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Power Industry
Influence of Model Selection, Constitutive Behavior Assignment and Parametric Sensitivity on Tunnel, Cavern and Pillar EDZ Assessment for a Long-Term Deep Geological Repository
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)
Abstract 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. 1. Introduction 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.
- Reservoir Description and Dynamics > Reservoir Characterization > Reservoir geomechanics (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Exploration, development, structural geology (1.00)
- Reservoir Description and Dynamics > Reservoir Fluid Dynamics > Flow in porous media (0.95)
Application of the Observational Method in the Äspö Expansion Project
Christiansson, Rolf (Swedish Nuclear and Fuel Waste Management Company) | Olofsson, Isabelle (Swedish Nuclear and Fuel Waste Management Company) | Martin, C. Derek (University of Alberta) | Holmberg, Mats (Tunnel Engineering AB) | Carlsson, Anders (Carlson GeoEngineering AB)
Abstract The Äspö Expansion project required the excavation of approximately 300mof new experimental tunnels on the 410 Level. At this depth there is a hydraulic head of approximately 365 m. The project design required that the maximum allowable draw down not exceed 50mrelative to the initial conditions. Borehole inflow tests carried out in the pilot holes before construction commenced provided a model for relating the inflows and draw downs. Based on previous experience at Äspö HRL, grouting was selected as a cost effective solution. The grouting strategy used the methodology developed for Real Time Grouting Control (RTGC). The principles of the Observational Method as specified in Eurocode 7, in conjunction with the RTGC were successfully used in the design and construction of the Äspö Expansion project that limited the drawdown to approximately 25 m. 1. Introduction New demonstration experiments supporting the technology required for the implementation of the design of the KBS-3 geological nuclear waste repository required construction of two main tunnels and several large niches at the 410-m level of the Äspö Hard Rock Laboratory (HRL), Figure 1. The construction of these facilities complete with the installation of infrastructure and furnishings suitable for the experimental purposes is referred to as the Äspö Expansion Project. One of the design constraints for the project was that the water pressure (expressed in metres) above the experimental area should be kept within 50mof its initial level prior to construction. Past experience at the HRL demonstrated that cement grouting technology at the 450 m-Level was a viable method for limiting inflows to small single heading tunnels. However it was not known if the technology would be suitable for controlling the head loss with more complex geometry and large caverns. A pilot hole was drilled along the axis of each tunnel and used to characterize the groundwater flow system. Amonitoring system and short duration flowtests demonstrated a rock mass permeability with good connectivity. It became obvious that the 50m drawdown constraint would easily be exceeded if the tunnel pregrouting was not successful. In order to reduce the project technical risks and costs to acceptable levels, it was proposed to design and construct the tunnels and caverns using the Observational Method as outlined in EUROCODE-7.
- Europe > Sweden (0.30)
- North America > Canada > Alberta (0.28)
Abstract Knowledge about the Excavation Damaged Zone (EDZ) is essential for underground construction design, underground facility layout, work environment issues and analysis of post-closure safety for a final repository for nuclear waste. The EDZ is defined as the zone around a tunnel where the damage is not reversible. The EDZ can be caused by the excavation method as well as by the actual strength – stress conditions. SKB has chosen the Forsmark site for disposal of spent fuel. The site conditions include hard crystalline rock and fairly high stresses. However, analyzes prior to site selection found that the risk for stress induced development of an EDZ is limited. The aim of this paper is to outline the blast design concept and quality control measures to ensure that the excavation method fulfills the requirements. Strategies for blast design and QA/QC measures for tunnel excavation were applied during construction works for the Äspö HRL expansion 2012. This provided an opportunity to demonstrate methods for tunnel excavation and verify that requirements on minimizing the EDZ could be met during the construction of the planned Swedish final repository for spent fuel. 1. Introduction Within different R&D projects, the Swedish Nuclear Fuel and Waste Management Company, SKB have studied various aspects of a possible generated disturbed or excavation damaged zone (EDZ) around a deposition tunnel. In 2011, SKB applied for a license to construct the final repository for spent nuclear fuel at Forsmark, Sweden. However some issues remain to be investigated and solved before the planned start of construction, one being related to the tentative development of a hydraulically connected EDZ. The Äspö HRL expansion project included the excavation of two new access tunnels with several experimental tunnels on the 410m level. Several of these experimental tunnels were designed with dimensions similar to the deposition tunnels in a KBS-3 repository for spent fuel. The excavation works at Äspö HRL provided an opportunity to apply strategies for blast design and QA/QC measures in order to demonstrate and verify methods for tunnel excavation aiming at limiting the EDZ. This paper presents the methods applied for limiting and controlling the EDZ with focus on the experimental tunnel TAS04, excavated on the 410 meter level at the Äspö HRL. The tunnel has dimensions according to the reference design for a deposition tunnel in the Swedish planned repository for spent fuel, Figure 1.
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Rock Type > Igneous Rock (0.86)
Abstract One of the most characteristic features of rocks is occurrence of different kinds and size cracks. This surface discontinuities have an important influence on rocks physical properties, especially on velocity of seismic waves propagating in the fractured rock mass. Preferred orientation of crack systems involves anisotropy of seismic wave velocity. The existence of relationship between crack and seismic allowed to use active seismic methods. Seismic refraction method and Multichannel Analysis of Surface Waves (MASW) were used to research. The present study was carried out in carbonate rocks located in the southern part of Poland. The seismic anisotropy of the rock mass were measured using P.A.S.I. Seismograph (Mod.16S24-N). The research was made along precise oriented radial seismic profiles. P-waves and S-waves velocities were established from recorded seismograms and also elastic parameters where also estimated using MASW. The adopted techniques have proved to be a useful tool for study the main crack systems. 1. Introduction The increased interest of the problems of elastic waves propagation in rocks is dated to the beginning of the sixties in connection with the development of geophysical methods, especially seismic methods used in oil exploration (Wyllie, 1956). The next step for the development of the study was to observe changes of seismic waves velocity in the focal zones before earthquakes, associated with the evolution of existing discontinuities in the rock mass. Since the beginning of the seventies it started to use seismic methods to assess the degree of fracturing rock mass in engineering problems associated with the construction of tunnels, nuclear power plants, etc. Theoretical studies depending on the purpose for which they were created describe the dependence between velocity and cracked rock mass in terms of static with or without taking into account the anisotropy of rock mass or in the context of dynamic systems associated with the evolution of crack systems in the case of changes of the stress state of rock mass (Crampin 1978,1980,1981, Oda 1982, 1984). Experimental observations were the basis for the creation of theoretical models verified by experimental work (Bamford and Nunn 1979, Idziak 1992, Idziak and Stan-Kłeczek 2011, Stan-Kleczek et al. 2012). The aim of this study was to investigate the relationship between fracturing and anisotropy of seismic wave velocity using the Multichannel Analysis of Surface Waves (MASW).
- Research Report > Experimental Study (0.69)
- Research Report > New Finding (0.49)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Structural Geology > Tectonics > Plate Tectonics > Earthquake (0.54)
- Geology > Rock Type > Sedimentary Rock > Carbonate Rock > Dolomite (0.42)
- Geophysics > Seismic Surveying > Seismic Processing (1.00)
- Geophysics > Seismic Surveying > Seismic Modeling > Velocity Modeling (1.00)
Abstract As a powerhouse, a transformer chamber or for other electromechanical equipments, large underground caverns are major elements of hydropower plant. On the contrary to galleries and shafts which present long linear underground structures, large caverns are designed with often complex geometries and large spans. Moreover, as these caverns are generally located on the bottom of the hydraulic scheme, the high over burden is often responsible of a high stress state. Thanks to current background in France and around the world, the Hydro Engineering Centre (CIH) of EDF has defined great principles for the design of caverns leading to a general methodology which mixes empirical methods and specific numerical modelling. This methodology is exposed in this article with some projects examples: Romanche-Gavet (France) for the discontinuous approach, Gilboa (Israel) for the local and continuous approach, and Tehri (India) for the continuous approach with global strain of the rock mass. 1. Introduction Large underground caverns are under construction all around the world. They often are element of hydraulic scheme, especially in the framework of new project of pumped storage power plant. But other purposes are possible, like for railways stations or for rinks. Among underground structures, large caverns present some specificity, which are:– A no circular geometry; – High dimensions (several decametres) but with a relative limited length (the geology is quite homogeneous). The hydroelectric powerhouses generally have a shape such as the height is twice the width; – A high overburden, and so high stresses; – Consequently to the high stresses due to the depth, the support is generally flexible: grouted bolts and a thin layer of shotcrete; – A lot of intersections (the excavation looks like a spider's web); – A lot of complex excavations steps with both geology and schedule considerations. With such specificities, the design methodology and the design criteria cannot be based on those generally used for common tunnels and shafts. The purpose of this article is to identify some principles for the cavern design, especially for the calculation of the support system. Each of the described methods will be illustrated by an example of project in which EDF has recently been involved.
- Europe > France (0.56)
- Asia > Middle East > Israel (0.25)
- Transportation > Ground > Rail (0.54)
- Energy > Power Industry > Utilities (0.34)
Abstract Research interest in the thermo-mechanical behavior of geomaterials is growing as a result of an increasing number of geomechanical problems involving thermal effects (including reservoir engineering, high-level nuclear waste disposal, heat storage, geothermal structures). A unified thermo-plastic/viscoplastic constitutive model, based on a generalized Hoek-Brown criterion, was formulated to describe the time independent and the time dependent behaviors of geomaterials under temperature effects. This constitutive model includes the evolution of the yield limits (elastoplastic and viscoplastic) and the evolution of the fluidity coefficient with temperature. The elastoplastic part of the model is described by an isotropic strain hardening and by an isotropic strain softening. The viscoplastic part of the model is described by the overstress concept of Perzyna. Even if typical responses to simple test-cases are briefly discussed in the last paragraph, the paper focuses on the concepts and on the mathematical formulation of the model. 1. Introduction The effect of temperature on the behavior of geomaterials is a crucial issue in geotechnical engineering. There are many applications based on the understanding of the thermo-mechanical behavior of rocks and soils, notably for high-level nuclear waste disposal, heat storage, geothermal structures, petroleum drilling, zones around buried high-voltage cables and others related to bituminous materials. Within the context of the storage of nuclear waste, rocks and soils will be exposed to an elevated temperature during many years and, therefore, will suffer from changes in their mechanical properties. For this reason, particular attention has recently been paid to the thermo-mechanical behavior of Boom Clay (Sultan et al. 2002, Delage et al. 2010, Baldi et al. 1988),Tournemire argillite (Masri 2010) and Callovo- Oxfordian argillite (Gasc-Barbier et al. 2004, Zhang 2007, Delage 2013) among others. Since Prager's first works (Prager 1958) about nonisothermal plasticity, many constitutive models have been developed to describe the brittle-plastic behavior of geomaterials at high temperatures (Hueckel et al. 1994, Modaressi & Laloui 1997, Laloui & Cekerevak 2008, Zhou et al. 2011, Dizier 2011). Most of these models are based on cap models extended to non-isothermal conditions. They are mainly used to describe the short term behavior of soft and indurated geomaterials under thermo-mechanical loads. Thus, except the models developed by Modaressi & Laloui (1997) and Zhou et al. (2011), delayed thermomechanical effects are often not duly coupled to rateindependent plasticity even if the long term behavior is the key to ensure the safety and the stability during design and construction analysis.
- Water & Waste Management > Solid Waste Management (1.00)
- Energy > Oil & Gas > Upstream (1.00)
- Energy > Power Industry > Utilities > Nuclear (0.75)
The Application of Stress Control Technologies in Design of Multiple Seam Layouts at Energy West Mining Company
Maleki, H. (Maleki Technologies, Inc.) | Fleck, K. (Energy West Mining Company) | Semborski, C. (Energy West Mining Company) | Christensen, J. (Energy West Mining Company) | Tonc, L. (Energy West Mining Company)
Abstract Based on experience, measurements and stress analyses, the authors have developed and implemented guidelines for stress control in multiple seam mining layouts. Mining sequence in deep coal areas of EWMC is in descending order. Measurements in the lower seam have confirmed yielding of upper seam gate pillars without any significant load transfer to the underlying workings, making the two-entry yield pillar system an important tool for stress control under multiple seam, burst-prone geologic environments of some Utah operations. The relative position of longwall panels in two-seam layouts is based on site specific stress analyses as presented in this paper. By shifting lower-seam longwall panels inside the destressed zone of the upper seam longwall panels, EWMC has achieved significant ground control advantages. Such designs, however, require an assessment of ground conditions during solid-gob crossings (i.e., where the lower seam workings must cross under the high stress zones surrounding the upper seam panels). Introduction Energy West Mining Company is currently operating the Deer Creek Mine, near Huntington, Utah, in a two-seam mining situation. To evaluate rock mass response to longwall stress in the Deer Creek Mine, Energy West (EW) mining staff is implementing a geotechnical monitoring program in cooperation with Maleki Technologies, Inc. (MTI) staff. This program already collected underground measurements at five locations in two neighboring mining districts located in the Hiawatha and Blind Canyon seams (Figure 1). Typical instrumentation is shown in Figure 2 consisting of Borehole Pressure Cells. Recent additional measurements in two-seam District 2 and 5 have been used for validation of initial measurements in District 1. Deformation measurements recently obtained at location 6 is used for verification of three-entry yield pillar system used for accessing reserves in Hiawatha District 5 located directly below District 2. Monitoring results have been used for the study of load transfer, seismicity, coal pillar performance and the calibration of numerical models including boundary-element code MULSIMTI and FLAC (Maleki and Lewis 2010). The regional seismic system developed by the University of Utah is used for monitoring mining-induced seismicity.
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock (0.32)
Case Histories of Rock Engineering Projects in China
Feng, Xia-Ting (Chinese Academy of Sciences) | Chuanqing, Zhang (Chinese Academy of Sciences) | Shaojun, Li (Chinese Academy of Sciences) | Bingrui, Chen (Chinese Academy of Sciences) | Shili, Qiu (Chinese Academy of Sciences) | Hui, Zhou (Chinese Academy of Sciences)
Abstract This paper summaries case history of rock engineering projects in China. The dynamic and optimal design methods has been established and applied for some of the projects. It includes two flowcharts. One is methods for rock mechanics modelling and rock engineering design analysis (Feng & Hudson, 2011) and another is the updated flowchart for the rock engineering design process (Feng & Hudson 2011). Two typical illustrative examples have been given to applicability of the developed design methods. One is stability analysis of permanent shiplock slope of Three Gorges Project, China, and another is stability control of rockburst risk mitigation of long headrace tunnels at Jinping II hydropower Station, China. Finally, some conclusions have been given. Introduction China is the largest developing country in the world. It is forecasted that its GDP growth rate will be around 7% during the period 2014–2020. Such rapid economic development has meant increasing demand for infrastructure development, including many largescale rock engineering projects. This explosive growth in the economy and infrastructure development will continue and expand well into the next decade and beyond. According to the national medium- and longterm development programs, more than 20 large-scale hydraulic power plants, such as Xiaowan, Longtan, Jinpin I & II, Xiluodu, Xiangjiaba, Baihetan and Wudongde, etc. (Table 1), with a total capacity of more than 50,000MW, have been, are being or will be constructed in western China within 20 years. The South-to-North Water Transfer Projects was conceived in order to ameliorate the conditions leading to a short supply of water in northern China. This grand scheme is divided into three water transfer route projects: the East Route Project, the Middle Route Project and the West Route Project. The Eastern Route Project runs along the eastern seacoast of China and transfers water from the mouth of Yangtze river to Tianjin city. It consists of three phases with a maximum transferablewater quantity of 17 billionm. The first phase will be started around 2010 and finalized around 2020. The remaining two phases will be finalized by 2050. The first phase consists of 7 tunnels, with lengths ranging from 13.6 to 73 km and the overburden ranging from 300–1100 m. The total length for the first phase of the project is 260.3 km, of which tunnel length accounts for a total of 244.1 km. The Middle Route Project aims to transfer water to Beijing, with its maximum transferable water quantity measuring in at about 13 billionm. The construction period of the first phrase lasted from 2003 to 2010, with a total investment of about 12 billion USD. The Western Route Project will be established to transfer water from the Qinghai-Tibet Plateau to the upstream of theYellow River. The maximum transferable water quantity is about 14.8 billion m.
- Energy > Oil & Gas > Upstream (1.00)
- Energy > Power Industry (0.88)
- Water & Waste Management > Water Management > Lifecycle > Storage/Transfer (0.54)