Stress deformation properties of macroporous loess soils

Milovic, D., 1988. Stress deformation properties of macroporous loess soils. Eng. Geol., 25: 283–302.

Herein are presented the results of laboratory and field tests which were carried out on loess in Yugoslavia.

Experience gained during recent decades show that the loess soil in some cases undergoes structural collapse and subsidence due to inundation. In order to find the explanation of such behaviour, numerous laboratory and field load tests on loess soil have been performed. Using the obtained results, several correlations have been established.

On the basis of the unconfined test results, a correlation between the initial dry density, initial water content and unconfined compression strength has been established.

A relatively large number of the consolidation subsidence tests (about 550), carried out on undisturbed loess samples, made possible the determination of the degree of subsidence and the corresponding values of the dimensionless coefficients of subsidence. These coefficients have been determined for several values of the initial dry density, for various degrees of saturation and for several stress levels upon wetting. Using these coefficients, the values of the additional settlement caused by flooding of loess under the foundation can easily be calculated. It is of particular interest to note that, in general, water penetrates under one part of the building, producing differential settlements, which are in most cases very dangerous.

By the comparative laboratory investigation of the undisturbed loess samples obtained by thin walled sampler and samples obtained from pits, it has been shown that the mechanical disturbance is an extremely important factor which governs the shear and deformation parameters of loess soils.

The laboratory test results obtained on undisturbed loess samples, cut from blocks in the vertical and horizontal direction, have shown that this soil exhibits anisotropic properties. For this reason a stress deformation problem in an anisotropic medium has been treated by the finite element method.

Static penetration tests and field load tests in loess soils with natural water content and also after saturation have been performed and are described.

The results of the observed settlements for two statically identical multi-storey buildings are also presented. Using the coefficients of subsidence for the undisturbed samples cut from blocks, very good agreement between the calculated and the observed settlements has been obtained.