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In-situ strength characteristics of soft clays
ABSTRACTS
101
The stress distribution was studied on soft paddy soil near the lugs of skeleton wheels, and the relationship between lug load and shape and soil conditions was examined mathematically. [N.LA.E.] 68. J. Maflsg. [Tyre sizes]. Landbouwmechanisatie, 1964, 15 (8) 817-820; illus. (Du.e.). Explanation of tyre construction and the meaning of the terms in common use to describe tyre sizes. [N.I.A.E.] 69. G . G . Meyedwf, "Shallow Foundations." J. Soil Mech. Foundations Divn, ASCE, Vol. 91, No. SM2, Proc. Paper 4271, March, 1965, pp. 21-31. A review of the design and performance of spread footin~ and rafts in relation to the prediction and control of settlement reveals that allowable bearing pressure for a given settlement of shallow foundations on sand and gravel, when estimated from standard or static cone penetration tests, are rather conservative. Based on the present analysis, the bearing pressures could safely be increased by 50 per cent, when the corresponding predicted settlements would vary from approximately 0"8 to 2 times the observed values. The allowable bearing pressures for shallow foundations on clay, when based on the sum of immediate and final consolidation settlements with an allowance for any lateral consolidation and the effects of shearing stresses, usually yield results of sufficient accuracy. More field observations are needed on the contact pressures and stresses in raft foundations to develop a rational method of their design. [A.S.C.E. Jonr. Soil Mech. Div.] 70. L Noormay and H. B. Seed. "In-Situ Strength Characteristics of Soft Clays." J. Soil Mech. Foundations Divn, ASCE, Vol. 91, No. SM2, Proc. Paper 4274, March, 1965, pp. 49--80. The change in effective stress condition resulting from sampling of saturated clays is examined. A link, in terms of Hvorslev strength parameters, ce and ~be, is established between the perfectly undisturbed sample strength and the in-situ strength. The theoretical analysis and the supporting experimental data indicate that for normally consolidated saturated sensitive clays, the in-situ strength and pore-pressure coefficient, AI, are significantly different from those measured on even perfectly undisturbed samples in unconsolidated-undrained triaxial compression tests. An expression is proposed for the evaluation of the in-situ strength of normally consolidated saturated clays in terms of the soil strength parameters, ce and 6e, and the pore-water pressure coefficient, Ap in-situ. [A.S.C.E. Jour. Soil Mech. Div.] 71. K . H . Norris. Design and development of a new moisture meter. Agric. Engng, St Joseph, Mich., 1964, 45 (7) 370-372; bibl. 4, illus. Data for the design of a moisture meter ware obtained by making absorption measurements with a recording spectrophotometer on wheat samples ground to < / z panicle size and saturated with carbon tetrachloride or anhydrous methanol to form a thin paste spread at a uniform 2 mm thickness. The zero moisture sample was oven dried for 2 h at 130oc. It was found that the meter should measure the difference in absorbence at two wavelengths in the near infra-red region, one of which should be 1-94 #, and transmittance values in the range 10-0"1 per cent, and should indicate the optical density difference between the two wavelengths. [N.LA.E.] 72. G . R . Quick. Tractor noise, vibration and jolt. Pwr Frog Aust. N.Z., 1965, 74 (2) 6-8, 85, 87; illus. Tractor vibrations are considered in relation to the dynamics of the body and the danger to health, and suspension seats described. The effect of noise on hearing is discussed, use of ear muffs advocated and an air-conditioned helmet described which also affords hearing protection. [N.I.A.E.] 73. K. Rehri. [The higher-powered tractor]. Prakt. Landteci~., 1964, 17 (17) 358-361; illus. (G.). The relationship between tractor h.p., tyre size and applications is indicated for tractors of ~> 30, ~> 50, 60-70 and > 70 h.p. [N.I.A.E.] 74. B. Sa~yanaraymm. "Earth Pressures for Bilinear Backfill Surface." Journal of the Soil Mechanics and Foundations Division, ASCE, Vol. 91, No. SMI, Proc. Paper 4209, January, 1965, pp. 99-110. An analytical investigation in the evaluation of earth pressures on a retaining wall with a straight back and with a bilinear surface for the backfill is presented. The solution is based on the Coulomb wedge theory. The solution, which includes an expression for the critical wedge angle as well as for the point of action of the earth pressure, is quicker and less tedious than available graphical methods. Several examples are presented to illustrate the solutions. [A.S.C.E. Jour. Soil Mech. Div.]
101
The stress distribution was studied on soft paddy soil near the lugs of skeleton wheels, and the relationship between lug load and shape and soil conditions was examined mathematically. [N.LA.E.] 68. J. Maflsg. [Tyre sizes]. Landbouwmechanisatie, 1964, 15 (8) 817-820; illus. (Du.e.). Explanation of tyre construction and the meaning of the terms in common use to describe tyre sizes. [N.I.A.E.] 69. G . G . Meyedwf, "Shallow Foundations." J. Soil Mech. Foundations Divn, ASCE, Vol. 91, No. SM2, Proc. Paper 4271, March, 1965, pp. 21-31. A review of the design and performance of spread footin~ and rafts in relation to the prediction and control of settlement reveals that allowable bearing pressure for a given settlement of shallow foundations on sand and gravel, when estimated from standard or static cone penetration tests, are rather conservative. Based on the present analysis, the bearing pressures could safely be increased by 50 per cent, when the corresponding predicted settlements would vary from approximately 0"8 to 2 times the observed values. The allowable bearing pressures for shallow foundations on clay, when based on the sum of immediate and final consolidation settlements with an allowance for any lateral consolidation and the effects of shearing stresses, usually yield results of sufficient accuracy. More field observations are needed on the contact pressures and stresses in raft foundations to develop a rational method of their design. [A.S.C.E. Jonr. Soil Mech. Div.] 70. L Noormay and H. B. Seed. "In-Situ Strength Characteristics of Soft Clays." J. Soil Mech. Foundations Divn, ASCE, Vol. 91, No. SM2, Proc. Paper 4274, March, 1965, pp. 49--80. The change in effective stress condition resulting from sampling of saturated clays is examined. A link, in terms of Hvorslev strength parameters, ce and ~be, is established between the perfectly undisturbed sample strength and the in-situ strength. The theoretical analysis and the supporting experimental data indicate that for normally consolidated saturated sensitive clays, the in-situ strength and pore-pressure coefficient, AI, are significantly different from those measured on even perfectly undisturbed samples in unconsolidated-undrained triaxial compression tests. An expression is proposed for the evaluation of the in-situ strength of normally consolidated saturated clays in terms of the soil strength parameters, ce and 6e, and the pore-water pressure coefficient, Ap in-situ. [A.S.C.E. Jour. Soil Mech. Div.] 71. K . H . Norris. Design and development of a new moisture meter. Agric. Engng, St Joseph, Mich., 1964, 45 (7) 370-372; bibl. 4, illus. Data for the design of a moisture meter ware obtained by making absorption measurements with a recording spectrophotometer on wheat samples ground to < / z panicle size and saturated with carbon tetrachloride or anhydrous methanol to form a thin paste spread at a uniform 2 mm thickness. The zero moisture sample was oven dried for 2 h at 130oc. It was found that the meter should measure the difference in absorbence at two wavelengths in the near infra-red region, one of which should be 1-94 #, and transmittance values in the range 10-0"1 per cent, and should indicate the optical density difference between the two wavelengths. [N.LA.E.] 72. G . R . Quick. Tractor noise, vibration and jolt. Pwr Frog Aust. N.Z., 1965, 74 (2) 6-8, 85, 87; illus. Tractor vibrations are considered in relation to the dynamics of the body and the danger to health, and suspension seats described. The effect of noise on hearing is discussed, use of ear muffs advocated and an air-conditioned helmet described which also affords hearing protection. [N.I.A.E.] 73. K. Rehri. [The higher-powered tractor]. Prakt. Landteci~., 1964, 17 (17) 358-361; illus. (G.). The relationship between tractor h.p., tyre size and applications is indicated for tractors of ~> 30, ~> 50, 60-70 and > 70 h.p. [N.I.A.E.] 74. B. Sa~yanaraymm. "Earth Pressures for Bilinear Backfill Surface." Journal of the Soil Mechanics and Foundations Division, ASCE, Vol. 91, No. SMI, Proc. Paper 4209, January, 1965, pp. 99-110. An analytical investigation in the evaluation of earth pressures on a retaining wall with a straight back and with a bilinear surface for the backfill is presented. The solution is based on the Coulomb wedge theory. The solution, which includes an expression for the critical wedge angle as well as for the point of action of the earth pressure, is quicker and less tedious than available graphical methods. Several examples are presented to illustrate the solutions. [A.S.C.E. Jour. Soil Mech. Div.]