Applicability of excavatability classification systems in underground excavations: A case study

摘要

In this study, applicability of the excavatability classification systems in underground excavations is investigated. For this purpose, the entrance portal of the Konakamp;ouml;namp;uuml; (Araklı-Trabzon) tunnel,excavated in volcanic rocks within the scope of Black Sea coastal highway project, is chosen as pilot study area. The entrance portal of tunnel is excavated through the rocks of Eocene-aged Kabakamp;ouml;y formation of basaltic-andesitic tuffs, aglomerate and basalt.In excavation, basaltic and andesitic tuffswere ripped by using hydraulic breaker;aglomerate and basalt were excavated by using explosives. Based on the resultsobtained fromfield and laboratory studies, rock masses are classified in terms of excavatability. According to Pettifer and Fookes (1994), basaltic and andesitic tuffs are included in amp;ldquo;hard rippingamp;rdquo;, aglomerate and basalt in amp;ldquo;blasting requiredamp;rdquo; categories. With reference to Tsiambaos and Saroglou (2009), basaltic and andesitic tuffs fall in amp;ldquo;rippingamp;rdquo;, agglomerate and basalt in amp;ldquo;hammer and blastingamp;rdquo; categories. It was found out that the classifications made according to these two methods are completelycompatiblewith in-situ excavation works. Also, it is determined that the parameters give the best results for determining excavation class in underground excavations are GSI (Geological Strength Index),Is (50)(Point load strength index) andIf(Discontinuity spacing index).