Effect of Moisture Content and Applied Load on Cutting Tool Wear and Clogging in Mechanized Tunneling

Abstract

This study is about a laboratory-based investigation into how moisture content and mechanical loading affect cutting tool wear during mechanized excavation in fine-grained marl soils. Using a scaled tunnel boring machine (TBM) simulation setup, two experimental series were conducted. The first series examined the effects of six applied-load levels, ranging from 0 to 15 kg, and four moisture contents between 5% to 20%. The second series investigated the combined effects of soil gradation and moisture content under no additional applied load, using moisture contents ranging from 0% to 25% and fine-particle contents between 80% and 100%. Tool wear was measured based on the mass loss of the cutting tools, while clogging behavior was evaluated through direct observation. The experimental results show that tool wear is strongly dependent on the interaction between load and soil moisture. Wear increases with applied load and reaches a peak at moisture levels of around 10%, where abrasion between the soil and the tool is highest. When the moisture content increases beyond this level, wear gradually decreases because the soil starts to stick more to the tool. In contrast, soil accumulation on the cutting tools becomes increasingly severe at moisture contents exceeding 15%, adversely affecting excavation performance. The observed results suggest a shift from predominantly abrasion-related wear toward greater adhesion-related soil accumulation at higher moisture contents. The results provide laboratory-based insights into the effects of moisture content and particle-size distribution on tool wear and soil accumulation under the tested conditions. These findings may contribute to the understanding of EPB-TBM excavation in fine-grained soils, although further field-scale validation is required.