Assessment of the impact of case parameters affecting abrasion and brittleness factors in alluviums of line 2 of theTabriz subway, Iran

摘要

Drilling long tunnels is usually done in a mechanized form and using tunnel-boring machines (TBM). One of the most important factors in drilling these tunnels is the abrasive effect of soil and rubble on cutting machines and other parts of TBM, which can result in a significant reduction in efficiency of drilling project. Numerous methods have been presented to examine soil and rubble abrasion in drilling sections by researchers. One of the tests in this field is the LCPC test. Different factors can cause abrasion in drilling machines, which have been investigated by researchers. In this study, case factors (moisture, lithology, grain size, and foam of drilling) affecting the abrasion and brittleness coefficient of alluviums of the tunnel route of line 2 of Tabriz Subway from west to east shaft are investigated. To this end, the moisture of 20 samples, lithology of 15 samples, the grain size of 20 samples, and foam effect of 24 samples from the tunnel route of line 2 of Tabriz Subway were prepared. To asses the effect of moisture on abrasion, three types of andesite, sandstone, and conglomerate of the route, examinations were done from dried state to 30% moisture. In two types of sandstone and conglomerate, an increase in moisture led to an increase in abrasion; however, in andesite the abrasion was reduced with a moiture level over 20%; the brittleness coefficient decreased with increased moisture, and in terms of the effect of mineralogy, the conglomerate had the most effect on abrasion. In terms of brittleness, andesite was the most brittle. With regard to the effect of grain size, increased size of grains could lead to more abrasion and less brittleness. The effect of foam on abrasion was such that the abrasion decreased when the foam was moisturized, but excessive levels of foam increasedit.