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Instability of loose saturated sands under monotonic loading
229A 866125 Effect of the extent of freezing on seismic velocities in unconsolidated permafrost Zimmerman. R xA; King, M S Geophysics 151..\6. June 1986. P1285-1290
866128 Study of elastic wave velocities in dry and water-saturated, regularly-jointed rock masses. Technical note Yang, H J P King. M S int J Rock Mech Min Sci V23..V3, June 1986, P277-280
A model is de',eloped to relate velocities of seismic waves in unconsolidated permafrost to the porosity and the extent of freezing. The theory of Kuster and Toksoz, based on wave scattering considerations, is used to determine the effective elastic moduli, and hence the wave speeds, The HashinShtrikman theoretical bounds on the elastic moduli of heterogeneous materials and other considerations establish the plausibility of the model. The theory is applied to laboratory measurements of shear- and compressional-wave velocities in 23 permafrost samples from different sites in the Beaufort Sea, Mackenzie Ri',er Valley, and Canadian Arctic Islands. Data are consistent with predictions of the model. It can be used to predict the extent of freezing of the water in the pore spaces. based on knowledge of the porosity and either of the two wave speeds.
A theoretical study of the elastic properties of a regularly jointed rock mass in the dry and water saturated states is presented. The model predicts P and S wave velocities to be dependent on the intrinsic elastic properties and bulk density of the rock mass and a dimensionless parameter, R. the product of the number of contacts per unit area on each plane of discontinuity, the average diameter of these contacts, and the spacing between planes of discontinuity. The model can be extended to anisotropic rock masses, with different values of R in each direction.
866126 Effect of boundary conditions upon centrifuge experiments using ground motion simulation Whitman, R V; Lambe, P C Geotech Te,~t J ['9, N2, June I9S6. P61-71 Thc eft'cots of the soil container walls and bases on stresses and strains in testing are a potentially serious problem. Centrifuge tests ~,,ere carried out on soils confined by series of stacked rings and by a rigid box. Overall, the stacked rings performed satisl\~ctorily, although almost certainly they did not I\)llow the exact movement of the soil. There is evidence of deviation from the condition of simple shear and arching. A few results using thc rigid box arc presented. It appears that even distant ~alls influence results when observing liquefaction phenomena.
866127 Comparison of transmitting boundaries in dynamic finite element analyses using explicit time integration. Short communication Simons, H A: Randolph, N1 F lnt J .~'um Anal 31eth Geomech t'lO, N3. Mat'-June 1986. P329-342 Explicit time integration schemes provide an efficient solution to non-linear d,,namic finite element analyses of geotechnical problems especially when high frequency response is i m p o f tant. Such schemes require one of two distinct transmitting boundary formulations to overcome the problem of radiation damping. These are the superposition boundary approach, which involves the cancellation of the reflected waves by combining the solutions of two different boundary conditions, and the viscous boundary approach, which involves the absorption of incident ,aa~e energy by frequency independent viscous dashpots. The theoretical justification of these two approaches and their means of implementation are reviewed. The solutions obtained using the two different boundary approaches to the problem of a rigid massless circular footing vibrating on an elastic half space are compared with an independent theoretical solution. The pcrformance of the boundaries for problems invol',ing step loading is also examined and the implications for any loading pattern with a non-zero time average are discussed. ,Auth.
866 ! 29 Dynamic compaction in friable loess. Technical note Lutenegger, A J J Geotech Engng Div ASCE VII2. N6. June 1986. P663-667 The results of a limited investigation to evah, ate the effect of dynamic compaction on the geotechnical properties of a collapsible loess from a test site located in the thick loess upland in Russe, Bulgaria, are reported. Results indicate that the collapse potential in the most stressed zone undcr a proposed shallow foundation muy be significantly reduced by dynamic compaction. This occurs through a breakdown of the natural soil structure, resulting in increased density. In addition, an increase in stillness of the material at constant moisture content is prodt,ced, as indicated by dynamic cone, Flat Dilatometcr, and prcsst, remetcr test results.
866130 Soil liquefaction evaluations by elastic shear moduli Tokimatsu, K: Yamazuki, T: Yoshimi, Y Soils Found V26. NI, Alurch 1986. P25-35 Cyclic triaxial tests on sands with different densities and stress histories show the elastic shear modulus can reflect soil fabric, relative density, stress strain and overconsolidation history effects, all of which can have significant effect on the liquefaction of sand. In addition, a ret,sonable correlation is seen between liquefaction and shear modulus for a given soil under given confining pressure. The effects of sampling disturbance on the laboratory measured value of shear modulus and methods of creating in situ conditions for laboratory testing are examined.
866131 Instability of loose saturated sands under monotonic loading Peters, J F Proc 5th Engineering Mechanics Division Speciality Conference, l~roming, I-3 Aug 1984 V2, P945-94& Publ New York: ASCE. 1984 Loosely deposited sands may. when loaded, reach a point of instability at which they undergo virtually instantaneous liquefaction. An analysis is presented of the incremental strain response of sand to undrained loading using the theory for strain hardening elastoplastic materials. It is shown that this theory is suitable for modelling instability under drained loading, provided the analysis is performed in terms of effective stress and the non-associated flow rule is used.
(i' 1986 Pergamon Journals Ltd. Reproduction not permitted
866128 Study of elastic wave velocities in dry and water-saturated, regularly-jointed rock masses. Technical note Yang, H J P King. M S int J Rock Mech Min Sci V23..V3, June 1986, P277-280
A model is de',eloped to relate velocities of seismic waves in unconsolidated permafrost to the porosity and the extent of freezing. The theory of Kuster and Toksoz, based on wave scattering considerations, is used to determine the effective elastic moduli, and hence the wave speeds, The HashinShtrikman theoretical bounds on the elastic moduli of heterogeneous materials and other considerations establish the plausibility of the model. The theory is applied to laboratory measurements of shear- and compressional-wave velocities in 23 permafrost samples from different sites in the Beaufort Sea, Mackenzie Ri',er Valley, and Canadian Arctic Islands. Data are consistent with predictions of the model. It can be used to predict the extent of freezing of the water in the pore spaces. based on knowledge of the porosity and either of the two wave speeds.
A theoretical study of the elastic properties of a regularly jointed rock mass in the dry and water saturated states is presented. The model predicts P and S wave velocities to be dependent on the intrinsic elastic properties and bulk density of the rock mass and a dimensionless parameter, R. the product of the number of contacts per unit area on each plane of discontinuity, the average diameter of these contacts, and the spacing between planes of discontinuity. The model can be extended to anisotropic rock masses, with different values of R in each direction.
866126 Effect of boundary conditions upon centrifuge experiments using ground motion simulation Whitman, R V; Lambe, P C Geotech Te,~t J ['9, N2, June I9S6. P61-71 Thc eft'cots of the soil container walls and bases on stresses and strains in testing are a potentially serious problem. Centrifuge tests ~,,ere carried out on soils confined by series of stacked rings and by a rigid box. Overall, the stacked rings performed satisl\~ctorily, although almost certainly they did not I\)llow the exact movement of the soil. There is evidence of deviation from the condition of simple shear and arching. A few results using thc rigid box arc presented. It appears that even distant ~alls influence results when observing liquefaction phenomena.
866127 Comparison of transmitting boundaries in dynamic finite element analyses using explicit time integration. Short communication Simons, H A: Randolph, N1 F lnt J .~'um Anal 31eth Geomech t'lO, N3. Mat'-June 1986. P329-342 Explicit time integration schemes provide an efficient solution to non-linear d,,namic finite element analyses of geotechnical problems especially when high frequency response is i m p o f tant. Such schemes require one of two distinct transmitting boundary formulations to overcome the problem of radiation damping. These are the superposition boundary approach, which involves the cancellation of the reflected waves by combining the solutions of two different boundary conditions, and the viscous boundary approach, which involves the absorption of incident ,aa~e energy by frequency independent viscous dashpots. The theoretical justification of these two approaches and their means of implementation are reviewed. The solutions obtained using the two different boundary approaches to the problem of a rigid massless circular footing vibrating on an elastic half space are compared with an independent theoretical solution. The pcrformance of the boundaries for problems invol',ing step loading is also examined and the implications for any loading pattern with a non-zero time average are discussed. ,Auth.
866 ! 29 Dynamic compaction in friable loess. Technical note Lutenegger, A J J Geotech Engng Div ASCE VII2. N6. June 1986. P663-667 The results of a limited investigation to evah, ate the effect of dynamic compaction on the geotechnical properties of a collapsible loess from a test site located in the thick loess upland in Russe, Bulgaria, are reported. Results indicate that the collapse potential in the most stressed zone undcr a proposed shallow foundation muy be significantly reduced by dynamic compaction. This occurs through a breakdown of the natural soil structure, resulting in increased density. In addition, an increase in stillness of the material at constant moisture content is prodt,ced, as indicated by dynamic cone, Flat Dilatometcr, and prcsst, remetcr test results.
866130 Soil liquefaction evaluations by elastic shear moduli Tokimatsu, K: Yamazuki, T: Yoshimi, Y Soils Found V26. NI, Alurch 1986. P25-35 Cyclic triaxial tests on sands with different densities and stress histories show the elastic shear modulus can reflect soil fabric, relative density, stress strain and overconsolidation history effects, all of which can have significant effect on the liquefaction of sand. In addition, a ret,sonable correlation is seen between liquefaction and shear modulus for a given soil under given confining pressure. The effects of sampling disturbance on the laboratory measured value of shear modulus and methods of creating in situ conditions for laboratory testing are examined.
866131 Instability of loose saturated sands under monotonic loading Peters, J F Proc 5th Engineering Mechanics Division Speciality Conference, l~roming, I-3 Aug 1984 V2, P945-94& Publ New York: ASCE. 1984 Loosely deposited sands may. when loaded, reach a point of instability at which they undergo virtually instantaneous liquefaction. An analysis is presented of the incremental strain response of sand to undrained loading using the theory for strain hardening elastoplastic materials. It is shown that this theory is suitable for modelling instability under drained loading, provided the analysis is performed in terms of effective stress and the non-associated flow rule is used.
(i' 1986 Pergamon Journals Ltd. Reproduction not permitted