Role of Boundary Conditions in the Evolution of Desiccation-Induced Cracking and Surface Strain and Displacement Fields in Compacted Expansive Soil

Evaporation of water from compacted expansive soils results in significant volumetric shrinkage due to the presence of montmorillonite clay mineral. The nonuniform shrinkage of these soils often results in the formation of desiccation cracks. The present study aims to investigate the role of lateral and basal boundary conditions in the initiation and propagation of desiccation-induced cracking and strain localization in compacted expansive soil. A laboratory-scale desiccation simulation chamber equipped with an automatic image acquisition system was employed to conduct desiccation cracking tests on compacted specimens under different external boundary conditions. Quantification of various geometrical and morphological parameters of desiccation cracking was done using the digital image analysis (DIA) technique. The dynamic evolution of two-dimensional localized displacement and strain fields over the specimen surface was investigated using the digital image correlation (DIC) technique. The results from this study reveal that a soil mass under a similar compaction state and desiccation environment can exhibit significantly different cracking morphologies and strain localization patterns due to slight changes in the basal and lateral boundary conditions around the specimen. The maximum crack intensity factor (CIF) increased from 3.9% under the smooth boundary condition to 10.5% under the highly laterally restrained condition, representing nearly a threefold increase. Similarly, the average crack width ranged between 0.4 and 0.6 mm for specimens with basal restraints but increased to 1.3–1.7 mm for laterally restrained specimens. This study also highlights the possible chances of underestimating the desiccation cracking potential of compacted soils owing to different boundary conditions used during laboratory experiments.