Evaluation of granular soil abrasivity for wear on cutting tools in excavation and tunneling equipment

This paper presents an experimental study of tool wear and abrasivity of granular soils using a testing system specifically designed for the evaluation of wear on earth-moving machines, especially soft ground tunneling applications where the impact of soil abrasion on the operation is significant. In the testing system, a propeller fitted with steel covers of different hardnesses is rotated at 60 rpm in granular soil samples in a chamber under ambient pressures of up to 10 bar. The developed system can quantitatively assess the abrasive characteristics of soils through the measurement of weight loss on the special covers of the propeller, accounting for soil gradation, mineral composition, sphericity and roundness, water content, and tool hardness. Preliminary test results indicate that water content, particle angularity, and relative hardness between the tool and soil have significant impact on tool wear and soil abrasion. For the tests conducted, it is observed that angular sands produce significantly higher tool wear than round sands in dry condition. Tool wear first increases with water content until the water content reaches approximately 7-10%; beyond this range, higher water content reduces tool wear. An increase in hardness ratio (tool/mineral), corresponding to an increase in tool hardness and/or a decrease in mineral hardness, results in a decrease in tool wear in dry sand mixtures, but this trend is not monotonic for sand mixtures with high water content.