain a hysteresis loop from which Young's modulus and damping ratio can be evaluated, is outlined. A quaternary silt (a loess from the last glaciation) has been tested in the device. Effects of cyclic frequency, confining pressure, and water content on the two parameters are discussed. 926050 Laboratory tests on the soft clayey soil of an old city Goldscheider, M; Scherzinger, T Proc lOth European Conference on Soil Mechanics and Foundation Engineering, Florence, 26-30 May 1991 VI, P101106. Publ Rotterdam. A A Balkema, 1991 Undisturbed samples of soft clays were taken at the old city of Constance and stored in specially designed pressure cells under in situ conditions, to prevent ageing before laboratory study. Preconsolidation stress, coefficient of earth pressure at rest, and hydraulic stagnation gradient were evaluated using oedometer and triaxial tests. Undrained triaxial tests on uniaxially and isotropically consolidated samples show shear behaviour is dependent on consolidation history. These results are used to calculate the bearing capacity of medieval foundations and the earth pressure on a rigid excavation wall. 926051 Investigations of the stiffness of a glacial clay till Hird, C C; Powell, J J M; Yung, P C Y Proc lOth European Conference on Soil Mechanics and Foundation Engineering, Florence, 26-30 May 1991 V1. PI07110. Publ Rotterdam: A A Balkema, 1991 Comparison is made between stiffness of a glacial clay obtained from triaxial or large diameter plate tests. In the former case, high quality undisturbed samples were taken and stored under simulated in situ conditions before trimming to size and testing. The plate load tests used 865mm diameter plates in trenches and boreholes. Special strain measurement equipment was used in both cases. Good agreement is seen in stiffnesses, even at relatively low strain levels, supporting the view that high quality laboratory testing can produce realistic values of soil stiffness. 926052 Cyclic and permanent deformation of saturated sand with initial static shear stress during cyclic loading Hyodo, M; Murata, H; Yasufuku, N; Fujii, T Proc lOth European Conference on Soil Mechanics and Foundation Engineering, Florence, 26-30 May 1991 V1, P111114. Publ Rotterdam: A A Balkema, 1991 Cyclic triaxial compression tests were carried out on saturated samples of Toyoura sand with different levels of initial static shear stress and subsequent cyclic shear stress. Residual axial strains during undrained cyclic loading and post cyclic volume
© 1992 Pergamon Press Ltd. Reproduction not permitted