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Settlements of bearing plate on collapsible loessial soil
PROPERTIES:DEFORMATION A new version of a hypoplastic constitutive equation is presented which is characterized by the introduction of a stress-like internal parameter called back stress. The back stress is a function of the void ratio and of the hydrostatic stress. Using a unique set of material constants, the new constitutive equation describes many aspects of the behaviour of cohesionless soils including the influence of density and stress level. (from Authors) 963112 Strain localization in extension tests on gramdar materials J. A. Yamamuro & P. V. Lade, Journal of Engineering Mechanics - AXE, 121(7), 1995, pp 828-836. An experimental study on granular materials in triaxial extension at confinine oressures from 0.25 to 68 MPa is presented. Drained &d undrained tests were performed utilizing cylindrical specimens. Strain localization was repeatedly encountered in the form of specimen necking. The cause of the strain localization was determined to be the inherent instability in the axisymmetric extension test, which allows stresses, and therefore deformations, to concentrate at the weakest part of the specimen. A method was developed to enforce uniform strains in triaxial extension tests on cylindrical specimens by the use of small metal plates separated by lubricated latex membranes. (from Authors) 963113 A theory for granular flow accommodated by material transfer via an intergranular fluid M. S. Paterson, Tectonophysics, 245(3-4), 1995, pp 135-151. A new model has been developed for the deformation of granular material based on a mechanism of relative movement of grains (granular flow) controlled by the rate of solution transfer involved in accommodating intergranular interferences. Using an analogy with particulate flow in soil mechanics to derive a flow equation for constant-volume flow and combining this with calculation of the rate of porosity reduction, general flow laws are derived for axisymmetric non-hydrostatic conditions. Application to the cases of quartz and rocksalt porous aggregates, with water as the pore fluid, suggest that, under geological conditions, source/sink diffusion control will tend to predominate where granular flow occurs. (from Author) 963114 Effects of sampling on tbe undrained behavionr of clayey sands
& STRENGTH
vertical loading increased with both overconsolidation and cement content. (from Authors)
115A ratio
963116 Cone penetration in very weakly cemented sand A. J. Puppala & M. T. Tumay, Journal of Geotechnical Engineering - ASCE, 121(8), 1995, pp 589-600. Cone penetration testing in very weakly cemented sands with unconfined compressive strengths of 60 kPa or less is investigated in a calibration chamber. Monterey O/30 sand is artificially cemented with 1% and 2% portland cement. The tip resistance and the sleeve friction are both found to increase with cementation. The friction ratio is found to be indifferent to the increase in cementation at very weak cementation levels and vertical effective stresses of SO-300kPa. (from Authors) 963117 Stress-strain modeling of sands using artificial neural networks G. W. Willis, C. Yao, R. Zhao & D. Penumadu, Journul of Geotechnical Engineering - ASCE, 121(5), 1995, pp 429-435. The investigation confirmed that a sequential ANN with feedback is more effective than a conventional ANN without feedback, to simulate the soil stress-strain relationship. The study shows that there is potential to develop a general ANN model that accounts for particle size distribution and stress history effects. The work also demonstrates the ability of neural networks to simulate unload-reload loops of the soil stress-strain characteristics. (from Authors) 963118 Settlements of bearing plate on collapsible loessial soils Y. M. Reznik, Environmental & Engineering Geoscience, l(2), 1995, pp 153-162. Presents results of collapsible loessial soil testing with 5000cm’-area around rigid plates. All field load tests were performed within a relatively small and uniform area in southwestern Ukraine. Results of more than 140 tests performed at depths of 1.8 to 9.0 m were analysed. The analytical expression for plate settlements has been presented as a function of an applied load, mechanical properties of tested soil, a thickness of a deformation zone and plate dimensions. The validity of empirical coefficients obtained as a result of performed analyses has been verified. (from Author)
D. W. Hight & V. N. Georgiannou, Geotechnique, 45(2), 1995, pp 237-247. The effects of tube sampling of normally consolidated clayey sands are examined. Triaxial strain path tests, which follow the sequence of strains imposed by a sampling tube on elements on its centre line, are described. Major reductions in effective stress are shown to occur as a result of sampling. Reconsolidation to in situ stresses causes significant reductions in granular void ratio and these, together with fabric changes, modify the behaviour of the sample from that of the in situ soil: undrained brittleness and the effects of ageing in situ may be eliminated. A framework for the behaviour of clayey sands is used to explain the response to sampling and reconsolidation. (from Authors)
963119 Shear resistance of fissured Neogene clays J. Feda, J. Bohac & I. Herle, Engineering Geology, 39(3-4), 1995, pp 171-184. Two types of fissured Neogene clays (SM and WB) were tested in the laboratory using undisturbed and reconstituted specimens. SM clays were deposited in a marine environment, WB are lacustrine clays with a complex tectonic history. Although the behaviour is similar, the origin of fissures is different. For the SM clays, weathering is the main cause and fissuring reaches a depth of about 20 m. WB clays are dissected by macro- and microfissures originating as the result of tectonic processes and volumetric changes (effect of the coal formation underneath the investigated massif). (from Authors)
963115 Factors affecting at-rest lateral stress in artificially cemented sands Fanyu Zhu, J. I. Clark & M. J. Paulin, Canadian Geotechnical Journal, 32(2), 1995, pp 195-203. Test results indicated that the at-rest lateral stress in cemented sands decreases significantly with increasing cement content; the relationship between the vertical and at-rest lateral stress is nonlinear and the value of & increases with increasing vertical stress; and the lateral stress decreases with sand density and curing period. When the specimens were cured under vertical stress, the value of KO during the removal of
963120 Undrained plastic modulus from original Cam clay P. W. Mayne, Journal of Geotechnical Engineering - AXE, 121(5), 1995, pp 448-451. One aspect of the original Cam-clay model is that the derived undrained stress-strain curve can be expressed in closed form and used to determine a finite value of stiffness at E = 0 that is equivalent to an undrained plastic modulus (or E,,) for normally consolidated clays. With respect to soil behavior, this predicted modulus will no way represent the initial modulus E,,,, that is fundamental and obtained from resonant column tests at small-strain levels, but interestingly
& STRENGTH
vertical loading increased with both overconsolidation and cement content. (from Authors)
115A ratio
963116 Cone penetration in very weakly cemented sand A. J. Puppala & M. T. Tumay, Journal of Geotechnical Engineering - ASCE, 121(8), 1995, pp 589-600. Cone penetration testing in very weakly cemented sands with unconfined compressive strengths of 60 kPa or less is investigated in a calibration chamber. Monterey O/30 sand is artificially cemented with 1% and 2% portland cement. The tip resistance and the sleeve friction are both found to increase with cementation. The friction ratio is found to be indifferent to the increase in cementation at very weak cementation levels and vertical effective stresses of SO-300kPa. (from Authors) 963117 Stress-strain modeling of sands using artificial neural networks G. W. Willis, C. Yao, R. Zhao & D. Penumadu, Journul of Geotechnical Engineering - ASCE, 121(5), 1995, pp 429-435. The investigation confirmed that a sequential ANN with feedback is more effective than a conventional ANN without feedback, to simulate the soil stress-strain relationship. The study shows that there is potential to develop a general ANN model that accounts for particle size distribution and stress history effects. The work also demonstrates the ability of neural networks to simulate unload-reload loops of the soil stress-strain characteristics. (from Authors) 963118 Settlements of bearing plate on collapsible loessial soils Y. M. Reznik, Environmental & Engineering Geoscience, l(2), 1995, pp 153-162. Presents results of collapsible loessial soil testing with 5000cm’-area around rigid plates. All field load tests were performed within a relatively small and uniform area in southwestern Ukraine. Results of more than 140 tests performed at depths of 1.8 to 9.0 m were analysed. The analytical expression for plate settlements has been presented as a function of an applied load, mechanical properties of tested soil, a thickness of a deformation zone and plate dimensions. The validity of empirical coefficients obtained as a result of performed analyses has been verified. (from Author)
D. W. Hight & V. N. Georgiannou, Geotechnique, 45(2), 1995, pp 237-247. The effects of tube sampling of normally consolidated clayey sands are examined. Triaxial strain path tests, which follow the sequence of strains imposed by a sampling tube on elements on its centre line, are described. Major reductions in effective stress are shown to occur as a result of sampling. Reconsolidation to in situ stresses causes significant reductions in granular void ratio and these, together with fabric changes, modify the behaviour of the sample from that of the in situ soil: undrained brittleness and the effects of ageing in situ may be eliminated. A framework for the behaviour of clayey sands is used to explain the response to sampling and reconsolidation. (from Authors)
963119 Shear resistance of fissured Neogene clays J. Feda, J. Bohac & I. Herle, Engineering Geology, 39(3-4), 1995, pp 171-184. Two types of fissured Neogene clays (SM and WB) were tested in the laboratory using undisturbed and reconstituted specimens. SM clays were deposited in a marine environment, WB are lacustrine clays with a complex tectonic history. Although the behaviour is similar, the origin of fissures is different. For the SM clays, weathering is the main cause and fissuring reaches a depth of about 20 m. WB clays are dissected by macro- and microfissures originating as the result of tectonic processes and volumetric changes (effect of the coal formation underneath the investigated massif). (from Authors)
963115 Factors affecting at-rest lateral stress in artificially cemented sands Fanyu Zhu, J. I. Clark & M. J. Paulin, Canadian Geotechnical Journal, 32(2), 1995, pp 195-203. Test results indicated that the at-rest lateral stress in cemented sands decreases significantly with increasing cement content; the relationship between the vertical and at-rest lateral stress is nonlinear and the value of & increases with increasing vertical stress; and the lateral stress decreases with sand density and curing period. When the specimens were cured under vertical stress, the value of KO during the removal of
963120 Undrained plastic modulus from original Cam clay P. W. Mayne, Journal of Geotechnical Engineering - AXE, 121(5), 1995, pp 448-451. One aspect of the original Cam-clay model is that the derived undrained stress-strain curve can be expressed in closed form and used to determine a finite value of stiffness at E = 0 that is equivalent to an undrained plastic modulus (or E,,) for normally consolidated clays. With respect to soil behavior, this predicted modulus will no way represent the initial modulus E,,,, that is fundamental and obtained from resonant column tests at small-strain levels, but interestingly