The Impact of Case Parameters Affecting Abrasive and Fragility Factor in Alluviums of Line 2 of Tabriz Subway

Drilling long tunnels is usually done in 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 rubbles on cutting machines and other parts of TBM, which could result in significant reduction in efficiency of drilling project. Numerous methods have been provided to examine soil and rubble abrasion in drilling sections by scholars. One of the tests in this field is LCPC test. Different factors could cause abrasion in drilling machines, which have been investigated by scholars. In this study, case factors (moisture, type, size and foam of drilling) affecting the abrasion and fragility coefficient of alluviums of tunnel route of line 2 of Tabriz Subway from west to east shaft are measured. To this end, moisture of 20 samples, type of 15 samples, grain size of 20 samples and foam effect of 24 samples of tunnel route of line 2 of Tabriz Subway are prepared. In the effect of moisture on abrasion, 3 types of andesite, sandstone and conglomerate of the route, examinations have been done from dried state to 30% moisture. In two types of sandstone and conglomerate, increase in moisture has led to increase in abrasion; although in andesite, the abrasion is reduced after 20% and the fragility coefficient in totally decreased with increased moisture and in the effect of mineralogy, conglomerate has the most effect on abrasion. In terms of fragility, andesite is the most fragile types. In the effect of grain size, increased size of grains could lead to more abrasion and less fragility. The effect of foam on abrasion is in such way that the abrasion is decreased to the extent of wetting and is increased after that.