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13. The vane test in organic soils
76
ABSTRACTS
11.
T. Mogami. On the critical state line proposed by Roscoe, et al (in English). Soils Foundations 8 (4) 1 (1968). Author's theory of mechanics of granular materials briefly developed in Proceedings of the VIlth International Conference on Soil Mechanics and Foundation Engineering, Mexico City, 1969, Vol. I, establishes equations of a critical state space curve in the three-dimensional space defined by void ratio (e), mean pressure (p), and shearing stress on slip plane (~-). Author assumes that critical state line proposed by Roscoe in a similar three-dimensional space is based on experimental evidence. On this basis, he represents the analogy between the shape of projections on the (e, p) or (r, p) planes of his theoretical and Roscoe's experinaental critical state space curve as an argument for the validity of his own theory. A conclusive opinion on the article is possible only by examination of materials explanning both author's and Roscoe's theories. (M.I.R.A.)
12.
Ivan Nelson and Melvin L Barons. Application of variable moduli models to soil behaviour. Int. J. Solids Struct. 7 (1971). A mathematical material model is described in which the basic constitutive law is an isotropic relation between the increments of stress and strain. No unique stress-strain relation, per se, exists. Neither is there an explicit yield condition. The bulk and shear moduli, however, are functions of the stress a n d / o r strain invariants. The behaviour of two simple models of this type is examined for the two generally available soil tests, i.e. uniaxial strain and triaxial compression. In each case qualitative agreement with the behaviour of real soils is obtained. For one model, unloading and reloading is also considered. The latter model is also compared with a simple elastic-plastic model. Many similarities between the two become apparent., but so do significant differences, e.g. the direction of the "plastic" strain increment. (Authors' Summary.)
131 R. P. Northwood and D. A. Sangrey. The vane test in organic soils. Can. Geotech. J. 8 (3) (1971). In Mttt vane tests were carried out in a number of different muskeg deposits to examine the mechanism of failure and the effect of variation in vane size and speed of testing. The failure mechanism in peat was found to be similar to that in soft clays. The apparent shear strength varied with vane size but was independent of testing speed. There was an optimum vane size of l0 cm diameter. Block samples were obtained from one site for laboratory vane tests to investigate anisotropy in the strength of the peat. In situ tests for anisotropy using vanes of varying shape confirmed the laboratory results, and showed that strengths on the vertical plane could be 100% higher than those on the horizontal plane. (Authors' Summary.) 14.
B. D. Soane. The effects of traffic and implements on soil compaction. J. Inst. Ag. Engr. 25 (3) (1970). Changes in soil management and machinery usage in recent years appear to be responsible for an increase in soil compaction and there is evidence that this has resulted in a deterioration in soil physical conditions. Soil compaction in the field is a complex process in which several soil and load characteristics interact. The vertical and horizontal distribution of changes in bulk density and air-filled porosity resulting from compaction can be studied with gamma-ray transmission equipment. Compaction occurs during seedbed preparation, spraying and harvesting operations as well as during tillage. Because of the deleterious effects of compaction on subsequent crop growth extra tillage is frequently required for both the topsoil and subsoil. Compaction is also likely to influence the hydrological balance of the soil and the incidence of clods at potato harvest. Both the incidence and adverse effects of compaction are more probable when soils are moist. So~ compaction can be reduced in a number of ways, but the economics of changes in current machinery design and soil management practices need to be established. Author's Summary.)
15.
L. Suklje. Rheological aspects of soil mechanics. Wiley, 1969. Text on th¢ fundamentals of classical soil mechanics with discussion of new concepts, theories and methods. Covers the viscous properties of soils, including certain theological schemes. N e w experimental and analytical investigations are also considered. Bibliography of 13 pages and 5 pages of suggested further readings. For research scientists and engineers,
ABSTRACTS
11.
T. Mogami. On the critical state line proposed by Roscoe, et al (in English). Soils Foundations 8 (4) 1 (1968). Author's theory of mechanics of granular materials briefly developed in Proceedings of the VIlth International Conference on Soil Mechanics and Foundation Engineering, Mexico City, 1969, Vol. I, establishes equations of a critical state space curve in the three-dimensional space defined by void ratio (e), mean pressure (p), and shearing stress on slip plane (~-). Author assumes that critical state line proposed by Roscoe in a similar three-dimensional space is based on experimental evidence. On this basis, he represents the analogy between the shape of projections on the (e, p) or (r, p) planes of his theoretical and Roscoe's experinaental critical state space curve as an argument for the validity of his own theory. A conclusive opinion on the article is possible only by examination of materials explanning both author's and Roscoe's theories. (M.I.R.A.)
12.
Ivan Nelson and Melvin L Barons. Application of variable moduli models to soil behaviour. Int. J. Solids Struct. 7 (1971). A mathematical material model is described in which the basic constitutive law is an isotropic relation between the increments of stress and strain. No unique stress-strain relation, per se, exists. Neither is there an explicit yield condition. The bulk and shear moduli, however, are functions of the stress a n d / o r strain invariants. The behaviour of two simple models of this type is examined for the two generally available soil tests, i.e. uniaxial strain and triaxial compression. In each case qualitative agreement with the behaviour of real soils is obtained. For one model, unloading and reloading is also considered. The latter model is also compared with a simple elastic-plastic model. Many similarities between the two become apparent., but so do significant differences, e.g. the direction of the "plastic" strain increment. (Authors' Summary.)
131 R. P. Northwood and D. A. Sangrey. The vane test in organic soils. Can. Geotech. J. 8 (3) (1971). In Mttt vane tests were carried out in a number of different muskeg deposits to examine the mechanism of failure and the effect of variation in vane size and speed of testing. The failure mechanism in peat was found to be similar to that in soft clays. The apparent shear strength varied with vane size but was independent of testing speed. There was an optimum vane size of l0 cm diameter. Block samples were obtained from one site for laboratory vane tests to investigate anisotropy in the strength of the peat. In situ tests for anisotropy using vanes of varying shape confirmed the laboratory results, and showed that strengths on the vertical plane could be 100% higher than those on the horizontal plane. (Authors' Summary.) 14.
B. D. Soane. The effects of traffic and implements on soil compaction. J. Inst. Ag. Engr. 25 (3) (1970). Changes in soil management and machinery usage in recent years appear to be responsible for an increase in soil compaction and there is evidence that this has resulted in a deterioration in soil physical conditions. Soil compaction in the field is a complex process in which several soil and load characteristics interact. The vertical and horizontal distribution of changes in bulk density and air-filled porosity resulting from compaction can be studied with gamma-ray transmission equipment. Compaction occurs during seedbed preparation, spraying and harvesting operations as well as during tillage. Because of the deleterious effects of compaction on subsequent crop growth extra tillage is frequently required for both the topsoil and subsoil. Compaction is also likely to influence the hydrological balance of the soil and the incidence of clods at potato harvest. Both the incidence and adverse effects of compaction are more probable when soils are moist. So~ compaction can be reduced in a number of ways, but the economics of changes in current machinery design and soil management practices need to be established. Author's Summary.)
15.
L. Suklje. Rheological aspects of soil mechanics. Wiley, 1969. Text on th¢ fundamentals of classical soil mechanics with discussion of new concepts, theories and methods. Covers the viscous properties of soils, including certain theological schemes. N e w experimental and analytical investigations are also considered. Bibliography of 13 pages and 5 pages of suggested further readings. For research scientists and engineers,