ISRM 2023 - PUBLICATIONS

T08: Hydropower projects and damsYi LUO, Hangli GONG, Qiaoliang LI, Xinping LIWuhan University of Technology, People's Republic of ChinaStudy on dynamic response characteristics of cave-type excavation of high and steep dam abutment slopeThe numerical simulation is carried out for the dynamic response characteristics of cave-type excavation at the left dam abutment of Zhongyu Hydropower Station. The results show that within the range of 20~100 m from the explosion source in the vertical direction, both the peak vibration velocity and the maximum principal stress of the particle present extremely obvious elevation amplification effect. Due to the influence of the ground stress and the excavation contour of the dam abutment, different layered blasting excavation and excavation unloading have different effects on the deformation and displacement of the surrounding rock of the dam abutment. In addition, during the excavation in a certain layer, the displacement change rate of the particles on the upstream and downstream sides of the dam abutment is usually first fast and then slow, and there will be obvious inflection points. | high and steep dam abutment slope, cave-type excavation, blasting vibration, dynamic response, elevation amplification effect
T08: Hydropower projects and damsRujiu ZHANG (1), Wenyu ZHUANG (1), Jianjun XU (2), Liang YIN (2), Haining WEI (2), Yaoru LIU (1)1: Tsinghua University; 2: POWERCHINA Huadong Engineering Corporation Limted.Deformation behavior analysis of an arch dam during initial impoundment based on clustering and panel data regressionDeformation behavior analysis is crucial for ensuring safe operation of the arch dam. This study investigates the deformation distribution and influencing factors of an arch dam in southwest China based on k-means clustering analysis and panel regression models. Results show that dam deformation is closely related to the impounding process and reservoir water level is the main influencing factor. The deformation of some monitoring points near the dam foundation are also affected by aging component. The effects of temperature are negligible in the short term. In general, the studied arch dam is in a condition for safe operation; the abnormal deformation of some monitoring points is basically affected by unbalanced hydraulic thrust, whose magnitude is small and tends to be stable. Analysis results also validate the applicability of cluster analysis and panel regression model in the evaluation of arch dam deformation behavior during initial impoundment. | arch dam, deformation behavior, panel data, k-means cluster, initial impoundment
T08: Hydropower projects and damsRupert STEIGER (1), Peter WETZLINGER (2)1: TIWAG, Austria; 2: Swietelsky, AustriaHEPP cavern Kühtai, excavation design and construction experienceThe Pumped Storage Scheme Kühtai 2 located between the existing reservoir Finstertal and the currently under construction reservoir Kühtai is part of the expansion of the existing hydro power plant group Sellrain-Silz. The new power station is housed in a cavern at an altitude of 2000 meters above sea level near the village of Kühtai in Sellraintal. The cavern is located within a gneiss formation (biotite-plagioclase gneiss), which is layered in bands and tectonically faulted. As the design progressed, a number of variants were investigated, including the simulation of different geological conditions, the variation of distance between the individual caverns (double cavern solution with machine cavern and separate transformer cavern), the arrangement of tunnels surrounding the caverns and the complex construction process, until a solution was developed. The paper provides an overview to the excavation design process as well as to the geotechnical design analyses, which were adopted, and the experience gained during the excavation of the caverns. | Cavern excavation design, construction experience
T08: Hydropower projects and damsTek Bahadur KATUWAL (1,2), Krishna Kanta PANTHI (1), Chhatra Bahadur BASNET (2)1: Norwegian University of Science and Technology, Trondheim, Norway; 2: Tribhuvan University, IOE, Pashchimanchal Campus, Pokhara, NepalChallenges associated with the construction of vertical and inclined shafts in the Himalayan RegionIn the Nepal Himalayas, hydropower projects having an installed capacity of over 10 MW usually consist of underground waterways. Most of these underground waterways consist of vertical or inclined pressure shafts, which are part of the headrace system of a hydropower project. Excavation of these shafts requires special techniques, and the performance is dependent on the quality of rock mass. Therefore, the selection of an efficient construction method for shaft excavation is most challenging work. This manuscript evaluates the challenges associated with the construction of shafts for three hydropower projects in the Nepal Himalayas. The achieved construction progress of each method is compared with actual geological conditions. It is concluded that the major challenges associated with the excavation of pressure shafts through the Himalayan rock mass conditions are frequent overbreak, water inflow, debris flow, difficulties in surveying and control of shaft alignment, ventilation, poor visibility, and pilot hole deviation. | Vertical/inclined Shafts, Construction methods, Himalayan rock mass, Overbreak
T08: Hydropower projects and damsMarco QUIRION, Dolice DONTSI MAKENHydro-Quebec, CanadaBehavior of the Rock Foundation of a Concrete Dam Affected by Alkali-Aggregate ReactivityThe Beauharnois dam is located near the city of Montreal (Quebec, Canada). The water intake and the powerhouse are founded directly on a quarzitic sandstone rock mass. The coarse aggregate used in the concrete to build the dam originates from these rocks and has a high reactivity to cement alkalis. This reactivity called alkali-aggregate reaction (AAR) is a slow reaction that causes the concrete to swell. Regarding the foundation, swelling of the concrete led to the transfer of stresses to the rock foundation. The intact rock is of high resistance and the rock mass of good quality. The dam foundation is stable to sliding despite the sub-horizontal bedding of the sandstone and the transferred stresses. However, it is shown that, locally, depending on the intensity and orientation of the stresses, they can contribute to the vertical opening of discontinuities near the concrete-rock interface. | Dam, Foundation, Alkali-Aggregate Reaction, Discontinuities, Stresses
T08: Hydropower projects and damsFrancisco RÍOS BAYONA (1), Fredrik JOHANSSON (2), Diego MAS IVARS (2,3), Carl-Oscar NILSSON (4)1: Typsa AB, Department of Civil Engineering, Stockholm, Sweden; 2: KTH Royal Institute of Technology, Department of Civil and Architectural Engineering, Stockholm, Sweden; 3: SKB Swedish Nuclear Fuel and Waste Management Co, Solna, Sweden; 4: Uniper – Sydkraft Hydropower AB, Östersund, SwedenA possible way forward to predict the peak shear strength of a natural, unfilled rock joint under concrete dams based on field dataThe prediction of a rock joint’s peak shear strength becomes complex when its joint surfaces are not fully accessible, such as the rock foundation under an existing concrete dam. This paper presents a case study with the application of a newly developed methodology that uses objective observations of the 3D roughness and joint aperture from drill cores to predict the peak shear strength of large natural, unfilled rock joints. Eight rock joint samples obtained after core-drilling an existing rock joint adjacent to the foundation of Storfinnforsen dam in Sweden were used. The main benefit of this approach is that it enables the prediction of both the mean value and the statistical uncertainty of the peak shear strength under conditions of difficult access. This information may be of importance in order to assess the safety in the foundation of an existing concrete dam. | Rock joints, peak shear strength, concrete dams, field observations, drill cores
T08: Hydropower projects and damsYuxi LIU (1), Qianbing ZHANG (1), Ivan CHING (2)1: Department of Civil Engineering, Monash University, Clayton, VIC, Australia; 2: SMEC Pty. Ltd., Sydney, NSW, Australia3D numerical modelling of stability of underground pumped storage hydropower (UPSH)In light of constructing larger and deeper underground pumped storage hydropower (UPSH) plants in deep valleys, a comprehensive study assesses their stability. Internal and external factors are analyzed for a typical underground hydropower station. Evaluating different rock mass types and mechanical qualities internally, the study also examines various station depths, major horizontal stress ratio (K), station angle, and station length. It is found that increasing station depth and size amplifies stress and deformation of surrounding rock, but rock types with higher compressive strength display better resistance against excavation-induced stress and deformation. Notably, the station walls are more stable when station long axis aligns with the major horizontal stress, but it is expected to be less favorable for station end-wall and tunnels connecting caverns. It is crucial to consider rock properties, in-situ stress, and other key aspects for proper engineering measures for the deeper and larger UPSH plants. | Stability analysis of underground pumped storage hydropower (UPSH), in-situ stress, rock type and quality, cavern length
T08: Hydropower projects and damsSteffen BAUER, Sebastian PERZLMAIERTIWAG-Tiroler Wasserkraft, AustriaThe material extraction for the Kühtai DamFor the construction of the Kühtai embankment dam, a total fill volume of 6.9 mio m³ is required. The main sources of the material are the overburden and hard rock of the Längental valley. The required rock material is produced in a quarry developed at the eastern reservoir slope. The rock mass consists mainly of granodiorite gneiss. To estimate the production volume a 3D rock contour model was developed. The total production volume is 2.2 mio m³ of hard rock and 3.2 mio m³ of overburden. The produced material has to fit the requirements of the dam zoning, considering mass balance and sequence of construction. The bench and overall slope stability is evaluated by stability calculations, visual inspections, engineering-geological mapping, geodetic monitoring and terrestrial laser scanning. The finale bench faces are blasted by pre-splitting method. Preparation for production has started in 2020 and production began in 2022. | Kühtai Dam, rock slopes, quarry, blast design, monitoring
T08: Hydropower projects and damsMike GEORGEBGC Engineering, United States of AmericaA Block Theory approach for rock erodibility assessment incorporating 3D high-resolution site characterization dataScour of rock in dam foundations and spillways during flood events is an important issue for dam safety. A new approach using Block Theory to evaluate erodibility of 3D rock blocks has been developed using physical hydraulic model and prototype testing. The use of high-resolution remote sensing technology for 3D site characterization of the rock mass (e.g., photogrammetry and LiDAR) in combination with the Block Theory Rock Erodibility (BTRE) method has permitted a more detailed, site-specific, examination of rock erodibility than previously attainable. This includes delineation/analysis of site-specific 3D rock blocks, monitoring/change detection of scour over time, and rapid collection of thousands of discontinuity measurements for probabilistic scour analysis. | Rock scour, Block Theory, remote sensing, erodibility, dams, spillways
T08: Hydropower projects and damsJohannes KLEBERGER, Irmina PÖSCHL, Jonas WEILiC consulenten Ziviltechniker GesmbH, Austria275 m high Yusufeli arch dam – Geotechnical modelling during constructionThe World’s highest double curved arch dam outside of China was recently completed near the town of Yusufeli in NE Turkey. The project was ordered, supervised and managed by the State Ministry of Hydraulic Works (DSI), and constructed by contractor LIMAK of Ankara. The implementation of the 275 m high dam necessitated the construction of almost 480 m high very steep cut-slopes in extreme terrain. The contractor decided early during his contract to perform a multi-staged site investigation and consequent 3D geotechnical modelling. Data from a large variety of SI methods, including detailed geological documentation of ~20km of tunnels and ~200,000m² excavated slopes were continuously integrated into this 3D geo model. Together with a co-operative approach between acting parties, an active project management and highly professional service providers, the flexible 3D model helped to effectively deal with the important geotechnical issues and complete this ultra-high dam project without significant delays. | 3D modelling, digital data base, steering tool, design and construction management
T08: Hydropower projects and damsYavar JALILI KASHTIBAN (1), Ali SAEIDI (1), Marie-Isabelle FARINAS (1), Javier PATARROYO (2)1: University of Quebec at Chicoutimi, Canada; 2: Hydro-Quebec, CanadaEvaluation of the effect of rock surface irregularities on energy gradient in unlined dam spillwaysRock scouring downstream of dams has raised concerns for dam safety. To assess hydraulic erodibility, it is important to consider both geomechanical and hydraulic factors. Unlined spillways are typically created through controlled blasting, resulting in irregular rock surfaces. Previous studies have not comprehensively considered various geometrical parameters, including joint opening, joint spacing, and surface irregularities, and their impact on hydraulic parameters. This study aims to investigate the influence of surface irregularities in 25 different configurations on hydraulic parameters. The findings will contribute to improving the current equation for the hydraulic erosive parameter in future research. ANSYS-Fluent CFD simulations were performed to analyze the determined unlined spillway geometries. Results showed that increased irregularity height reduced maximum velocity and energy, but led to increased total head loss and rock mass erosion. Furthermore, the water-rock interface experienced three times higher energy loss compared to the water surface. | Rock mass, Geomechanics, Unlined spillways, Erodibility, CFD
T08: Hydropower projects and damsMarie-Hélène WISSE (1), Ali SAEIDI (1), Marco QUIRION (2)1: Université du Québec à Chicoutimi, Canada; 2: Hydro-QuébecExperimental study of joint opening and block protrusion effects on rock mass erosion in unlined spillwaysRock mass erosion in dams’ spillways can cause damages to the spillway structure and result in expensive repairs. In order to study rock mass characteristics having an effect on rock mass erosion in unlined spillways, a scaled physical model of a real dam spillway was built in a laboratory of Université du Québec à Chicoutimi. This physical model also allows studying the hydraulic parameters of the flow which have an effect on rock mass erosion. Some tests were undertaken to study the effects of joint opening and block protrusion on the hydraulic parameters in the simulated rock joints. The distribution of water pressure was measured on the faces of an instrumented block. The results obtained show that the main force having an effect on the block uplift is the water force acting on the top of the block. This force is mostly affected by protrusion configuration. | Physical model, Spillway, Rock Mass, Erosion