- A Classification Parameters And Their Ratings Range Of Values 2 4 Mpa 1 2 Mpa For This Low Range Uniaxial Compres 1 (806.86 KiB) Viewed 31 times
Rating (RMR) values for the fault Intersection and described rock
mass separately for the above conditions.
A. CLASSIFICATION PARAMETERS AND THEIR RATINGS Range of values 2 - 4 MPa 1 - 2 MPa - For this low range uniaxial compressive test is preferred 5 - 251-5 < <1 MPa MPa MPa 2 1 0 1 50 - 100 MPa 25 - 50 MPa material 7 4 25% - 50% < 25% Parameter Point-load Strength strength index >10 MPa > 4 - 10 MPa of intact rock Uniaxial comp. >250 MPa 100 - 250 MPa strength Rating 15 12 Drill core Quality RQD 90% - 100% 75% - 90% Rating 20 17 Spacing of discontinuities > 2 m 0.6 -2.m Rating 20 15 Very rough surfaces Slightly rough Not continuous surfaces Condition of discontinuities No separation Separation < 1 mm (See E) Unweathered wall Slightly weathered rock walls 2 8 3 3 3 50% - 75% 13 200 - 600 mm 10 Slightly rough surfaces Separation < 1 mm Highly weathered walls 60 - 200 mm < 60 mm 8 5 Slickensided surfaces Soft gouge >5 mm or thick Gouge <5 mm thick or or Separation > 5 mm Separation 1-5 mm Continuous Continuous 10 0 25 - 125 > 125 > 4 20 10-25 0.1, -0.2 0.2-0.5 > 0.5 Wet Dripping Flowing Rating 30 25 Inflow per 10 m None < 10 tunnel length (l/m) Ground (Joint water press) 0 < 0.1 5 5 water (Major principal o) General conditions Completely dry Damp Rating 15 10 B. RATING ADJUSTMENT FOR DISCONTINUITY ORIENTATIONS (See F) Strike and dip orientations Very favourable Favourable Tunnels & mines 0 0 -2 Ratings Foundations 0 -2 Slopes 0 0 -5 7 4 0 Unfavourable Very Unfavourable Fair -5 -10 -12 -7 -15 -25 -25 -50 40 21 6041 III <21 V IV Fair rock Poor rock Very poor rock IV 1 week for 5 m span 10 hrs for 2.5 m span m 200-300 100 - 200 25 - 35 15 - 25 V 30 min for 1 m span < 100 < 15 C. ROCK MASS CLASSES DETERMINED FROM TOTAL RATINGS Rating 100 81 80 61 Class number 1 II Description Very good rock Good rock D. MEANING OF ROCK CLASSES Class number 1 II Average stand-up time 20 yrs for 15 m span 1 year for 10 m span Cohesion of rock mass (kPa) > 400 300-400 Friction angle of rock mass (deg) > 45 35 - 45 E. GUIDELINES FOR CLASSIFICATION OF DISCONTINUITY conditions Discontinuity length (persistence) < 1 m 1 - 3 m 6 4 4 Separation (aperture) None < 0.1 mm Rating 6 5 Roughness Very rough Rough Rating 6 . 5 Infilling (gouge) None Hard filling <5 mm Rating 6 4 Weathering Unweathered Slightly weathered Ratings 6 5 Rating 3 - 10 m 2 0.1 - 1.0 mm 4 Slightly rough 3 Hard filling >5 mm 2 Moderately weathered 3 10 - 20 m 1 1 - 5 mm 1 Smooth 1 1 Soft filling < 5 mm 2 Highly weathered > 20 m 0 >5 mm 0 Slickensided 0 Soft filling >5 mm 0 Decomposed 0 F. EFFECT OF DISCONTINUITY STRIKE AND DIP ORIENTATION IN TUNNELLING** Strike perpendicular to tunnel axis Strike parallel to tunnel axis Drive with dip - Dip 45 - 90° Drive with dip - Dip 20 - 45° Dip 45 - 90° Dip 20 - 45 Very favourable Favourable Very unfavourable Fair Drive against dip - Dip 45-90° Drive against dip - Dip 20-45° Dip 0-20 - Irrespective of strike Fair Unfavourable Fair