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An engineering geological appraisal of the sandstones of the Clarens Formation, Lesotho, in relation to tunnelling
202A
PROPERTIES:DEFORMATION & STRENGTH
Composition, structure, texture and density 965078 Primary and tectonic fabric intensities in mudrocks S. R. Paterson, Hao Yu & G. Oertel, Tectonophysics, 247(14), 1995, pp 105-119. Presents a summary of quantitative measurements of the preferred orientation of phyllosilicategrains in a variety of tectonically weakly deformed to undeformed, fine-grained, peliticrocks. It also brieflyexamines a small amount of data on clay fabrics in deep sea cores, and compares them to fabrics in deformed equivalents from the Mariposa Formation and Calaveras Complex, Sierra Nevada, California.The measured fabric ellipsoidssupport the following conclusions: I) a bedding-parallel foliation forms in peliticrocks during compaction than in the samples is associated with shortening between 3 % and 74%; 2) the amount of compaction is in part controlled by the quartz-feldspar content, and 3) it is impossible to determine preciselythe amounts of compaction, horizontal shortening, and later tectonic strain in deformed samples because of the variability of initial compactions. (from Authors) 965079 The relation between the moisture-release curve and the structure of soil J. W. Crawford, N. Matsui & I. M. Young, European Journal of Soil Science, 46(3), 1995, pp 369-375. Theoretical results are presented which show that, in the absence of additional information, the interpretation of the moisture-release curve is ambiguous for several reasons. A power-law exponent is a consequence of either a fractal pore volume; a fractal solid volume; a fractal pore wall; or a nonfractal, self-similar pore wall, and one cannot infer from the measurement which is the case. Experimental results are presented which confirm that direct measurement of the fractal dimension of the solid matrix is a good predictor of the Brooks-Corey exponent for the soils studied here. Therefore, the moisture-release curve cannot be used as a detailed measure of soil structure. (from Authors) 965080 Variation of textural porosity of a clay-loam soil during compaction A. Bruand & I. Cousin, European Journal of Soil Science, 46(3), 1995, pp 377-385. The effect of compaction on the porosity of aggregates was studied in the laboratory using mercury porosimetry and hackscattered electron scanning images (BESI) of polished thin sc~dons. Porosity was divided into structural and textural porosity, and then textural porosity into lacunar and clayey porosity. For aggregates equilibrated at a water potential of -1 kPa and pressures of 50 and 200 kPa, compaction of structural porosity resulted in an increase of textural porosity. For aggregates equilibrated at a water potential of -1 kPa and an applied pressure of 600 kPa, the structural porosity strongly decreased but did not result in a variation of textural porosity. For aggregates equilibrated at water potentials of -63 and -103 kPa and the three values of pressure studied, textural porosity was unaffected by compaction whatever the evolution of structural porosity. (from Authors)
Deformation and strength characteristics 965081 An engineering geological appraisal of the sandstones of the Clarens Formation, Lesotho, in relation to tunnelling D. J. Castro & F. G. Bell, Geotechnicai & Geological Engineering, 13(3), 1995, pp 117-142.
The Delivery Tunnel South forms part of a system of tunnels for conveying water from Lesotho to South Africa. The tunnel was excavated primarily by tunnel boring machine in the sandstones of the Clarens Formation. These sandstones are uniformly graded and fine grained with quartz being the most abundant mineral. The long-term durability of these sandstones was investigated to establish criteria for concrete lining of the tunnel. Tests included a number of soaking tests using different fluid media, wet and dry testing, erosion tests and brushing tests. This testing programme suggested that concrete lining of the intact sandstone was probably only required where the strength of the sandstone was less than 20 MPa and that therefore only a small percentage of the tunnel need be lined. (from Authors)
965082 Nonlinearity of strain in hard crystalline rocks F. F. Gorbatsevich, International Journal of Rock Mechanics & Mining Sciences, 33(1), 1996, pp 83-91. For most hard crystalline rocks it is assumed that the dependence of their strain on the applied stress is close to linear and for practical calculations only two elasticity constants are used: the modulus of elongation E and the lateral strain factor v. To reveal general regularity in strain the author tested crystalline rocks samples from the Kola peninsula. According to the test results, five main types of strain can be distinguished. (from Author) 965083 The mechanical properties of materials with interconnected cracks and pores J. A. Hudson, E. Liu & S. Crampin, Geophysical Journal International, 124(1), 1996, pp 105-112. Provides effective medium models for the calculation of elastic wave propagation with wavelengths greater than the dimensions of the cracks. The method follows that of earlier papers in which the overall elastic properties are directly related to parameters governing the microstrncture, such as crack number density and the mean radius and spacing distance of the cracks. Expressions derived by the method of smoothing are evaluated to second order in the number density of cracks, thereby incorporating crack-crack interactions through both the strain field in the solid and the flow field of fluids in the pores. (from Authors) 965084 Anisotropic parameters of layered media in terms of composite elastic properties J. Brittan, M. Warner & G. Pratt, Geophysics, 60(4), 1995, pp 1243-1248. In the case of a sequence of layers of two materials, the parameters describing the anisotropy of the equivalent homogenous medium can be derived from the elastic parameters of the original materials. To produce a highly anisotropic equivalent medium from a stack of two isotropic layers, the layers must have significantly different shear moduli and Vp/Va ratios. (Authors) 965085 An experimental and theoretical study of the behaviour of a calcarenite in trlaxial compression R. Lagioia & R. Nova, Geotechnique, 45(4), 1995, pp 633648. The essential feature of the observed behaviour is the occurrence of a destructuration phase, which marks the transition from rock-like to soil-likebehaviour. During this phase the state of stress remains constant, while strains increase steadily. Three phases can be distinguished: an initial elastic, a destruction phase and a hardening or softening phase which ends on an ultimate state locus which is linear in the p'-q plane. The observed behaviour is more and more ductile for increasing confining pressures. In the softening regime the specimen is unstable. It is shown that by means of a mathematical model based on the theory of strain-hardening plasticity it is possible to describe mathematically the
PROPERTIES:DEFORMATION & STRENGTH
Composition, structure, texture and density 965078 Primary and tectonic fabric intensities in mudrocks S. R. Paterson, Hao Yu & G. Oertel, Tectonophysics, 247(14), 1995, pp 105-119. Presents a summary of quantitative measurements of the preferred orientation of phyllosilicategrains in a variety of tectonically weakly deformed to undeformed, fine-grained, peliticrocks. It also brieflyexamines a small amount of data on clay fabrics in deep sea cores, and compares them to fabrics in deformed equivalents from the Mariposa Formation and Calaveras Complex, Sierra Nevada, California.The measured fabric ellipsoidssupport the following conclusions: I) a bedding-parallel foliation forms in peliticrocks during compaction than in the samples is associated with shortening between 3 % and 74%; 2) the amount of compaction is in part controlled by the quartz-feldspar content, and 3) it is impossible to determine preciselythe amounts of compaction, horizontal shortening, and later tectonic strain in deformed samples because of the variability of initial compactions. (from Authors) 965079 The relation between the moisture-release curve and the structure of soil J. W. Crawford, N. Matsui & I. M. Young, European Journal of Soil Science, 46(3), 1995, pp 369-375. Theoretical results are presented which show that, in the absence of additional information, the interpretation of the moisture-release curve is ambiguous for several reasons. A power-law exponent is a consequence of either a fractal pore volume; a fractal solid volume; a fractal pore wall; or a nonfractal, self-similar pore wall, and one cannot infer from the measurement which is the case. Experimental results are presented which confirm that direct measurement of the fractal dimension of the solid matrix is a good predictor of the Brooks-Corey exponent for the soils studied here. Therefore, the moisture-release curve cannot be used as a detailed measure of soil structure. (from Authors) 965080 Variation of textural porosity of a clay-loam soil during compaction A. Bruand & I. Cousin, European Journal of Soil Science, 46(3), 1995, pp 377-385. The effect of compaction on the porosity of aggregates was studied in the laboratory using mercury porosimetry and hackscattered electron scanning images (BESI) of polished thin sc~dons. Porosity was divided into structural and textural porosity, and then textural porosity into lacunar and clayey porosity. For aggregates equilibrated at a water potential of -1 kPa and pressures of 50 and 200 kPa, compaction of structural porosity resulted in an increase of textural porosity. For aggregates equilibrated at a water potential of -1 kPa and an applied pressure of 600 kPa, the structural porosity strongly decreased but did not result in a variation of textural porosity. For aggregates equilibrated at water potentials of -63 and -103 kPa and the three values of pressure studied, textural porosity was unaffected by compaction whatever the evolution of structural porosity. (from Authors)
Deformation and strength characteristics 965081 An engineering geological appraisal of the sandstones of the Clarens Formation, Lesotho, in relation to tunnelling D. J. Castro & F. G. Bell, Geotechnicai & Geological Engineering, 13(3), 1995, pp 117-142.
The Delivery Tunnel South forms part of a system of tunnels for conveying water from Lesotho to South Africa. The tunnel was excavated primarily by tunnel boring machine in the sandstones of the Clarens Formation. These sandstones are uniformly graded and fine grained with quartz being the most abundant mineral. The long-term durability of these sandstones was investigated to establish criteria for concrete lining of the tunnel. Tests included a number of soaking tests using different fluid media, wet and dry testing, erosion tests and brushing tests. This testing programme suggested that concrete lining of the intact sandstone was probably only required where the strength of the sandstone was less than 20 MPa and that therefore only a small percentage of the tunnel need be lined. (from Authors)
965082 Nonlinearity of strain in hard crystalline rocks F. F. Gorbatsevich, International Journal of Rock Mechanics & Mining Sciences, 33(1), 1996, pp 83-91. For most hard crystalline rocks it is assumed that the dependence of their strain on the applied stress is close to linear and for practical calculations only two elasticity constants are used: the modulus of elongation E and the lateral strain factor v. To reveal general regularity in strain the author tested crystalline rocks samples from the Kola peninsula. According to the test results, five main types of strain can be distinguished. (from Author) 965083 The mechanical properties of materials with interconnected cracks and pores J. A. Hudson, E. Liu & S. Crampin, Geophysical Journal International, 124(1), 1996, pp 105-112. Provides effective medium models for the calculation of elastic wave propagation with wavelengths greater than the dimensions of the cracks. The method follows that of earlier papers in which the overall elastic properties are directly related to parameters governing the microstrncture, such as crack number density and the mean radius and spacing distance of the cracks. Expressions derived by the method of smoothing are evaluated to second order in the number density of cracks, thereby incorporating crack-crack interactions through both the strain field in the solid and the flow field of fluids in the pores. (from Authors) 965084 Anisotropic parameters of layered media in terms of composite elastic properties J. Brittan, M. Warner & G. Pratt, Geophysics, 60(4), 1995, pp 1243-1248. In the case of a sequence of layers of two materials, the parameters describing the anisotropy of the equivalent homogenous medium can be derived from the elastic parameters of the original materials. To produce a highly anisotropic equivalent medium from a stack of two isotropic layers, the layers must have significantly different shear moduli and Vp/Va ratios. (Authors) 965085 An experimental and theoretical study of the behaviour of a calcarenite in trlaxial compression R. Lagioia & R. Nova, Geotechnique, 45(4), 1995, pp 633648. The essential feature of the observed behaviour is the occurrence of a destructuration phase, which marks the transition from rock-like to soil-likebehaviour. During this phase the state of stress remains constant, while strains increase steadily. Three phases can be distinguished: an initial elastic, a destruction phase and a hardening or softening phase which ends on an ultimate state locus which is linear in the p'-q plane. The observed behaviour is more and more ductile for increasing confining pressures. In the softening regime the specimen is unstable. It is shown that by means of a mathematical model based on the theory of strain-hardening plasticity it is possible to describe mathematically the