ABSTRACT ABSTRACT: Analysis of a rock slope requires a geometric description of the surface and knowledge of fracture patterns and their properties. Advances in digital technology provide tools that allow the generation of digital terrain models at the centimetre-scale. In this research a terrestrial based LiDAR and a digital photogrammetry survey were conducted of a large rock slope to obtain detailed three-dimensional elevation models for interpretation of major and minor geological structure present in the slope. The paper compares both approaches and discusses how the surveys were performed and how the data were processed and interpreted. The digital elevation models from both surveying techniques are compared with each other as well as with known survey locations and other features on the rock slope to assess accuracy and detail within the 3D models. Finally, assessment of the surface models for use in mapping both large and small scale geological structures is given. 1 INTRODUCTION There is often a need in rock engineering to establish the geology and structure of the rock mass remotely. In such situations the choices are traditional photogrammetry techniques enhanced by the advantages of digital photography and an adaptation of the airborne laser technology known as LiDAR to terrestrial based technology. Light Detection And Ranging (LiDAR) uses the same principle as RADAR. The LiDAR instrument transmits light out to a target. The transmitted light interacts with the target and some of this light is reflected back to the instrument. The time for the light to travel out to the target and back to the instrument is used to determine the distance to the target. Advances in both LiDAR and digital photogrammetry technologies have been rapid in past few years and the technology can be now considered mainstream options for rock mass characterisation.

ABSTRACT ABSTRACT: Current geotechnical modelling tools are focused on the numerical analyses and generally not designed to facilitate synthesis of data from site investigation and characterisation. Site characterisation must address key geospatial issues, e.g., complex geology, highly irregular pore-water pressure, complex surface geometry and slip surface definition. An integrated digital methodology is presented that combines geospatial data management techniques with mining geological visualization software and numerical modeling tools. Specialised tools were created that facilitated geospatial analyses of piezometer data and displacement data from inclinometers. The methodology is applied to bedrock landslide in Edmonton, Canada. 1 INTRODUCTION Natural and human-induced slope movement and slope failures are complex geotechnical engineering problems involving both surface and subsurface conditions and their interactions to triggering factors (Renaud et al. 2000). Assessment of slope movement and associated hazards demands an understanding of the site characteristics and their spatial and temporal variability. In practice, engineers use modern computer software, such as Geostudio (Krahn 2003) to determine the minimum factor of safety associated with the critical slip surface (Renaud et al. 2000, Cheng 2004). Because important decisions are often based on this minimum factor of safety, it is important that the slope stability analyses accurately capture the essential features determined from the site characterisation. Current geotechnical modelling tools are focused on the numerical analyses and generally not designed to facilitate the requirements of site investigation and characterisation. Site characterisation must address key geospatial issues, e.g., complex geology, highly irregular pore-water pressure, complex surface geometry and slip surface definition (Krahn 2003). Figure 1 shows the detailed surface geometry often found in complex slope failures that was captured by modern LiDAR airborne technology.

ABSTRACT ABSTRACT: An essential step in a site characterisation program is the development of a geological model that captures the geological complexity of the site. This geological site descriptive model is then used as the basis for developing the ground engineering model which forms the basis for design. Advances in technology have led to new methods for conducting site investigation and for building the geological site descriptive model. Examples are provided that highlight the development of a geological site descriptive model and the impact of the geological complexity on the ground engineering model. 1 INTRODUCTION Geotechnical engineering is fundamentally about managing risk. Morgenstern (1995) summarized risk assessment concepts using the framework for risk management adopted by the Canadian Standards Association. Figure 1 is a generalised framework for risk management that would need to be modified for individual projects. But in all cases risk assessment requires identification of the hazard and quantifying the risk associated with each hazard. Morgenstern noted that while quantitative risk analysis (QRA) is one aspect of the framework, qualitative risk assessment is also a valuable component of risk management. With risk defined as the combination of the probability of occurrence of an undesired event and the possible extent of the event''s consequence, risk can, in principle, be calculated. The full potential of QRA is best met with the establishment of acceptable risk criteria. Establishing acceptable risk criteria in geotechnical engineering is a challenge that is evolving. Relating consequences to cost/benefit analysis provides a simpler basis for evaluating acceptable risk. The link between risk and benefit must be balanced and within the context of geotechnical engineering the risks are usually reduced to an acceptable standard by the best practical means. Site characterisation is one means of reducing risk to acceptable levels, yet routine site investigations invariable lead to wrong conclusions.

ABSTRACT ABSTRACT: “Hazard” in this context is a relative index measuring risk of ground failure. We have developed a 3D GIS-based application that accepts a wide range of real-time data inputs to compute and display a user-defined hazard index on a mine model or other geotechnical model. It is applicable to underground and open-pit mines, tunnels, dams, slopes, and general seismic risk evaluation. In principle it can be used to estimate risk of ground failure of any type. We present a case study from an underground mine in which the system is used to create a relative hazard index as a function of direct observational reporting, microseismicity, excavation geometry, stress, geological structure, and rock type. It responds in real time to data updates and presents a full 3D visualization of hazard index with respect to all aspects of the mine geometry. 1 INTRODUCTION This work is an extension and adaptation of previously successful work in multi-disciplinary, 3D integrated data interpretation in mineral exploration applications (McGaughey 2006). The previous work has resulted in significant exploration success, including new orebody discoveries based on the analysis of historical data. Here we apply a proven conceptual methodology for extracting optimum interpretation from complex, multi-disciplinary, 3D data and apply it to the difficult, general challenge of geotechnical hazard estimation. 2 THE “COMMON EARTH MODEL” Successful geotechnical understanding and monitoring of hazardous sites depends on the ability to evaluate dynamically changing ground conditions quickly and accurately. This depends on an accurate and timely understanding of multiple three-dimensional data sets from which we discern the relative level of geotechnical hazard. Whatever we are able to infer from our data becomes our geotechnical “model” of the site, which is used to justify both short-term and long-term safety and economic decisions.

ABSTRACT ABSTRACT: The ability of laser scanners to rapidly provide structural data in high inaccessible rock slopes has been frequently and correctly documented as an important advantage of the technique. Researchers have also shown the potential for characterizing varied rock mass characteristics including discontinuity orientation, spacing, persistence and roughness. In this paper, the authors, using laser scans of several rock slopes, illustrate the limitations and bias in structural data collection that must be allowed for. Orientation bias can occur both horizontally (laser plan angle bias) and vertically (laser elevation bias). It is suggested that the elevation angle of the laser scanner may produce point clouds that, when processed to derive structural data, may at best underestimate or even completely miss critical joint sets. Censoring can result in underestimating discontinuity size. Limitations related to rock mass reflectivity and textures are also highlighted. 1 INTRODUCTION Terrestrial laser scanning is being increasingly used in rock slope engineering. Recent developments have seen the introduction of point cloud processing software to allow the determination of discontinuity characteristics (Kemeny & Donovan 2005, Monte 2004, Slob et al. 2005). Researchers have shown the potential for characterization of discontinuity orientation, spacing, persistence and roughness (Feng & Roeshoff 2004). The ability of laser scanners to rapidly provide structural data in high inaccessible rock slopes has been frequently and correctly documented as an important advantage of the technique. In contrast, relatively few published studies exist outlining the limitations of laser scanning in rock slope investigations. Bias related to conventional sampling techniques for discontinuity characterization has been widely documented (Terzaghi 1965, Priest 1993, Zhang & Einstein 1998). Sources of bias include: - Orientation: discontinuities sub-parallel to the sampling line or window are under-represented - Censoring: discontinuities larger than the sampling window are not completely characterized - Truncation: discontinuities smaller than a certain size are neglected

ABSTRACT ABSTRACT: This paper focuses on the performance of the finite element (FE) equivalent continuum approach in simulating the behaviour of layered rock. The effect of length scale, which is a function of the layer thickness or joint spacing and shear stiffness of the joints, is investigated through the elastic behaviour of the laminar continuum. The performance of the classical equivalent continuum approach based on a conventional transversely isotropic formulation is been compared with that of a Cosserat equivalent continuum approach, and the FE explicit joint model. 1 INTRODUCTION Rock mass discontinuities include structural features such as fractures, faults and bedding planes that may be treated as thin layers of material distinct from the adjacent intact material. The joint planes separating the layers result in a directional dependence in behaviour of the continuum. Two main approaches have been used to simulate these highly anisotropic materials: i) techniques which explicitly model the jointed nature of the material, e.g., Discontinuous Displacement Analysis (DDA), Shi (1998), Discrete Element Method (DEM), Cundall et al. (1978), and the Finite Element Method (FEM) utilizing an explicit joint model, Goodman (1968), and ii) the FEM equivalent continuum approach, Zienkiewicz & Pande (1977). Due to its many advantages, the equivalent continuum or smeared joint model using FEM has been widely used to simulate the behaviour of layered rock masses. In this approach, the layered material is replaced by a conventional anisotropic material. Consequently, despite its widespread use, it remains problematic where the characteristic length of the problem or bending stiffness cannot be neglected. This shortcoming is a consequence of the fundamental assumption of classical continuum theory which neglects the effects of micro moments on equilibrium of the system. In Section 2, the basics of the equivalent continuum approach, its mathematical basis and finite element (FE) formulation are discussed.

ABSTRACT ABSTRACT: Although tensile strength can often be neglected for weak or highly jointed rock masses, the strength of rock bridges in moderately fractured and blocky hard rock masses contributes significantly to their self-supporting capacity and should be considered in engineering design. This self-supporting capacity can often be attributed to the distributed load bearing capacity of rock bridges separating joint segments and fractures. A rock bridge provides an effective cohesion to the joint and a rock block cannot fall or slide until all the rock bridges fail. In this study, we generate various combinations of geometric conditions of discontinuities using UDEC. Non-persistent joints generated in the UDEC models are assigned distributed joint properties randomly. A degradation model is developed in UDEC to simulate the combined failure process of intact rock and joints. Equivalent rock mass strength considering joint persistence is obtained and compared to theoretical results. The objective is to analyze how the joint persistence will increase the overall rock mass strength in jointed hard rock masses, with the focus on the verification of a previously proposed approach to consider the influence of joint persistence on the rock mass strength by the concept of equivalent block volume in the GSI system. 1 INTRODUCTION To provide a practical tool to estimate the rock mass strength for use with the Hoek-Brown failure criterion (Hoek & Brown 1980, 1988, Hoek et al. 2002), the GSI system was introduced (Hoek et al. 1995). The value of GSI ranges from 0 to 100. The GSI system consolidates various versions of the Hoek- Brown criterion into a single simplified and generalized criterion that covers all of the rock types normally encountered in rock engineering. A GSI value is determined from the interlocking structure and joint surface conditions.

ABSTRACT ABSTRACT: Microseismicity has been extensively used to monitor rock mass response to stress changes; in particular excavation induced damage at underground mines and engineered structures. A methodology has been developed to extract information on fracturing mode and orientation from existing microseismic catalogues. The interpretation is completed with the analysis of the temporal evolution of the energy content and growth patterns of the yielded volumes. The results from this analysis form the basis for the validation of the Synthetic Rock Mass Model for jointed rock presented in a companion paper by Pierce et al. Particle bond breaks in PFC3D are clustered into synthetic microseismic events following size and spacing criteria in order to simulate the activity recorded by a typical seismic array. The method to characterise the seismicity recorded in-situ is also applied to the clustered PFC3D bond breaks. The validity of the approach will be demonstrated by the good correlation found between the fracturing orientation and modes predicted by the model and those observed from in-situ recorded microseismicity. This combined approach can provide a robust method for understanding the factors controlling the behaviour and damage development within a jointed rock mass subject to different stress paths. 1 INTRODUCTION Block cave mining is an effective method for the exploitation of large underground orebodies with relatively low grade. At present, this method is extending to deeper bodies, for which it is impossible to obtain representative samples for laboratory testing in order to understand the critical factors controlling the fracturing process. The development and testing of Synthetic Rock Mass (SRM) samples in PFC3D provides a unique method to simulate the stress conditions undergone by the rock mass under the conditions typical of deep block caved orebodies.

ABSTRACT ABSTRACT: Uniaxial compression tests on rocks, if conducted at stresses below failure, typically show nonlinearity in the stress-strain curve, and hysteresis. Walsh (J. Geophys. Res., 1965) explained this behavior in terms of frictional sliding along the faces of closed cracks. Although well known and widely cited, Walsh’s model has not previously been developed in sufficient detail to be used for quantitative predictions. We revisit and extend his model, by including the effect of the stress required to close an initially open crack, and we examine the unloading process in detail. Our analysis leads to closed-form expressions for the loading and unloading portions of the stress-strain curve, as functions of elastic modulus of the uncracked rock, the crack density, the characteristic aspect ratio, and the crack friction coefficient. The model provides a good fit to the loading and unloading portions of the stress-strain curves, for experimental data on sandstones taken from the literature. 1 INTRODUCTION The mechanical behavior of rocks is to a great extent controlled by the presence of cracks and crack-like voids. This is true both with regards to the elastic behavior of the rock (see Jaeger et al. 2007), and with regards to inelastic processes such as yielding and failure (Paterson & Wong 2005). In 1965, Walsh (1965a, b ,c) published a set of three papers that provide the conceptual basis of much of our understanding of the influence of cracks on elastic rock deformation. Under hydrostatic loading (Walsh 1965a), open cracks initially (i.e., at low stresses) contribute an excess compliance to the rock. But each crack closes up at a stress that is roughly equal to aE , where E is the Young’s modulus of the uncracked rock, and a is the initial aspect ratio of the crack.

ABSTRACT ABSTRACT: We performed more than 700 hydraulic fracturing stress measurements in 140 test boreholes in various parts of Korea during the past 7 years. In this paper, the overall characteristics of the initial rock stress state in Korea are studied. For depths less than 310 m, the stress ratio (K) had a tendency to decrease and stabilize with depth. However, for some areas, excessive horizontal stresses with stress ratios greater than 3.0 were observed. A highly predominant orientation of the maximum horizontal stress component was not apparent but azimuths in the range of 70° to 90° (N70°E-EW) were superior in frequency. The results from the investigation of excessive horizontal stresses showed that there existed several regions where the localized excessive horizontal stress was large enough to potentially induce brittle failures around openings at depths of less than 300 m depth. Finally, results from a case study are briefly introduced in this paper. 1 INTRODUCTION Rock stress measurement and its estimation has been regarded as one of the major branches of study in the geo-science fields including rock mechanics, structural geology, civil engineering, mining engineering, etc. Especially for civil and mining engineering problems, the initial rock stress state is one of the key factors required to evaluate the stability and failure around an excavated underground opening, and its importance increases as constructions go deeper and the scale of rock structures become larger. The stress induced failure around an opening does not directly mean the overall collapse of the rock structure but it may bring a temporary stoppage of excavation work and/or redesigning of the supporting system. In the long run, the stress induced problem can act as a serious obstacle to ensure the stability and the economical efficiency of underground construction procedures, especially for civil engineering sites.

ABSTRACT ABSTRACT: The application of Geological Strength Index (GSI) to Japanese rocks is discussed. There have been very few attempts at using the GSI in Japan. First, we tried to compare GSI to the Japanese conventional classification for NATM tunneling. The support requirement of a tunnel in Japan is derived from the distribution of P-wave velocity over objective areas. In our case histories the authors considered that the GSI was close to the Japanese system. Second, we discuss the relationship between GSI and deformability of soft sedimentary rocks through borehole loading tests. Rocks are soft sedimentary, but discontinuities are dominant in some depth. We analyzed the influence of discontinuities by identifying moduli of elasticity, deformability and moduli of permanent deformation in comparison of those obtained through GSI for each result of loading test. The moduli of deformability estimated by GSI are pretty close to those of permanent deformation. 1 INTRODUCTION Rock mass classification has been used for characterizing rock masses in designing rock structures. It has provided some approximate properties of rock, such as rock mass strength and deformability. Systems commonly used worldwide are the Rock Mass Rating (RMR) by Bieniawski (1976), the Q-system by Barton et al. (1974), and the Geological Strength Index (GSI) by Hoek (1994). In particular, we focus here on the application of the GSI to Japanese rocks. First, we tried to compare the GSI to the Japanese conventional classification for NATM tunneling, which is based on the description of the structure of discontinuities in a rock mass. Second, we discussed the relationship between GSI and the deformability of soft sedimentary rocks through borehole loading tests. We analyzed the influence of discontinuities by identifying the elastic moduli, deformability and moduli of permanent deformation in comparison to those obtained through the GSI for each result of the loading test.

ABSTRACT ABSTRACT: Gotvand rock fill dam is being constructed in Khoozestan province (Iran) on the Karun river. Its foundation will be founded on the Aghajary formation, which consists of interbedded siltstone and mudstone layers. It is expected that creep deformation will occur during the operation life of the dam, requiring investigation of the time dependant behavior of the foundation. These investigations will include both numerical and analytical methodologies, which in turn will require the determination of creep parameters for the rock foundation layers. For this, creep tests were carried out on the rock samples and the strain vs. time curves were obtained. Considering the Burger’s creep model, the constants of creep law were determined. Comparison between the results of numerical modeling and laboratory creep tests showed that the difference between deformations in the two methods was less than 6%. Also the time required for both rocks to enter the tertiary creep stage was determined to be 40 days for sandstone under 17.72MPa uniaxial stress and 35 days for mudstone under 7.8 MPa uniaxial stress. 1 INTRODUCTION One of the more important deformation characteristics of weak rock is it’s time-dependent or creep behavior. Creep is identified as irrecoverable deformation as a function of time and without fracture. This behavior is seen in the soft rocks such as rock salt and coal. Hard rocks also show creep behavior, but only over relatively long time periods (Cristescu & Hunsche 1998). As such, one of the fundamental assumptions in the design of a rock foundation is to choose the correct modeling parameters for time-dependant analysis. Different problems may be attributed to creep of rocks including differential settlement of structures, cracking of concrete linings in tunnels, and roof failure of tunnels and caverns.

ABSTRACT ABSTRACT: The weathering characteristics of rock containing pyrite sometimes have serious influences on its environment since the oxidation of pyrite (FeS2) generates acid drainage, resulting in accelerated rock weathering and the discharge of heavy metals into the environment. Pyrite is a common and abundant sulfide mineral and it is oxidized upon exposure to oxygen at the earth’s surface. Such accelerated weathering of rock can degrade its mechanical properties and therefore menace the stability of rock structures such as slopes and tunnels. The evaluation of the physical properties of rocks and the chemical composition of the drainage were evaluated by leaching tests using a double soxhlet extractor for one month in the laboratory. Three groups of biotite gneiss were used for the soxhlet extraction experiment: Group A:<0.1 % of pyrite; Group B: about 5 % of disseminated pyrite; Group C: about 6 % of vein type pyrite. Groups A and B showed no significant quick absorption ratio after one month experiment but Group C showed about a 10 % increase in value. The uniaxial compressive strength of the three groups decreased about 20%, 10 % and 45 % for Groups A, B and C, respectively. The mechanical properties of the samples and the chemical composition of the drainage indicate that the oxidation of pyrite contained in the samples accelerated weathering, resulting in the deterioration of the mechanical properties of rocks and the possibility of discharging heavy metals and acid into the environment. 1 INTRODUCTION Natural weathering cannot be generally recognized due to its slow rate, whereas we sometimes find that rock containing pyrite FeS2) which has been exposed to the atmosphere is considerably weathered in a relatively short period.

ABSTRACT ABSTRACT: This paper presents results generated using high-resolution 3D monitoring of rock slopes and focuses upon the development of slope surface strain prior to failure. The data suggest that given sufficient measurement precision, precursory behavior, including both the rates of small rock fall activity and creep in the rock mass prior to large slope failure can be detected, measured and monitored. Combined with models of the temporal nature of slope failure evolution, for example first time failure due to brittle crack nucleation and coalescence, these data have the potential to be used to predict both the time of failure and the geometry of the mobile mass. Results are presented from monthly monitoring using 3D laser scanning of 100,000 m2 of near-vertical rock face over a three year period. During the monitoring period a dataset of in excess of 500,000 rock falls has been derived, ranging in volume from 0.0001 m3 to over 1,000 m3. The temporal patterns in the rockfall dataset suggest that the cumulative volumes of small rockfall can be treated as precursory indicators of larger failures. Environmental conditions have a perhaps surprisingly limited impact on triggering rockfall. Precursory behavior also appears scale dependant both in time and space. The behavior of the rock mass prior to the largest events recorded appears consistent, following a hyperbolic acceleration through time prior to ultimate failure. This has implications for understanding of both the conditions within the rock mass that lead to rockfalls and those environmental factors which bring the rock mass closer to failure. 1 BACKGROUND Strain accumulation manifest through slope surface deformation and disruption before failure is regularly monitored and commonly forms the basis of failure warning systems. This paper considers this behavior as a precursory signal prior to slope failure.

ABSTRACT ABSTRACT: Anisotropy plays a key role in fracture propagation models and rock fragmentation processes by rock drilling and cutting. Drilling tests with a percussive rock drill have been performed to examine the influence of anisotropy and inhomogeneity on fracture propagation in different rock types. Subsequently, thin sections of the bottom of the borehole were analyzed to get the associated crack patterns. Based on that, the attempt was made to simulate the drilling process in a specific rock material with the Particle Flow Code (PFC). Since the code is based on the discontinous mechanical approch, a rock sample is converted into an assembly of spheres, where the particles are able to interact with each other and fractures are able to propagate. Different rock cutting tools were applied such as button bits or disc cutters to penetrate different rock samples. 1 INTRODUCTION Geological parameters such as foliation, acting as weakness planes in the rock, may have a high impact on the fragmentation process underneath rock cutting tools. Extensive field and laboratory studies have been performed to examine drilling or cutting progress in correlation with the orientation of foliation and other rock properties (Thuro 1997, 2002, 2003, Thuro & Spaun 1996, Thuro et al. 2002). It has been found, that the drilling velocity as well as the disc cutter penetration is best orthogonal to foliation or schistosity and poor parallel to it. Between those angles, the drilling or cutting rates decrease significantly. After these field studies it seemed promising to investigate the obtained microscopic fracture patterns underneath rock cutting tools in different rock types and to perform a numerical simulation of it. Using the Particle Flow Code “PFC”, which is based on discontinuous mechanical properties, virtual rock samples were modeled and virtual drilling and cutting tests were performed.

ABSTRACT ABSTRACT: The discrete fracture network (DFN) approach is attractive for applications in which the geometry and properties of discrete fractures play a significant role in hydraulics, geomechanics, and resource assessment. This paper describes the development of approaches to address the particularities of carbonate geologies, including karstic features, layer boundary and through-going fractures, correlations between fracture intensity and bedding thickness. 1 INTRODUCTION The discrete fracture network (DFN) method has been used extensively for carbonate rocks since at least 1988 (Dershowitz & Doe 1988). This paper describes recent developments to improve the realism of DFN models, and their application to practical engineering problems. The following areas are addressed • Karstic Features • Bedding Controlled Fractures • Fracture Termination Modes Following the discussion of the implementation of DFN models for carbonate rocks, site characterization issues are addressed. 2 KARSTIC FEATURES Carbonate rocks typically contain enhanced porosity caused by acid solution of carbonate minerals. The formation of these ¡°vugs¡± generally requires flowing water, and as a consequence vugs have a tendency to form on fracture surfaces, or at fracture intersections. Within the DFN approach, these fracture related vugs can be implemented as a local change to the fracture aperture pattern, with higher apertures (mm to meter scales) at locations where vugs occur. Vugs also occur which are related to flow through the matrix porosity of carbonate rocks, without a spatial relationship to fracture patterns. Depending on scale, these vugs can be implemented in DFN approaches as an enhancement to the rock matrix porosity, or as a separate class of discrete features, with their own spatial process. 2.1 Preferential vug porosity at fracture intersections Solution enhanced porosity at fracture intersections can be very significant for flow through carbonate rocks, as well as fluid storage within the rock.

ABSTRACT ABSTRACT: When sands are buried in sedimentary basins the additional overburden mechanically compact the sands to a denser configuration. Burial also increases temperature and the porosity is reduced by chemical compaction. Therefore, the geomechanical behavior of sandstones is to a large extent controlled by mechanical and chemical compaction. To investigate the relationship between the geological processes and geomechanical properties we conducted rock mechanical tests and petrographical analyses on different sandstones from the North Sea. For all tested sandstones with different degrees of cementation the peak strength is closely correlated with the Young’s modulus. There seems to be a strong correlation between porosity and strength. This correlation was further improved by taking into account the primary layering. Sonic travel times also correlate with the peak strength and can be used as a method for calculating rock strength. 1 INTRODUCTION 1.1 Introduction After sands are deposited they become sandstones during the geological history. The main driver for this process is the porosity reduction in the sand caused by deeper burial. Understanding the effect geological history has on the strength and deformation properties of sands is important. For example, the oil industry needs to plan and conduct safe drilling, design completions and manage sand production. The objective of this paper is to investigate the relationship between geological processes and geomechanical properties. A rock mechanical test program and petrographical analyses of different sandstones from the North Sea were conducted. 1.2 Sandstone diagenesi s When sand is deposited it usually has a porosity around 35-50% dependent on the initial sorting of the sand, mineralogy content and amount of fines (Bjørlykke 1989). During burial these sediments experience porosity reduction in the form of sediment volume reduction or increase in bulk density due to mechanical and chemical compaction.

ABSTRACT ABSTRACT: This paper introduces a new in-situ technique for characterizing rock mass mechanical strength and the associated spatial distribution in the ground. The technique involves automatic drilling process monitoring (DPM). Case examples are given to show the original DPM data and analyzed results in a weathered rock mass. The drilling machines in the examples are pneumatic rotary-percussive drilling machines with down-the-hole hammers. The DPM data can directly show the in-situ rock mass drilling resistance strengths and their spatial distribution along the drillhole in the ground. The DPM is a simple, reliable and practical tool for furthering the practice and knowledge of rock mechanics and engineering in the underground environments comprising weathered soils and rocks. 1 INTRODUCTION Characterization of rock mass quality has been an important area of research and development in rock mechanics since Ritter (1879) attempted to formalize an empirical approach to tunnel design. For more than 100 years, a number of rock mass classification methods have been developed and adopted to quantify rock mass quality in rock engineering design (for example, tunnel and cavern support design). They include the Rock Quality Designation Index (Deere et al. 1967), the Rock Structure Rating (Wickham et al. 1972), the Rock Mass Rating (Bieniawski 1973, 1976, 1989), the Rock Tunnelling Quality Index (Barton et al. 1974, Barton 2006), the Basic Quality and the Host Rock Rating (Lee et al. 1996). 1996). An examination of these methods indicates that similar parameters are used in all the methods in describing rock mass quality. These parameters include the rock quality designation (RQD), uniaxial compressive strength of intact rock (UCS), rock structural conditions (block size, frequency of joints), conditions of joints (spacing, size, aperture, infilling, roughness), orientation of the joints relative to opening axis, groundwater conditions and insitu stresses

ABSTRACT ABSTRACT: A noncircular tunnel was excavated in massive granite. The tunnel geometry and orientation relative to the stress field had been selected to minimize the potential for the development of an excavationinduced damage zone. The extent and characteristics of this excavation damage zone was measured using velocity profiling and permeability measurements in radial boreholes. The results showed the distribution of damage was contained in a zone less than 1-m thick adjacent to the excavation boundary and that the damage was not uniformly distributed around the excavation. A damage model was formulated in a discrete element code and calibrated to laboratory properties. The model was then used to analyze the noncircular tunnel. The development of the damage zone in the numerical model was found to be in good agreement with the field measurements. 1 INTRODUCTION It is well known that the creation of an underground excavation disturbs the stress field. When the stress magnitudes on the boundary of the excavation exceed the rock mass strength yielding occurs and an excavation damage zone (EDZ) can be readily observed (Martin et al. 1997). However, in many situations the stress magnitudes may not exceed the rock mass strength and in such cases it is not obvious if an EDZ has formed or not. Tsang et al. (2005) noted that an EDZ will form around all underground openings and that in crystalline rock the dominant processes are micro and macro fracturing. These processes can lead to significant increases in flow and transport properties. Hence, quantifying the extent and characteristics of the EDZ is important for the nuclear waste industry which relies on the sealing of underground openings to minimize the risk for radionuclide transport. It is well known that the presence of cracks affects the strength and mechanical properties of a rock.

ABSTRACT ABSTRACT: Prediction of fluid flow through rock masses is important in mining and civil projects, oil and underground water extractions and geothermal and environmental issues. It is well known that the fractures in rock masses produce main paths of fluid flow, thus, the fracture properties such as normal stiffness, shear stiffness, aperture etc, govern flow through fractures in hydraulic (H) and hydro-mechanical (HM) analysis. In this study H and HM analysis of fractured rock masses were performed and water inflow into underground excavations were determined. Also, the effects of fracture properties such as normal stiffness, shear stiffness and aperture on inflow were studied. Results show that inflow increases with increasing normal stiffness, shear stiffness and aperture size. Furthermore, flow rate resulting from H analysis is greater than that from HM analysis. Finally, the inflow through fractures around the tunnel shows different distribution pattern in H and HM analysis. It is concluded that hydromechanical coupled analysis results are more realistic compared to uncoupled hydraulic analysis. 1 INTRODUCTION Prediction of fluid flow through rock masses is significant in mining and civil projects, oil and underground water extraction, and when considering certain geothermal and environmental issues. The inflow into an excavation could affect the stability of the excavation and from an environmental point view, it can transport contaminants; minimum water inflow is therefore typically required. However in oil and underground water extraction, maximum flow is desirable. Therefore the prediction of inflow into an excavation and fluid flow main paths are important factors in underground construction, such as tunnels. It is well known that fractures are main paths for fluid flow in rock masses, thus fracture properties such as normal stiffness, shear stiffness, aperture, friction angle, dilation angle etc, could affect the inflow and hydraulic conductivity.