The Mechanism of Liquefaction of Clayey Soils (M124)

Abstract

An experimental study on the liquefaction of clayey soils was conducted under ICL Project M124 “The influence of clay mineralogy and ground water chemistry on the mechanism of landslides” in order to better understand the mechanism of this phenomenon. The first section of this study deals with artificial mixtures of sand with different clays while the second is concerned with natural soils collected from landslides. The results from the first section are presented in this article. The investigation was conducted by means of a ring-shear apparatus and a scanning electron microscope (SEM). The results obtained for artificial mixtures enabled us to draw a line between liquefiable and non-liquefiable clayey soils and to define a criterion to estimate their liquefaction potential. In addition, the influence of clay content and clay mineralogy on the cyclic behavior of clayey soil was studied. It was found that an increase in clay content as well as the presence of bentonite clay raised the soil resistance to liquefaction. The analysis of microstructures of bentonite-sand mixtures along with the results from ring-shear tests revealed that the soil microstructure is the key factor in determining the dynamic properties of soil. For example, in the microstruc-tures of soils vulnerable to liquefaction, the clay matter was observed to form “clay bridges” between sand grains that were easily destroyed during cyclic loading. In the microstructures of soils resistant to liquefaction, the clay matter seemed to form a matrix that prevented sand grains from liquefaction. The influence of pore water chemistry on the liquefaction potential of artificial mixtures was also studied. It was found that the presence of ions in pore water changed the microstructure of clayey soil, thus making it more vulnerable to liquefaction.