Rock mass quality

Although both the RMR and Q-system estimated the quality of rock mass at the same level of cavern is fair to good, rock mass quality above the cavern... 

Q system methods are used to evaluate rock mass quality. 

According to the results of rock mass physical and mechanical parameters test and engineering geological survey, rock mass quality evaluation results were obtained. As shown in Table 2 and 3. 

Based on store condition of coal seam and survey results and tests of joints surface in Xiezhuang mine, rock mass structure types are analyzed, and rock mass quality is quantificationally evaluated. The conclusion shows that engineering geological conditions of the working face roof belong to medium. Allowable hydraulic radius are calculated... 

Rock mass Quality (Q) 1.53-3.04 Poor rock 0.86-1.14, Poor rook 1.15-3.04, Poor rock... 

An estimate of the numerical value of the deformation modulus of a jointed rock mass can be obtained from various in situ tests (see Chapter 7). The values derived from such tests are always smaller than those determined in the laboratory from intact core specimens. The more heavily the rock mass is jointed, the larger the discrepancy between the two values. Thus, if the ratio between these two values of deformation modulus is obtained from a number of locations on a site, the engineer can evaluate the rock mass quality. Accordingly, the concept of the rock mass factor, J, was introduced by Hobbs (1975), who defined it as the ratio of deformability of a rock mass to that of the intact rock (Table 2.5). 

Barton et al. (1975) pointed out that Bieniawski (1974), in his analysis of tunnel support, more or less ignored the roughness of joints, the frictional strength of the joint fillings and the rock load. They, therefore, proposed the concept of rock mass quality, Q, which could be used as a means of rock classification for tunnel support (Table 9.6). They defined the rock mass quality in terms of six parameters ... 

When making estimates of the rock mass quality (Q) the following guidelines should be followed, in addition to the notes listed in the tables ... 

They provided a rock mass description and ratings for each of the six parameters that enabled the rock mass quality, Q, to be derived from ... 

Sjogren, B., Ofsthus, A., Sandberg, I., 1979. Seismic classification of rock mass qualities. Geophys. Prospect. 27, 409-442. 

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. 

We estimated from the maintenance results that the thermal loss in Gonjiam underground cold storage cavern is mostly induced from the groundwater flow and latent heat of freezing due to the poor quality of rock mass of surrounding storage cavern. 

These dynamic moduli correspond to the initial tangent moduli of the stress-strain curve for an instantaneously applied load and are usually higher than those obtained in static tests. The frequency and nature of discontinuities within a rock mass affect its deformability. In other words, a highly discontinuous rock mass exhibits a iower compressional wave velocity than a massive rock mass of the same type. The influence of discontinuities on the deformability of a rock mass can be estimated from a comparison of its in situ compressional velocity, /pf, and the laboratory sonic velocity, /p, determined from an intact specimen taken from the rock mass. The velocity ratio, /pf/t/pi, reflects the deformability and so can be used as a quality index. A comparison of the velocity ratio with other rock quality indices is given in Table 2.7. 

Percolation of water through the foundations of concrete dams, even when the rock masses concerned are of good quality and low permeability, is a decisive factor in the safety and performance of such dams. Such percolation can remove filler material that may be occupying joints that, in turn, can lead to differential settlement of the foundations. It also may open joints, which decreases the strength of the rock mass. 

The essence of velocity inversion phenomenon is the disappearance structural control effect and integrity enhancement of rock-mass. This phenomenon tells us that the existing quality classification method for rock-mass is flawed. 

Reese (1997) proposed a procedure to calculate p-y curves for rock using basic rock and rock mass properties such as compressive strength of intact rock q. Rock Quality Designation (RQD), and initial modulus of rock E-. A description of the procedure is presented in the following. 

In engineering, different parameters are used to characterize the rock quality . Frequently, they are derived from the occurrence of joints and cracks. Johnson and DeGraff (1988) noted The engineering use of rock—whether as foundation material, in excavations and tunnels, or in maintaining stable slopes—involves rock masses in which the presence of discontinuities often determines the engineering character to a greater degree than do the physical properties of the intact rock. ... 

One problem with methods that produce polycrystalline or nanocrystalline material is that it is not feasible to characterize electrically dopants in such materials by the traditional four-point-probe contacts needed for Hall measurements. Other characterization methods such as optical absorption, photoluminescence (PL), Raman, X-ray and electron diffraction, X-ray rocking-curve widths to assess crystalline quality, secondary ion mass spectrometry (SIMS), scanning or transmission electron microscopy (SEM and TEM), cathodolumi-nescence (CL), and wet-chemical etching provide valuable information, but do not directly yield carrier concentrations. 

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