Water Pressure Research Articles

Laboratory Model Tests on the Deformation and Failure of Terraced Loess Slopes Induced by Extreme Rainfall

Heavy rainfall is the main factor inducing the failure of loess slopes. However, the failure mechanism and mode of terraced loess slopes under heavy rainfall have not been well investigated and understood. This paper presents the experimental study on the deformation and failure of terraced loess slopes with different gradients under extreme rainfall conditions. The deformation and failure processes of the slope and the migration of the wetting front within the slope during rainfall were captured by the digital cameras installed on the top and side of the test box. In addition, the mechanical and hydrological responses of the slope, including earth pressure, water content, pore water pressure, and matric suction, were monitored and analyzed under rainfall infiltration and erosion. The experimental study shows that the deformation and failure of terraced loess slopes under heavy rainfall conditions exhibit the characteristic of progressive erosion damage. In general, the steeper the slope, the more severe the deformation and failure, and the shorter the time required for erosion failure. The data obtained from sensors embedded in the slope can reflect the mechanical and hydraulic characteristics of the slope in response to rainfall. The earth pressure and pore water pressure in the slope exhibit a fluctuating pattern with continued rainfall. The failure mode of terraced loess slopes under extreme rainfall can be summarized into five stages: erosion of slope surface and formation of small gullies and cracks, expansion of gullies and cracks along the slope surface, widening and deepening of gullies, local collapse and flow-slip of the slope, and large-scale collapse of the slope. The findings can provide preliminary data references for researchers to better understand the failure characteristics of terraced loess slopes under extreme rainfall and to further validate the results of numerical simulations and analytical solutions.

Numerical Simulation and Critical Threshold Analysis of the Failure Process for Shield Tail Sealing System under High Water Pressure

Numerical Simulation and Critical Threshold Analysis of the Failure Process for Shield Tail Sealing System under High Water Pressure

Analysis and monitoring of the behavior of a rock fill dam ten years after construction: a case study of the Iran-Madani Dam

AbstractIn this study we compared dam monitoring results with those of numerical analysis to propose a plan for the first reservoir impounding of the Iran-Madani Rock fill dam, ten years after the completion of its construction. The stability of the dam body has been assessed using numerical analysis and data obtained from sensors installed in the dam. The correctness and accuracy of the geotechnical parameters of the dam body materials were confirmed by comparing the results of numerical analysis and monitoring through back analysis. The linear correlation coefficients between the experimental data and the numerical results for settlement, pore water pressure, and total stress are 84%, 67%, and 99%, respectively. In addition, the agreement between the design assumptions with both the numerical analysis results and instrumentation data was examined. The arching ratio values obtained from instrumentation and numerical analysis in the core of the dam are 0.47 and 0.35, respectively, indicating the safety of the dam. Finally, a numerical sensitivity analysis was conducted to present a special impounding program for the dam, with a focus on controlling simultaneous changes in pore water pressure and effective stress in the clay core, ten years after the completion of the dam body construction.

Estimation of Turbulent Mixing Factor and Study of Turbulent Flow Structures in Pressurized Water Reactor Sub Channel by Direct Numerical Simulation

Abstract Subchannel analysis codes are presently a requirement for design and safety analysis of nuclear reactors. Among the crucial inputs for these codes, the turbulent mixing factor holds particular significance. However, acquiring this factor through experimental means proves to be a challenging endeavor, primarily due to the necessity for precise pressure equilibrium between subchannels. Consequently, this requirement leads to the undertaking of expensive and intricate experiments for each new reactor or in cases where there are modifications in fuel bundle design. The need for direct numerical simulation (DNS) stems from the challenges and costs involved in experimental techniques, and the uncertainties due to empiricism in computational fluid dynamics (CFD) models. In this study, DNS has been conducted across six Reynolds numbers, ranging from 17,640 to 1.176 × 105, in the geometry of a pressurized water reactor (PWR) subchannel. The resulting turbulent flow structures have been computed and their dynamics are examined. Furthermore, this paper presents a methodology for directly calculating the turbulent mixing factor from the fluctuating velocity field obtained from DNS data. The turbulent mixing process has been scrutinized in-depth, and a correlation for the turbulent mixing factor is developed. It is noted that most of the mixing occurs in the near-wall region. The study suggests different mixing factors for mass and momentum mixing. This paper aims to provide a comprehensive insight into the turbulent mixing phenomenon.

TSUNAMI Analyses of the Similarity and Applicability of Zero Energy Deuterium 2 Critical Experiments for Reactor Physics Code Benchmarking for a Pressurized Water Reactor Small Modular Reactor Design Concept

Abstract This paper presents the findings of studies conducted at Canadian Nuclear Laboratories (CNL) to support the development of small modular reactor (SMR) designs. The primary focus of this research was to evaluate the suitability of the zero energy deuterium 2 (ZED-2) critical facility in replicating the reactor physics environment for a pressurized water reactor small modular reactor (PWR-SMR) design concept through similarity and nuclear data sensitivity studies, using the TSUNAMI code suite. It was found that previous ZED-2 experiments would be quite promising for application to a PWR-SMR design. Further similarity and sensitivity studies of hypothetical mixed-lattice substitution experiments, where PWR-SMR fuel assemblies were placed into a substitution region of the ZED-2 critical facility demonstrated improved similarity. Subsequent analyses focused on the impacts of dissolved Gadolinium (Gd) and boron (B) neutron absorbers, suggesting the feasibility of using future ZED-2 experiments to more closely replicate PWR-SMR reactor physics behavior. Building on these initial findings, the design for PWR-SMR fuel assembly substitution experiments in the ZED-2 facility were explored further. These hypothetical experiments feature water-cooled PWR-type fuel assemblies inside a shroud, surrounded by heavy-water-moderated CANdu FLEXible, Low Enriched Uranium, Recovered Uranium (CANFLEX-LEU/CANFLEX-RU) fuel channels. Similarity and sensitivity studies indicate a very high level of similarity of these experiments for PWR-SMR design applications.

Tracking the Filling, Outburst Flood and Resulting Subglacial Water Channel From a Large Canadian Arctic Subglacial Lake

AbstractWe use digital elevation models (DEMs) and ICESat‐2 data to study the filling and outflow from a large subglacial lake under Manson Icefield in the Canadian Arctic. When full, the lake is ∼17 × 3 km with an area of 52 km2. Early in 2021 the ice surface over the center of the lake sank by >140 m implying a subglacial outburst flood of ∼4 km3. Rapid outflow occurred over ∼30 days at an average rate of ∼1,500 m3s−1 resulting in the formation of a single ∼15 km subglacial outflow path detectable from post‐outflow surface depression. The shape of the surface depression, 600–800 m wide by 2–4 m deep, reflects the shape of the subglacial channel prior to closure. Downstream ice movement appears unaffected by the outflow. After outflow ends the surface depression persisted over weeks, apparently dependent on the difference between water and overburden pressures.

Determining Groundwater Table in Slopes with Horizontal Drains and Design Framework for Length and Spacing

ABSTRACT Horizontal drains (HDs) are commonly implemented in slope stabilization to reduce the pore water pressure (PWP); however, they also cause complex three-dimensional (3D) variations in the groundwater table (GWT), which require intricate 3D flow models. To address this challenge, we propose a novel semi-empirical method based on a series of numerical simulations validated through numerical and field studies to determine the GWT of a slope with HDs. Subsequently, the proposed method was extended to calculate the average PWP (U) acting on a predefined slip surface via linear integration. The decrease of U (ΔU) resulting from HDs can be used to evaluate the performance of HDs. To create design charts that consider the impact of length and spacing of HDs on ΔU for a specific slope, we developed a Python-based computer program. Two case studies were conducted, which showed that ΔU increases with longer HDs and shorter spacing. The results also indicated that extending the HDs beyond a particular length does not significantly affect ΔU; it is highly sensitive to the spacing in short HDs and not sensitive in long HDs. Furthermore, we found that the total length of HDs required to achieve a target ΔU is less in wide spacings than in short spacings. In conclusion, long HDs with wide spacings are more effective and economical. Owing to the unique nature of each slope stability problem, this study offers a practical tool for analyzing the effectiveness of HDs instead of providing a general guide.

Experimental study on physico-mechanical responses and energy characteristics of granite under high temperature and hydro-mechanical coupling

Thermal and hydro-mechanical coupling effects on granite's physico-mechanical responses and energy characteristics can influence its carrying capacity, hydraulic and heat transfer performance. The evolution of these properties is crucial for geothermal reservoir stability assessment and the optimization of deep geothermal energy development techniques. Hence, a variety of physical tests and rock mechanics experiments were conducted. Key findings include: (1) As temperature rises, granite undergoes thermal expansion and structural integrity degradation. The peak strength σp, elastic modulus E, total energy density U, and elastic energy density Ue initially rise at 25 °C–150 °C and subsequently decrease above 150 °C, while the proportion of dissipated energy ηd is opposite. Granite also initially experiences hardening, then turns to brittle-ductile transition. (2) The crystallinities of quartz, albite, and orthoclase demonstrate substantial deterioration beyond 450 °C. (3) 150 °C and 450 °C are regarded as the temperature thresholds for mechanical properties. (4) As confining pressure rises, granite experiences hardening, with σp, E, U, and Ue increasing, and ηd decreasing. (5) Pore water pressure increases ηd and decreases σp, E, U, and Ue, and its effect on the mechanical responses is pronounced when it reaches 80 % of confining pressure or exceeds 450 °C.

Pore water pressure dynamic response in asphalt mixture: A measurement system development

The pore water pressure dynamic response in asphalt pavements is complex and distinct, which is closely related to pavement damage and seepage characteristics. However, existing measurement methods often don’t simulate the dynamic pore water pressure realistically and combine with measuring position and pavement saturation adequately. This study develops a system to measure pore water pressure in asphalt mixtures under dynamic loading. It simultaneously considers vehicle-pavement interactions, sensors embedding and pavement saturation. The test results shows that the output equivalent loads accuracy of the system reaches 80 % and higher. The noise interference from air is identified, and the FFT digital filters are designed to minimize it. The application result shows pore water pressure response varies under different loading modes. The pressure rapidly rises, peaks, then diminishes to 0 under intermittent loading, while it rebounds after decreasing but never reaches 0 under continuous loading. A turning point at 9.8 % void ratio is noted, where denser mixtures exhibit more hysteresis and longer dissipation times, suggesting increased resistance to water transfer.

Theory for plunger-type wavemakers to generate second-order Stokes waves and Smoothed Particle Hydrodynamics verification

Plunger-type wavemakers are used in ocean engineering laboratories globally. However, the wave-making theories remain incomplete due to the complex geometries of the plungers. This work derives the motion equations for an arbitrary-geometry plunger to generate second-order Stokes waves, along with the generic constraints on wave parameters. Taking wedge-shaped and cylinder-shaped plungers as examples, the motion equations and constraints are detailed. Subsequently, a smoothed particle hydrodynamics (SPH) model for the plunger-induced waves is established and validated by accurately reproducing published experimental results. Finally, the SPH model is applied to simulate the wave generation by the two plungers. The computed wave profiles, water pressures, and flow velocities are compared with their analytical solutions in terms of spatial distribution and time history. Additionally, the wave field stability and the wave generation process are evaluated. The results demonstrate that second-order Stokes waves with target waveforms can be precisely generated using an arbitrary-geometry plunger-type wavemaker within a short transition distance and time, thereby verifying the reliability of the proposed wavemaker theory.

Stability of slopes in partially saturated soils: Incorporating the combined effects of seismic forces and pore water pressure

Earthquakes and groundwater are pivotal factors affecting slope stability. However, the majority of previous studies have focused on these factors individually, neglecting their combined effects. Hence, this paper aims to develop a framework using the kinematic approach of limit analysis to investigate the stability of slopes in partially saturated soils under the combined effects of seismic force and pore-water pressure. The pseudo-dynamic method (PDM) was employed to capture the temporal-spatial effect of horizontal and vertical seismic waves. Variations in suction and effective unit weight profiles with moisture content under steady-state unsaturated flow were considered. External rates arising from both static pore-water pressure and earthquake-induced excess pore-water pressure were incorporated into the energy-balance equation. With the aid of gravity increase method (GIM), an explicit expression of safety factor (FS) was derived and optimized using a genetic algorithm (GA). The validity of this approach was verified through a comparison with existing solutions. Parametric analyses were conducted to explore the influence of varying groundwater level, seismic coefficients, suction, three-dimensional effects, excess pore water pressure, unsaturated flow types, and pseudo-dynamic parameters, on the FS and critical sliding surface of slopes in partially saturated slopes. This framework can provide a good reference for the safety design of reservoir slope under the combined effects of earthquakes and groundwater.

Analytical solution for radial consolidation of combined electroosmosis-vacuum-surcharge preloading considering free strain and cyclic loading

In this study, electro-osmotic consolidation considering smear effect and free strain under cyclic loading was investigated. The analytical solution of radial consolidation of electroosmosis-vacuum-surcharge combined preloading is derived by using the Bessel function and eigenfunction methods. Subsequently, the effectiveness of the proposed method is validated through comparison with existing numerical solutions. Based on the derived solutions, the influence of the smear effect, applied voltage, vacuum pressure, and cyclic loading on soil consolidation characteristics was analyzed. The results showed that the smearing effect slows the rate of consolidation, but the final average consolidation and negative excess pore water pressure are enhanced. Compared with only cyclic loading, the combined effect of electroosmosis, vacuum, and surcharge preloading enables the soil to achieve higher strength and consolidation. When the effect of electroosmosis alone on reinforcing low-permeability soils is not significant, the combination of electroosmosis with vacuum preloading helps enhance the soil reinforcement effect.

Investigation of the particle crushing characteristics of stacked stone materials under different stress path conditions

Stone fill materials are widely used in engineering projects such as earth-rock dams, railways, and highway embankments. Nevertheless, they are susceptible to particle breakage, which can lead to a decline in engineering performance. A complete set of studies on crushed stone aggregates was carried out to investigate particle crushing characteristics under various stress path conditions. To quantify the amount of particle crushing, the relative particle crushing rate was utilized as an indicator. The plastic work performed during the trials was compared across different stress routes, and the relationships between particle crushing and average stress p and generalized shear stress q were investigated. In triaxial testing, the differences in particle crushing behavior under different stress routes were thoroughly examined. The results show that particle crushing is substantially lower in the modelling of a rockfill dam constructed with a core wall and subjected to reservoir water pressure pathways than in conventional triaxial tests. A clear relationship was discovered. Across several stress routes, a clear link between plastic work and the relative particle crushing rate was detected, which was successfully characterized by a power function. Notably, the contributions of different stress components to the overall plastic work varied significantly. The plastic work exerted by the generalized shear stress q accounted for a large percentage of traditional triaxial testing, although the proportion of plastic work given by p and q changed significantly in complex stress path tests. This research enhances the understanding of the particle breakage characteristics of stone fill materials under complex stress paths.

Bayesian inference of coupled groundwater flow and radiogenic helium-4 production and transport at the catchment scale

Hydrogeological numerical models are essential for assessing radioactive waste disposal by understanding groundwater flow systems. These models typically rely on hydraulic head data, with other state variables often underutilized in model inversions. In Flanders' Neogene aquifer, where safety studies for Boom Clay are ongoing, existing models face uncertainties due to dependence on hydraulic heads alone. This study aims to: i) develop a conceptual model of radiogenic Helium-4 (4Herad) production and transport to reproduce observed concentrations; ii) evaluate the usefulness of 4Herad observations as an additional state variable for inverse conditioning; and iii) assess how including 4Herad affects model calibration and uncertainty reduction. We address these objectives by incorporating radiogenic Helium-4 (4Herad) as an unconventional state variable in model inversion to tackle parameter non-uniqueness. Utilizing a Bayesian approach, we employ two 3D models: a groundwater flow (GWF) model conditioned by hydraulic heads and a coupled GWF model with 4Herad production and transport, conditioned by both hydraulic heads and 4Herad concentrations. We hypothesize that integrating 4Herad will improve model accuracy and reduce uncertainties compared to using hydraulic head data alone. Findings indicate that major 4Herad sources include crustal fluxes (~57 %) and in situ Boom Clay production (~25 %). The coupled inference narrows the posterior distributions of parameters, especially for hydraulic conductivity (e.g., Mol, Diest, Berchem formations, and the Rauw Fault) and recharge, showing that 4Herad observations effectively reduce uncertainty beyond hydraulic head data. Including 4Herad improves model reliability and prediction accuracy, highlighting its importance for refining groundwater flow parameters and derived fluxes. To the best of our knowledge, this study marks the first-ever attempt at harnessing 4Herad quantitative insights into flow and transport parameters following a Bayesian approach at a catchment scale, setting a precedent for future research and emphasizing the innovative nature of this work. This study showcases a state-of-the-art approach in hydrogeological modelling, demonstrating the effectiveness of integrating 4Herad with hydraulic head observations to produce more reliable model predictions. By reducing uncertainties in crucial groundwater fluxes, this approach offers significant potential for improving geological disposal safety studies. This pioneering work advocates for the continued use of 4Herad in hydrogeological modelling, emphasizing its innovative contribution to future research and safety studies. Plain language summaryUnderstanding how groundwater flows is crucial for safely storing radioactive waste. Traditionally, models used to study groundwater rely mostly on measurements of water pressure, while other valuable data often go unused. In the Neogene aquifer in Flanders, where researchers are studying the Boom Clay formation for potential waste storage, relying only on water pressure has created uncertainties in the models. This study explores a new approach by using a different type of measurement: radiogenic Helium-4 (4Herad). The goals of the study are threefold: first, to build a model that accurately represents how 4Herad is produced and moves through the groundwater; second, to test whether including 4Herad as an additional measurement improves the model compared to using only water pressure data; and third, to see how using 4Herad affects the accuracy and reliability of the model. The study uses two types of models: one that relies only on water pressure data and another that includes both water pressure and 4Herad measurements. The idea is that 4Herad could provide additional insights and help reduce uncertainties in the model. The findings show that 4Herad comes mainly from two sources: the surrounding crust and the Boom Clay itself. Including 4Herad in the model helps narrow down uncertainties, particularly regarding how water moves through different layers and how much water is being replenished. This research is the first to use 4Herad in this way, using a formal statistical method to improve groundwater models. The results suggest that 4Herad is a valuable addition for making more accurate predictions and improving safety assessments for radioactive waste storage.

Multicriteria risk assessment of water inrush in underground mines with large-scale curtain grouting: a mine disaster risk reduction strategy

This paper presents a synthetic method to assess the risk of mine water inrush before and after large scale curtain grouting based on GIS platform. Firstly, nine factors were selected from three aspects: geological conditions, hydrogeological conditions and curtain grouting parameters, to construct a multi factor assessment model. The combined weight of every factor was determined using the minimum deviation comprehensive weighting method, which can reduce the polarization effect of various assessment methods in multicriteria decision. Then, the effectiveness of the synthetic method was validated through the Maoping lead–zinc mine in Southwest China. The mining area was divided into five zones, namely safe zone, relatively safe zone, transitional zone, relatively dangerous zone, and dangerous zone. The assessment results show that the relatively dangerous and dangerous zones were significantly reduced, while the safe, relatively safe and transitional zones were significantly increased after large scale curtain grouting. Finally, we analyze the impact of curtain grouting on the risk of mine water inrush and the mechanism of zoning evolution from three aspects: water source control, pathway sealing, drainage, and pressure reduction. This work provides an effective strategy for mine disaster risk reduction.

Modeling pore fluid pressure and deformation in unsaturated soils under gravitational compaction and cyclic loading

Cyclic loading of fluid-bearing soils often induces excess pore water pressure, leading to accumulation of strain in the solid matrix. Additionally, variations in material density and volumetric fraction due to gravitational effects generate momentum forces, which subsequently cause deformation in the soil. In this paper, we present a mathematical framework of poroelasticity that generalizes the simultaneous action of gravitational body forces and cyclic loading to analyze solid deformation and fluid pressure dissipation in partially-saturated porous media. To account for the effect of gravity, the gradient of the vertical displacement needs to be treated as an additional dependent variable alongside pore air and water pressures.We numerically solve a mixed strain-controlled and pressure-prescribed boundary-value problem using a finite difference scheme as a representative example to quantify the impact of gravitational forces. Our results show that gravitational compaction affects both total settlement and excess pore water pressure, with its influence being particularly significant at lower water saturations, regardless of excitation frequency, soil depth, or type. The effect of gravity is more pronounced in soils with higher compressibility but appears insensitive to excitation frequency. Notably, the gravitational effect correlates linearly with the depth of the soil deposit and, therefore, should be well integrated into the consolidation theory of poroelasticity.

Effects of Temperature and Water Pressure on Mild Steel Strength: A Comparative Study

This study delves into the dynamic realm of mild steel strength variations under the influence of temperature fluctuations and alterations in water pressure during the rolling process. With a focus on elucidating the nuanced relationship between these factors and steel durability, the research employs a systematic investigation approach. The experimental design involves controlled temperature adjustments and varying water pressure scenarios to assess their impact on the structural integrity and tensile strength of mild steel. Through meticulous analysis and measurement, the study aims to uncover the intricate interplay between temperature, water pressure, and steel strength, providing valuable insights for optimizing rolling processes in industrial settings. The experimental works have been conducted at 870°C, 890°C, 910°C, 930°C, 950°C of temperature and 5.800 Kg, 6.000 Kg, 6.200 Kg, 6.400 Kg, 6.600 Kg of water pressure. At 870°C, 890°C, 910°C, 930°C, 950°C of temperature, the yield point values are 548 Mpa, 541 Mpa, 533 Mpa, 525 Mpa and 520 Mpa respectively. At 5.800 Kg, 6.000 Kg, 6.200 Kg, 6.400 Kg, 6.600 Kg of water pressure, the yield point values are 521 Mpa, 527 Mpa, 534 Mpa, 538 Mpa, 544 Mpa. The Yield Load, Yield Strength, Maximum Force, Tensile Strength, TS/YS Ratio, and Elongation after Fracture were carried out in the Metrocem and Mohammadi Steel Works Ltd (MSW) laboratory. However, the results of two laboratories are almost similar. The findings aspire to contribute to enhanced manufacturing techniques and the development of more resilient steel products, thereby advancing the understanding of material behavior in mechanical applications.

Water Turbine Guide Blades Effect of Quartz Sand on Abrasion Rate

Abstract Hydroelectric power plants with the aim of being used to generate electrical energy are mostly operated in areas with sedimentation content which can cause wear and tear on the components of the hydropower plant. This activity is emphasized to determine the effect of quartz sand on the rate of abrasion on the guide vanes of the Francis type water turbine. This activity was carried out using a water turbine guide blade abrasion test tool with a guide blade test object made of SUS 304 stainless steel material. The results are presented quantitatively and qualitatively, the greater the concentration and diameter of the quartz sand particles, the water pressure and the angle given at the same time, the greater the rate of abrasion that occurs in the francis type water turbine guide vane. The highest abrasion rate was 5.10 (g/cm2 x hour) in the angle variation test with a constant Q and a water: sand ratio of 70%: 30%.

Design and Performance study of Francis turbine for high head applications.

Abstract Francis Turbines are widely employed globally for their adaptability and operational versatility across a broad range of water flow rates and pressure heads. This study explores the design and optimization of a Francis turbine configured for exceptionally high heads, specifically targeting a design head of 700 m. Traditionally, Pelton turbines are favoured for such high heads, but this study investigates the viability of Francis turbines in this range. Through comprehensive testing, including the development of hill chart diagrams to evaluate performance under various conditions, the study demonstrates promising efficiency levels. Utilizing a simplified approach, the design process involves empirical relations and the Khoj program, resulting in turbine designs representing three different speed numbers: 0.32, 0.42, and 0.52. Efficiency and sediment erosion rates were computed for each and compared between the three designs. The comparison indicates that while the turbine with a speed number of 0.32 exhibits lower efficiency, it offers superior erosion resistivity. Conversely, turbines with speed numbers 0.42 or 0.52 show better efficiency, especially in handling fluctuations in operating conditions. The findings suggest a balance between efficiency and erosion resistivity, recommending the turbine designed for a speed number of 0.32 for superior erosion resistance, and the turbine with a speed number of 0.42 for greater efficiency and operational range. This study broadens the horizon for Francis turbines in high-head applications, offering insights into their potential and viability in extreme conditions.

Study on the Performance of Pressure Balance Pipe of Pump-turbine

Abstract For pump-turbine, axial water thrust can cause damage to the unit. It is important to realise automatic levelling by using pressure balance pipe. To study the influence of the pressure balance pipe on the performance of the reversible pump-turbine, axial water thrust and pressure fluctuation have been carried out for reversible pump-turbine with different guide vane opening and different operating heads by numerical and experimental analysis. The unsteady simulation results for the full flow channel of the pump-turbine show that the 298 mm guide blade opening meets the test standards of flow and power. Furthermore, CFD tests were carried out for different water heads at 298mm guide vane opening. At last, under the typical working conditions of 298mm guide vane opening and 400 m water head, pressure fluctuation, the axial water thrust in the vaneless zone are analyzed.