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Also discussed will be steps necessary for planning of a geophysical program and ground truthing of the results presented in a geophysical report. It is the sincere hope of the instructors that the participants come away from this short course with a better understanding of geophysics and its potential as a tool for geotechnical investigations.

Christopher Phillips, M. He completed his Masters on the subject of estimating ground engineering properties using seismic surface waves and has published numerous papers on topics ranging from new methods for estimating ground engineering properties of soils, underground void detection, mapping of abandoned mine workings, methods for measuring engineering properties of soils and rock, aggregate resource evaluation, and the use of non-invasive methods for profiling thickness of pavement structures.

Short Courses

Michael Maxwell, P. He has conducted geophysical investigations on diverse mining, geotechnical, and environmental projects ranging from small to large scale, including pipeline and road routing, hydrocarbon, contaminant and other hazard detection, marine port and linear infrastructure surveys, underground mining exploration, and mining and infrastructure development.

He has extensive experience in various environments including arid and cold regions, mountain, arctic and Antarctic surveys, marine and terrestrial work, underground and surface mining. Maxwell also continues geophysical research work in a range of geophysical techniques and particularly 2D and 3D ERI through his affiliation with the University of British Columbia as an Honorary Research Associate.

The objective of this course is to provide a background in 3D numerical modeling for slope stability, groundwater analysis, and settlement using Rocscience software tools Slide3 and RS3. In this course you will learn how to get the most out of the Rocscience slope stability suite through a balanced mix of lectures and hands-on computer analyses using practical examples collected over the years.

All participants are required to bring a laptop since the course will involve hands on usage of our software. Trial versions of the software will be available for download ahead of time. Sina Javankhoshdel is a Geomechanics Specialist at Rocscience. He holds his Ph. Sina joined Rocscience in and he was one of the geotechnical developers of Slide2 software, to which he added Spatial Variability Analysis. He has published more than 20 papers on the topic of probabilistic analysis of slopes and retaining structures considering spatial variability.

Robert Johnson, P. In four of those years, over four million vertical square feet of MSE structures have been designed and are in service. The last four years have consisted of developing internal and external engineers, overseeing the design work of the Tensar engineering group focused on wall and slope applications, and building relationships with local universities.

Benefit quantification and performance validation of geogrids in roads will include laboratory testing, field testing and numerical modeling. An overview of typical current software design tools for flexible and unpaved roads and how to incorporate geogrid in the design will be discussed. Several design examples will be presented to illustrate software application.

Lois G. Schwarz, Ph. She holds a Ph. Schwarz has more than 25 years of experience in geotechnical engineering and research. What only if the Auth identifies sent? I run you have the business to speculate the honest Sex. You should drink a archivesHave at ScrapBook, a Firefox savoir. It is an sickening firm starsVery.

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Phillip C. Helwig, Canada; and Mr. Bajaj, ceramic engineer, Roorkee. We are very thankful to A. We appreciate their kind permission to use excerpts from their publications. In addition, we thank all the eminent researchers whose work is mentioned here. We are also deeply grateful to our beloved families for their sacrifice, love, deep moral support, and suggestions; and to all of our friends and students.

We also thank Holy Teacher Dr. We wish to encourage all enlightened engineers and geologists to kindly send their important suggestions for improving this book to us.

Rock Mechanics from CRC Press - Page 1

Rock mass classifications form the backbone of the empirical design approach and are widely employed in rock engineering. Engineering rock mass classifications have recently been quite popular and are used in feasibility designs. When used correctly, a rock mass classification can be a powerful tool in these designs. On many projects the classification approach is the only practical basis for the design of complex under- ground structures.

Engineering rock mass classification systems have been widely used with great suc- cess in Austria, South Africa, the United States, Europe, and India for the following reasons: 1. They provide better communication between planners, geologists, designers, contrac- tors, and engineers.

Engineers prefer numbers in place of descriptions; hence, an engineering classifica- tion system has considerable application in an overall assessment of the rock quality. The classification approach helps in the organization of knowledge and is amazingly successful. An ideal application of engineering rock mass classification occurs in the planning of hydroelectric projects, tunnels, caverns, bridges, silos, building complexes, hill roads, rail tunnels, and so forth. Reliability may decrease for medium rock conditions. No single classification is valid for assessment of all rock parameters.

Selection of a classification for estimating a rock parameter is, therefore, based on experience. The objective should be to classify the undisturbed rock mass beyond excavated faces. Precaution should be taken to avoid the double-accounting of joint parameters in the classification and in the analysis.

Thus, joint orientation and water seepage pressure should not be considered in the classification if these are accounted for in the analysis. It is necessary to account for fuzzy variation of rock parameters after allowing for uncertainty; thus, it is better to assign a range of ratings for each parameter. There can be a wide variation in the engineering classifications at a location.

When designing a project, the average of rock mass ratings RMR and geological strength index GSI should be considered in the design of support systems. For rock mass quality Q , a geo- metric mean of the minimum and the maximum values should also be considered in the design. A rigorous classification system may become more reliable if uncertain parameters are dropped and considered indirectly.

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This classification is a holistic whole approach, considering all parameters. Hoek and Brown realized that a classification system must be non-linear to classify poor rock masses realistically. In other words, the reduction in strength param- eters with classification should be non-linear, unlike RMR in which strength parameters decrease linearly with decreasing RMR. Mehrotra, , found that strength parameters decrease non-linearly with RMR for dry rock masses.

More research is needed on the non-linear correlations for rock parameters and rock mass characterization. Sound engineering judgment evolves out of long-term, hard work in the field. More attention should be focused on the weak zones joints, shear zones, fault zones, etc.

Rock failure is localized and three dimensional in heterogeneous rock mass and not planar, as in homogeneous rock mass. First, a geological map on macro-scale , should be prepared before tunneling or laying foundations. Then an engineering geological map on micro-scale should be prepared soon after excavation. This map should highlight geological details for an excavation and support system. The engineering geological map helps civil engineers immensely. Such detailed maps prepared based on thorough investigation are important for tunnel excavations.

If an engineering geological map is not prepared then the use of a tunnel boring machine TBM is not advisable, because the TBM may get stuck in the weak zones, as experienced in Himalayan tunneling. An Iraqi proverb eloquently illustrates this idea: Ask questions, but do not make a single mistake. The empirical approach, based on rock mass classifications, is the most popular because of its simplicity and ability to manage uncertainties. Geological and geotechnical uncertainties can be tackled effectively using proper classifications.

Moreover, this approach allows designers to make on-the-spot decisions regarding sup- porting measures if there is a sudden change in the geology. The analytical approach, on the other hand, is based on assumptions and obtaining correct values of input parameters. This approach is both time-consuming and expensive.

The observational approach, as the name indicates, is based on monitoring the efficiency of the support system. Classifications are likely to be invalid in areas where there is damage due to blasting and weathering such as in cold regions, during cloudbursts, and under oceans. If the rock has extraordinary geological occurrence EGO problems, then these should be solved under the guidance of national and international experts. According to Fairhurst , designers should develop design solutions and design strategies so that support systems are ductile and robust, that is, able to perform ade- quately even in unknown geological conditions.

For example, shotcreted and reinforced rock arch is a robust support system. The Norwegian Method of Tunneling NMT after 30 years, has evolved into a successful strategy that can be adopted for tunnel supporting in widely different rock conditions. Experience led to the following strategy of refinement in the design of support systems. In feasibility studies, empirical correlations may be used for estimating rock parameters.

At the design stage, in situ tests should be conducted for major projects to determine the actual rock parameters. It is suggested that in situ triaxial tests with s1, s2, and s3 applied on sides of the cube of rock mass should be conducted extensively, because s2 is found to affect both the strength and deformation modulus of rock masses in tunnels. This is the motivation for research, and its presentation in this book is likely to prove an urgent need for in situ polyaxial tests. At the initial construction stage, instrumentation should be carried out in drifts, caverns, intersections, and other important locations with the objective of acquiring field data on displacements both on the supported excavated surfaces and within the rock mass.

Instrumentation is also essential for monitoring construction quality. These data should be utilized in computer modeling for back analysis of both the model and its parameters Sakurai, At the construction stage, forward analysis of rock structures should be carried out using the back analyzed model and the parameters of rock masses. Repeated cycles of back analysis and forward analysis BAFA may eliminate many inherent uncer- tainties in geological mapping and knowledge of engineering behavior of rock masses. The predicted displacements are very sensitive to the assumed model, parameters of rock masses and discontinuities, in situ stresses, and so forth.

The principle of dynamic programming should be adopted. Construction strategy will evolve with time in every step to reach the goal quickly; for example, grouting may improve ground conditions significantly. The aim of computer modeling should be to design site-specific support systems and not just analysis of the strains and stresses in the idealized geological environment. In a non-homogeneous and complex geological environment, which is difficult to pre- dict, slightly conservative rock parameter values may be assumed for the purpose of designing site-specific remedial measures lines of defenses and for accounting in- herent uncertainties in geological and geotechnical investigations.

Be prepared for the worst and hope for the best. This revised edition offers an integrated prac- tical knowledge on the rock mass characterization for use in software packages along with extensive tables. This text is a specialized book on rock mass classifications and is written for civil engineers and geologists who have basic knowledge of these classifications. There are several types of popular software for non-linear analysis, but they need an approximate solution to be useful, which is provided by the engineering rock mass classification.

This book is written to help civil engineers and geologists working on civil engineer- ing jobs such as hydroelectric projects, foundations, tunnels, caverns, and rapid landslide hazard zonation. Some engineers work under the assumption that a rock mass is homogeneous and isotropic, but this may not always be correct as shear zones are encountered frequently.

Because of this, shear zone treatment is discussed in Chapter 2. Analysis and design in rock mechanics—The general context. In Comprehensive rock engineering Vol. New York: Pergamon. Hoek, E. Practical estimation of rock mass strength. Hudson, J. Rock engineering systems — Theory and practice p. Chichester, UK: Hor- wood Ltd. Estimation of engineering properties of rock mass p. Sakurai, S.

Back analysis in rock engineering. Singh, B. Software for engineering control of landslide and tunnelling hazards p. Rotterdam, A. A shear zone is the outcome of a fault where the displacement is not confined to a single fracture, but is distributed through a fault zone. Shear zones vary in thickness from a fraction of meters to hundreds of meters. Depending upon the thickness, the shear zone has a variable effect on the stability of underground openings and foundations.

The thicker the shear zone, the higher chance it will be unstable. Clay-like gouge in shear zones is generally highly over-consolidated and shows high cohesion. Similarly, weak zones, fault zones, and thrust zones can also cause instability. It is envisaged that the rock mass affected by a shear zone is much larger than the shear zone.

Hence, this rock mass must be downgraded to the quality of the shear zone so that a heavier support system can be installed. In this method, weak zones and the surrounding rock mass are allocated their respective Q-values from which a mean Q-value can be deter- mined, taking into consideration the width of the weak zone. Equation 2. The strike direction y and thickness of the weak zone b in relation to the tunnel axis is important for the stability of the tunnel; therefore, the following correction factors have been suggested for the value of b in Eq.

Similarly, the weighted mean of joint alteration number Jam may also be estimated. Further, when multiplying Eq. These computations are quite encouraging.

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  • If the surrounding rock mass near a shear zone is downgraded by using Eqs. Figure 2. First the shear zone is excavated with caution up to some depth. Immediately after excavation one thin layer of steel fiber reinforced shotcrete SFRS is sprayed. This methodology is urgently needed if the New Austrian Tunneling Method NATM or Norwegian Method of Tunneling NMT is to be used in the tunnels of the Himalayan region, as seams, shear zones, faults, thrusts, and thin intra-thrust zones are frequently found along tunnels and caverns there.

    The excavation is made manually. Steel ribs are placed closely and shotcreted until the shear zone is crossed. Each round of advancement should be limited to 0. In the Himalayan tunnels the rock mass above the shear zone is often water charged. This may be because of the presence of impermeable gouge material in the shear zone. Hence, engineers should be prepared to tackle this problem from the start of the project.

    The infilling and crushed weathered rock is oozed out by water jet at very high pressure and then backfilled by rich concrete. No blasting is used to avoid damage to the rock mass. Unfortunately, it was too late to change the site of this dam. The treatment of shear zones, joints, solution cavities in limestone, and so forth is essential for the long life of building foundations.

    The strategy for their treatment should be the same as that adopted for dam foundations and as shown in Figures 2. Undulating rock profiles are a major problem in the construction of footings, well foundations, and piles.


    However, massive rocks do not pose instability problems, because their behavior is similar to that of the rock material intact rock. Application of Q-system in design decisions con- cerning dimensions and appropriate support for underground installations. In Subsurface Space pp. Oxford: Pergamon. Bhasin, R. Geotechnical evaluation and a review of remedial measures in limiting deformations in distressed zones in a powerhouse cavern.

    New Delhi, India. Updating of the Q-system for NMT. Oslo: Fagernes, Norwegian Concrete Association. Structural safety of buildings on shallow foundations on rock—Code of practice p. New Delhi: Bureau of Indian Standards. Lang, T. Theory and practice of rock bolting. AIME Trans. Samadhiya, N. Influence of shear zone on stability of cavern p. Uttarakhand, India: Dept. Software for engineering control of landslides and tunnelling hazards p. Rotterdam: A. Design of gravity dams pp. Bureau of Reclamation. In other words, this is the smallest element of rock block not cut by any fracture.

    There are always some micro-fractures in the rock material, but these should not be treated as fractures. Rock material has the characteristics shown in Figure 3. Also, if a rock is massive and contains very little discontinuity, it could ideally behave as a homogeneous medium. Hoek and Brown showed that homogeneity is a characteristic dependent on the sample size. If the sample size is considerably reduced, the most heterogeneous rock will become a homogeneous rock Figure 3.

    In the figure s is a constant that depends on rock mass characteristics as discussed in Chapter Deere et al. An inhomogeneous rock is more predictable than a homogeneous rock because the weakest rock gives distress signals before final collapse of the rock structure. ISO proposed classification of rock material based on uniaxial compres- sive strength UCS as shown in Table 3. It is evident that rock material may show a large scatter in strength, say of the order of 10 times; hence, the need for a classification system based on strength and not mineral content.

    Source: ISO , The UCS can be easily predicted from point load strength index tests on rock cores and rock lumps right at the drilling site because ends of rock specimens do not need to be cut and lapped. Table 8. There are frequent legal disputes on soil-rock classification. Deere and Miller John, suggested another useful classification system based on the modulus ratio, which is defined as the ratio between elastic modulus and UCS. Physically, a modulus ratio indicates the inverse of the axial strain at failure.

    Thus, brittle materials have a high modulus ratio and plastic materials exhibit a low modulus ratio. Class I: Fracture propagation is stable because each increment of deformation beyond the point of maximum load-carrying capacity requires an increment of work to be done on the rock.

    Class II: Rocks are unstable or self-sustaining; elastic energy must be extracted from the material to control fracture. If end restraint becomes severe, it is possible that a Class II rock might behave like a Class I material. Wawersik conducted experiments on six rock types to demonstrate the features of Class I and II rocks Figure 3. Typical S-shape stress-strain curves may be obtained for rocks with micro-fractures. Further, the post-peak curve for Class II rocks shows reduction of strain after failure. The lateral strain increases rapidly after peak stress in Class II rocks. Brittle rocks, therefore, may be kept in the Class II category.

    A deep tunnel within dry, massive, hard Class II and laminated rocks may fail because of rock bursts due to uncontrolled fracturing where tangential stress exceeds the strength of the rock material see Chapter Hence, it is necessary to test rock material in a Servo-controlled closed loop testing machine to get the post-peak curve. Axial cleavage fracture is a local stress-relieving phenomenon that depends on the strength anisotropy and brittleness of the crystalline aggregates as well as on the grain size of the rock.

    Local axial splitting is virtually absent in fine-grained materials at stress levels below their compressive strength. Shear failure manifests in the development of boundary faults followed by interior fractures , which are oriented at approximately 30 degrees to the sample axis. In fine- grained materials where the inhomogeneity of the stress distribution depends only on the initial matching of the material properties at the loading platen interfaces, boundary and interior faults are likely to develop simultaneously and appear to have the same orientation for any rock type within the accuracy of the measurements on the remnant pieces of collapsed specimens basalts, etc.

    Local axial fracturing governs the maximum load-carrying ability of coarse-grained, locally inhomogeneous Class I and II rock types.

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    Thus, in coarse-grained rocks the ultimate macroscopic failure mode of fully collapsed samples in uniform uniaxial com- pression cannot be related to peak stress. In fine-grained, locally homogeneous rock types, which most likely are Class II, the peak stress is probably characterized by the development of shear fractures seen in continuous failure planes. In controlled fracture experiments on very fine-grained rocks, the final appearance of a collapsed rock spec- imen probably correlates with its compressive strength.

    However, if rock fracture is uncontrolled, then the effects of stress waves produced by the dynamic release of energy may override the quasi-elastic failure phenomenon to such an extent that the latter may no longer be recognizable. The extent of the development of the two basic failure modes, local axial splitting and slip or shear failure, determines the shape of the stress-strain curve for all rocks subjected to uni- directional or triaxial loading.

    Partially failed rocks still exhibit elastic properties. However, the sample stiffness decreases steadily with increasing deformation and loss of strength. Macroscopic cleavage failure e. The dynamic tensile strength of rocks granite, diorite, limestone, and grigen is found to be about four to five times the static tensile strength Mohanty, Brazilian tensile strength of laminated rocks and other argillaceous weak rocks like marl do not appear to be related to the UCS of rock material Constantin, personal communication.

    The potential for disintegration of rock material in water can be determined by immersing rock pieces in water for up to one week. Their stability can be described using the terms listed in Table 3. Ultrasonic pulse velocity in a saturated rock is higher than in a dry rock because it is easier for pulse to travel through water than in air voids. However, the UCS and modulus of elasticity are reduced significantly after saturation, particularly in rocks with water sensitive minerals. On the other hand, the post-peak stress-strain curve becomes flatter in the case of undrained UCS tests on saturated samples because increasing fracture porosity after failure creates negative pore water pressure.

    There are no visible connections between durability and geological age, but durability increased linearly with density and inversely with natural water content. Based on his results, Gamble proposed a classification of slake durability as seen in Table 3. The slake durability classification is useful when selecting rock aggregates for road, rail line, concrete, and shotcrete. Rock in field is generally jointed. It was classified by core recovery in the past and later in the s by modified core recovery RQD , which will be discussed in Chapter 4.

    TABLE 3. A study of jointed and fractured rock. Part I. Rock Mechanics and Engineering Geology, 5—6 2—3 , — Deere, D. Washington, D. Department of Transportation. Fairhurst, C. The phenomenon of rock splitting parallel to the direction of maximum compression in the neighborhood of a surface. Gamble, J. Durability—Plasticity classification of shales and other argillaceous rocks p. University of Illinois. Strength of rock and rock masses. Underground excavations in rocks.

    Institution of Mining and Metallurgy p. London: Maney Publishing. ISO Geotechnical investigation and testing—Identification and classification of rock — Part 1: Identification and description pp. Geneva: International Organization for Standardization. Mohanty, B. Measurement of dynamic tensile strength in rock by means of explosive-driven Hopkinson bar method. Wawersik, W. Detailed analysis of rock failure in laboratory compression tests p.

    University of Minnesota. If nature has given weakness, nature will compensate. No one is perfect. It is more sensitive as an index of the core quality than the core recovery. The RQD is a modified percent core recovery that incorporates only sound pieces of core that are mm 4 in.

    The following methods are used for obtaining RQD. Artificial fractures can be identified by close fitting cores and unstained surfaces. All of the artificial fractures should be ignored while counting the core length for RQD. A slow rate of drilling will also give better RQD. The relationship between RQD and the engineering quality of the rock mass as proposed by Deere is seen in Table 4.

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    The correct procedure for measuring RQD is shown in Figure 4. This method is relatively cheap and rapid to apply and is helpful when studying a large volume of rock masses. For details of a seismic method, any textbook dealing with this topic may be useful. Volumetric Joint Count When cores are not available, RQD may be estimated from the number of joints discon- tinuities per unit volume Jv. Palmstrom proposed a new equation Eq. The volumetric joint count Jv has been described by Palmstrom , , and Sen and Eissa Nr can be estimated from joint observations, because it is based on measurements of random frequencies.

    In cases where random or irregular jointing occurs, Jv can be found by counting all of the joints observed in an area of known size. Table 4. Palmstrom reported that Eq. However, when cores are not available, Eq. Although RQD is a simple and inexpensive index, when considered alone it is not sufficient to provide an adequate description of a rock mass because it disregards joint orientation, joint condition, type of joint filling, and stress condition.

    In principle, it is based on the measurement of the angle between each joint and the surface or the drill hole Figure 4. To solve the problem of small intersection angles and to simplify the observations, the angles have been divided into intervals for which a rating of fi has been selected, as shown in Table 4. The selection of intervals and the rating of fi have been determined from a simulation.

    To make the approach clear, examples are given in the next section for both surface and drill hole measurements. TABLE 4. The observation area in both the examples is 25 m2, and the results from the observations are given in Table 4. In the second example all of the joints belong to joint sets and there is no ran- dom joint. As observed, the weighted joint density measurement produces values that are somewhat higher than the known value for the volumetric joint count Palmstrom, The rock block shape should be described according to the terms in Table 4.

    The shape of rock blocks should be correlated to the joint spacing. Terms Figure Description 1 Polyhedral blocks Irregular discontinuities without arrangement into distinct sets, and of small persistence 2 Tabular blocks One dominant set of parallel discontinuities, for example, bedding planes, with other noncontinuous joints; thickness of blocks much less than length or width 3 Prismatic blocks Two dominant sets of discontinuities, approximately orthogonal and parallel, with a third irregular set; thickness of blocks much less than length or width 4 Equidimensional Three dominant sets blocks of discontinuities, approximately orthogonal, with occasional irregular joints, giving equi- dimensional blocks 5 Rhombohedral Three or more dominant, blocks mutually oblique, sets of joints, giving oblique- shaped, equidimensional blocks 6 Columnar blocks Several, usually more than three, sets of discontinuities; parallel joints usually crossed by irregular joints; length much greater than other dimensions Sources: ISO , ; Palmstrom, The 5 m long part of the core has been divided into the following three sections with similar density of joints: For each section the number of joints within each angle interval has been counted and the results are shown in Table 4.

    The evaluation of weighted joint density requires small additional effort over currently adopted logging practices. The only additional work is to determine the number of joints within each angle interval. The angles chosen for the intervals between the joint and the drill hole should be familiar to most people, and this should make the observa- tions for wJd quick. The use of only four intervals makes the registration simple and easy.

    Eventually, wJd may prove a useful parameter to accurately measure the joint density. Priest and Hudson derived the following relationship Eq. The reason for low RQD values must be determined: poor drilling techniques, core breakage upon handling, stress-relief or air staking, thinly bedded or closely jointed zone, or zone of poor rock conditions with shearing, weathering, and so forth.

    It is the last condition that would be of most concern. If these conditions were found to exist, additional borings or other types of explorations might be required to as- sess the orientation and characteristics of the weak zone and its potential effect on the engineering structure to be built. RQD value is always equal to or less than the core recovery. Thus the zone would be adequately red-flagged; the worse the rock, the larger the red flag. By use of this simple technique a quick comparison can be made among boring logs in various parts of the site and, upon occasion, a weak structural feature can be followed from boring to boring.

    The depth of weathering and its general decrease in severity with depth as indicated by the RQD is successfully depicted with the red-flag concept. The depth of required foundation excavation often can be determined early with a quick study of the red-flag display. The RQD is sensitive to the orientation of joint sets with respect to the orientation of the core; that is, a joint set parallel to the core axis will not intersect the core unless the drill hole happens to run along the joint.

    A joint set perpendicular to the core axis will intersect the core axis at intervals equal to the joint spacing. For intermediate orienta- tions, the spacing of joint intersections with the core will be a cosine function of angle between joints and the core axis. Thus, RQD is a directionally dependent parameter and its value may change significantly, depending upon the borehole orientation. The use of the volumetric joint count can be useful in reducing this directional dependence.

    Laubscher and Taylor proposed modifications in RQD values because of poor blasting practices. Therefore, in a same rock mass, the RQD may tend to increase with depth. The limit of 10 cm is based on extensive experience. Some approximate corrections are available to remove these effects.

    In addition, RQD has also been used to estimate the deformation modulus of the rock mass. Rock mechanics design in mining and tunneling p. Bieniawski, Z. Engineering rock mass classifications p. New York: John Wiley. Cording, E. Rock tunnel support and field measurements. In Proceedings of the rapid excavation tunnelling conference pp.

    Geological considerations, rock mechanics in engineering practice pp. Zienkiewicz Eds. New York: Wiley. Rock quality designation RQD after twenty years U. The rock quality designation RQD index in practice—Rock classification systems for engineering practice. Kirkaldie Ed. Philadelphia: American Society for Testing and Materials. Hack, R. An evaluation of slope stability classification.

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    Gama et al. Portugal, Madeira, Funchal, 25—28 November. Lisboa: Sociedade Portuguesa de Geotecnia. Geotechnical investigation and testing—Identification and classification of rock—Part 1: Identification and description pp. Geneva, Switzerland: International Organization for Standardization. Laubscher, D. The importance of geomechanics classification of jointed rock masses in mining operations. Johannesburg, South Africa. Palmstrom, A. The volumetric joint count—A useful and simple measure of the degree of jointing. Application of the volumetric joint count as a measure of rock mass jointing.

    Bjorkliden, Sweden. A general practical method for identification of rock masses to be applied in evaluation of rock mass stability conditions and TBM boring progress. Oslo, Norway. RMi—A system for characterising rock mass strength for use in rock engineering. Journal of Rock Mechanics and Tunnelling Technology, 1 2 , 69— Measurement and characterization of rock mass jointing, in situ characterization of rocks. Saxena Eds. Measurements of and correlations between block size and rock quality designation RQD. Tunnelling and Underground Space Technology, 20, — Priest, S.

    Discontinuity spacings in rock. Romana, M. A geomechanical classification for slopes: Slope mass rating in comprehensive rock engineering, principles—Practice and projects, J. Hudson, Ed. Sen, Z. Rock quality charts for log-normally distributed block sizes. Singh, S. Mining industry and blast damage. Journal of Mines, Metals and Fuels, December, — Zhang, L. Using RQD to estimate the deformation modulus of rock masses. Judgement enters through engineering geology. Terzaghi proposed that the rock load factor Hp is the height of the loosening zone over the tunnel roof, which is likely to load the steel arches.