Kengo Tachibana

Improvement of particle simulationmodel for weathering of geomaterial

Ohtsuka Satoru

Weathering phenomena mainly in mudstone cause multiple cracks on the surface and inside, which may cause ground disasters such as landslides and slope failures. In particular, mudstone containing swelling clay minerals is subjected to repeated wet and dry, which promotes weatheringdue to the swelling of the clay minerals and greatly affectsthe surrounding structures. Is one of the important issues from the viewpoint of ground disaster prevention In this study, in order to 
understand the detailed mechanism of the slaking phenomenon due to water absorption expansion and drying shrinkage of mudstone containing swelling clay minerals, mudstone containing swelling clay minerals was recently analyzed using DEM. The applicability of the dimension calculation model was verified. In order to deal with phenomena such as expansion and contraction of mudstone containing swelling clay minerals by DEM, the model of soil material was introduced by introducing inter-particle adhesion model, rolling friction model, and expansion and contraction model. In addition, in the analysis of this study, a simple assumption that the particle change changes linearly with time is given to simplify the computational model. By setting the maximum and minimum values ??of the bonding stress and changing over time, the reduction of the bonding force due to swelling and the recovery of the bonding force due to drying shrinkage were considered  From the simulation results, it was confirmed that cracks and muddy behavior were observed when using the same level of bonding force as soft rock as the parameter for the maximum value of bonding force.  In some cases, weathering was insufficient when the general strength of mudstone was used for the bonding stress, and the applicability was expanded by considering the change in bonding force.In addition, in the conventional model where the interparticle sticking stress is constant, the weathering was greatly promoted only during the first expansion, but due to the change in the sticking force, 
the model was weathered even after the first expansion. The results showed that the material became brittle each time it was subjected to wet and dry conditions, which means that it was closer to the actual weathering behavior of the mudstone sample.
In the future, we will introduce parameters considering moisture content and water content from uniaxial compression tests and observations of expansion and contraction processes using actual mudstone, and we want to make this DEM model closer to the actual ground material