Characterization of the effect of disturbance on the hydro-mechanical behavior of a highly collapsible loessial soil

Highly collapsible loessial soils are characterized by an open void structure that can experience significant settlement upon loading. In the field, these partially saturated Aeolian deposits are particularly susceptible to wetting-induced collapse. Due to difficulties in preparing undisturbed specimens from highly collapsible soils, previous studies have generally performed laboratory tests on reconstituted specimens with different water contents and densities, and the effect of disturbance on the initial state of the soil was ignored. Disturbance in highly collapsible soil specimens may significantly affect the natural composition of the soil matrix, the non-homogeneous distribution of macro-or micro-pores, and the weak inter-particle bonding between the grains. The current study utilizes a new experimental approach to assess the effect of disturbance on the hydro-mechanical behavior of a highly collapsible loessial soil. Results from tests on undisturbed and reconstituted specimens prepared at the same water content and dry density indicate that disturbance can in some cases significantly affect the observed hydro-mechanical behavior of a collapsible soil during the wetting process. For low mean net stress testing, for tests conducted on specimens at the same values of mean net stress, the deformation measurements for undisturbed specimens were lower than those that were observed when testing reconstituted specimens. At higher values of mean net stress, both undisturbed and reconstituted soil specimens showed very similar wetting-induced volumetric strain behavior. This observation is believed to be due to the effect of the mechanical stress on the natural composition of the soil matrix, which can break cemented bonds between soil particles and reduce the effect of non-homogeneity in the distribution of pores on the deformation behavior of the soil.