New soil abrasion testing method for evaluating the influence of geological parameters of abrasive sandy ground on scraper wear in TBM tunneling

When shield TBM tunneling in abrasive sandy ground, scrapers are loaded with heavy forces resulting from the extrusion and friction processes of sand particles. Scraper wear reflected as displacement or desquamation is related to soil parameters. Due to the lack of reliable test methods, experimental studies on the influence of soil parameters on scraper wear are limited. In the present study, existing soil abrasion testers have been reviewed to discuss the advantages and deficiencies. An improved WHU-SAT soil abrasion tester has been developed to study the influence mechanism of soil parameters on scraper wear. Experimental studies have been conducted to evaluate the variation of scraper wear with quartz content, particle size, particle shape and water content. Two soil abrasion tests have been performed for each case. Scraper wear has been considered to be the average value. The results indicate that scraper wear increases with the increase of quartz content and the growth rate increases. It is related to the particle crushing and adhesion effect of limestone sand. As the average particle size increases, the extrusion and friction between the modeled scraper and the sand particles increases first and then decreases. Thus, scraper wear increases first and then decreases with the increase of average particle size. The trend is generally comparable to the corresponding changes in scraper wear with water content. As quartz balls collide with sand particles and destroy the microscopic friction system composed of scrapers and asperities, scraper wear decreases as the increase of roundness and the falling rate decreases. Optimized solutions such as soil abrasivity evaluation, tunnel alignment optimization and soil discharge improvement have been proposed to alleviate the influence of soil parameters on scraper wear. The present study promotes the rational estimation of sand abrasivity and scraper consumption during the feasibility study of abrasive sandy gournd tunneling using shield TBM.