Scale Model Test Results Research Articles

The role of geosynthetic materials and vegetation on slope erosional control: Results of scale model tests

Geosynthetic materials for erosion control have the potential to significantly reduce the soil loss and to ensure the shallow stability of slopes. The paper presents the results of a scale model tests of a 2:3 (V:H) slope made from a very erodible soil, a sandy soil without and with 5 cm of topsoil, with and without vegetation, without and with different types of geosynthetics for erosional control. The slope models were subjected to heavy rainfall using a rainfall simulator. Results of the study show that the geosynthetics and vegetation generates a delay in the erosion process caused by the raindrops. Another result highlighted in this paper is the fact that the roots system improves the soil shear strength of the upper soil mass.

Coupling error modeling and compensation of beam-column endplate connection system

To investigate the composition form and evolution law of similar errors between full-scale prototype joints and reduced-scale model joints in steel structure beam-column connections, a full-scale benchmark model test and a 1:2 reduced-scale model test of beam-column end-plate connections were carried out respectively, focusing on the similarities and differences between the hysteretic curves of the two. The test results show that there is an irreparable gap between the test results of the two models without considering the similarity error, and the test results of the scaled model cannot accurately represent the full-scale model. Based on the test results, finite element models are established, and a calculation method to compensate the similarity error of the scale model is proposed. The relative independence between similarity error and test operation error is proved. The similarity error can be accurately simulated by response surface method based on multi-factor correlation. This paper focuses on three test error sources, namely, boundary conditions, plate thickness differences and bolt specification differences, meanwhile the contribution weights of the three error sources and their influence forms on the hysteretic curve are well investigated. Based on the proposed error compensation algorithm, the test results of the scale model are compensated and compared with full scale test results, which proves the effectiveness of the error correction algorithm. The compensated scale model test results are in good agreement with the prototype data, and the error is decreased from 70% to 5%.

Effect of pile spacing in helical pile groups in soft clays under combined loading

Helical piles have lately emerged as a viable alternative foundation solution in offshore geotechnical applications. The helical piles are typically installed in groups to resist large loads from the structures and may encounter combined loading due to some factor such as the waves from the water surrounding it. Recent research works on group helical piles focused mostly on piles embedded in sand and their response to individual loading regimes. This research has been carried out to examine the behaviour of the helical pile groups embedded in soft clay subjected to combined uplift and lateral loading considering three different configurations (rectangular, triangular, and square) and different spacings between the helical piles (2 to 5 times the helix diameter). A three-dimensional finite element model is developed to predict the load-displacement response of the group and is validated against the 1 g laboratory scale model test results. The findings from the analyses reveal that the influence of combined loading reduces the lateral capacity of the group helical pile. The spacing between the helical piles also has a substantial impact on the response to combined loading. The role of critical spacing ratio for various configurations has also been discussed in this paper.

Prediction of unstable full load conditions in a Francis turbine prototype

Francis turbines operating in full load conditions feature an axisymmetric vortex rotating in the opposite direction of the turbine runner. In low-pressure conditions, the resulting cavitation vortex may enter in an unstable self-exciting process, leading to large pressure pulsations and oscillations in the generating unit power output. In this research work, prototype on-site and reduced scale model test results are presented where the turbine changes from a stable to an unstable full load condition due to an increase in discharge. Measurements are compared in the frequency and time domain, where similarities are evidenced between model and prototype. Using the measurements on the reduced scale model and 1-D numerical models of both the reduced scale model and the turbine prototype, eigenvalue calculations are performed to predict the discharge value of transition from stable to unstable conditions. The transition point on the prototype is then predicted with a small deviation. Transient simulations in the time domain are performed replicating the self-exciting behavior of the unstable full load condition.

Composite materials in ICTS-CEHIPAR

The Center for Hydrodynamic Research of El Pardo (ICTS-CEHIPAR) is a Unique Scientific and Technical Infrastructure (ICTS) part of the Deputy Directorate of Naval Systems (SGSN) of the National Institute of Aerospace Technique “Esteban Terradas” (INTA). A new research line to study the use of advanced composite materials in the naval industry has been recently opened in the Technology and Tests Department of ICTS-CEHIPAR. One of the main goals of this new research line is the monitoring of structural stresses in composite materials by means of fiber optical sensors in structural diffraction Fibers Bragg Gratings (FBGS). ICTS-CEHIPAR is enhancing the constructive procedures for the production of models of ships and naval devices made in composite materials. The implementation of instrumentation techniques for the monitoring of structural stresses in this kind of materials is necessary to detect possible damage due to different causes during the product lifetime. Results of scale model tests will be applied to the full scale ship construction and instrumentation methodologies, increasing ship safety and optimizing maintenance procedures.

Size effect on reinforced concrete slabs under direct contact explosion

The static size effect of concrete is well known; however, investigations on the size effect of reinforced concrete slabs under direct contact explosion remain scarce. It is of great importance to understand the size effect so that the scale model test results can be applied to real damage of full-scale structures subjected to explosion. This paper presents an experimental investigation consisting of eleven direct contact explosion tests carried out to investigate the size effect phenomenon in reinforced concrete slabs. The results indicate that the explosion size effect is clearly observed; that is, the specimens of smaller sizes had less bottom spalling damage even if the upper crater size was approximately the same proportion. Furthermore, the damaged area tended to decrease as the steel ratio increased. Non-destructive testing can detect the damage location and depth of reinforced concrete slabs after explosion by imaging. Finally, finite element model based on LS-DYNA is developed and validated by experimental results for the numerical investigation of the reinforced concrete slab under direct contact explosion.

Scale-model test for disposal pit of high-level radioactive waste and theoretical evaluation of self-sealing of bentonite-based buffers

Bentonite is attracting greater attention in Japan and some other countries as a buffer for use in repositories of high-level radioactive waste (HLW). Bentonite-based buffers for HLW disposal are expected, because of their swelling deformation, to fill spaces between buffers and walls of disposal pits or between buffers and waste containers designated as overpack. Bentonite has a self-sealing capability. This study conducts scale-model tests simulating the relation between the buffer and interstitial space. It also investigates the validity of theoretical equations for swelling presented by Komine and Ogata (published in 2003 and 2004) to evaluate buffer self-sealing capabilities by comparing calculated and experimentally obtained results of scale-model tests. Results of the experimental work and calculations described herein highlight bentonite’s self-sealing capability and demonstrate the high applicability of these Komine and Ogata equations to quantify filling of interstitial spaces by bentonite-based buffer swelling.

Environmentally sustainable mining: a case study on surface subsidence control of grouting into overburden

This paper presents an investigation on the effect of grouting into multi-bed-separation to control mining-induced surface subsidence. In the overburden without obvious thick-and-hard strata for generating large-scale bed separation, overburden grouting is carried out by increasing the number of boreholes and grouting strata. The scale model test, numerical simulation, and field measurements are used to study distribution and process of bed separation and to compare the overburden failure with surface subsidence due to pre- and post-overburden grouting, with a case study of the Qi’nan Coal Mine, Anhui Province, China. The scale model test and numerical simulation results of the overburden grouting process are in close agreement with those obtained from the field measurements. Filling masses with different diffusion radii are commonly formed in the different bed separation, which are overlaid to control the surface subsidence. It is proven that overburden grouting can successfully mitigate overburden failure and subsidence without obvious hard strata and bed separations. This provides an effective and cost-efficient approach for addressing the surface subsidence and overburden deformation problems due to mining.

Rock mechanics comperhensive study of tunnel anchorage for super large suspension bridge

Aiming at bearing capacity problem of tunnel anchorages at Yaan side for Luding super large suspension bridge over the Dadu river, to study systematically the deformation, creep characteristics and bearing capacity of the tunnel anchorage and its surrounding rockmass by a comprehensive research method based on rock mechanic tests are proposed. The approach included in the research consists of in-situ geological investigation and rock mechanical tests, the 1:10 anchorage physical model test with the same rockmass at site of the actual schemed tunnel anchorage, and the numerical simulations related to bearing capacity evaluations of the actual tunnel anchorage. Several conclusions have been drawn. Geological representation of model tunnel anchorage is verified by comparing the surrounding rock geological condition and mechanical characteristics of model tunnel anchorage and actual tunnel anchorage is basically similar. Recommended test values of mechanical parameters of rockmass are proposed based on rock mechanical tests. In-situ scale model test results show that: (1) the maximum deformation of anchoring concrete-plug is 0.42, 2.50, 6.41 mm respectively under 1 P (design load), 3.5 P and 7 P, while the maximum deformation of surrounding rock is 0.25, 1.86, 6.59 mm respectively under 1 P , 3.5 P and 7 P. (2) Anchoring concrete-plug, surrounding rock and their dislocation experience deceleration creep and then tend to be stable, which belongs to attenuation type creep. (3) A characteristic point of anchoring concrete-plug model system is 5.25 P, which comforts code requirement. In addition, the technological line and achievement is an example for bridge construction in some other similar engineering.

Protection of Buried Pipe under Repeated Loading by Geocell Reinforcement

With increase in cities’ population and development of urbane life, passing buried pipelines near ground’s surface is inevitable in urban areas, roads, subways and highways. This paper presents the results of three-dimensional full scale model tests on high-density polyethylene (HDPE) pipe with diameter of 250 mm in geocell reinforced soil, subjected to repeated loading to simulate the vehicle loads. The effect of geocell’s pocket size (55*55 mm and 110*110 mm) and embedment depth of buried pipe (1.5 and 2 times pipe diameter) in improving the behaviour of buried pipes was investigated. The geocell’s height of 100 mm was used in all tests. The repeated load of 800 kPa was applied on circular loading plate with diameter of 250 mm. The results show that the pipe displacement, soil surface settlement and transferred pressure on the pipe’s crown has been influenced significantly upon the use of geocells. For example, the vertical diametric strain (VDS) and soil surface settlement (SSS), in a way that using a geocell with pocket size of 110*110 mm reduces by 27% and 43%, respectively, compared with the unreinforced one. Meanwhile, by increasing buried depth of pipe from 1.5D to 2D, the use of geocell of 110*110 mm delivers about 50% reduction in SSS and VDS, compared with the unreinforced soil.

Scale model test of a semi-active heave compensation system for deep-sea tethered ROVs

The deep-sea ROV system is usually equipped with a heave compensation system under harsh sea states, and a semi-active heave compensation system that consists of a passive and an active subsystem is presented, the compensation mechanism of which is derived theoretically and illustrated in detail. A novel scale model for the underwater umbilical cable system is brought forward according to the Froude criterion, and the natural frequency is scaled rigorously to guarantee the dynamics similarity for physical implementation. Then four kinds of model test, including the generation of heave motion, resonance zone, passive and semi-active heave compensation, are investigated in sequence. The test results show that the scale underwater system without compensation will resonate at a critical depth, which corresponds to the resonance zone of its prototype system, and the passive heave compensation is more suitable to compensate tension instead of motion. The semi-active heave compensation has better efficiency than the passive counterpart and is more suitable for compensating the motion instead of the tension. Based on the scale model test results, this paper can provide important references to improve the operation safety of the deep-sea tethered ROVs.

BONDED POROUS REVETMENTS – EFFECT OF POROSITY ON WAVE-INDUCED LOADS AND HYDRAULIC PERFORMANCE

The porosity and roughness of bonded revetments are both crucial for the hydraulic performance and the wave loading of the revetment and its foundation, and thus for the stability and durability of the entire structure. This is briefly shown by the selected results of a tentative comparative analysis of two large-scale test series performed in the Large Wave Flume (GWK) Hanover with two significantly different revetments: a highly porous and rough polyurethane bonded aggregate (PBA) revetment and an almost impermeable and relatively smooth interlocked pattern placed block (IPPB) revetment. These results motivated the initiation of the three years research project BoPoRe (Bonded Porous Revetments) which has the primary objective to investigate more systematically and separately the relative importance of both porosity and roughness for different slope steepnesses. This project is briefly introduced and the first results of preliminary scale model tests using 9 configurations for the porosity and roughness of the revetment subject to a wide range of wave conditions (surf similarity parameters 0.93-7.21) are briefly discussed.

Evaluation of dust emissions from conveyor transfer chutes using experimental and CFD simulation

This paper focuses on a study concerned with reducing dust emissions from belt conveyor transfer chutes in bulk material handling plants. Several transfer chute configurations were investigated with the aim of analysing the system performance. Scale model laboratory testing was undertaken to determine the effectiveness of each design in reducing dust emission. Computational Fluid Dynamics (CFD) was used to investigate the flow pattern of the granular material and entrained air in each of the transfer chute configurations. To verify the feasibility of CFD for dust emission prediction, a two-phase three-dimensional Euler–Euler model was adopted to qualitatively predict the performance of six transfer chute configurations with respect to dust generation. The predicted dust emissions obtained from the simulations were compared with the scale model test results. The simulation predictions compared favourably with the experimental results, demonstrating that CFD can be used to qualitatively evaluate the performance of transfer chute designs with regard to dust emission.

Evaluation of Acoustic- and Flow-Induced Vibration of the BWR Main Steam Lines and Dryer

The boiling water reactor (BWR-3) steam dryer in the Quad Cities (QC) Unit 2 Nuclear Power Plant was damaged by high-cycle fatigue due to acoustic-induced vibration. The cause of the dryer failure was considered as flow-induced acoustic resonance at the stub pipes of the safety relief valve (SRV) in the main steam lines (MSLs). The acoustic resonance was considered to be generated by the interaction between the sound field and an unstable shear layer across the closed side branches of SRVs. We have started a research program on BWR steam dryers to develop methods of evaluating the loading. Moreover, it is necessary to evaluate the dryer integrity of BWR-5 plants, which are the main type of BWR in Japan. In the present study, we conducted 1/10-scale BWR model tests and analysis to investigate the flowinduced acoustic resonance and acoustic characteristics in MSLs. The test apparatus consisted of a steam dryer, a steam dome, and 4 MSLs with 20 SRV stub pipes. Computational fluid dynamics (CFD) analysis was conducted to evaluate the acoustic source in MSLs. Finite element method (FEM) was applied to calculate the three-dimensional wave equations for acoustic analysis. We demonstrated that large fluctuating pressure occurred in the high- and low-frequency regions. The high-frequency fluctuating pressure was generated by the flow-induced acoustic resonance in the SRV stub pipes. We evaluated the acoustic source (that is, the fluctuating pressure) in MSLs by unsteady CFD calculations, and we evaluated the pressure propagation by acoustic analysis. These results were verified by comparison with the results of scale-model tests, and they showed good agreement with the experimental results. The effects of the difference between the properties of air and steam were numerically investigated, and it was found that the effects on the acoustic resonance in the SRV stub pipes were not significant.

Evaluation of Acoustic- and Flow-Induced Vibration of the BWR Main Steam Lines and Dryer

The boiling water reactor (BWR-3) steam dryer in the Quad Cities (QC) Unit 2 Nuclear Power Plant was damaged by high-cycle fatigue due to acoustic-induced vibration. The cause of the dryer failure was considered as flow-induced acoustic resonance at the stub pipes of the safety relief valve (SRV) in the main steam lines (MSLs). The acoustic resonance was considered to be generated by the interaction between the sound field and an unstable shear layer across the closed side branches of SRVs. We have started a research program on BWR steam dryers to develop methods of evaluating the loading. Moreover, it is necessary to evaluate the dryer integrity of BWR-5 plants, which are the main type of BWR in Japan. In the present study, we conducted 1/10-scale BWR model tests and analysis to investigate the flowinduced acoustic resonance and acoustic characteristics in MSLs. The test apparatus consisted of a steam dryer, a steam dome, and 4 MSLs with 20 SRV stub pipes. Computational fluid dynamics (CFD) analysis was conducted to evaluate the acoustic source in MSLs. Finite element method (FEM) was applied to calculate the three-dimensional wave equations for acoustic analysis. We demonstrated that large fluctuating pressure occurred in the high- and low-frequency regions. The high-frequency fluctuating pressure was generated by the flow-induced acoustic resonance in the SRV stub pipes. We evaluated the acoustic source (that is, the fluctuating pressure) in MSLs by unsteady CFD calculations, and we evaluated the pressure propagation by acoustic analysis. These results were verified by comparison with the results of scale-model tests, and they showed good agreement with the experimental results. The effects of the difference between the properties of air and steam were numerically investigated, and it was found that the effects on the acoustic resonance in the SRV stub pipes were not significant.

Acoustic measurement for 12% scaled model of NREL Phase VI wind turbine by using beamforming

Wind tunnel test for the 12% scaled model of NREL Phase VI wind turbine was conducted at Korea Aerospace Research Institute (KARI) low speed wind tunnel. Test condition for the scaled model was decided to match the blade tip mach number with real scale model test which was conducted at NASA Ames (80′ × 120′) Tunnel. Aerodynamic performance represented by torque of the blades was measured by using the torque sensor installed in rotating shaft and compared with real scale model test results. Acoustic noise for scaled model was also measured at closed type test section with acoustic array of 144 microphones. Time based beamforming method to identify the rotating noise source position was applied to analyze the test results. 1/3 octave band was used in post processing for various wind speeds. Test results shows that the main acoustic noise source position moves toward the blade tip as frequency increases and the noise level at low frequency below 2 kHz has much higher when the blade is in stall condition.

Large Scale Tests on Buoyancy-Driven Vertical Piling Breakwater with Buoyancy-Driven Piles

This report describes the results of the large scale model tests on the buoyancy-driven vertical piling breakwater by using the buoyancy-driven piles. This breakwater consists of rows of steel pip. piles and each pile consists of upper and lower steel pipes. The overall performance of this breakwater has been verified, but the relation between stress and wave power is not cleared at the part of lap joint between upper pipes and lower pipes, at which large stress may be occurred. So, the large scale model tests by using the buoyancy-driven piles were conducted. Main results of this paper are that movement of the upper pile under waves is confirmed and the relationship between the strain at the lap part and the wave power is clarified qualitatively.

MOTION CONTROL IN WAVES OF A 140M SES

This paper introduces the air cushion pressure control of the 140m Techno Super Liner (TSL), which Mitsui Engineering & Shipbuilding Co., Ltd. (MES) has constructed. TSL is an air-supported catamaran ship, which contains pressurized air between rigid side hulls. The ship dynamic performance is investigated through simulations, for the first, which is based on 3DOF motion (Heave/Pitch/Roll) and air cushion dynamics. It was performed for both model and full scale in various wave headings. The scale effect is discussed through simulation results. Then, the results of towing model tests in both regular and irregular waves are described. The model is equipped with lift fans and all the tests are carried out under the on/cushion conditions. The results of model scale simulations and model tests are compared and verified. With these results from the simulations and model tests, the design of the air cushion control system is discussed in terms of the fan stability and ship vertical accelerations. The basic concept of air-vent louver control is presented. As for the sea trial of the ship, it was successfully completed on October 12, 2005. Some of her splendid performances were demonstrated. A brief introduction of the trial is also presented in this paper.

Ground settlement and wall deformation from a large scale model test on a single strutted sheet pile wall in sand

The ground settlement and wall deformation of a sheet pile wall during different stages of excavation have been studied using a large scale model test in a bin with dry sand at the Norwegian University of Science and Technology, NTNU. The model sheet pile wall was built prior to raining in the sand in a bin (4 m × 4 m in plan and 3 m deep). This paper deals with results from tests on a relatively loose sand with 43.2% porosity. Strain gauges, load cells and potentiometers were used to monitor the wall movement, the bending moments in the wall, the strut loads and the ground settlements. The large scale model test results were compared with finite element simulations based on an elastoplastic soil model calibrated only against conventional oedometer and triaxial test results performed on the sand used in the model tests. Discrepancies between the physical model test results and the simulations are discussed trying to identify the cause of the discrepancy when a discrepancy may have been observed and suggest improved procedures for parameter determination. However, in conclusion, the comparison generally shows good agreement, and illustrates how a finite element analysis can be used to predict the behaviour of a supporting wall.

A shape variable acoustic panel system for multipurpose rooms

This work proposes an acoustically effective alternative to current passive acoustic solutions. Typical systems involve moving panels to one of either reflective, absorptive, or diffusive surface states. By varying the shape of an array of ceiling reflectors, acousticians can achieve more precise control of the room response to better serve a wider range of acoustic scenarios. The results of scale model testing show how a single system can direct, absorb, or diffuse sound energy so that the room will be appropriate to four distinct programmatic events: lectures, gathering, simultaneous sources, and flat effect. By including microphones and a digital signal processing system the panel system may be designed to adaptively change its behavior to suit that of the current room use.