Rock-mass rating system

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

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. 

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). 

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 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). 

Although slope mass ratings for rock slopes and a new system for soil slopes are used in this paper, different evaluation systems (e.g., factors of safety using the limit equilibrium method and numerical simulation, and the probability of failure from probabilistic analysis) may also be used. 

Using the numbers quoted above and the derived mass of the Earth gives pc = 5.52 gem-3, which, by comparison with the density of other materials measured in the laboratory, means that the Earth must be made of rock, and heavy rock at that. The mass of the other planets can be determined from their orbital periods and their radii can be measured, for example, from rates of transit in front of the Sun, and so the density of the other planets within the solar system can then be determined (Table 7.1). 

Meade (1966) shows that claystones have a porosity decreasing to 0% at 1 Km depths and sandstones, 20% porosity at the same depth. Manheim (1970) shows that ionic diffusion rates in sediments are 1/2 to 1/20 that of free solutions when the sediments have porosities between 100 - 20%. It is evident that the burial of sediments creates a very different physical environment than that of sedimentation. As a result of reduced ionic mobility in the solutions, a different set of silicate-solution equilibria will most certainly come into effect with the onset of burial. The activity of ions in solution will become more dependent upon the chemistry of the silicates as porosity decreases and the system will change from one of perfectly mobile components in the open sea to one approaching a "closed" type where ionic activity in solution is entirely dictated by the mass of the material present in the sediment-fluid system. Although this description is probably not entirely valid even in rocks with measured zero porosity, for practical purposes, the pelitic or clayey sediments must certainly rapidly approach the situation of a closed system upon burial. 

In Figure 10.30 the survival rate of the total sedimentary mass for the different Phanerozoic systems is plotted and compared with survival rates for the total carbonate and dolomite mass distribution. The difference between the two latter survival rates for each system is the mass of limestone surviving per unit of time. Equation 10.1 is the log linear relationship for the total sedimentary mass, and implies a 130 million year half-life for the post-Devonian mass, and for a constant sediment mass with a constant probability of destruction, a mean sedimentation rate since post-Devonian time of about 100 x 1014 g y 1. The modem global erosional flux is 200 x 1014 g y-1, of which about 15% is particulate and dissolved carbonate. Although the data are less reliable for the survival rate of Phanerozoic carbonate sediments than for the total sedimentary mass, a best log linear fit to the post-Permian preserved mass of carbonate rocks is... 

Mass-balance studies are widely considered to be the most reliable means of making quanta-tive determinations of elemental transfer rates in natural systems. Garrels (1967) and Garrels and Mackenzie (1967) pioneered the use of mass-balance calculations for mineral weathering in their classic study of Sierra Nevada springwaters. These waters were chosen because a careful set of water analyses and associated primary igneous rock minerals and the soil mineral alteration products were known. Since the actual compositions of the minerals were not known, Garrels and Mackenzie used the theoretical formulas for the minerals. 

Here, we have examined water/rock interaction processes in the geothermal systems, from the perspective of kinetic/rate reaction processes and mass transport phenomena. By careful attention to the dynamic function on water/rock interaction processes, this study applies experimental analysis and development of a geochemical simulator to answer questions about reaction mechanisms in the active hydrothermal setting. 

Thus, the entire path of relaxation for the system water-rock up to total equilibrium may be presented as some distance and the process itself as moving along this distance. At that, the distance passed maybe expressed either in fractions of unit as part o the distance or in imits of time At, if the process rate is known. For hypergene secondary minerals, this time is often disregarded. But between most hypogene primary minerals, especially aluminum silicates and silicates, the mass transfer with water is irreversible and has the lowermost rates. 

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