Hydro-mechanical behavior of collapsible soils in unsaturated soil mechanics context

This paper is related to the studies taken place during last decade to understand the intact behavior of a Collapsible Loess subjected to loading and wetting at Advanced Soil Mechanics Laboratory of Sharif University of Technology, Tehran, Iran. In this regard intact block samples are carefully taken from Hezar Pich Hill in the city of Gorgan, Iran, and various tests are performed on undisturbed specimens recovered from the intact block samples. In this way three automated unsaturated oedometer are built and a conventional triaxial apparatus is upgraded to a fully automated unsaturated triaxial device to accommodate rigorous and different stress and wetting path with continuous data acquisition of various parameters. The tests are conducted mainly on undisturbed samples, however, some tests are also performed on reconstituted specimens to observe the differences between the behavior of intact and reconstituted specimens. The results indicate that the hydro-mechanical behavior of intact Collapsible Loess is substantially different from that of the reconstituted specimens. Therefore, it is strongly recommended to perform undisturbed sampling and conduct tests on intact natural loess to be able to predict the collapse behavior, shear strength and hydro-mechanical behavior of this type of collapsible soil reasonably. Also in order to investigate on the type, optimized amount and methods of application of stabilizing agents a number of agents and improvement techniques are implemented. Various tests are conducted on the improved specimens as well and the results are compared with those of unimproved ones to verify the effectiveness of the used agents and methods.

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