Double-yield-surface model II: implementation and verification

98A results reasonably well. The former is simpler and acceptable at small displacements, the latter preferred when displacement is large. 912280 Constitutive model for cyclic behaviour of interfaces with variable dilatancy Aubry, D; Modaressi, A; Modaressi, H Comput Geoteeh V9, NI/2, 1990, P47-58 A cyclic interface constitutive model is presented, which has been developed from a variable dilatancy, elastoplastic body constitutive law. Stick, slip, debonding, and rebonding at the interface are modelled using a cyclic loading function with a memory of the last loading cycle. The model is developed using effective stress vectors, and is thus especially suitable for analysis of pore pressure influences. 912281 Numerical modellisation of contact with friction phenomena by the finite element method Charlier. R; Habraken, A M Comput Geotech vg, NI/2, 1990, P59-72 A finite element to model contact with friction in two dimensional, axisymmetrical, and three dimensional cases is presented. It can accommodate large strains, large displacements, and large rotations and is suitable for use in large strain soil mechanics problems such as piling. Interface behaviour is based on a penalty method and the Coulomb dry friction law. The element is illustrated within the finite element code LANGAMINE. 912282 Numerical simulation of penetration in sand based on FEM Sikora, Z: Gudehus. G Comput Geotech vg, NI/2, 1990, P73-86 Penetration resistance and the stress and strain state around the penetrating rod are estimated using finite element analysis. The Kolymbas constitutive model is used for the soil. The boundary problem for static penetration is first formulated, and the unknown stress state on the penetrator surface determined using an iterative method. Numerical problems due to time integration and convergence criteria for incrementally nonlinear constitutive laws are discussed. The influence of friction coefficient on penetration resistance is evaluated. 912283 Localisation in the presence of excess porewater pressure Shuttle. D A: Smith. 1 M Comput Geotech V9, NI/2, 1990, P87-99 Strain Iocalisation (shear banding) of soils under plane strain conditions has been modelled. Two different constitutive models were applied for drained loading. The Mohr-Coulomb model is adequate to describe behaviour, but the results are different to those obtained using the Monot double hardening law. The latter only was applied to undrained loading. The deformation pattern is seen to be strongly influenced by the dilatanc) or contractancy of the soil model used. 912284 Three-dimensional discrete element method for granular materials Ghaboussi, J: Barbosa. R Int J Num Anal Aleth Geomech VI4, N7, Sept-Oct 1990. P451 -472 A three dimensional DEM analysis is presented for granular materials, which are modelled as 6-sided rigid solids with 6 degrees of freedom. Corner to face. edge to face. edge to edge, (

and face to face contacts are considered. The computational scheme is outlined, with techniques for contact determination and the data structure addressed. Applications to chute flow. muck flow in a fast TBM, and particle pouring simulation are presented and discussed. 912285 Shear stress-strain curve generation from simple material parameters. Technical note Prevost, J H; Keane, C M J Geoteeh Engng Div ASCE V116, NS. Aug 1990, P12551263 The commonly used hyperbolic stress strain relation, although easily fitted to initial conditions, does not accurately model behaviour through to failure. A modified hyperbolic function is proposed, which includes a power term. This offers greater versatility and accuracy in modelling shear constitutive behaviour at high and low strains in both monotonic and cyclic loading. 9 i 2286 Double-yield-surface Cam-clay plasticity model, i: theory Hsieh, H S; Kavazanjian, E; Borja, R I J Geotech Engng Div ASCE VII6, N9, Sept 1990, PI3811401 An extended Cam-clay model incorporating time dependent effects is developed. Immediate and delayed components of total strain are evaluated. The former is found by applying the non-associative flow rule on two distinct yield surfaces, defined by the ellipsoid of the modified Cam-clay model and the Von Mises cylinder incribed within the ellipsoid. Time dependent strain is computed by employing the normality rule on the equivalent ellipsoidal and cylindrical yield surfaces associated with the current stress state, and compelling the resultant creep rate tensor to satisfy phenomcnological creep laws. 912287 Double-yield-surface model !I: implementation and verification Borja, R I; Hsieh, H S; Kavazanjian. E J Geotech Engng Div ASCE VII6, Ng, Sept 1990, P14021421 A previously developed double yield surface time dependent constitutive model (ibid, V116. PI381-140t)is used in a nonlinear finite element program based on Blot's three dimensional consolidation theory. Coupled soil deformation-fluid flow with creep effects is modelled. Parametric. laboratory. and field case studies have been used to validate the model. Numerical simulations include drained, undrained, consolidation, creep, and relaxation tests under triaxial and plane strain conditions. The new constitutive model describes behaviour of wet clays better than the earlier, single yield surface model. 9 ! 2288 Constitutive relations for sand under cyclic loading based on elasto-plasticity theory Nishi. K; Kanatani, M Soils Found V30. N2. June 1990. P43-59 Constitutive relations for sand under earthquake loading are proposed. They are formulated with a yield function in terms of effective stress ratio, a plastic function derived from the stress ratio-plastic strain incremental ratio, and employ Seguchi and Ohta's stress parameter to account for rotation of principal stress axes, and a modified Masing rule. Material constants can be easily obtained from conventional laboratory tests. The model is validated against results of undrained cyclic shear tests on sand at a wide range of density.

1991 Pergamon Press pie. Reproduction not permitted