No Recovery Process Question No A tunnel is to be driven thr

No Recovery Process Question No (A tunnel is to be driven through slightly weathered sandstone of Nagri formation at 102-MW Gulpure Hydropower project in district Kotli of AJK, with a dominant joint set dipping at 60°, strike parallel to the tunnel axis. The average uniaxial compressive strength of sandstone is 28 MPa and average ROD values of 70%. The slightly rough and slightly weathered joints with a separation of

Solution

Answer:

Since the RQD value is 75% & this refects the majority of rocks are \"moderately weathered\" as per the classification. Also, it is mentioned as Sandstone having uniaxial compressive strength of 28 Mpa.As per RMR system, the rock is classified as \"Good\" with values between 60-80.

And since the rock is good, then i would recommend the use of side wall & crown support for the tunneling work and the requirement of the supports is already in the given table under \"good rock\" head.

Thanks.