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Stress-strain relationships for soil with variable lateral strain
ABSTRACTS
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the fuel consumption of various vehicles at different speeds. Each vehicle has its own operating range where the influence of tyre rolling resistance on fuel consumption is greatest, this depending on relationship between the proportion of tyre rolling resistance in the overall resistance-to-motion balance, degree of engine loading, and vehicle speed. Under the more usual vehicle-operating conditions, one per cent reduction in tyre rolling resistance lowers fuel consumption by 0.25-0.35 per cent. On hard surfaces, the major source of tyre rolling resistance comprises hysteresis losses within the tyre. Tyres made from different types of polymer rubber can differ in rolling resistance by up to 50 per cent least rolling resistance being occasioned by natural rubber and the most by the butadiene-styrene type. All other conditions being equal, an increase in tyre temperature from 30 to 70°C leads to a reduction in rolling resistance of 25-30 per cent. Tyre rolling resistance is considerably affected by the thickness of the tread, approximately 30 per cent of the rolling-resistance losses occurring in the tread and 70 per cent in the tyre carcass. A decrease of 1-2 m m in the tread thickness of truck tyres reduces their rolling-resistance coefficient by 3-7 per cent while a corresponding reduction in the tread thickness of car tyres lowers their rolling-resistance coefficient by approximately 1 per cent. The number of cord layers, type of cord material, and tyre deformation also exert a material influence on tyre roiling resistance. Experience shows that the opportunity now exists for curtailing tyre rolling resistance by approximately 15 per cent. (M.I.R.A., 1968).
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68. A. S. Korolev. Determing the compressional properties of clay soils and peat by graphical analysis. J. Soil Mech. Fdns. Engng (6), 372-375 (1965). (Translation of Osnovaniya, Fundamenty i Mekhanika Gruntov (6), 26-28 (Nov./Dec. 1965)). A study has been made of the nonlinear relationship between pressure and absolute modulus of uniaxial compression of clay and peat samples. The increase of the modulus is principally due to a n increase in the number of contacts per unit soil volume. This increase can be evaluated quantitatively by the contact cross section or by the ratio of actual contact area to the nominal area. It is assumed that the number of contacts in the soil system changes proportionally to the relative strain. The graphical treatment of more than 200 soil samples has shown that 90 per cent of the compression curves can be defined by a hyperbolic relationship between pressure and modulus of compression. The method described in the paper presents an interesting approach to an important practical problem. The experimental results should, however, be checked by additional tests on local soils before the method is applied to soil layers of different geological origin. (Applied Mechanics Review, March 1968). 69. T. P. Ojha and A. C. Pandya. Optimum Size of bullock cart wheels. J. agric. Engng Res. 13 (2), 134-140 (1968). The performance of rigid model wheels was studied in the laboratory on two deformable surfaces (sand clay loam and sand). On the basis of the results obtained it was possible to predict the performance of full size wheels. This was verified by trials with a prototype wheel of 60 in. dia. and 2¼ in. rim. (Author's Summary). 70. Osamu Kitani and Sverker P. E. Persson. Stress-strain relationships for soil with variable lateral strain. Trans. ASAE 10 (6), 738-741 (1967). A study was carried out to investigate the behavior of a cylindrical soil sample which was axially compressed and laterally confined with a flexible wall held together with springs of various spring constants. Two-dimensional, stress-strain relationship for soil was obtained. The experimental part was made with only one soil and soil condition for a limited lateral expansion. Further tests of similar nature are therefore required to prove if the found relationships are general. (Author's Summary). 71. K. Preiss. Paths of gamma-ray photons in soil. Civ. Engng PubL Works Rev. May (1968). Civil engineers are used to visualising an item with which they deal, whether this be the deformation of a structure or the operation of some testing apparatus. Gauges which measure the density of soil by back-scattering of gamma-rays are gradually finding wider application, but the difficulty in visualising just what happens to the radiation in the soil under the gauge is a handicap to some engineers who would like to understand the method. A project was recently undertaken to calculate some aspects of the operation of gamma-ray backscatter density gauges. Some of the results of these calculations were arranged in such a way as to be capable of tabulation. This paper shows the distribution of radiation in the soil beneath a gauge; these were calculated by the Monte Carlo method. (Author's Summary).
89
the fuel consumption of various vehicles at different speeds. Each vehicle has its own operating range where the influence of tyre rolling resistance on fuel consumption is greatest, this depending on relationship between the proportion of tyre rolling resistance in the overall resistance-to-motion balance, degree of engine loading, and vehicle speed. Under the more usual vehicle-operating conditions, one per cent reduction in tyre rolling resistance lowers fuel consumption by 0.25-0.35 per cent. On hard surfaces, the major source of tyre rolling resistance comprises hysteresis losses within the tyre. Tyres made from different types of polymer rubber can differ in rolling resistance by up to 50 per cent least rolling resistance being occasioned by natural rubber and the most by the butadiene-styrene type. All other conditions being equal, an increase in tyre temperature from 30 to 70°C leads to a reduction in rolling resistance of 25-30 per cent. Tyre rolling resistance is considerably affected by the thickness of the tread, approximately 30 per cent of the rolling-resistance losses occurring in the tread and 70 per cent in the tyre carcass. A decrease of 1-2 m m in the tread thickness of truck tyres reduces their rolling-resistance coefficient by 3-7 per cent while a corresponding reduction in the tread thickness of car tyres lowers their rolling-resistance coefficient by approximately 1 per cent. The number of cord layers, type of cord material, and tyre deformation also exert a material influence on tyre roiling resistance. Experience shows that the opportunity now exists for curtailing tyre rolling resistance by approximately 15 per cent. (M.I.R.A., 1968).
on
68. A. S. Korolev. Determing the compressional properties of clay soils and peat by graphical analysis. J. Soil Mech. Fdns. Engng (6), 372-375 (1965). (Translation of Osnovaniya, Fundamenty i Mekhanika Gruntov (6), 26-28 (Nov./Dec. 1965)). A study has been made of the nonlinear relationship between pressure and absolute modulus of uniaxial compression of clay and peat samples. The increase of the modulus is principally due to a n increase in the number of contacts per unit soil volume. This increase can be evaluated quantitatively by the contact cross section or by the ratio of actual contact area to the nominal area. It is assumed that the number of contacts in the soil system changes proportionally to the relative strain. The graphical treatment of more than 200 soil samples has shown that 90 per cent of the compression curves can be defined by a hyperbolic relationship between pressure and modulus of compression. The method described in the paper presents an interesting approach to an important practical problem. The experimental results should, however, be checked by additional tests on local soils before the method is applied to soil layers of different geological origin. (Applied Mechanics Review, March 1968). 69. T. P. Ojha and A. C. Pandya. Optimum Size of bullock cart wheels. J. agric. Engng Res. 13 (2), 134-140 (1968). The performance of rigid model wheels was studied in the laboratory on two deformable surfaces (sand clay loam and sand). On the basis of the results obtained it was possible to predict the performance of full size wheels. This was verified by trials with a prototype wheel of 60 in. dia. and 2¼ in. rim. (Author's Summary). 70. Osamu Kitani and Sverker P. E. Persson. Stress-strain relationships for soil with variable lateral strain. Trans. ASAE 10 (6), 738-741 (1967). A study was carried out to investigate the behavior of a cylindrical soil sample which was axially compressed and laterally confined with a flexible wall held together with springs of various spring constants. Two-dimensional, stress-strain relationship for soil was obtained. The experimental part was made with only one soil and soil condition for a limited lateral expansion. Further tests of similar nature are therefore required to prove if the found relationships are general. (Author's Summary). 71. K. Preiss. Paths of gamma-ray photons in soil. Civ. Engng PubL Works Rev. May (1968). Civil engineers are used to visualising an item with which they deal, whether this be the deformation of a structure or the operation of some testing apparatus. Gauges which measure the density of soil by back-scattering of gamma-rays are gradually finding wider application, but the difficulty in visualising just what happens to the radiation in the soil under the gauge is a handicap to some engineers who would like to understand the method. A project was recently undertaken to calculate some aspects of the operation of gamma-ray backscatter density gauges. Some of the results of these calculations were arranged in such a way as to be capable of tabulation. This paper shows the distribution of radiation in the soil beneath a gauge; these were calculated by the Monte Carlo method. (Author's Summary).