The book contains 88 papers accepted for presentation at the 3rd international symposium on numerical models in geomechanics, Niagara Falls, May 1989. Most are abstracted separately. The organisation is in 7 sections: 1) constitutive models of geological materials (models for granular media, for clays, for soils and reinforced soils); 2) experimental behaviour and evaluation of constitutive models; 3) limit analysis and modelling of instabilities; 4) soil dynamics; 5) fluid flow and consolidations; 6) numerical methods and software developments; 7) applications of numerical techniques to practical problems (tunnels and excavations, embankments and slopes, piles, other applications). There is an author index. -M.A.Bass