Modelling of Groundwater Conditions in Silts and Fine Sands. A Study of Induced Groundwater Changes Based on Laboratory and Full-Scale Field Tests

Abstract: Every day, geotechnical engineers have to deal with groundwater problems. In order to find suitable solutions to these problems, modelling of the groundwater conditions and their variations in time has to be performed.

A study of the groundwater conditions in silts and fine sands was made including laboratory and full-scale field tests. The purpose of the study was to investigate the possibility to use numerical models to simulate variations in the groundwater conditions in different situations.

A laboratory equipment was built in order to study the reliability of different instruments used for measuring soil matric suction. Laboratory tests were also made for studying the behaviour of silts and fine sands during and after induced changes in the groundwater conditions. Thereafter, numerical simulations have been performed, and the results were compared with the observed behaviour.

Full-scale field tests were also performed at one site in Sweden. During these tests, the level of the groundwater table was changed using a drainage system, and the variations in the groundwater conditions in the surroundings were monitored. These tests were also simulated using a numerical model for comparison between observed and computed behaviour.

The results showed that the behaviour of a partially saturated soil is not only controlled by the position of the groundwater table in the area, but also by the water retention characteristics of the material. The comparison of the results of the simulations with the monitored behaviour, showed that such simulations are reliable in fully saturated soils, but do not describe properly the changes in groundwater conditions above the capillary zone.