Mathematical Simulation of Honeycomb Weathering via Moisture Transport and Salt Deposition

Abstract

Honeycomb weathering is a common phenomenon found on various rock surfaces all around the world. However, honeycomb formation mechanisms are still poorly understood. In this study, we propose a model describing moisture transport within the sandstone and erosion resulting from salt deposition during evaporation of moisture off the rock surface. The moisture transport model is based on the non-linear diffusion equation, where the volumetric moisture content is a combined parameter accounting for the moisture and gas (vapor) content. The moisture transport model accounts for the several-orders-of-magnitude decrease in moisture diffusivity, observed during drying. It was assumed that erosion occurs when the evaporation front is located close to the rock surface. The depth of erosion is proportional to the moisture flow rate through the drying surface. The ABAQUS finite-element software suite was used for numerical solution of the non-linear diffusion equation. The iterative scheme of erosion simulation for different drying cycles was implemented using the Python programming language. Computations were conducted in the 2D setting for the square model with dimensions of 50 mm × 50 mm. Simulation results demonstrate the possibility of obtaining various landform shapes (honeycombs, tafoni) by varying only the value of the distribution of moisture content at the bottom side, simulating the rate of internal wetting of rock.