The investigation of the applicability of block punch index in the rock mass classification systems for weak rocks and the application of shallow urban tunnels

In rock engineering, knowledge and understanding of behavior and characterization of rock masses are essential for the safe design of surface and underground structures. Indirect tests are often employed to predict the UCS empirically, via such as Point Load Index (PLI), Schmidt Hammer (SH) Rebound Number tests.. Recently, Block Punch Index (BPI) test was developed to minimize the errors arisen from the structural deficiencies, especially in laminated-foliated, anisotropic rocks with low RQD and strength. In this study, to benefit from BPI advantage, in order to determine the rock mass behavior in laminated-foliated Bornova Melange (yellowih-brown flysch and greyish-black flysch) and well jointed Yamanlar Volcanics-Altindag Formation, in which the 2nd Stage of Izmir Metro tunnels were excavated the BPI ratings were directly used in RMR calculations and also BPI values were indirectly used to estimate the UCS values of rock materials which were then input in numerical models along with the rock mass strength and modulus of elasticity (E) of rock materials. The results obtained from the numerical models agreed with that obtained from tunnel convergence and ground settlement measurements and have proven that use of BPI values for such rocks will yield reliable results in search of rock mass properties.