Year

1988

Degree Name

Doctor of Philosophy

Department

Department of Civil and Mining Engineering

Abstract

The research reported in this thesis is concerned with the observed static and dynamic behaviour of two saturated sands under static and dynamic loading conditions. Several models for predicting the static stress-strain response of soils are reviewed. Some of these have been generally considered relevant only for saturated remolded clays. However, in a general sense, even these models are applicable to all particulate frictional materials. The observed, detailed stress-strain behaviour of the two saturated sands under various (Ottawa standard sand and Li-Kang sand) test conditions is reported. This behaviour is then compared to the stress-strain response predicted from a number of theoretical models which include those developed at the University of Cambridge over several decades. The stress-strain models considered for these comparisons are:

(1) Cam-clay model (Roscoe and Wroth, 1968),

(2) Modified Cam-clay model (Roscoe and Burland, 1968),

(3) Miura modified Cam-clay model (Miura, 1982) and

(4) Cap model (Baladi, 1979).

A complete series of static consolidated drained and undrained triaxial compression tests was performed on each of the two sands i.e. Ottawa standard sand and Li-Kang sand. The CKC automated triaxial system was used to carry out all the laboratory tests and programs were written on a personal computer to make the best analysis of the results.

Dynamic stress-strain behaviour of the two saturated sands was studied under undrained and drained conditions. Results are presented for effective stress paths with cyclic loading under undrained conditions. Results are also presented for the influence of previous cyclic deviator stress on resistance to liquefaction. Results are finally presented for volumetric strain characteristics of saturated sand considering cyclic loading under fully drained conditions. In particular the results of investigation concerning the effect of fine on volumetric strain are also presented. Estimation of settlement for design purposes is discussed and an illustrative example is presented with the seismic stability of under-sea tunnel project. Bardet's (1983) model for prediction of dynamic behaviour is discussed. Results of effective stress paths at various ellipse aspect ratios are presented. Based on the investigations and the model a new formula is then proposed for the ellipse aspect ratio.

In the final chapter careful corrections are proposed to the parameters in different models with particular reference to Eqs. 9.1, 9.2 and 9.3. Although the thesis is primarily concerned with fundamental aspects of stress-strain behaviour, the application of the experimentally determined parameters to foundation design for settlement is given some attention. Finally, as regard the dynamic behaviour of sand under an actual earthquake, support is provided by the excellent performance of the tunnel (referred to in illustrative example) during the earthquake of November 15, 1986 as predicted by the approach adopted in this thesis.

Share

COinS