In recent years, many tunnel projects were carried out and will go on to create alternative ways of transportation as well as shorten the distance driven in parallel with the increasing population and number of vehicles also to achieve savings from time, energy, fuel, etc. In drill and blast method in tunneling (railway tunnels, road tunnels, pedestrian tunnels, subway tunnels, sewer tunnels, diversion tunnels, etc.) drilling constitutes the largest cost and time. Choosing the wrong bit and wrong operating parameter causes cost increase and delays in the work plan. Drilling performance of Atlas Copco Rocket Boomer 282 Jumbo Driller was examined in this study that was used in Altan Ayağ Tunnel (T3 Tunnel) Located in Antalya-Kemer-Tekirova Highway. The physical and mechanical properties of the rocks where the drilling machine was running were determined both in the field and laboratory tests. Drilling machine was run with 3 different types of bits. Time studies were carried out for each drilling bit’s penetration rate. Drilling machine parameters (rotation, thrust force, flushing etc.) were kept constant during drilling. Level of the noise caused by drilling was measured by audiometer. As a result, considering the penetration rates of each bits used in drilling operations and suitable bit type was determined for the rocks where the drilling machine was running. Also, the noise levels depending on the bit type were examined by comparing.
In modern tunnel and underground cavern excavations, it is easy to select from many different excavation methods. The method of drilling and blasting has been used for excavation of underground spaces in rock for a long time in tunnels, rock caverns and mines. The major part of underground excavation is drill and blast (NTS, 2004). In drill and blast method in tunneling drilling constitutes the largest cost and time. In order to reduce the cost, the selection of the most appropriate bit according to formation is very important. Choosing the wrong bit and wrong operating parameter causes cost increase and delays in the work plan.
The most widely researched parameter is compressive strength in analyses of tunneling and drilling operations. Paone & Madson (1966), Paone et al. (1969a, b), Barendsen (1970), Brown & Phillips (1977), Hughes (1986), Karpuz et al. (1990), Kahraman (1999) investigated the relationship between penetration rate and the various rock properties. Thuro (2002) and Plinninger (2002) researched the performance of the drilling machines and wear mechanisms of the drilling bits on intact rocks. Kahraman et al. (2006) examined the performance of a drilling machine in Ankara-Pozanti Highway tunnel. Controllable parameters (rotational speed, thrust, blow frequency and flushing) and uncontrollable parameters (rock properties and geological conditions) affect the rock drillability (Kahraman, 2003). The main parameters of rocks that affect drillability are given in Table 1.
Agioutantis, Z. (Technical University of Crete) | Mertikas, S. (Technical University of Crete) | Daskalakis, A. (Technical University of Crete) | Tripolitsiotis, A. (Technical University of Crete) | Kritikakis, G. (Technical University of Crete) | Apostolou, E. (Technical University of Crete) | Steiakakis, C. (General Consulting Ltd “ISTRIA”) | Kaplanidis, G. (General Consulting Ltd “ISTRIA”)
Rockfall incidents that may lead to road closure, infrastructure damage and loss of human life are common in European highways and mountainous roads. The “ISTRIA” research project aims to establish a low-cost rock-fall monitoring and warning system based on a variety of multidisciplinary sensors and instruments. This paper presents the setup and preliminary results of several experiments conducted to evaluate the performance of geophones to capture low energy ground vibrations caused by small rock free fall. It was determined that geophones have the potential to be used as monitoring sensors for rock-fall identification. Moreover, the empirical equations that were utilized to optimize geophone spacing yielded promising results.
Rockfall incidents occur on a frequent basis in mountainous areas, significantly affecting the local and national economy, infrastructure and human safety. Public authorities are faced with the need to provide remedial measures and minimize risks associated with rockfall risks.
Project “ISTRIA” was recently approved by the Greek Secretariat of Research and Technology and funded by the Operational Program Competitiveness and Entrepreneurship (co-funded by the European Regional Development Fund (ERDF)) to come up with a rockfall monitoring and warning system. The main goal of this project is to develop an operational rockfall monitoring and early detection system by integrating instruments, innovative algorithms and a database with a user-friendly interface.
The first objective of the project is to identify the most prominent triggering mechanisms for rockfalls, the instruments needed for their monitoring and the overall design and architecture of the proposed system. The second objective is to develop algorithms that will correlate triggering mechanisms and rockfall incidents.
This paper presents the experimental setup and results obtained in order to a) verify the suitability of geophones to detect ground vibration caused by rockfalls, b) investigate the spacing between geophones, c) evaluate the applicability of empirical equations to determine the energy decay rate, and d) determine the frequency range generated by rockfalls.
Slope stability on low-wall part controlled by material properties and geometry bedding. Geometry bedding is separated by layering/bedding contact between both materials. Bedding contact could be a thin layer, which is important in the slope stability. Generally, the bedding contact material is high elasticity and it has a bad geo-mechanic properties. The difficulties in taking samples at the bedding contact due to thickness are restrictive and sometimes are not sufficient for laboratory testing. Geo-mechanic testing for bedding contact material is difficult due to core sample, it didn’t perpendicular toward dip of bedding or covered material and generating failure shape in which it didn’t match with actual condition. Bedding contact is giving significant impact for slope stability although thickness of this material is restrictive, thus determination material properties with some method is very important in keeping stability on the low-wall part of coal mining. This study focused on determining material properties on bedding contact using back analysis method. This method is required when geo-mechanic testing result using laboratory testing can’t be conducted with some reason; such as it has not adequate sample or geo-mechanic testing result is not representative. Cohesion value of 0 kPa with 13o of friction angle is in accordance with the actual conditions. This figure will be used as the basis of slope stabilization and also reviewing the existing designs so the failure incident will not exist.
Slope stability analysis in open pit coal mining activities is very important for maintaining pit slope stability. Good stability will provide many benefits. Open pit mine activities will form the slope.
Coal deposit is currently associated with the rock sediment so that slope formation always follows the existing sediment layer or it is called by bedding.
In the open mine predominantly on coal mining, there are two terms: high-wall and low-wall (Fig. 1).
High-wall slope is perpendicular to the layers and low-wall is in line to rock layers (bedding). High-wall stability has been much discussed in several studies and it is an absolute requirement in mining activities. The stability of low-wall is a bit forgotten because the assumption of rock layer is rigid and rock material is the rest on a rock layer. But in fact, a lot of things need attention to the low-wall stability. Several factors that concern to the low-wall stability are:
a. Material properties
b. Geometry bedding/layer
c. Rock structure
Novel rock breakage techniques are becoming more viable and attractive to industry. Microwave energy, as a thermal energy which is capable of inducing micro cracks through differential heating (therefore expansion of Minerals) is a technology gaining considerable attention in mineral processing and ore comminution applications. Recently, use of microwave has been evaluated as a possible avenue for terrestrial and extraterrestrial drilling applications and full face tunneling or rock breaking machines. As part of an overall research on use of microwave in rock breaking systems, the influence of microwave energy on the mechanical properties of some common hard rock types has been investigated. Experimental and simulation results underlined the potential impact of the use of microwave energy in underground or surface excavation applications such as mining and tunneling. This will also contribute economically when mine-to-mill operation is fully considered. It also outlines the potential impact of a future microwave assisted tunnel boring machine enhanced with microwave and its performance.
To date, many methods have been used in rock breakage applications. Some of these methods essentially break rocks by applying heat either directly or indirectly. Using microwave energy is an alternative method of rock breakage that has been introduced since the 1960s but, as yet, it has not proven to be economically viable, as a single method, to become commonly used (Maurer, 1968). Microwaves have since been applied in mineral processing applications to reduce grinding energy (Kingman et al., 2000 & 2004). However, microwave assisted mechanical rock breaker equipment has been recently highlighted with significant potentials in this area.
Mechanical rock breaker equipment has limited performance with high level of bit or disc wear and maintenance in breaking hard rocks in mining and civil applications. The performance of an underground excavation in hard rock with mechanical equipment can be estimated through correlating mechanical rock properties with applied forces and machine specifications. Preconditioning the natural rock prior to be broken by the machine is a novel approach that is to be studied. Flame torch assisting rock excavation systems or tunnel boring machines had been taken in consideration (Lauriello et al., 1974) but has not been economically feasible due to huge consumption of fuel.
Temporary support for a tunnel excavated in weak rock can involve (but is not limited to) the utilization of a combination of steel-sets, rock bolts, shotcrete, spiles/forepoles and/or face stabilization technologies. The purpose of such tunnel support is to maintain confinement for the rock mass in order to help the rock mass support itself. This research is concerned with the forepoles as components of this system. Within this context, this paper describes a novel application of a distributed optical sensing technique specifically for monitoring the continuous strain profile along forepole elements. The procedure employs a distributed optical sensing technique using optical fiber that is based on Rayleigh backscattering which has been previously employed with grouted rock bolts. The paper outlines the technology, describes how it has been adapted for monitoring of forepoles, and assesses its potential and limitations based on initial laboratory experiments.
Classical tunnel designs have been based on the Rock Mass Ratio (RMR) (designing with respect to deformations) and Terzaghi based designs (designing primarily to support all loads including overburden pressure by the final lining). A newer tunneling method, such as the New Austrian Tunneling Method (NATM), incorporates an observational approach that is deformation based. This method integrates the surrounding rock into the overall support structure (i.e. the supporting formations will themselves be a part of the supporting structure as the rock is able to support itself to a certain degree) (Romeo, 2002). Using the NATM, a controlled deformation of the rock mass is permitted (a limited strain of approximately 1%) and this gives the stresses an opportunity to be partly released and less stiff and thus a less-expensive support system can be used (Kondogianni and Stiros, 2002).
Optimizations of tunnel support design (to include individual support elements, forepoles, shotcrete, rockbolts etc.) can therefore be achieved within the framework of this observational (well instrumented) approach whereby the behaviour of rock/soil, support elements, geomaterial-support interactions, and behaviours can be explicitly determined. Through back-calculations, material properties can be clearly derived. However, there exists a gap in knowledge in terms of the distinct performance of each support element in isolation and its performance as part of a multi component support system. This investigation, then, suggests a strategy in order to determine the continuous behaviour and performance of a forepole temporary support elements as part of the overall temporary support scheme.
Sliding through the foundation is one of the most common mechanisms under which a gravity dam can fail and is one of the most difficult modes of failure to determine the safety due to uncertainties that the rock mass properties provides. This paper evaluates the sliding stability of existing gravity dams with a failure mechanism characterized by a sub-horizontal joint set acting as a sliding plane and with a potential failure path through the rock mass. For the study, a simplistic static analysis is considered, using the criteria of Barton-Choubey (1977) and Hoek-Brown (1980; 1992) to determine the shear strength for discontinuity and for rock mass respectively. The finite difference program FLAC 6.0 has been used to validate the model. Results show in a sensitivity analysis executed, that it is possible to define with acceptable accuracy a sliding safety factor for the mechanism proposed in a preliminary study, with a simple spreadsheet.
In the risk assessment framework, the dam safety analysis has taken a very important role due to the catastrophic impact that would mean gravity dam failure over population and environment. In Spain there are 1300 large dams, 20% of which were built before the 60s . The fact that there are still many old dams in operation has lead scientific community to develop new tools that contribute to reach a better understanding on dam’s behavior over time.
Dam-reservoir-foundations systems have a complex behavior, which has been solved by using simplified formulations. Traditional deterministic approaches are based on explaining the sliding of gravity dams through the dam-foundation interface using Mohr-Coulomb model, where friction angle and cohesion are the main parameters that describe shear strength.
This article aims to evaluate the sliding stability of a gravity dam with a foundation failure mechanism characterized by a sub-horizontal joint set acting as a sliding plane and with a potential failure path through the rock mass. The mechanism proposed considers the possible occurrence of cracking in the dam’s base, as well as its effects on this mechanism. For the study, a simplistic static analysis is considered, using the criteria of Barton-Choubey  and Hoek-Brown  to determine the shear strength of the joint and of the rock mass, respectively. The finite difference program FLAC 6.0 by Itasca  is employed as a computational tool to validate the model and an example has been solved to illustrate the results.
This paper describes the analysis performed in order to obtain the relationship between the static and the dynamic modulus of one sedimentary rock (the San Julián’s stone) heated at different temperatures. The rocks have been subjected to heating processes at different temperatures (reaching up to 600°C in steps of 100°C), and two cooling methods for each temperature, to produce different levels of weathering on 24 cylindrical samples. The static and dynamic modulus has been measured for every specimen. Two analytic formulae are proposed for the relationship between the static and the dynamic modulus for this stone. The results have been compared with some relationships proposed by different researchers for various types of rocks. Generally low elastic modules imply highly fissured or damaged rocks. The mechanical properties, including static modulus, are highly dependent of the cracks size, orientation, and spatial distribution of these cracks. The ability to adequately detect the physical changes that affect rock mechanical capabilities by studying the propagation of ultrasonic waves has been widely discussed in many scientific papers. In this work, a high correlation between static and dynamic modules has been observed. It is concluded that in the studied range (i.e. Edyn values lower than 50 GPa) and for the soft rocks, static modulus can be obtained from dynamic tests, being the dynamic modulus (i.e. ultrasonic waves propagation velocities) a good indicator of the material degree of deterioration. The obtained relationships will allow the computation of the static modulus of elements of cultural heritage of Alicante city made of San Julián’s stone, from non-destructive field tests, for the analysis of the integrity level of historical constructions affected by high temperatures.
Young’s modulus, also called elastic modulus, is one of the most important mechanical characteristic parameters of the rocks in relation to its use as a construction material. The dynamically determined elastic modulus (Edyn) is generally higher than that statically determined, and both methods provide high divergent results for low elasticity modulus rocks (Ide, 1936). Several studies (Ide, 1936, Vanheerden, 1987, Al-Shayea, 2004, Kolesnikov, 2009) explain these differences by means of the nonlinear elastic response at different ranges of amplitude of the strains (ε:) involved in the distinct techniques. Other authors (Kolesnikov, 2009, Ciccotti & Mulargia, 2004) consider that the static test is a dynamic test at a very low frequency, and they highlight the nonlinear elastic response to different associated frequencies (f).Kolesnikov (2009) uses the Kjartansson constant Q-model (Kjartansson, 1979) to analyse the effects of intrinsic dispersion of pressure waves velocities in absorbing media (and it is well known that all rocks absorb energy of elastic waves to a greater or lesser extent).
The Cracked Chevron Notch Brazilian Disc (CCNBD) method has been used to determine rock fracture toughness value of rocks in rock mechanics since many years. The CCNBD method has advantages over the other proposed fracture toughness tests in terms of the simplicity of sample preparation and less material requirement for testing. In this study, the specifications of Brisbane tuff sample geometry have been selected according to the suggestions of International Society of Rock Mechanics (ISRM). The main aim of this research is to evaluate the effect of amplitude variations and change of chevron notch angles on the fracture toughness of rocks under both static and cyclic loading. The cyclic loading was applied in three different levels of amplitudes, 10%, 20% and 30% of the static ultimate loading (SUL). In addition, three different chevron crack angles 30?, 45? and 60? have been chosen to investigate the effect of initial crack angle on the rock fracture toughness value. A series of multiple variation analyses by using Analysis of Variance (ANOVA) were carried out in this study to evaluate the effect of amplitude and inclination angle of chevron crack on the rock fracture toughness value of rocks. Statistical results demonstrated that rock fracture toughness values are very sensitive with the change of amplitudes less than 20% of SUL whereas rock fracture toughness is less sensitive with the change of amplitudes between 20% and 40% of SUL. Moreover, 45° notch crack inclination angle used to investigate the mixed Mode I–II fracturing behavior of rocks was found the most critical inclined pre-existing crack under various amplitude cyclic loading in other crack inclination angles. These outcomes are believed very important findings for many rock mechanics applications such as investigations of behavior of bedded rocks, anisotropic rocks and discontinuities in rock masses encountered with dynamic loads and fatigue.
Diederichs, M. S. (Queens University) | Lam, T. (Nuclear Waste Management Organization) | Jensen, M. (Nuclear Waste Management Organization) | Perras, M. (Swiss Federal Institute of Technology in Zurich (ETHZ)) | Damjanac, B. (Itasca Consulting Group)
A proposed Deep Geologic Repository (DGR) for Low and Intermediate Level Radioactive Waste beneath the Bruce nuclear site, near Kincardine, Ontario, is currently under-going an Environmental Assessment. The site is underlain by an 840 m thick near-horizontally bedded Paleozoic sedimentary sequence. Within this sequence the DGR has been positioned within a massive, laterally extensive, low permeability Ordovician argillaceous limestone formation at a depth of 680 m. Several hundred metres of massive shales overlie the repository and will act as a vertical cap, although two shafts must penetrate this shale enroute to the repository horizon. In support of mechanical analysis and other studies, an extensive program of investigation was undertaken to obtain material properties for the various layers to be encountered and to provide boundary conditions for analysis. Analysis of long-term stability has been carried out for the shaft, the main storage caverns and intervening pillars over a time frame up to one million years as influenced by glaciation, gas and pore pressure evolution, seismic disturbance and long term strength degradation.
Ontario Power Generation (OPG), has proposed the development of a Deep Geologic Repository (DGR) at a depth of 680m at the southern base of the Bruce Peninsula near Kincardine, Ontario. This facility will be used for long-term management of Low (LLW) and Intermediate (ILW) Level Waste generated at OPG owned and operated nuclear facilities. The DGR would be developed in an argillaceous limestone overlain by 200m of very low permeability shale protecting the upper 480mof mixed sedimentary rock units and their aquifers. The DGR layout is shown in Figure 1 with the two shafts that will connect to surface. There is a network of service excavations as shown at the shaft station from which main tunnels extend to the main emplacement rooms. Across section between adjacent emplacement rooms is shown, as well as a schematic representation of the waste emplacement.
The waste will be placed without backfill to allow room for gas expansion during decomposition. The near-shaft service areas will be backfilled and sealed after the operating period of 100 years. The shaft seal design will provide an integrated engineered sealing system intent on mitigating the influence of damaged wall rock or the Excavation Damage Zone (EDZ) as a potential pathway for mass transport.
In this article the complex case of the toppling of large granite blocks in an opencast lignite mine, which has produced displacements of the slope greater than 50m with speeds that reached 1 m/week, will be discussed. Not all the slope was composed of granite; the lower part consisted of Tertiary deposits which suffered deformations owing to the pressure exerted upon them by the inferior block of the granitic part of the slope in its tendency to tilt. The mine reached the anticipated final depth of 310m owing to the movements of the slope being monitored with topographic prisms, time-domain-reflectometry (TDR) installations and inclinometers, and to the appropriate solutions to reduce the slope movements to admissible limits being applied: setbacks to reduce the angle of the slope and drainage wells, up to 400m in depth, to lower the piezometric level. Once the open pit was finalised, it was partly filled with waste and is currently filling up with water.
In this article, a case of toppling deformation, which affected to practically the entire northeast slope of the opencast lignite mine at Meirama (situated in northwest Spain, around 30 km from the city of A Coruña), will be described.
2. General Geological Features of the Deposit
The extreme northwest of Spain and specifically the location where the mine is situated forms part of the Variscan orogen. Plutonic and metamorphic rocks, probably from the Ordovician and pre-Ordovician periods, were affected by complex metamorphic and tectonic processes and, in particular, by phases of late- Variscan fracturation which led to faults which were remobilised much later, on the Miocene period, by Alpine forces. The lignite deposit at Meirama is a small intracratonic basin of the pull-apart kind associated with displacements in the Tertiary of one of these late-Variscan faults in a NW-SE direction. This fault is situated at the foot of the northeastern slope of the Meirama mine and separates the granodiorite of Mount Xalo, to the northeast above it, from the Miocene sediments amongst which lignite is found.
The fault of the foot of the northeast slope, that has dozens of km of longitude, was reactivated by compressive N-S Alpine forces which produced a strike-As a result of this fault displacement, the basin where the deposit grew was created. The compressive N-S forces, which had an effect upon the basin during the entire sedimentation process, gradually narrowed their initial limits, strongly folding the sediments (lignite, clay, sand and gravel), and gave a reverse character to the fault at the NE slope and to those of the SW slope, sub parallel to the preceding one; that is, they tilted them slightly towards the Miocene basin (Santanach Prat, P., 1994).