- Email: [email protected]
Sliding friction of soil over metal and plastic surfaces
ABSTRACTS
93
derived to fit the data. The creep stress is also normalized in terms of unconfined compressive strength to account for variations between specimens. Application of creep compliance covered in the paper is limited to a specific type of soil creep test. General value and methods of application are not covered. (Applied Mechanics Review) 59. V. N. godanaa. Reduction of low-frequency vibrations transmitted to the tractor driver. Trakt. Selkhozmash., 1965, 35 (4) 3-6; bibl. 5, illus. (R.) In a theoretical appreciation of the effect of tractor seat suspension on the vibrations transmitted to the driver, equations are developed for calculating the frequency coefficient (natural frequency of tractor and of driver), the kinematic factor (the movement of the sprung part of the seat and its effect on the comfort of the driver) and the coefficient of absorption (static and dynamic deflection of seat suspension). The design of an experimental seat, embodying torsion bar suspension and hydraulic shock absorber, is outlined and the superiority of this seat over production models demonstrated in tests in which vibration accelerations were measured on the body of the driver during the passage of the tractor over a single obstacle and over a series of obstacles spaced at 1200 mm intervals. (N.I.A.E.) 60. R. J. Kxizek and R. L. Kondner. Use of a miniature specimen in compression tests of cohesive soils. Proc. Amer. Soc. Test. Mater. 64, 944-957, 1964. Unconfined compression tests were run on 80 cylindrical specimens with various combinations of 1-9-8-2 crn length and 0-8-3.6 cm diameter. Strain at 2-6 ~o per minute was applied to extruded clay (about 90 % saturated) with moisture content ranging from the shrinkage limit to near the liquid limit. All Stress-strain curves had a similar hyperbolic shape with no consistent effect of moisture or sample geometry. Uncontrolled variation in compressive strength was greater than the effect of sample geometry. Advantages of miniature samples for dynamic tests were outlined and illustrated. (Applied Mechanics Review) 61. A. C. Meigh and B. O. Skipp. Gamma-ray and neutron methods of measuring soil density and moisture. Gdotechnique 1960, 10 (3) 110-126; bibl. 24, illus. The methods are reviewed, the theory outlined and the performance of a gamma probe, a surface density unit and a combination of the two discussed. Laboratory studies of a neutron scatter moisture measuring system and a transistorized unit which combines a moisture and density measuring system for use in surface compaction control, are given. (N.I.A.E.) 62. G. G. Meyerlmf. Shallow foundations. Proc. Amer. Soc. Civil Eng,rs. 91, SM 2 (J. Soil Mech. Found. Div.) (Part 1), 21-31, Mar. 1965. The paper deals with spread footings and rafts on various soil type~. Based on several studies performed by other investigators, author states that, for foundations placed on coarse-grained soils, the allowable bearing pressures deduced from static or standard penetration tests are rather conservative. The actual settlements are also 1-2 to 2.5 times smaller than the predicted ones. For foundations on clays, the values are much closer; the ratio varies from 0.8-1-4 with an average of 1.2. Some consideration is given to contact pressures and to the influence of raft stiffness and soil compressibility on bending stresses. Author's opinion is that bearing pressures on sand and gravel could safely be increased by 50~o in comparison with those predicted by penetration tests; for clays, the currently used calculation methods give satisfactory results. (Applied Mechanics Review) 63. P. E. Nikiforov and M. I. Bredun. Sliding friction of soil over metal and plastic surfaces. Vest. sel.-khoz. Nauki, Mosk., 1965, 10 (7) 112-116; illus. (R.e.g.fr.) In experiments on clayey loam chernozem with tools of steel (rough and polished), electrically boronized steel and steel coated with caprone, polyamide resin, polyethylene and polyfluoroethylene resin, soil adhesion increased with m.c. up to 30--35%, was greatest for unpolished steel and least for plastics and increased linearly with specific applied pressure. At a sliding velocity of 0-5 m/s and specific applied pressures of 0.05-0-25 kg/cm e resistance to sliding decreased parabolically with the increase in velocity. The theory is expounded. (N.I.A.E.) 64. J. V. Parcher and P. -C. Liu. Some swelling characteristics of compacted clays. Proc. Amer. Soc. Civil Engrs. 91, SM 3 (J. SoiI Mech. Found. Die.) (Part I), 1-17, May 1965. Laboratory swelling tests of compacted and undisturbed clay specimens have been accomplished using an apparatus that permits vertical and horizontal swelling to be measured inde-
93
derived to fit the data. The creep stress is also normalized in terms of unconfined compressive strength to account for variations between specimens. Application of creep compliance covered in the paper is limited to a specific type of soil creep test. General value and methods of application are not covered. (Applied Mechanics Review) 59. V. N. godanaa. Reduction of low-frequency vibrations transmitted to the tractor driver. Trakt. Selkhozmash., 1965, 35 (4) 3-6; bibl. 5, illus. (R.) In a theoretical appreciation of the effect of tractor seat suspension on the vibrations transmitted to the driver, equations are developed for calculating the frequency coefficient (natural frequency of tractor and of driver), the kinematic factor (the movement of the sprung part of the seat and its effect on the comfort of the driver) and the coefficient of absorption (static and dynamic deflection of seat suspension). The design of an experimental seat, embodying torsion bar suspension and hydraulic shock absorber, is outlined and the superiority of this seat over production models demonstrated in tests in which vibration accelerations were measured on the body of the driver during the passage of the tractor over a single obstacle and over a series of obstacles spaced at 1200 mm intervals. (N.I.A.E.) 60. R. J. Kxizek and R. L. Kondner. Use of a miniature specimen in compression tests of cohesive soils. Proc. Amer. Soc. Test. Mater. 64, 944-957, 1964. Unconfined compression tests were run on 80 cylindrical specimens with various combinations of 1-9-8-2 crn length and 0-8-3.6 cm diameter. Strain at 2-6 ~o per minute was applied to extruded clay (about 90 % saturated) with moisture content ranging from the shrinkage limit to near the liquid limit. All Stress-strain curves had a similar hyperbolic shape with no consistent effect of moisture or sample geometry. Uncontrolled variation in compressive strength was greater than the effect of sample geometry. Advantages of miniature samples for dynamic tests were outlined and illustrated. (Applied Mechanics Review) 61. A. C. Meigh and B. O. Skipp. Gamma-ray and neutron methods of measuring soil density and moisture. Gdotechnique 1960, 10 (3) 110-126; bibl. 24, illus. The methods are reviewed, the theory outlined and the performance of a gamma probe, a surface density unit and a combination of the two discussed. Laboratory studies of a neutron scatter moisture measuring system and a transistorized unit which combines a moisture and density measuring system for use in surface compaction control, are given. (N.I.A.E.) 62. G. G. Meyerlmf. Shallow foundations. Proc. Amer. Soc. Civil Eng,rs. 91, SM 2 (J. Soil Mech. Found. Div.) (Part 1), 21-31, Mar. 1965. The paper deals with spread footings and rafts on various soil type~. Based on several studies performed by other investigators, author states that, for foundations placed on coarse-grained soils, the allowable bearing pressures deduced from static or standard penetration tests are rather conservative. The actual settlements are also 1-2 to 2.5 times smaller than the predicted ones. For foundations on clays, the values are much closer; the ratio varies from 0.8-1-4 with an average of 1.2. Some consideration is given to contact pressures and to the influence of raft stiffness and soil compressibility on bending stresses. Author's opinion is that bearing pressures on sand and gravel could safely be increased by 50~o in comparison with those predicted by penetration tests; for clays, the currently used calculation methods give satisfactory results. (Applied Mechanics Review) 63. P. E. Nikiforov and M. I. Bredun. Sliding friction of soil over metal and plastic surfaces. Vest. sel.-khoz. Nauki, Mosk., 1965, 10 (7) 112-116; illus. (R.e.g.fr.) In experiments on clayey loam chernozem with tools of steel (rough and polished), electrically boronized steel and steel coated with caprone, polyamide resin, polyethylene and polyfluoroethylene resin, soil adhesion increased with m.c. up to 30--35%, was greatest for unpolished steel and least for plastics and increased linearly with specific applied pressure. At a sliding velocity of 0-5 m/s and specific applied pressures of 0.05-0-25 kg/cm e resistance to sliding decreased parabolically with the increase in velocity. The theory is expounded. (N.I.A.E.) 64. J. V. Parcher and P. -C. Liu. Some swelling characteristics of compacted clays. Proc. Amer. Soc. Civil Engrs. 91, SM 3 (J. SoiI Mech. Found. Die.) (Part I), 1-17, May 1965. Laboratory swelling tests of compacted and undisturbed clay specimens have been accomplished using an apparatus that permits vertical and horizontal swelling to be measured inde-