Abstract:
This research is focused on the effects of joint orientation with
respect to the direction of tunnel axis. It is expected that the stability of surrounding
rock is affected by the strike and dip of the joints and the direction of the tunnel axis,
whether it is with the dip or against dip etc. similarly the spacing of joints will also
affect the stability. The orientation of joints in different directions can form blocks
liable to fall. The objective of this research project is to determine the degree of
influence of joints' strike and dip orientation in tunneling. Field works related to this
project was carried out at the Bogala Graphite Lanka Ltd. Tunnel mapping and
other observations related to the project were made at 489.6m level in Bogata mine.
Models were made with joint spacing of 15mm with two joint sets (joint sets parallel
to tunnel axis and joint sets perpendicular to tunnel axis). Tunnels were created with
90mm diameter with dip angles of joints are 00,300,600,and 900. The tunnels models
are loaded using UCS machine and observed the behavior of rock mass around the
tunnels during loading. From the results the most preferable dip angle for the joint
strike perpendicular to the tunnel axis would be the 900 and for the joint strike
parallel to the tunnel axis would be 00.
