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Numerical Analysis Of Time-Dependent Behavior Of Siah Bisheh Cavern
Nadimi, S. (MSC student, Faculty of Mining & Metallurgical Engineering, Amirkabir University of Technology) | Shahriar, K. (Professor, Faculty of Mining& Metallurgical Engineering, Amirkabir University of Technology) | Sharifzade, M. (Assistant Professor, Faculty of Mining& Metallurgical Engineering, Amirkabir University of Technology) | Moarefvan, P. (Assistant Professor, Faculty of Mining& Metallurgical Engineering, Amirkabir University of Technology)
Abstract: The understanding of time dependent effects or creep behavior is important in further development of knowledge in the field of rock mechanics. Increasing pressure on support system because of creep behavior of rock is one of the most important problems in underground structure which surrounded with weak rock mass. This paper presents a time dependent behavior analysis of Kiah Boshes pumped storage powerhouse cavern with complex geometry, available geological formations and diverse geotechnical properties of rocks, is under construction on the Chalks River at the north of Iran. Because of the fractured and jointed rock mass, the Discrete Element method Code 3DEC used to compute convergence and pressure on the support system. The power constitutive creep model which is able to model the primary and secondary creep regions of rock masses is applied. In this paper, results of the Kiah Boshes cavern as a case study dealing with a comparison between long-term deformation data from in situ measurements and obtained data from an analytical solution and numerical simulations with special consideration of anisotropic effects will be presented. The differences between the obtained values might be because of discontinuous media or different inputs parameters were used for analysis. 1. Introduction The rheology and time-dependent behavior of rock are fundamental mechanical properties of the rock material, which can be used as an important bases in explaining and analyzing the long-term stability for rock engineering. Especially, time dependent deformation of rocks has significant effect on stability of underground structures, such as nuclear waste storage facilities, tunnels and powerhouse caverns. It is particularly common in underground structures excavated in soft rock, heavily sheared weak rock masses or rock masses subjected to high in-situ stresses (German, et al, 1988; Carla, 1995; Basin & Grim stand, 1996). In order to study the stability of the underground structures and designing their support system, time dependent deformations should be highly considered (Salami, 2004; Thai, 2008). Therefore, time dependent behavior of underground structures as well as predicting the long-term behavior, is of great importance. This paper presents a time dependent behavior analysis of Kiah Boshes pumped storage powerhouse cavern with complex geometry. The cavern is being built in a region that is highly prone to sheared and fault zones where their failures could cause severe damages to underground spaces. It is therefore essential to analyze and design underground structures for preventing any serious long-term damages in the region. The rock mass may exhibit continuous or discontinuous deformations due to the existence of large underground openings: shear of joints and creep deformation. 2. Kiah Boshes pumped storage project The Kiah Boshes pumped storage project is located at the Labors chain Mountains being mainly formed and folded during the Alpine organic phase. The most important tectonic phenomenon of Kiah Boshes area is the fault called as the Main Thrust Fault (MTG), with a dip direction of 78/028 and an almost E-W trend. The site of powerhouse caverns is generally located at the Permian Formation part.
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Structural Geology > Fault > Dip-Slip Fault > Reverse Fault (0.34)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock (0.31)
- North America > United States > Texas > Permian Basin > Yeso Formation (0.98)
- North America > United States > Texas > Permian Basin > Yates Formation (0.98)
- North America > United States > Texas > Permian Basin > Wolfcamp Formation (0.98)
- (22 more...)
Design Of Powerhouse Cavern At Koyna Left Bank Dam Foot Project Using Three Dimensional Numerical Modelling
Loui, John P. (Central Institute of Mining and Fuel Research (CIMFR)) | Rathod, Roshan A. (Central Institute of Mining and Fuel Research (CIMFR)) | Sinha, Amalendu (Central Institute of Mining and Fuel Research (CIMFR))
ABSTRACT: At Moyna Hydro-electric Project, an 80MW powerhouse is currently proposed at the left dam foot of Moyna river dam in Maharashtra. The underground powerhouse cavern needed for housing the two turbine units of 2 X 40MW is designed using three-dimensional numerical modelling. Three possible geometries for the powerhouse are designed considering the weaker rock mass layers of Volcanic Becca existing in the vicinity of the proposed cavern. These configurations are simulated in FLAC3D software. Their stability is analysed using Hook and Brown rock mass failure criterion. Taking cues from the stability predicted for the three configurations, a final configuration is designed. The final configuration is further subjected to three dimensional modelling and stability analysis. The cavern is expected to have good overall stability. The crown region, since it will be located in stronger Compact Basalt rock layer, will have superior stability. However, the cavern will have weaker sides, where Volcanic Becca will be exposed. A support plan for the entire cavern is also designed incorporating 100mm thick steel fire reinforced shotcrete (SIRS) and 6.0m long full column grouted resin bolts. 1.0 INTRODUCTION Moyna Hydro-electric Project of Maharashtra State Government produces electricity of the order of 2000MW in four stages. This environmental friendly and cheap power generation caters to the energy demands of the neighbouring region. As an extension of Stage IV, an 80 MW (2x40 MW) capacity powerhouse is proposed at the Moyna dam foot at the left bank of the Moyna River. Underground powerhouse chambers are proposed for power generation. From the geological survey conducted by Moyna Project authorities, the rock types existing in this vicinity was found to be Deccan Trap Basalts, viz. 2.0 ROCK PROPERTIES AND INCITE STRESS The intact rock properties tested earlier by CAPES (Anon (2004) and Anon (2005)) and rock mass parameters such as RM (Bieniawski (1976)) for compact basalt and volcanic Becca are given in Table 1. The Hook and Brown rock mass parameters are also evaluated (Hook and Brown (1980)) and given in the table since they are to be used in the numerical modelling. 3.0 DESIGN STRATEGY Three optional configurations were initially chosen to comparatively analyze the stability scenario. Depending on their stability, the most stable configuration shall be chosen as the final powerhouse design. The three configurations modelled for their stability analysis has the following salient features. Configuration 1: A powerhouse cavern of 21m width, with crown level at 599m EL and springing level at 592.5m EL A valve house of 10m width, with axis at 600 to that of the powerhouse cavern, with crown level at 595.5m EL and springing level at 592.5m EL Configuration 2: A powerhouse cavern of 21m width, with crown level at 595m EL, and springing level at 588.5m EL A valve house of 10m width, with crown at 591.5m EL and springing level at 588.5m EL Configuration 3: A single powerhouse cavern of 25m width, with crown level at 595m EL and springing level at 588.5m EL, and without a valve house
- Geology > Geological Subdiscipline > Geomechanics (0.88)
- Geology > Geological Subdiscipline > Volcanology (0.69)
- Geology > Rock Type > Igneous Rock > Basalt (0.68)
- Energy > Power Industry (0.55)
- Materials > Metals & Mining (0.47)
ABSTRACT: Design and construction of underground cavern involves fixing the size, layout and orientation of cavern, design of rock support, blasting pattern, excavation sequence, rock support, instrumentation etc. This is a case study paper on planning, design and construction aspects of Transformer cavern of the Pykara Ultimate Stage Hydro Electric project (3x50MW) already commissioned in the Nilgiris District of Tamil Nadu, India. In this project, a separate transformer cavern of 68m long, 12m wide, 15m high to house 3 three phase transformers orienting parallel and downstream to the Power house cavern was constructed. The Transformer cavern is accessible from Access tunnel, cable tunnel as well as Power house cavern. Bus ducts from three units are routed through three bus duct tunnels independently from power house to the transformer cavern. An escape tunnel around the transformer cavern was provided as an escape route in the event of emergency. The power house and transformer caverns are separated by a rock pillar of 30m wide. The transformer cavern is located in a medium of fresh and massive Charnokite rock. The rock cover over the cavern is about 500m. The orientation of major axis of the cavern was chosen parallel to the direction of in-situ major horizontal principle stress and parallel to the major axis of the power house cavern. The excavation of the cavern was commenced from crown and continued in stages and proper sequence up to the service bay floor level. The rock support consisting of rock bolts and shotcrete was designed based on the rock mass classification and 3D numerical modeling of entire power house complex. Each stage was supported before commencing next stage. The cavern was dry. No seepage of water was encountered. However, holes were drilled to drain seepage water if any during operation stage. Presence of shear zone and fracture zone were noticed in the floor of the cavern at service bay level. Such zones were treated properly before laying of foundation for the Transformers and columns supporting cable spreading floor. Multipoint borehole extensometers were installed in the crown as well as side walls of the cavern to measure rock deformation. Instrumentation was continued for two years to assess stability of the cavern as the cavern contains numerous cavities. The cavern is stable for the past six years. This paper attempts to describe planning, design and construction aspects of the Transformer cavern and problems encountered and will be much useful for the Engineers involved in planning, design and construction of underground caverns. 1.0 BRIEF DESCRIPTION OF THE PROJECT Pykara Ultimate Stage Hydroelectric Project was constructed commissioned already in the Nilgiris district of Tamil Nadu to utilize available flows of Pykara River and its tributaries for power generation. The main components of the project are as indicated below. The general layout of the project is shown in Fig. –1. A Headrace tunnel (2.1x2.42 m) of 377 m long from existing Glenmorgan forebay dam A Gate shaft (5 m dia.) and a Surge shaft (8 m dia.)
- Energy > Renewable > Hydroelectric (0.72)
- Energy > Power Industry > Utilities (0.62)