Abstract The Alhama de Murcia Fault (AMF) is an active fault located in the SE of Spain. This fault developed a ~80 m thick band of highly deformed clay rich gouge with a marked tectonic fabric (foliated gouge) that constitute a notable anisotropy. In this work we present the result of consolidated-undrained triaxial tests (CU) performed under low confining pressure (50, 150 and 300 kPa) to several sets of core specimens carved with different orientation of the tectonic fabric. We analyse strain-stress relationships of each test, as well as failure modes, obtaining a brittle behaviour at lowest confining pressure, and ductile at highest. The resistance results show that the gouge of the AMF behaves as a hard soil or very soft rock. Those results are adjusted by the non-linear Hoek&Brown criteria for every orientation by considering two working hypotheses: (i) considering the fault gouges as intact rock, and (ii) considering the fault gouge as tectonised rockmass. Both working hypotheses are consistent, reaching maximum values of resistance when axial load (σ 1 ) is applied perpendicular to the foliated planes of the gouge, decreasing for lower angles with the anisotropy planes which favour failure. Anisotropy index R c has been estimated in a range between 1.40 and 3.16, which classify the fault gouge as low to medium anisotropic behaviour. Nevertheless, results from specimens with the tectonic fabric oriented most favourably for failure occurrence do not fit such a pattern, since strength for this orientation is greater than intermediate orientation. Such an anomalous result could be related to an increase in the roughness of the failure planes controlled either by the presence of larger fragments of protolith or by an asymmetry on the roughness of the weakness planes related to the original microscale structures characterized by a strong reorientation of clays. These results will be useful to applications related to slope and tunnel stability, and also to the understanding of the relationships between aseismic creep deformation and earthquakes nucleation within the AMF.

Abstract Drilling directional and horizontal wellbores plays an important role in the exploitation of hydrocarbons. In the case of long operated and unconventional fields the importance of this type of drilling is fundamental. The horizontal and directional drilling technologies are also applicable in other fields. Directional and horizontal holes are among other various types of drilling under buildings, microtunnels, injection and storage holes. This technology is also used in obtaining coal-bed methane and in underground coal gasification methods. Compared to holes with vertical axes, directional drilling is a much more complex issue. The curvature of the wellbore's axis, passing through the horizontally stratified rock mass, causes the conditions around its cross section to be strongly anisotropic. Not infrequently, the same rock material of each layer exhibits anisotropic properties. Ensuring the stability of the well is very difficult under such conditions. The proper determination of the state of stress, strain and displacement of the rock mass around the hole is critical in the design of directional holes. Numerical analysis tools which take into account the structure of the rock mass and the mechanical properties of rocks along the well trajectory are used for this purpose. The article presents numerical simulations of changes of the rock mass state around a directional well. The calculations were conducted with various material models of rock: the linear-elastic model, the linear-elastic with regard to pore fluid flow model, the elastic – plastic model, the Drucker-Prager cap model with pore fluid flow, the concrete damage plasticity model (CDP), and the cracked material model. The impact of primary pressure, lamination and anisotropy of the rock mass are also included in the calculation. Based on the results of the calculations we analyze the impact of the behavior of rocks on the wellbore's stability. 1. Introduction Directional wells have become common in hydrocarbon exploitation mainly due to increased contact with the deposit. They are used especially for thin and low-pressure reservoirs. Drilling more horizontal lateral holes renders a project even more profitable.

Abstract In Japan, natural gas that has been dissolved in water is mainly produced by gas lifted through a perforated casing. Since abnormal formation pressure causes abnormal cross flow among production sections, a technique for sealing the sections with abnormal formation pressures is required, in order to increase natural gas production. In this study, we propose a new drilling technique for the fresh sealing cement using waterjet. Preliminary laboratory drilling tests were conducted under air condition to clarify the fundamental drillability of a waterjet for the purpose of sealing cement. The main results obtained in this study can be summarized as follows: The waterjet has a good drilling performance for the fresh sealing cement. The suitable aging time before sealing cement for drilling should be determined based on the mechanical properties required for sealing the sections with abnormal formation pressures. 1. Introduction In the South Kanto natural gas fields of Japan, natural gas that has been dissolved in water is mainly produced by gas lifted through a perforated casing that serves as production tubing. In this gas field, the typical length of a production zone in a production well is several hundred meters. Since abnormal formation pressures cause abnormal cross flows [1] among production zones, it is important to select the appropriate production zone to prevent the gas flow from developing cross flow [2]. However, such cross flow often occurs during the lengthy gas-production process. Therefore, a technique to seal the sections with abnormal formation pressure is required, both to prevent cross flow and to increase the production of natural gas. The conventional sealing technique calls for cementing the target formation that has caused the cross flow. After the cement has cured, the cured cement is drilled out with a drill bit, an operation that requires a large drilling facility. A lighter drilling system suitable for use with sealing cement is needed. In this study, we propose a new drilling technique for fresh sealing cement in using a waterjet. Preliminary laboratory drilling tests were conducted under air conditions to clarify the fundamental drillability of a waterjet for the fresh sealing cement. The drilling performance related to the cement sealing and the suitable curing time for the sealing cement needed before drilling are discussed in this paper.

ABSTRACT: The strength and deformability properties of rock mass are required in many mining and civil engineering projects. As rock masses have a complex and uncertain nature, to deal with such complexity the use of probabilistic approaches seems to be more appropriate than the use of conventional deterministic approaches. In this paper, a recently presented quantitative approach was combined with the probabilistic approach to determine GSI value and predict rock mass strength and deformability parameters. Using the estimated GSI and measured intact rock properties the probability density distributions of rock mass strength and deformability properties were calculated through a Monte Carlo method. A comprehensive database is constructed using the information from the drill holes in the mine located in the Eastern part of Turkey. By means of the presented methodology a wide array of strength and deformability parameters to be used in any preliminary design studies were obtained. 1 INTRODUCTION Currently, a vast majority of the mineral extraction is conducted by underground and open pit mining operations. With the improvements in mining industry, mines have become progressively deeper leading to stability problems. To solve these problems empirical, numerical and analytical methods are frequently used. All of the mentioned methods require input parameters such as strength and deformability properties of rock mass. Conventionally, insitu large-scale tests are required to determine the rock mass properties. On the other hand such kind of test are generally considered as both time consuming and expensive, especially at the preliminary design stage. Therefore rock mass classification and characterization systems are frequently used to determine these strength and deformability properties. RMR (Bieniawski 1989), Q (Barton et al. 1974) and the GSI system (Hoek et al. 1995) are the widely used systems among others. In this paper, the GSI system is preferred by the authors for the determination of rock mass properties. The GSI system is based on the description of rock structure and block surface conditions. The strength and deformability properties of rock mass such as rock mass strength, deformation modulus (E m ), Hoek-Brown strength parameters (m, s and a) can be calculated by knowing the UCS, GSI and the material constant (m i ) values. Initially GSI values were determined at the field based on the geological description of rock mass (Hoek et al. 1995). Hoek et al. (2013) mentioned that the observations in the field would be made by qualified and experienced geologists or engineering geologists. Whereas, with the increased use of numerical modelling techniques the observations were made by individuals who did not have strong geological background. Therefore, recently Hoek et al. (2013) proposed the quantification of the GSI chart to increase the interpretability of the GSI chart. In the proposed chart two well established parameters such as joint condition (Jcond89) as defined by Bieniawski (1989) and rock quality designation (RQD) by Deere (1963) are used.

ABSTRACT: Hydraulic fracturing (HF) stimulation of oil wells have made possible the current flourishing oil production from pay zones. Longer initial fractures length and shorter spacing increases oil production. However, these operations usually are expensive and may even cause interference and subsequent reduction in oil production. Analytical models do not consider fracture interference and assume equal fracture half-lengths. Therefore, optimizing initial fractures geometry using numerical methods is of high importance in a successful HF operation. Various geometrical parameters of initial HF cracks including patterns, spacings and crack lengths have been modeled using a higher order displacement discontinuity method (HODDM) in a horizontal oil well. Some of the most encountered problems in HF processes such as fracture interference and fracture arrest have been detected through numerical simulations. Considering several different loading cases, most suitable crack geometrical parameters have been obtained. The results are also confirmed by in-situ measurements available in the literature. 1 INTRODUCTION The combination of multiple hydraulic fracturing (HF) and horizontal drilling has led to an enhanced production of hydrocarbon from reservoirs with low permeability. The primary objective of HF is to improve the natural connections of wellbores and reservoirs. Many fundamental aspects in HF are yet ambiguous and require further investigations. One of these aspects is the arrangement and orientation of the initial perforations. The orientation of a wellbore and the in-situ stress regime have important effects on the initiation of a HF process (Rahman et al. 2000, Abdollahipour et al. 2016). Multiple transverse hydraulic fractures are the main contributor to a high hydrocarbon production (Freeman et al. 2013, Zhao et al. 2014, Guo et al. 2014, Abdollahipour et al. 2016). Optimization of the hydraulic fracture parameters such as the fracture spacing and fracture half-length is of paramount importance. Previous works have established that higher number of fractures in the formation around the wellbore results in a faster hydrocarbon production (Kalantari-Dahaghi 2011, Fazelipour 2011). In some cases, more than 20 fracture stages have been tried in a horizontal well in order to increase the fracture contact with the formation, and to produce high initial rates. The studies have suggested that the initial production increases linearly with the number of fractures but a high flow rate is not sustainable and declines sharply once the fractures interfere over a given lateral length (Castaneda et al. 2010, King 2010). It is obvious that the longer the initial fracture length and the shorter their spacings, the higher the oil production will be.

ABSTRACT: Raise boring machines are used for excavation of shafts and other vertical structures in mining and civil engineering fields for material and human transportation and ventilation purposes. In the classical raise bore method, machine from the top of the shaft begin to drill a pilot hole down to the required depth. Then, the pilot drill bits are removed and replaced with a large diameter reaming head. However, ground conditions need to be favorable to allow the use of raise bore method. The circular smooth walls characteristic of bored raises tend, in many cases, to make them self-supporting. Although, during reaming operation over-break could be occurred and lead to instability of shaft. In addition, there may be some concern about wedge type block failures from the excavation walls. Due to these concerns the stability of raise bored shaft should be analyzed to minimize the risk of using this method. This study aim to investigate the stability of raise bored shaft which recently was finished in Balya PB-ZN underground mine. The ventilation shaft was excavated between the 1200 and 1000 m levels. The depth and diameter of the shaft are 200 m and 2.44 m, respectively. In addition, in this paper, the simple numerical modeling will be presented due to analyze the stability of excavated shaft. 1 INTRODUCTION Raise boring technology was developed to meet the demands of the mining industry, but has also found numerous applications in tunneling or infrastructure projects for ventilation purposes, even in very hard rock formations or in opening deep shafts. A raise boring machine operate on the principle of first drilling a small diameter pilot hole and the reaming the hole in one or more stages to the desired size. RBM is the most newsworthy, secure and fast way for boring shaft in mining and tunneling projects. RBM creates a shaft with smooth walls which usually does not require lining. The hole is more stable than a drilled and blasted method and has better air flow, making it ideal for ventilation shafts. Operational staff safety is another important factor for choosing RBM in different projects. Short excavation time, low environmental impact, and regularity of finished surfaces are another benefits of RBM. However, it should be noted that, the initial cost of this machine is high and this fact should be considered in selecting machine. Moreover, several problems are faced in geological formations where geological discontinuities are dominant. In such cases, shaft boring time extends to several months for supporting shaft walls. Visser (2009) stated that rock formations having several geological discontinuities were risk factors prolonging the termination of shaft boring process. In such cases, a detailed geotechnical evaluation or ‘raise bore rock quality assessment’ based on the McCracken and Stacey method was recommended in the case of deep and/or large diameter shafts (Peck and Lee 2008).

ABSTRACT: Drilling is one of primary operations in open-pit mining cycle. Any failure in drilling equipment affects operational production schedule directly. Therefore, analysis of drilling system reliability and availability are to sustain operation. In this paper, whether the drilling machine exhibits trend; if so, type of trend, a fitting a model and determination of availability are investigated on a case study. This case study focuses on analyzing system failure data of three drilling machines to detect any trend. Laplace trend test was applied to test null hypothesis. Graphical methods were used to identify degrading trend. In addition, the system intensity function was modelled and tests by a statistical goodness of fit test, called Cramer-von Mises. Full factorial design was also used to determine critical factors for drilling operation. Finally, availability of the each system was calculated. 1 INTRODUCTION Drilling plays a vital role in open-pit operations prior to blasting. The cost of drilling is a significant element. Given lowering commodity prices and resource degradation, a reduction in drilling costs will help mine management to sustain operations. Thus, drilling equipment monitoring and optimization of the drilling parameters are crucial for mining operation. Thanks to improved technology, mining companies modernize mining operations. However, mining equipment is getting more complex and mining cost is increasing rapidly (Dhillon 2008). Economies of scale also force the companies to work with larger and larger equipment. Therefore, better equipment reliability is demanding by mining companies. Drilling operation is affected by many factors which are related to mechanical parameters of drilling machine (e.g. rotary speed, weight on the bit and bailing pressure), and rock mass properties (e.g. compressive strength, density of the rock, rock types and quartz content) (Zang & Huang 2013). Geology has also influenced on drilling operation directly. There is a negative exponential relation between rock compressive strength - density - quartz content and drilling rate (Zang & Huang 2013). In other words, it is accepted that geological properties affect drillability inversely proportional (Hoseinie et al. 2009). The effects of formation hardness, mineral composition, structure and binding properties have been investigated by several researchers. The most important parameters which affect penetration rate are uniaxial compressive strength (UCS), shore hardness and quartz content (Singh 1983). The relationship between texture properties of the rock and rock drillability is defined that there is a statistically high correlation, which is demonstrated by analysis of rock's texture, between rock strength and drillability (Bilgin et al. 2000). Drill rate also depends upon the rock type. In softer rock which has low strength, drill rate will be high, and in hard rock which has high strength, drill rate will be low (Zang & Huang 2013). Therefore, the strength is the key parameter to measure the performance of drilling operation. In other words, In other words, drilling rate would be stable if drilling parameters of the machine and the type of drill bit were the same. However, in practice, due to the system degradation and bit wear, drilling rate cannot be stable. Mechanical performance must be considered to understand drilling operation. Hence, the analysis of equipment reliability and availability using historical data is a key to evaluate equipment performance for a drilling activity.

ABSTRACT: The 27.3 km long Semmering Base Tunnel with deep access shafts will be the third longest railway tunnel of Austria. The overburden depth is between 40 m and 800 m. The tunnel construction is divided into three lots. From the view of design and geotechnics, the project has many challenges. Overall more than 40 ground types were defined. The tunnel runs through many fault zones. Measures against squeezing, swelling and flowing ground have been designed. The carbonate rocks are partly karstified with a large groundwater reservoir. Extensive pregrouting works from up to 300 m long horizontal directional drillings are foreseen in order to reduce the predicted entering groundwater volume from up to 300 l/s and to protect the groundwater reservoirs. In accordance with the Austrian guideline for conventional tunnelling, a detailed geotechnical design was carried out. 1 GENERAL OVERVIEW The Semmering Base Tunnel (SBT) is situated in Eastern Austria and is part of the Baltic-Adriatic Corridor, which is one of the most important cross-Alpine lines in Europe. Based on extensive geological investigation in the station and alignment selection procedure and environmental impact assessment a detailed tender design was possible (Gobiet & Nipitsch 2015). Therefore, the driving method could be selected and furthermore various important technical, geotechnical, structural and environmental measures could be taken into account on time (Ekici et al. 2011). The tunnel is about 27.3 km long and is being driven from the portal at Gloggnitz and three additional intermediate construction accesses in Göstritz, in the Fröschnitzgraben and in Grautschenhof. For reasons of organization, scheduling and topography, the tunnel is divided into three construction lots (Gobiet & Wagner 2013). The eastern contract "SBT1.1 Tunnel Gloggnitz" is under construction since the middle of 2015 (Wagner et al. 2015), the middle contract "SBT2.1 Tunnel Froschnitzgraben" started at the beginning of 2014 (Daller et al. 2013) and the western contract "SBT3.1 Tunnel Grautschenhof" will follow in spring of 2016 (Klais et al. 2015). Subject of this article is the methodology of the geotechnical design for the entire tunnel system. The geotechnical design work started with the commissioning of the project in early 2005 and was done step-by-step more in detail in every design phase of the project.

ABSTRACT: This project was supported by Turkish Coal Enterprises and was carried out at the Ilgin-Konya open pit coal mine. Horizontal displacements along boreholes were measured using an inclinometer at 0.5 m intervals. In the same boreholes, vertical displacements were assessed at 3 m intervals using a magnetic colon probe. To measure in situ displacement, two boreholes were drilled in separate open pit benches and displacements monitored over a 7 month period. We found that the horizontal displacement value was ~ 10 mm (north-east) in the upper borehole and ~5 mm (north-east) in the lower borehole, with vertical displacements of —8 mm and — 1 mm, respectively. The shear zones of the unstable mine slopes were determined as 4.5 and 6 m in the upper and lower boreholes respectively. Vertical deformation values, as horizontal displacement measurements, could not be taken every 0.5 m. Therefore, it was encountered with some difficulties in evaluations. Here, based on our data, we developed a method to determinate vertical displacements from inclinometer measurements. By this approach, the estimated vertical displacement values were in line with experimentally-determined (magnetic colon) vertical displacement values. The estimated depths of the shear zone were comparable when using the experimental and mathematically determined displacement values. 1 INTRODUCTION Slope safety is important during surface excavation (e.g., in open-pit mining, the construction of road and rail cut slopes and dams and modification of natural slopes). Slope safety during surface excavation projects is the responsibility of design engineers. Slope stability investigations determine the depth and thickness of the shear zones and monitor the magnitude, rate and direction of slope movement. Engineers often determine the time dependent long-term deformation behavior by in situ measurements (Pinheiro et al. 2015 and Piccinini et al. 2014). Geodetic methods are commonly used to monitor unstable slopes and can record displacements in the topography across three dimensions. Whereas the inclinometer measurement method is often preferred by site engineers when determining the depth and thickness of the shear zones (Dunnicliff 1993). The developed measurements are the most common alternative method. The most commonly applied inclinometer method involves drilling a borehole and monitoring the horizontal deformations that form along the borehole axis (ISRM 2007, Machan & Bennett 2008). The displacement behavior of the rock mass can be monitored using an inclinometer probe. However, in this method, only the horizontal displacements can be monitored. The vertical displacements along the borehole axis are not measured by the inclinometer system. Therefore, site engineers must use a magnetic colon measurement system within the same borehole. The vertical measurement values are obtained through magnetic rings, which are inserted to the required depth along the borehole axis. Thus, engineers must establish two separate measurement systems to adequately follow the borehole's displacement events. This is disadvantageous because: greater investment is required; and the horizontal and vertical displacement values are not recorded at the identical borehole depth. To address this, here we developed a calculation approach to determine vertical displacements from inclinometer measurements.

Abstract Probabilistic wedge stability analyses of a cavern are carried out considering two sets of joints J1 and J2 as random parameters with uncertain dip direction and strength parameters. Probabilistic numerical models are constructed employing Monte Carlo and four different point estimate methods. It is represented that due to the variability of the dip directions of the two joint sets J1 and J2, two failure modes are possible to take place comprising sliding on J1 and J2 as well as sliding on J1 only. The investigations reveal that with respect to the calculation of probability of failure, there is a good agreement among all methods but in respect of failure mode, some point estimate methods could never find the failure mode which corresponds to sliding on J1 only while some models are able to find this mode of failure if number of realization points or number of random variables are increased. 1 Introduction When stability of a geotechnical structure is investigated, uncertainties can be taken into account by means of a probabilistic model that in which a probabilistic tool is employed. Since there are various probabilistic methods, different probabilistic models could be created. Nowadays, Monte Carlo Simulation (MCS) as become very popular in geotechnical engineering because it can be used easily without needing to do complicated statistical calculations; as a result, some commercial geotechnical tools were equipped to MCS in order to make probabilistic models (Rocscience Inc. 2015). An important issue that is associated with MCS (Rubinstein & Kroese 2008), is this that when model computation is time consuming, it would be infeasible because small number of simulations leads to inaccurate results and on the other hand large number of simulation leads to inefficiency. Under such circumstances, point estimate method (PEM) (Rosenblueth 1975) is more applicable as it needs smaller amount of computations. Some workers on reliability such as (Zhou & Nowak 1988), (Harr 1989) and (Hong 1998) have commented on Rosenblueth's PEM in order to make some improvements. In previous studies (Ahmadabadi & Poisel 2014a, 2014b, 2014c), authors presented an intensive comparison among aforesaid PEMs and other probabilistic methods including MCS, First-order reliability method (FORM) (Hasofer & Lind 1974) and second-order reliability method (SORM) (Breitung & Hohenbichler 1989) utilizing illustrative examples of rock slope. Also, issues of Harr's and Hong's PEMs in respect of correlated non-normally distributed random parameters was addressed through the NATAF transformation (M.A. 1962). At the present study, abovementioned PEMs and MCS are compared with the help of an example of a cavern highlighting another shortcoming of probabilistic numerical models which employed PEMs.

Abstract The paper describes the development of a geological and geotechnical model which has been elaborated for the design of a hydro power plant and its large RCC (roller compacted concrete) dam. Rock mass parameters have been derived introducing different in situ and laboratory investigation methods and rock mass classification for definition of subsurface parameter. The mechanical parameter of the rock masses were the basic input for different finite element models in order to evaluate the interacting static system of foundation and structures. The insights gained from these efforts were used to implement sound design amendments in the design of the hydropower plant. 1 Introduction The process of defining an appropriate geological model and the material properties attributed to the different layers is demonstrated for the design of a hydropower plant currently under construction. The scheme consists of a 150 m high RCC (Roller – Compacted – Concrete) gravity dam with straight axis and a powerhouse located at the toe of the dam. The RCC dam type has the main advantages of a simple and fast construction process and an individually specified concrete mix design, which makes it possible to adapt the dam's strength and stiffness properties (i.e. the deformational behavior) to the governing situation. Nevertheless, it is still a concrete structure, so it is important to assure that the geological and geotechnical conditions at the site permit its feasible and safe application. Geological Conditions The area of the project is situated in a volcanic environment of tertiary and quaternary age. The topographical form of the valley is U-shaped. Rocks of basaltic and andesitic composition are the predominant rock types. In the geological terminology of the project, these rocks are summarized as "basalt". This type describes hard and durable rocks with different degree of jointing which can be observed at the flanks of the valley. Tuff layers have been encountered at greater depth, especially in the central valley zone as shown in Figure 2. The basalt layers and the basalt-tuffite boundary is rather flat but slightly dipping to upstream (US) as shown in Figure 1. The tuff layers can be separated in two different subtypes, a coarse-grained type which resembles a sandstone with angular components and a fine-grained type without discernible grains. Both types of tuff are to a certain degree lithified, hence, the term "tuffite" is appropriate. Within the tuffite sequence, the coarser types are overlying the fine grained type. In the early investigation phases, the existence of the fine tuffite was not known and core loss sections had been attributed to drilling difficulties. With ongoing design process, further drillings and first outcrops clarified the geometrical arrangement and showed progressively that the fine grained tuffite was of significant lower strength and stiffness than the coarse type. The lower boundary of the fine tuffite unit could not be reached in every drill hole. Nonetheless, information provided by some of the drillings about depth and geometry of this zone let the thickness of tuffite reasonably assume in the range of 20 - 50 m.

Abstract The process of rock mass cutting by rotary drilling belongs to the most frequently applied technologies in the underground construction. As rotary drilling is quite energy-demanding process, it makes sense to pay sufficient consideration to the efficiency of the applied operational regime of drilling. Only the efficient drilling mode can guarantee the overall quality of this process. This contribution builds upon previous works of the authors in the field of application of abstract Hilbert spaces in control of specific processes. Several possibilities and aspects of visualization of vibrations accompanying the rock drilling are outlined, related to the efficient control of rock drilling process. 1 Introduction Rotary drilling of rocks belongs to one of the most widely applied technologies of rock cutting in mining and geotechnical applications. Drilling is a very energy- and material-demanding process, which has to be controlled in order to achieve the efficient operational regime considering the energy consumption. The drilling regime is usually controlled by several regulating parameters, such as the thrust force of the drilling bit, the revolutions of the drilling bit and by the amount and quality of drilling mud. It is possible to express the rock drilling efficiency by the specific drilling energy. Conventional methods of process control (based on direct measurement of the process variables) are used only seldom, as direct measurement of specific energy is not feasible using common means. Heterogeneity of drilled rock types, variety of drilling bits and different drilling conditions cause that it is almost impossible to determine a generally valid relationship between the drilling regime and its efficiency. The paper outlines a possible approach to the control of such complex process as rock drilling. The approach applies the signal of vibrations accompanying the process of rock drilling as the main source of information on the nature process. As proved by the previous research by the authors' research groups, the character of properly measured vibration signal corresponds to the mechanical properties of rocks and to the applied drilling mode (e.g. Krepelka et al. 2008, Miklúšová et al. 2011, Krúpa & Lazarová 2011).

Abstract A probabilistic analysis is applied to rock slope stability with an example case of a rock slope with translational potential failure mode. The capacity and the demand are represented as independent triangular random variables. The distribution of the factor of safety is found analytically and its reliability measures are evaluated, allowing for decisions to be taken in terms of risk and reliability. The same slope is examined in its limit state by applying the partial factors approach of Eurocode 7. The Eurocode design is compared to the traditional factor of safety and probability of failure. 1. Introduction Numerous uncertainties, arising from natural variability in space and time, experimental errors, imprecise information, insufficient knowledge, up-scaling, simplistic assumptions, etc., are pervasive in rock engineering. These are commonly taken into account, indirectly, in the traditional factor of safety design, where acceptable safety factors are selected through experience or regulation, depending on application and its importance (e.g. Priest & Brown 1983). Some drawbacks may be recognized in this approach (Yucemen et al. 1973). The same value of the safety factor is adopted (or imposed) for a particular type of application, regardless of the degree of uncertainty involved (Duncan 2000), the risk level associated with it, or the amount and quality of information available before and acquired during construction. The type of uncertainty is also relevant to rock engineering (Bedi & Harrison 2013) and its assessment essential for reliable design (Bagheri & Stille 2011). Limit States Design (LSD) in Eurocode 7 (CEN 2004) introduced several changes to the previous geotechnical design practice. Verification at the ultimate limit state requires that the design actions, increased to reflect a low probability of occurrence, be lower than the design resistances, which have been factored down to reflect prescribed (or intended) probabilities of being exceeded. The values of the partial factors of the characteristic actions and material parameters are largely associated to variability and other uncertainties and therefore the partial factors approach may be considered as a form of reliability based design, although for complex systems the relation of the partial factors to the intended failure probabilities may be somewhat difficult to observe. Calibration of the partial factor design equations has been primarily based on method a of Figure 1, where the relation between the various calibration methods considered by EN 1900 (CEN, 2002) is presented. There, the probabilistic calibration procedures are divided into Level II reliability and Level III probabilistic methods.

Abstract Quantifying shale strength anisotropy associated with the presence of relatively weak sedimentary laminations is particularly important for extended reach drilling as interaction between borehole stresses and anisotropic formation strength can ultimately lead to catastrophic wellbore instability. To increase fundamental understanding of this failure mechanism, we investigate the potential for treating shales as composite bilaminate materials and use finite element models with variably inclined layers to simulate direct laboratory testing. Resultant strength anisotropy exhibits many of the features observed from laboratory testing of orientated shale samples and suggests that strength reduction due to the activation of weak bedding laminations should be predictable from knowledge of the bulk trans-laminar strength without recourse to costly and time-consuming laboratory testing, which has significant implications for the successful drilling of high-angle/horizontal wells. 1. Introduction Shales constitute over 75% of drilled formations worldwide and the majority of drilling problems encountered in the subsurface leading to nonproductive time can be directly attributed to some form of shale instability (Azar & Robello Samuel, 2007). It is well-established in the industry that a common chemical mechanism responsible for instability results when smectite-rich shales swell and weaken on exposure to water-based muds (Lal, 1999). A second mechanical failure mechanism particular to shales that has been largely overlooked by the industry relates to the presence of weak bedding laminations which can impart significant strength anisotropy to shale formations. This effect is particularly pronounced for Extended Reach Drilling (ERD) wells in which the borehole trajectory can achieve near-parallelism with bedding such that interaction between the borehole hoop stress and the anisotropic formation can result in oblique loading of these weak bedding laminations leading to premature shear failure (Fig. 1). Depending on the relative magnitudes of anisotropic rock strength and borehole stress concentration, breakouts may occur at "unexpected" positions around the borehole different from those conventionally found in isotropic rock (Willson et al , 2007) leading ultimately to catastrophic failure.

Abstract In engineering practice, rock ledge stability analysis is often performed as a two-dimensional failure analysis, where the single sliding plane is defined by the problem geometry and not the actual joints geometry. This was the case with the Yard Trench Lead in Sunnyside Yard, an element of the East Side Access Project in NYC. A probabilistic wedge stability analysis, including surcharge load and rock bolt reinforcement, was presented and discussed as a design alternative. The transition from 2D to 3D and from a deterministic to a stochastic approach, with the use of the geological joint orientation data, was shown to provide a more realistic view of the initial support design and to have the potential of leading to reductions in the initial support costs. Introduction Reinforcement and support requirements in blocky rock mass have commonly been assessed by means of a rigid blocks limit equilibrium stability analysis. This approach has been confirmed by site observations and proven in engineering practice when empirical, rock mass quality classification-based methods are unable to project structural failure. The relevant solutions have been presented, inter alia, by Wittke (1965), Priest (1980), Lucas (1980) and Bray & Brown (1976). The problem of arbitrary polyhedral block stability analysis was solved by Warburton (1981), Goodman and Shi (1985), Lin and Fairhurst (1988) and others. The method put forward by Goodman and Shi (1985) was used in this study for computations. It is popular and refers not only to a particular block, but to blocky rock mass in general, as well. While most of the methods consider the sliding and falling modes of failure, the problem of rotational failure has also been addressed (Mauldon 1995a,Wittke 1990). As a result of the limited information on discontinuities and their highly stochastic nature, uncertainty constitutes the central problem of analyses and their interpretation in jointed, blocky rock mass. A solution to this problem is brought about by probabilistic methods, either analytical or simulation (for example, McMahon 1971, Priest & Brown 1983, Park et al. 2005, Hatzor 1993, Hoerger & Young 1990, Mauldon 1995b, Jakubowski & Tajdus 1995, Jakubowski 2011). The statistical description of a joint network is crucial for stochastic joint geometry modeling and probabilistic stability analysis in a blocky rock mass (Hudson & Priest 1983, Mauldon et al. 2001, Zhang & Einstein 2000, Kulatilake 2001, Shanley & Mahtab 1976, Chiles 1987, Dershowitz & Einstein 1988).

Abstract In this paper we show how the appropriate uncertainty model to apply in an analysis depends on the nature of the available information. We explore this through the analysis of a rock slope using probabilistic models that incorporate alternative subjectively assigned probability distributions. These alternatives mimic the opinion of multiple experts. The results are shown to depend strongly on the shape of the input distributions, and hence the expert opinion utilised. We conclude by showing that an analysis using fuzzy mathematics is more appropriate than a probabilistic approach when objective data are limited or absent, and present a novel technique for decision making using the results of a fuzzy analysis. Introduction In rock engineering, practitioners are often required to make critical decisions based on little or no objective data. This lack of information requires subjective estimation of parameters used in any analysis, and thus introduces uncertainty. Some have suggested that even with little or no information, stochastic methods can be used to make pragmatic decisions by adopting a subjective view of probability (Aven 2010, Lindley 2000). This forms the basis of the Bayesian approach, which suggests that expert opinion can be applied to assign precise probability distributions (so-called ‘priors’) based solely on the knowledge or judgement of an expert. Within this framework, a probability distribution function (PDF) represents an expert's subjective degree of belief in a value's probability of occurrence. However, others argue that the subjective assignment of priors can lead to misinformed decisions and dissonance amongst experts (Ferson & Ginzburg 1996). In this paper, we investigate the latter argument via a case study on slope stability – that of the previously published Sau Mau Ping Road slope in Hong Kong (Hoek 2007). In this paper we compare the results from Monte- Carlo simulation based on a subjectivist approach to probability and a non-probabilistic approach using fuzzy sets. We show the significant differences in design decisions that may result depending on the model adopted to characterise and propagate uncertainty.

Abstract: Most serious problems encountered in mining and tunnelling, that plagued for decades in countries throughout the world, are associated with falling or breakouts of rock from the roofs and the sidewalls. They constitute hazards by injuring people, damaging workings, and delaying production. It is therefore desirable to consider the problem in some detail, because with the increasing extent and depth of mining, it becomes more serious. The factor of safety, defined as the ratio of the capacity of the rock to the pertinent demand, allows for the estimate of the structural reliability of mining operations. However, this factor does not account for the variability of the parameters involved. A probabilistic approach enables the evaluation of the reliability by taking into account the randomness of the involved parameters. Nevertheless, for such estimates sophisticated probabilistic models and large computing resources are required. By representing the capacity and the demand as uniform random variables, analytical solutions for the probability distribution of the factor of safety may be em-ployed. Application of these solutions for the probabilistic analysis of two under-ground mining cases follows straight forward. The first case concerns the potential for spalling rock in an underground nuclear waste repository. The spalling strength and the stress field are considered as random variables, and the more sophisticated numer-ical evaluations for the probability of spalling are compared to the analytical ones. The second one concerns the potential for falling rock from the Excavation Disturbed Zone (EDZ) of a bolted underground opening. Analytical and numerical evaluations are employed to define the probability of failure, and a parametric study illustrates a methodology to design the support. 1 INTRODUCTION Most serious problems encountered in mining and tunnelling are associated with fal-ling or breakouts of rock from the roofs and the sidewalls.

Abstract: Damaged and disked core from boreholes are indicators of high stress relative to the intact rock strength at the drilling location. While core disking is mainly used as a means to estimate the in situ stress state, core damage (micro-fractures) and its level need to be identified to allow for the accurate estimation of the in situ intact rock strength and therefore proper design of underground infrastructure such as tunnels and pillars. It is generally recommended that laboratory testing be done on samples from boreholes drilled parallel to the major principal stress. In this study, results are reported from an investigation on the influence of borehole orientation on the drilling-induced core damage and associated strength and modulus reductions. The drilling-induced coring stress paths, for boreholes drilled parallel to σ1 and σ3 within a stress state representative for the 420 Level at the Underground Research Laboratory, were first obtained from an elastic three-dimensional finite element model. The coring-induced stress path for the borehole drilled parallel to σ3 was then applied to a two-dimensional discrete element model previously calibrated to the undamaged Lac du Bonnet granite to create damage in the form of micro-cracks. Once the model was calibrated to both undamaged and damaged LdB granite, it was used to predict the damage level and the unloading-induced micro-crack characteristics of the core from the borehole drilled parallel to σ1. The results confirm the effect of sample disturbance on rock strength and modulus measured in the laboratory and potentially offer a mean to model this process and quantify drilling-induced core damage. 1 INTRODUCTION Based on field evidence, core disking and core damage are more likely to occur when the boreholes are drilled perpendicular to the maximum principal stress orientation (Martin and Christiansson, 1991).

Abstract: The contribution summarizes the experiences from intensive dam site in-vestigations in Germany during the last years and will show how different investiga-tion techniques can be used not only for rock, but also for porous mass concrete struc-tures. These structures intensively have been used in German waterways for weir sys-tems and river locks at the beginning of the 19th century. The maintenance and renova-tion of these structures, due to aging, nowadays becomes more important and obvious-ly will last for several decades. It therefore may turn into a major new area of opera-tion also for civil-engineers with a background in rock- and soil-mechanics. Two site investigations for an earth- and rockfill dam, with dam heights of 20–35 meters, including also a rare direct comparison of refraction seismic and geoelectric resistivity imaging are introduced, an example of a typical porous mass concrete struc-ture (weir-system) is given. Results and comparison of different drilling techniques in rock, concrete, borehole imaging (scanning), water-pressure- and grouting-tests and experiences on testing different fineness grades of ultrafine cements during grouting are presented. Results of grouting in respect to sealing, increase in compressibility and durability of porous mass concrete as well as results of anchor pile tests and tests with rein-forcement concrete steel bars for anchoring are shown. EARTH- AND ROCKFILL DAMS The planning region of the rockfill dam is assigned to the gneiss formations of the ore mountains in Saxony. Typical is a metamorphic rock complex as basement with weathered rock, Holocene fluviatile and quaternary sediments as overlying strata with a thickness up to about 8 m in the valley floor. For both sites comprehensive ground investigation programs were carried out in two stages including vertical and inclined core drilling up to about 25 m below the dam foundation.

ABSTRACT: In-situ stress orientations were determined by two independent methods in a scientific ocean drilling project in southwest Japan subduction zone. The first method is a core-based three-dimensional method called anelastic strain recovery (ASR) method; the second one is a traditional method using borehole wall image to analyze borehole wall compressive failures (breakouts) developed in oil industry which yields orientations of the principal horizontal stresses. The horizontal stress orientations at two drilling sites C0002 and C0006 showed having almost right angle; one is parallel with the direction of plate motion, however, the other one is perpendicular with it. The stress orientations independently determined by ASR measurements and borehole breakout analyses were consistent well at both the drilling sites. 1 INTRODUCTION An IODP (Integrated Ocean Drilling Program) scientific deep drilling project, NanTroSEIZE (Nankai Trough Seismogenic Zone Experiments) is undergoing in the southwest Japan subduction zone to understand the physics of an active fault (Kinoshita et al., 2006). Determination of current in-situ stress is one of the main scientific objectives. In the first stage of NanTro- SEIZE, several vertical boreholes were drilled by the deep drilling vessel CHIKYU . The first method is a core-based three-dimensional method called anelastic strain recovery (ASR) method; and the other one is a traditional method using borehole wall image to analyze drilling induced borehole wall compressive failures (breakouts) and tensile fractures developed in oil industry which yields orientations of the principal horizontal stresses (Zoback et al., 2003). The highlights of these stress measurement results and its interpretations have been reported by Byrne et al. (2009) and Chang et al. (2009). Hereafter, we focus on the comparison between the orientations of the in-situ stresses determined by the ASR measurements and borehole breakout analyses, and give a stress orientation summary in the region.