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Studies of off-road vehicles in the riverine environment
ABSTRACTS
127
is an optimum gradation in terms of both high ultimate strength and high mobilized strength. Uniform coarse gravel is shown to have poor mobilized strength, but at confining pressures high enough to cause particle crushing the improvement in gradation and packing leads to a high ultimate strength, although large axial strains are necessarily induced. The optimum gradation is shown to be close to Fuller's curve for maximum density. The effect of increasing the confining pressure from 50 to 350 p.s.i. (3-52 to 24.61 kg/cm 2) leads to a decrease in 9 peak of 6 to 10', but modifications for dilatancy lead to q)~ parameters that are sensibly constant for any one material. (Author's summary.) 85.
D. Sloss, I. R. Ehrlich and G. Worden. Studies of off-road vehicles in the riverine environment. Vol. I1. Analytical method for egress evaluation. 67 pp. (Oct. 1969). A limited computer-simulation model describing the dynamics of a swimming vehicle egressing from a stream is formulated. The effects of soil reactions, hydrostatic forces, suspension and tire dynamics, and auxiliary egress assist forces are considered. Results of a parametric study are presented for a four-wheeled, box-shaped vehicle egressing on to a hard, uniformly sloped bank. Length, freeboard, center of gravity, suspension spring and damping rates, initial velocity, and bank coefficient are varied in the analysis. A correlation study, which validates the computer simulation model, is also described. Plots of normal wheel-loading versus distance up the bank, showing a comparison between the computer simulation and scale-model tests, are included. Recommendations for a comprehensive parametric study and a correlation study with fullscale vehicles are made. (U.S. Gov. Res. Dev. Rep., 25.1.70, AD-697160.)
86.
1. M. Smith. A finite element approach to elastic soil-structure interaction. Can. Geotech. J. 7 (2), 95 (1970). An application of the displacement finite element method to axisymmetric soil-structure interaction problems is described. Since the structure and foundation are analyzed as an entity, the distribution of contact pressure does not have to be assumed. The accuracy of the method is first assessed in the analysis of some simple problems to which other solutions exist. Then a series of laboratory results and one field case record, all involving flexible structures bearing on cohesionless foundations are analyzed, the foundations being treated as elastic but inhomogeneous. Both "Winkler" and elastic solid foundations are considered and it is shown that for the latter type physically reasonable distributions of the elastic modulus do not lead to very good predictions of the deflections of the structure although the deflections within the foundation itself are in agreement with observed values. (Author's summary.)
87.
R. N. Yong, R. D. Japp and S. J. Windish. Soil bin studies. 49 pp. (Sept. 1968). The object of the tudy was to provide input information for application of the visioplasticity method of analysis for soil-vehicle interaction. In addition soil fabric studies were performed to assess the feasibility of applications of energy methods of analysis. (U.S. Gov. Res. Dev. Rep., 10.12.69, AD-695363.)
88.
T. L. Youd. Densification and shear of sand during vibration. J. Soil Mech. Fndns Div. ASCE, 96 (SM3), 863-880 (May 1970). The shear strength reduction and density changes that occur in a confined mass of dry, uniformly graded, granular material subjected to horizontal steady-state vibration were quantitatively investigated by testing Ottawa sand and ~J6 in. steel balls in a direct shear apparatus mounted on a shaker table. The samples were first densified until a constant volume state was reached and then sheared while subjected to the same or a less intense vibration. It was found that the constant volume void ratio for samples densified and sheared under the same vibrational conditions; this value decreases with increased vibrational acceleration and is not dependent on frequency. Both the maximum and ultimate coefficients of internal friction decrease with increasing acceleration. Both the interlocking and frictional components of the coefficient are likewise reduced during vibration. An increase of normal pressure tends to counteract the vibrational effects listed above. The behavior noted in these and previous experiments can be exnlained by mechanisms involving energy barrier concepts. (Author's summary.)
These abstracts have been collected by Dr. T. Kurtay of the Department of Agricultural Engineering. The University of Newcastle upon Tyne. The following is a list of publications searched. (1) (2) (3)
British Technology Index, The Library Association, London. Monthly Summaries, Motor Industry Research Association, Lindley. Applied Mechanics Review, Am Soc. Mech. Eng0, New York.
127
is an optimum gradation in terms of both high ultimate strength and high mobilized strength. Uniform coarse gravel is shown to have poor mobilized strength, but at confining pressures high enough to cause particle crushing the improvement in gradation and packing leads to a high ultimate strength, although large axial strains are necessarily induced. The optimum gradation is shown to be close to Fuller's curve for maximum density. The effect of increasing the confining pressure from 50 to 350 p.s.i. (3-52 to 24.61 kg/cm 2) leads to a decrease in 9 peak of 6 to 10', but modifications for dilatancy lead to q)~ parameters that are sensibly constant for any one material. (Author's summary.) 85.
D. Sloss, I. R. Ehrlich and G. Worden. Studies of off-road vehicles in the riverine environment. Vol. I1. Analytical method for egress evaluation. 67 pp. (Oct. 1969). A limited computer-simulation model describing the dynamics of a swimming vehicle egressing from a stream is formulated. The effects of soil reactions, hydrostatic forces, suspension and tire dynamics, and auxiliary egress assist forces are considered. Results of a parametric study are presented for a four-wheeled, box-shaped vehicle egressing on to a hard, uniformly sloped bank. Length, freeboard, center of gravity, suspension spring and damping rates, initial velocity, and bank coefficient are varied in the analysis. A correlation study, which validates the computer simulation model, is also described. Plots of normal wheel-loading versus distance up the bank, showing a comparison between the computer simulation and scale-model tests, are included. Recommendations for a comprehensive parametric study and a correlation study with fullscale vehicles are made. (U.S. Gov. Res. Dev. Rep., 25.1.70, AD-697160.)
86.
1. M. Smith. A finite element approach to elastic soil-structure interaction. Can. Geotech. J. 7 (2), 95 (1970). An application of the displacement finite element method to axisymmetric soil-structure interaction problems is described. Since the structure and foundation are analyzed as an entity, the distribution of contact pressure does not have to be assumed. The accuracy of the method is first assessed in the analysis of some simple problems to which other solutions exist. Then a series of laboratory results and one field case record, all involving flexible structures bearing on cohesionless foundations are analyzed, the foundations being treated as elastic but inhomogeneous. Both "Winkler" and elastic solid foundations are considered and it is shown that for the latter type physically reasonable distributions of the elastic modulus do not lead to very good predictions of the deflections of the structure although the deflections within the foundation itself are in agreement with observed values. (Author's summary.)
87.
R. N. Yong, R. D. Japp and S. J. Windish. Soil bin studies. 49 pp. (Sept. 1968). The object of the tudy was to provide input information for application of the visioplasticity method of analysis for soil-vehicle interaction. In addition soil fabric studies were performed to assess the feasibility of applications of energy methods of analysis. (U.S. Gov. Res. Dev. Rep., 10.12.69, AD-695363.)
88.
T. L. Youd. Densification and shear of sand during vibration. J. Soil Mech. Fndns Div. ASCE, 96 (SM3), 863-880 (May 1970). The shear strength reduction and density changes that occur in a confined mass of dry, uniformly graded, granular material subjected to horizontal steady-state vibration were quantitatively investigated by testing Ottawa sand and ~J6 in. steel balls in a direct shear apparatus mounted on a shaker table. The samples were first densified until a constant volume state was reached and then sheared while subjected to the same or a less intense vibration. It was found that the constant volume void ratio for samples densified and sheared under the same vibrational conditions; this value decreases with increased vibrational acceleration and is not dependent on frequency. Both the maximum and ultimate coefficients of internal friction decrease with increasing acceleration. Both the interlocking and frictional components of the coefficient are likewise reduced during vibration. An increase of normal pressure tends to counteract the vibrational effects listed above. The behavior noted in these and previous experiments can be exnlained by mechanisms involving energy barrier concepts. (Author's summary.)
These abstracts have been collected by Dr. T. Kurtay of the Department of Agricultural Engineering. The University of Newcastle upon Tyne. The following is a list of publications searched. (1) (2) (3)
British Technology Index, The Library Association, London. Monthly Summaries, Motor Industry Research Association, Lindley. Applied Mechanics Review, Am Soc. Mech. Eng0, New York.