Multi-Scale modeling of the interface behavior between steel micro piles during wetting-drying cycles

Abstract

The performance of steel micro-piles in expansive soils is the result of a complex soil-pile interaction that degrades significantly during cyclic wetting and drying. In many cases, traditional macroscopic models do not account for the principles of interface softening and gap formation, which result from microstructural changes in the soil matrix. This paper introduces a Multi-Scale model which puts together micro scale particle interactions and macro scale structural response. In this study, we used the Discrete Element Method (DEM) to look at micro-level clay particle behavior and their interaction with steel surfaces, using the Finite Element Method (FEM) for the large-scale pile and soil system. The model includes variation in matrix suction, which causes swelling and shrinkage. The tests showed that after five wetting and drying cycles, the interface shear strength went down as much as 45%, which resulted from the growth of permanent microcracks and particle rearrangement. Proposed is a multi-scale approach, which we present as a robust solution for the design of micro pile foundations in climate-sensitive regions, and it puts forth what single-scale analysis doesn’t. This multi-scale approach we put forth is for the development of sustainable infrastructure, which prevents us from overdesigning in climate-sensitive areas. Results present that value in adding microstructural information, which, in turn, we note that, by use of it, we can reduce steel resources by 15 to 20% and also report a large drop in the project’s carbon output, which also supports development of what are more resilient and green geotechnical solutions.