368A 936280 Constitutive model for cyclic behavior of clays, h Theory Wathugala, G W; Desai, C S J Geotech Engng Div A S C E 1/119, N4, April 1993, P714-729
The Hierarchical Single Surface (HISS) approach of Desai et al (1986) is used to develop an integrated approach in which different factors relevant to cyclic behaviour of piles can be simulated in a unified manner. The HiSS plasticity-based concept is modified to accommodate normal and overconsolidation, general stress paths and fluid pressures. Model parameters have been determined for Sabine clay from Texas. The model can accurately predict typical laboratory behaviour of the clay. 936281 Deformation of brittle rocks under compression - with particular reference to microcracks Li, C; Nordlund, E Mech Mater V15, N3. May 1993, P223-239
A constitutive model for brittle rocks developed on the basis of analysis of microcracks is presented. Macroscopic deformation has three components: matrix response; closure of open cracks; and deformation due to the fracture of microcracks. Macroscopic deformation induced by microcracking can be predicted. The basic model units are sliding cracks. Relations between compressive stress, length of the growing crack, and deformation due to fracture of cracks are derived. Nonlinear deformation behaviour results from either closure of open cracks at low stress levels or fracture of microcracks at high stress levels. Model predictions agree well with laboratory test data for granite and gneiss in the prefailure stage. 936282 Elastic stress and strain in jointed rock masses by means of crack tensor analysis Oda, M; Yamabe, T; Ishizuka, Y; Kumasaka, H; Tada, H; Kimura, K Rock Mech Rock Engng V26, N2, April-June 1993, P89-112
An elastic stress strain relation formulated in terms of crack tensors is presented, which enables the effects of discontinuities on elastic behaviour of rock masses to be explicitly described. Practical applications are demonstrated. The relation is implemented within a 3D finite element analysis to investigate stress concentration due to surface loading and displacement by excavation of an intersecting tunnel. Predictions are compared to laboratory and field tests results respectively. The importance of the value of joint stiffness ratio chosen for the analysis is discussed. 936283 Three invariant dependent cap model with application to a cohesionless soil Abduljauwad, S N; Faruque, M O; Azeemuddin, M; A1Ghamedy, H N Trans lnst Engrs Aust Civ Engng VCE34, N4, Dec 1992, P355-367
A plasticity based modified cap model for cohesionless soils is presented,which takes into account all three stress invariants. Isotropic hardening is assumed. The detailed derivation of the elastoplastic stress strain relations is illustrated. The model is written in an incremental form and implemented in a nonlinear finite element code. The performance is tested against results of a series of triaxial and hydrostatic tests at different confining pressures and loading tests of a rigid model footing on sand.
Design methods See also: 936213 936284 Data acquisition and input for numerical analysis Beer, G Proc ISRM Symposium: Eurock'92, Chester, 14-17 September 1992 P310-317. Publ London: Thomas Telford, 1992
Data collection methods in rock mechanics have altered little over the past 20 years, despite rapid advances in numerical analysis. An overview is presented of the techniques used in rock mass modelling: finite element method, boundary element method, discrete element method, and their combinations. Input data and methods for their acquisition are discussed with new ways of collecting data explored. 936285 Principles of engineering design for rock mechanics Bieniawski, Z T Proc 33rd US Symposium on Rock Mechanics', Santa Fe, 3-5 June 1992 P1031-1040. Publ Rotterdam." A A Balkema, 1992
Engineering design principles specifically for rock mechanics applications are discussed. Design theory is described and design principles outlined: independence principle; maximum uncertainty principle; simplicity principle; state-of-the-art principle; optimization principle; and constructibility principle. Design constraints are considered. A design methodology is developed on the basis of these design principles. 936286 Rock mechanics in civil engineering design Schmidt, B Proc 33rd US Symposium on Rock Mechanics, Santa Fe, 3-5 June 1992 P1051-1059. Publ Rotterdam. A A Balkema, 1992
Many advances have been made in rock mechanics theory and practice, but variability of geological materials and lack of sufficient data for rigorous design and appropriate selection of construction method remain major challenges to the engineer. Methods of design are outlined and some difficulties associated with continuum, discontinuum, and empirical approaches are discussed. Advice is given on coping with uncertainty. Engineering intuition and experience remain important design tools.
Rock Breakage and Excavation Rock fracture under dynamic stresses 936287 Exploring the ultrasonic comminution of copper ores Yerkowicz, C; Menacho, J; Gaete, L Miner Engng V6, N6, June 1993, P607-617
The Utah ultrasonic roll device uses a vibrating plate driven by an ultrasonic transducer against a spinning roll. Several breakage events occur during passage of a particle, due to the superimposition of ultrasonic vibrations and compressive stress between the metal surfaces. Performance of this device is compared to that of a laboratory scale ball mill for Chilean porphyry copper ore. Similar performance is seen at small gap settings, but as gap opening increases the ball mill becomes
© 1993 Pergamon Press Ltd. Reproduction not permitted