Failure modes in shallow tunnels and galleries [Si{dotless}g tünellerde ve galerilerde yenilme türleri]

Boren;DEMiR Export;et al;metso Expect results;Outotec;TMMOB Maden Muhendisleri Odasi23rd International Mining Congress and Exhibition of Turkey, IMCET 2013 -- 16 April 2013 through 19 April 2013 -- Antalya -- 105453The stability of shallow tunnels and galleries is rather specific but an important area of interest in civil and mining engineering. In this study, failure modes occurring in circular tunnels excavated at shallow depths have been investigated. First, the concept of shallow tunnel was emphasized, and the factors that affect the stability of shallow underground openings were summarized. Then, the important failure modes observed in shallow tunnels were mentioned. Finally, in order to determine the failure geometries encountered in shallow tunnels, a series of parametric analyses were carried out by using a computer code that involved two-dimensional finite element stress analysis. In the analyses, the effects of various combinations of in-situ stresses on the stability of a shallow circular tunnel were investigated. Different depths were considered for the tunnel located in a rock mass where the principal in-situ stresses varied with depth. For this purpose, the effects of in-situ stresses on the geometry of the region, occurring around the opening and having failure potential, were examined. An index (i.e., IOZ: index of overstressed zone) was used for comparing the relative sizes of overstressed regions obtained from various cases