A Combined Experimental and Modeling Approach Unraveling the Mechanics Behind Drying-induced Fractures in Soils

This dissertation aims to understand the physics of geomaterial under different loading rates, employing a combination of experimental analysis and theoretical modeling. After obtaining a comprehensive understanding of geophysics, the objective shifts to exploring methods for enhancing the mechanical properties of materials to mitigate or prevent structural failures.

One particular focus in experimental studies is placed on understanding the phenomenon of desiccation, where the volumetric shrinkage rate of the geomaterial can be manipulated by adjusting atmospheric conditions. The experimental results from desiccation tests, supported by triaxial tests, reveal that the behavior of geomaterials is dependent on the loading rate, indicating a rate-dependent response. This observation highlights the need to consider viscoplasticity in the mechanical analysis of these geomaterials. Subsequently, a theoretical mathematical model incorporating viscoplasticity is utilized to describe the stress distribution within the geomaterial. By comparing the predicted locations and the number of stress singularities obtained from the model with the observed locations and the number of cracks in desiccation tests conducted under controlled atmospheric conditions, the effectiveness of the model in capturing the mechanical behavior of the geomaterial is assessed.

Once the mechanical behavior is understood and the corresponding theoretical model is validated, modifications in soil properties can be achieved through adjustments to viscosity. Initially, increasing the viscosity results in the formation of more cracks with narrower spacing. However, as viscosity continues to increase, it eventually leads to the complete prevention of failure. Desiccation experiments containing fluids with varying viscosities were conducted to validate the predicted failure pattern. The experimental results align with the theoretical predictions, providing confirmation of the anticipated behavior.

During desiccation tests conducted on amended soil samples, it was observed that crack development was mitigated, indicating that cracks initially appeared but remained suspended during the dehydration process. Due to the complexity of solving time-dependent partial differential equations with shifting boundary conditions, capillary experiments were introduced to provide insights into the force development within soil particles with the loss of water. The morphology and force development from capillary tests revealed distinct outcomes during dehydration: in the capillary system with distilled water and low viscosity fluid, a rapid force reduction (drop to zero) occurred as the capillary bridges broke, while the presence of high viscosity fluid resulted in a rebound followed by a high attraction force due to bonding formation in the capillary system.

In all, this dissertation offers a novel perspective on describing soil behavior and provides a micro-scale explanation of force development in soil dehydration.