Rock Mass Rating

Classification of the rock mass around caverns was made according to the Rock Mass Rating (RMR) System (Bieniawski, 1989) and the Tunnelling Quality Index (Barton et al, 1974). Parameters were selected by the geological site investigation, the characteristic data for the intact rock, the joint sets and the in-situ stresses. 

Rock mass Rating (RMR) 46-49, Class III, Fair 37-44, Class IV, Poor 52-57, Class III, Fair... 

Table 9.4. The rock mass rating system (geomechanics ciassification of rock masses) (after Bieniawski, 1989). With kind permission of Wiiey... 

Bieniawski (1989) developed a rock classification system called Rock Mass Rating (RMR) . Six parameters are used to classify a rock mass uniaxial... 

Applications. In the following paragraphs, the conditions (temperature, time, water/rock mass ratio, surface area) and the results on closed system oxygen consumption and redox conditions of the basalt-water experiments are compared to expected conditions in the open system backfill and near-field environment of an NWRB. Crushing of basalt for pneumatically emplaced backfill could result in a substantial fraction of finegrained basalt with a variety of active surface sites for reaction similar to the crushed basalt used in the experiments. The effects of crushing on rates of mineral-fluid reactions are well documented (10,26). 

Figure 10.2. Observed and model sedimentary rock mass-age distributions. Observed mass distribution is represented by stippled area. Dashed curve is a model calculation for constant deposition and destruction rates of sediments of all age groups, whereas the histogram represents the results of a model calculation in which variations in these rates are permitted. The mean age of the sedimentary rock mass is about 350 million years. (After Garrels et al., 1976.)...

Figure 10.5. Mass-age distribution of carbonate rocks and other sedimentary rock types plotted as survival rate (S) versus age. Total rock mass data from Gregor (1985) and estimates of carbonate rock mass from Table 10.1.

Figure 10.30. Phanerozoic sedimentary rock mass-age relationships expressed as the logarithm of the survival rate in tons y-1 versus time. The straight lines are best fits to the total mass data (solid line) and to the carbonate mass data (dash-dot line) for particular intervals of Phanerozoic time. The difference between the logarithm of S for the carbonate mass and that of the dolomite mass is the survival rate of the calcite mass. Filled star is present total riverine flux to the oceans, whereas open star is carbonate flux.

Experimentally determined dissolution kinetics are applicable to natural weathering processes of silicate rocks. Mass transfer from the mineral to the aqueous phase was determined to be incon-gruent under a range of experimental conditions. Transfer rates of individual species (Q) at times (t) can usually be described by one of two rate expressions ... 

The outside boundaries of the rock mass are assumed to be fixed against normal displacement, and are specified to remain at a constant temperature (12°C). The measured steady state pressure in the rock in the vicinity of the gallery varies between 0 (atmospheric) and less than I MPa. These values are very small to influence the hydraulic response of the bentonite. For the sake of simplicity, we assumed that the outside boundary of the rock mass is maintained at a constant pressure of 0 MPa. The heaters are not explicitly represented instead, the boundaries between the heaters and the bentonite are assumed to be fixed at zero normal displacement and zero fluid flux (very rigid and impermeable heaters), and an imposed power output is specified at either a constant rate or... 

The results from two and three-dimensional numerical analyses show that fluid-pressure responses observed in the rock mass during TBM drilling of the FEBEX tunnel could not be captured using current estimates of regional stress. It was shown that the measured pressure responses can be captured in both two and three-dimensional simulations if the stress field is rotated such that contraction (compressive strain rate) and corresponding increases in mean stress occur near borehole FEX 95.002 on the side of the drift. From the results of the two-dimensional analysis, it appears that good agreement between measured and simulated evolution of fluid... 

For the low rock permeability case, a correct prediction of the pore pressure in the rock mass requires a full THM analysis, as shown on Figure 9 for point B6 of the rock adjacent to the buffer. At early times, due to its low permeability, the rock could not supply water to the buffer at a sufficient rate, leading to a drop in pore pressure. Rebuilding of the hydrostatic pressure starts at about 30 years for the THM case, and about 60 years for the HM case, while it is still unsaturated after 100 years in the TH case. 

The equations for the gas leak flow and the equations for the coal/rock mass deformation are regarded as two separate, yet coupled systems to numerically solve them. Firstly, the solid coal/rock mass deformation rate e, the effective total stress e , the initial pore gas pressure values at both the upper and lower coal seams Pj and at the time (= >0 are substituted into the gas teak flow equation for the upper coal seam to calculate the pore pressure values (at each grid point) of the upper coal seam at the time /,=((, +A/ (denoted as Pjti,)). Secondly, the pore gas pressure values of the lower coal seam at the time t, (denoted as Pi(r,)) are calculated by coupling the numerical results of the first step. Thirdly, the coal/rock mass deformation rate at the time /, (denoted as e(t,)) is calculated by substituting P (j,) and a,(i ) into the equations for coal/rock mass deformation. Consequently, the effective total stress at the time (, (denoted as 0 ((i)) is also calculated. Finally, (-(i,) and 0 ( i) are substituted into the equations for gas leak flow to get the pore gas pressure values at the time <2 = ii + a/ (denoted as Pjdj) and p,(i2)). 

The Coaraze site, located in the coastal part of the French Alps, consists of a small limestone reservoir with a volume of approximately I9,0(X) m drained by a spring running at an annual mean flow rate of 10 1/sec (see Fig. 1). This spring has been equipped with a valve that, when closed, causes water to rise in the rock mass until reaching a height of approximately 10 m. The evolution in hydromechanical behavior of the fractures within the saturated zone is recorded by variations in both water pressure and time, Guglielmi (1999). 

The most common method for determining rippability is by seismic refraction. The seismic velocity of the rock mass concerned then can be compared with a chart of ripper performance based on ripping operations in a wide variety of rocks (Fig. 9.3). Kirsten (1988), however, argued that seismic velocity could only provide a provisional indication of the way in which rock masses could be excavated. Previously, Weaver (1975) had proposed the use of a modified form of the geomechanics classification as a rating system for the assessment of rock mass rippability (Table 9.1). 

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