Question

A tunnel is excavated in a granite rock mass, which contains 3 joint sets yet their orientations are all very favorable , average RQD is 88%, average joint spacing is 0.24 m, joint surfaces are stepped and very rough, tightly closed and unweathered (unaltered) with occasional stains. The excavation surface is wet but not dripping. Average rock material uniaxial compressive strength is 160 MPa, and the tunnel is 150 m below the ground (geotectonic stress ?1 = 150 m * 2.7 t/m3 = 405 t/m2 = 4.05 MPa) Based on the conditions described above, give the rock mass rating and class by (a) RMR method and (b) Q method, respectively. Also list the contributions of all related parameters, respectively.

Answer 1

Answes Given that is ase Rock may Ran ng u hich is sum Raking Following 6 Pawametess to cloyity the stseugth df Rock. i, Rock avality Degignation CReD) ju, SPacing . Discontinuity iv, ondition d Dis continuiby DisontinoiHy Vi, osieutatton Fos the giveu yuestion, the volve ae giveu aud we cau com above Paramutess Pana with taudavd Valoe Ucs is given 160 mpa Naring woold be Re D is 9i ven 887. , Rating would be e Spa ang ot Discontinuiry is giveu 50 mm, sating woold beg condition of Discontinoity is DiscontinoitH is giveu O-QUmノčaki ng, would be la

osieuutation of discontinuity is given none meams a Now , the meam Rati ng d RmR chipication woold be ua According to Descsíption (2-uo toho coma onder the chy nombes v). the Rock uoold be cosider as poor Rock Refexs to Rock tonnelrg quality Index value 8/ ool to toeo which can be calcolaked by following Fosmvla Where R&D 40, 3n Joint get nomber . S Joint Roughne fautos 3 (Because glightly Rovh Sa -Joint altelarion e l'IBecause Highly weathered) Jo Joint aates Irylow 2( Because of soft. Fijljng SRF 2 sties Reduction factos -25/accozding to conditio Nou put the vole in ean 048