At present, along with conventional energy sources continually consumed, renewable energy sources are increasingly favored, especially the clean and inexhaustible geothermal resources have been universally valued both at home and abroad. In particular, the Enhanced Geothermal Systems (EGS), which is mainly aimed to exploit the thermal energy of Hot Dry Rock (HDR) at depths of 3 to 10 kilometers underground, has been full of interest to many countries. However, so far there hasn't been an EGS being successfully put into commercial operation because of its shortcomings such as small scale, low efficiency, etc. In this article, in response to the bottleneck of the study on the development of traditional EGS based on drilling technology (EGS-D), a conceptual model of EGS based upon excavation technology (EGS-E) is innovatively proposed and its main components of underground structure are described in this paper. As for ‘High ground stress, High ground temperature and High osmotic pressure’ initial conditions with regards to deep rock mass, the excavation experience, which is worth being learnt from extensive review of previous study as well as practical experience such as the successful excavation of ultra-deep mines in the gold field of South Africa, is summed up. The underground spatial structure that may be reasonable to the so-called EGS-E is being tried establishing. It is expected to provide with a basis for our subsequent numerical modeling.
Currently, seeking and developing clean new energy is the basic energy exploitation strategy, and the clean and inexhaustible geothermal resources have been universally valued both at home and abroad. Geothermal energy is the heat energy mainly generated by the transmutation of radioactive elements in rocks, which is 2.0934×1018 kJ annually. And the geothermal energy stored at depths of less than 10 kilometers underground was estimated to be 170 million times the amount of heat released from all the coals stored in the earth by Pollack and Chapman in 1977 (Wang Ruifeng, 2002). It can be seen that the reserves of geothermal energy are very considerable.
In spite of its advantages of stability, continuity and high utilization coefficient, the scale of the geothermal energy with temperature less than 150 °C at depths of less than 3 kilometers underground is usually too small to maintain the demand for long-term stable electricity production which is mainly hydrothermal and only accounts for 10% of all the geothermal energy stored in the earth (Guo Jian et al., 2014). Therefore, the enhanced geothermal system (EGS) which aims at exploiting the geothermal energy from hot dry rock (HDR) at depths of 3 to 10 kilometers has gradually attracted people's attention.
Vu, Minh Ngoc (Agence Nationale pour la Gestion des Dechets Radioactifs) | Zghondi, Jad (Agence Nationale pour la Gestion des Dechets Radioactifs) | Armand, Gilles (Agence Nationale pour la Gestion des Dechets Radioactifs) | Vu, Chi Cong (Agence Nationale pour la Gestion des Dechets Radioactifs)
The French National Radioactive Waste Management Agency (Andra) has built the Underground Research Laboratory at Meuse\Haute-Marne (MHM-URL) for research on the feasibility of a possible deep repository dedicated to high level waste and intermediate level-long lived waste. Actually, several types of retaining structure have been constructed and instrumented in the URL to follow stress/strain evolutions, as well as better understanding of the interaction between the concrete structure and the surrounding rock. The lining stress measurement is an important input value in a way to evaluate or optimize the engineering design of lining. It is a complicated measurement and often performed indirectly from the strain measurement. One of the rare direct stress measurement is the flat jack technique, which provides a relatively simple and almost non-destructive punctual measurement of stress. Typically, the flat jack is withdrawn from the structure after the test and the structure is restored to the original state before the test. This is not the case in MHM-URL where the flat jack is kept in place, in a way to follow the stress time evolution by conducting regularly the test. This article proposes an interpretation method of flat jack measurement based on semi analytical methods and numerical modelling to follow orthoradial stress evolution in a tunnel lining as function of time. Those analysis have been conducted on measurements performed at MHM-URL.
Clay formations in their natural state exhibit very favorable conditions for repository of radioactive waste, as they generally have a very low permeability, small molecular diffusion and significant retention capacity for radionuclide. In France, the National Radioactive Waste Management Agency (Andra) is in charge of the study on the possibility of disposal for radioactive waste in a deep claystone formation. Following the 2006 Waste Act adopted by the French parliament, Andra started work in preparation for the licence application to construct a deep geological disposal facility called Cigéo. Cigéo will be located at the fringe of the Meuse and Haute-Marne departments at the middle of the Callovo-Oxfordian claystone formation (COx), lying between 420 m and 550 m in depth and overlain and underlain by poorly permeable carbonate formations (Fig. 1).
Compressed air energy storage (CAES) power plants are one of the most reliable systems available for energy storage, and they use conventional technology. A salt dome is usually used for the high-pressure air reservoir in the CAES plants currently in commercial operation. However, due to the complicated geological conditions in Japan, it is not easy to design and construct an underground high-pressure air storage tank there. To address this problem, the authors devised a mud slurry lining (MSL) system for storing compressed air underground.
The MSL is a pressurized mud slurry injected into the gap between a reinforced concrete lining and bedrock that provides pre-stress on the lining.
This report outlines the MSL design and considers the two central features affecting practical applications of MSL. The installation conditions are modeled in terms of the rock mechanics under high pressure, and the self-clogging behavior of the mud slurry is discussed with experimental results.
If the maximum pressure is 3 MPa, analysis confirmed that a minimum installation depth of about 100 m is sufficient. Laboratory tests indicate that the critical pressure of the mud slurry is 3 MPa with an artificial joint width of about 3 mm.1. Background
Energy storage technology is essential for the widespread adoption of renewable energy generation, because the outputs of solar and wind generation plants tend to fluctuate. Compressed air energy storage (CAES) converts electrical energy into compressed air, and is a promising technology for grids that incorporate fluctuating renewable generation.
Recently the storage efficiency of CAES plants has been improved with the application of effective heat energy storage technology referred to as adiabatic CAES (A-CAES1)).
The concept of A-CAES is diagrammed in Fig. 1. An A-CAES plant can start up quickly and is responsive to load fluctuations. Further, since it only requires conventional equipment, it is highly reliable and has no risk of chemical deterioration.
For A-CAES to be implemented widely, storage capacity must be maximized. Subsurface space is generally used to make the development of a large storage reservoir economically feasible.
The high-speed railway between Beijing and Zhangjiakou in China that is a very famous project all around the world is now under construction. Badaling station is at the middle of this railway line and is designed as an underground station. The transition zone between the running tunnel to Zhangjiakou direction and Badaling station has a large span cross section with a dimension of up to 30 meters. Meanwhile, this large cross section also goes through the fault fracture zone. As a result, the supporting scheme and stability of the surrounding rock as well as seismic safety are the main concern about this major project. In this paper a 3-D rock-tunnel dynamic interaction finite element modeling is carried out to analyze the construction stage and seismic performance of the large span tunnel cross section. Numerical results have demonstrated the rationality of support system and revealed the seismic performance of the large span cross section.
The new Badaling Tunnel is located between Changping Nankou Town and Badaling Town in Yanqing County. The world’s deepest and largest high-speed train station (Badaling underground station) which will be an important part of the 12km long tunnel between Beijing and Zhangjiakou will be 102m deep with a floor area of about 36000 m2. Starting section of the transition section of the station in Beijing directions is DK67+653 and that in Zhangjiakou direction is DK68+285. This tunnel station comprises of three different sized cross sections namely: small distance spaced section, large-span and triple arch section. The transition zone towards Zhangjiakou direction spans through a fault fracture zone which makes it vulnerable to seismic activity and needs to be investigated. Figure 1 shows the plan of the station.
Based on the prevailing geological conditions, seismic effects and station structure details form the comprehensive geological survey report, it is necessary to analyze the overall seismic performance of the Badaling underground station. The transition tunnel is of a maximum net width and height about 30.83m and 17.57m, respectively, with a height - span ratio of 0.57. The Zhangjiakou direction transition section passes through a fault fracture zone and is the focus of this investigation. The plan of this transition section is shown in figure 2. The surrounding rock is graded 3-5 and the Norwegian method is adopted for the excavation. Initial support system against the rock includes shotcrete, prestressed cables and prestressed anchors.
In this paper, the forces acting on tunnel lining due to dry condition and groundwater pressures were studied. Firstly, the effect of the forces acting on tunnel lining under dry condition was studied numerically for the Sabzkouh tunnel as an actual case study. This tunnel is a deep tunnel that is bored through Zagros Mountains in Iran by a hard rock Tunnel Boring Machine (TBM). Secondly, the effect of hydrostatic pressures on tunnel lining was evaluated. The lining of a bored tunnel usually consists of precast concrete segments that are reinforced by steel bars. These segments must be capable to withstand all loads caused by earth (e.g. rock and water pressures), construction conditions (e.g. thrust forces) and utilization (e.g. traffic loads) without unallowable deformations. A Finite difference code was used to analyze Sabzkouh tunnel lining. The final results show that the values of bending moments, axial forces and shear forces in the precast concrete lining can be reduced under fully-drained conditions, although, the drainage is more effective in weak rocks rather than strong rocks.
In recent years, mechanized tunneling has developed increasingly, and the benefits of full-face tunnel boring machines have been recognized. Design methods for segmental tunnel linings used in mechanized tunnel constructions typically employ numerical bedded beam models and/or classical analytical solutions for the determination of structural forces (i.e. moments and shear and axial forces) and simple load spreading assumptions for the design of the reinforcement in joint areas (Gall et al., 2018). Basically, the forces acting on the tunnel lining depend on construction procedures and in many cases, these forces enhances during construction rather than after construction. The measurement of the induced bending moments and normal forces are difficult, but the numerical analyses give more reliable results than analytical and closed form solutions. The behavior of lining segments is affected by the complex construction features, for example the sequential excavation process and backfill grouting. Therefore, developing a framework to accurately predict the lining forces and deformations is essential for the purpose of structural safety and optimum design (Zhao et al., 2017).
Many shield tunnels have been constructed, in urban and mountainous areas, which should be maintained properly to confirm the structural stability and secure the users’ safety. However, the influence of geological conditions, the fluctuation of water pressure and the difference of lining structure on the mechanical behavior of lining is uncertain in many cases. Also, the inspection method for shield tunnels has not been established due to lack of comprehensive knowledge of critical defects on shield tunnels.
In order to examine the above and establish maintenance method of the tunnel by shield tunneling method, we report on the result of the basic behavior of lining by measurement for approximately 18 months and the consideration of the factors behavior. We grasp the temperature inside and outside a tunnel and the displacement of the joint both of linings and segments. The object of measurement is a utility tunnels in urban area by shield tunneling method. The condition is approximately overburden of 25 m, and the geology around the excavated area is the diluvial deposit. Also, alluvial clay accumulated on the upper part, and the natural groundwater level was about 2 m to 5m below the surface.
From the measurement results, the fluctuation of temperature in the tunnel was confirmed according to the seasonal change, as well as, the expansion and contraction of the joint of lining and segment. This expansion and contraction was confirmed with the same tendency as the change in temperature although there was a time lag. And the behavior of them in a long cycle of one year was admitted. In addition, we confirmed the fluctuation of the groundwater level in the vicinity of the tunnel, about 10 cm within this measurement period. Influence on the expansion and contraction of the lining was limited within the range of this variation in the diluvial deposit layer and temperature change in the tunnel should be considered when the durability of tunnel is discussed.
Many shield tunnels have been constructed, in urban and mountainous areas, which should be maintained properly to confirm the structural stability and secure the users’ safety. However, the influence of geological conditions, the fluctuation of water pressure and the difference of lining structure on the mechanical behavior of lining is uncertain in many cases. Also, the inspection method for shield tunnels has not been established due to lack of comprehensive knowledge of critical defects on shield tunnels.1)
In order to examine the above and establish maintenance method of the tunnel by shield tunneling method, we report on the result of the basic behavior of lining by measurement for approximately 18 months and the consideration of the factors behavior. We grasp the temperature inside and outside a tunnel and the displacement of the joint both of linings and segments.
With recent innovations and developments, PVDF electrostatically applied powder coatings can now achieve thicknesses from 2 to 10mm. There is significant opportunity for extending the service life of equipment in harsh chemical and abrasive applications with thick PVDF coatings. We have observed failures of traditional elastomeric, epoxy, FRP, and urethane linings and coatings where PVDF has greatly increased the service life of equipment such as mixers, agitators, vessels, and drum filters. Heretofore, this PVDF electrostatic coating technology was limited in scope due to poor adhesion, porosity and shrinkage. These problems have been overcome creating a very viable alternative to less chemical resistant materials for chemical and mineral processing. The advantages of a seamless, non-glued or welded lining are significant. PVDF fluorocarbon polymers possess a number of key advantages over other non-fluorinated materials and lining systems. The discussion and presentation of case histories illustrating these advantages and examples will be outlined in the paper.
Furthermore, with the utilization of thermal spray equipment PVDF can be applied in the field joining together traditional oven coated parts making it possible to join together very large rake arms and clarifier components. By careful steps in the coating process and also the use of corrosion resistant fillers the upper thicknesses achievable can be as high as 10mm. These filled and unfilled PVDF coatings are bonded and adhere to metal substrates in excess of 2000 PSI.
For more than several decades, equipment utilized in the mineral and chemical process industry has utilized PVDF extruded and lined piping systems, injection molded valves, molded pump impellers and housings. The wide and successful use of this fluorocarbon polymer has established it as one of the preferred materials for a multitude number of successful applications. Its high physical strength and properties, coupled with its resistance to permeation and abrasion often make it the material of choice by a number of engineers and end users.
ABSTRACT: The 200 m long water carrying canal tunnel was excavated for passing the main canal of lower valley Wardha project across the railway line and nearby the habitants on the surface. The tunnel width during excavation was at 8.5 m with the finished width after lining at 7.3 m. The rock mass classification approaches including Barton’s Q and Bieniawski’s RMR was used to classify the rock mass. From these obtained parameters, estimation of unsupported span, the tunnel deformation and the tunnel support pressure were estimated. These parameters were then used to classify the tunnel and estimation of the support requirement including lining. The outcome of these study revealed that the entire tunnel needs to be stabilized by the application of fully grouted 4.0 m long rock bolts of 25 mm diameter and by steel ribs spaced at 0.6 -1.0 m and permanently providing concrete lining throughout the tunnel length. In addition to this, design for smooth wall blasting was also suggested to minimize the blast induced damage and over-break in the tunnel wall. Tunnel was classified considering surface features on the surface and suitable support was recommended.
The water carrying tunnel of 200 m length was excavated near the district place Wardha of the state Maharashtra in India. The tunnel was proposed for passing the main canal of Lower Wardha Valley Project across the railway line and near the habitants. The broad gauge railway line crosses this tunnel at an angle of 19 degrees. The Left Bank Canal of Lower Wardha Project was crossing the broad gauge railway line and siding at one location. In this reach the canal was passing through deep cuttings of about 11 to 18 m in good compact basaltic rock mass. In this portion a 200 m length long underground tunnel was proposed. The excavation width of the tunnel was 8.5 m while the finished (inner) base width after lining of the tunnel was 7.3 m. The tunnel was D-shaped and the height from base up to springing level and to that crown was 3.75 and 6.15 m, respectively.
ABSTRACT: This paper investigates the possibility of thermal activation of future tunnels to heat and/or cool buildings or underground infrastructures such as subway stations in the context of Grand Paris Express, more than 200km of automatic underground railway for public transport in the region Île-de-France. The principle is to insert pipes in the tunnel lining, which are connected to a geothermal pump. Heat transfer fluid antifreeze circulates inside the pipes to exchange heat with the surrounding environment (tunnel air and surrounding rock). A 3D finite element model is devoted to study the mechanisms of the thermo-hydraulic problem with the equations of mass and heat transfer in porous medium, concrete (solid), and fluid in pipes, and to predict the thermal potential of the rock according to thermal properties. This model is employed for comparative studies to analyze the influence of fluid properties, rock thermal properties and mode of functioning, on the effectiveness of the exchange system and the thermal equilibrium of the rock. The influence of groundwater flow velocity is also studied in order to identify the range in which heat storage within the surrounding rock is possible from the summer season to the winter when needs for easy available energy are greater.
1.1 Context and objectives
To face the climate threat confirmed by numerous scientific studies, France has pledged to the international community to multiply by 6 the contribution of geothermal energy in its energy mix by 2020. In the context of increasing needs for exploitation of renewable energy sources, sensible heat storage in the subsoil appears as an opportunity to seize by disseminating heat pumps in civil works.
This standard provides guidelines that assist in specification writing for handling and installing nickel-based alloy, stainless steel, and titanium linings in air pollution control equipment (e.g., flue gas desulfurization [FGD] systems, ducts, and stacks). It Includes information on materials, design, delivery, storage, and handling, as well as substrate preparation and installation, and detailed information on welding, welder performance qualifications, inspection, and repair.
This standard is intended for use by those specifying and installing thin metallic linings (nickel alloy, stainless steel, and titanium) in air pollution control and other process equipment subject to corrosive conditions.
Extremely corrosive conditions are encountered by certain types of air pollution control equipment. Such equipment is subject to wide temperature fluctuations and formation of condensates containing sulfuric, sulfurous, and other acids. Flue gas desulfurization (FGD) slurry environments may contain significant aggressive contaminants of halides and oxidizing ions (e.g., Fe). High-performance metals and alloys are being used to resist these environments. The application of these materials to a carbon steel or other substrate as thin metallic linings is commonly called wallpapering. Wallpapering has been identified as a practical and effective method of providing anticorrosive linings in both new equipment and retrofit installations. Wallpapering is widely applied in response to power industry (utility) FGD experiences, and is equally applicable to use in other air pollution control and process equipment subject to corrosive conditions.
This standard practice provides technical and quality assurance guidelines for handling and installing nickel alloy, stainless steel, and titanium linings in air pollution control equipment (e.g., FGD systems, ducts, and stacks). The concepts and guidance included in this standard may also be useful in other process industries, but may require modification to meet the requirements of a particular process. This standard is intended to be a basis for preparation of a specification to be agreed on by contracting parties for the installation of wallpaper lining in air pollution control and other process equipment. It is the responsibility of users of this standard to determine the suitability of specific procedures, metals, and alloys for particular applications.
This standard practice is intended for use by those specifying and installing thin metallic linings (nickel alloy, stainless steel, and titanium) in air pollution control and other process equipment subject to corrosive conditions.
This standard was originally prepared in 1992 by Task Group (TG) T-5F-5 of NACE Unit Committee T-5F, “Corrosion Problems Associated with Pollution Control,” and was revised by that TG in 1998. TG 129, “Welding: Flue Gas Desulfurization (FGD) Techniques,” revised this standard in 2003, 2012, and 2018. TG 129 is administered by Specific Technology Group (STG) 45, “Pollution Control, Waste Incineration, and Process Waste.” This standard is issued by NACE International under the auspices of STG 45.