Advanced Materials Research Vols. 243-249

Abstract: The adhesion strength tests of freshwater ice frozen to concrete material were performed in a reservoir by the precise control-temperature unit of ice at five temperatures (-2 °C, -4 °C, -6 °C, -8 °C, -10 °C) and the displacement rate in a range of 10^-4-10⁰ mm/s. The fitting curve of the peak adhesion strength and ice temperature was presented. The test results show that the frozen adhesion strength is very sensitive to the displacement rate. The frozen adhesion strength reaches the peak value at the ductile-brittle transition region, and the region is close to the lower strain-rate with decreasing temperature. The transition region of displacement rate is 3.0×10^-4-7.5×10^-3 mm/s. The results provide some design parameters for reservoirs in cold regions.

Abstract: In this paper, dynamic characteristics analysis is carried out for a large aqueduct of South-to-North Water Transfer Project using large finite element analysis software. Two kinds of connection supports are considered, namely elastic support and completely simple support. Six kinds of water depths are calculated by additional mass method: empty aqueduct, 1/4 water depth, 1/2 water depth, 3/4 water depth, designed water depth, full water depth. Results show that basin type rubber support strengthens the constraint to aqueduct, and strengthens the connection of aqueduct to pier, and also increases the system stiffness, therefore the natural frequency is higher than that of completely simple support; The influence of water to dynamic characteristics of the aqueduct is quite obvious, so water effect must be considered in computation; Water has no influence on the principal mode shapes of the aqueduct structure, i.e. the dry mode shape and the wet mode shape are similar in appearance.

Abstract: Basing on triaxial experiments, the paper conducts the research to Cemented Sand and Gravel constitutive model. Using virtual rigid spring method, the Cemented Sand and Gravel constitutive model with considering the softening characteristics of material is established, and parameters needed are determined, the model establishes the foundation of non-linear analysis of Cemented Sand and Gravel structure. Mechanical properties and constitutive model study of Cemented Sand and Gravel is key to Cemented Sand and Gravel faced eath-rockfill dam. Basing the Mechanical properties triaxial experiment of the material, the paper gives further discussion on the constitutive model of Cemented Sand and Gravel. From the results of the triaxial test, when the cemented material content is smaller than 20kg/m3, the stress strain curve agrees quite well with hyperbolic law to which the normal gravel test curve also obeys, the exception is the increase of shearing strength. If the cemented material content is more than 30kg/m3, there is a peak value on the stress strain curve, the curve (before peak value) shows that axial strain increase with deviatoric stress with the increment gradually changing slowly, i.e. the stress strain curve has obvious nonlinear feature. the curve peaks value at the axial strain =2％, the stress strain curve present softening pattern that deviatoric stress decreases with the strain increase if continuous applying axial load. When axial strain lies between 2% and 6%, the shearing strength of samples decreases rapidly, after this interval, the shear strength tends to the stable value in the final. It is core problem the paper try to solve that how to describe Cemented Sand and Gravel constitutive model.

Abstract: CSG is a kind of new dam type between earth- rockfill dam and concrete gravity dam. It proved to be feasible under massive experiment about the mechanical properties of CGS. Our research group believes that the sectional form changes correspondingly different content of gelled material and controlling factors of dam stability. Then the research of thought and design theory are put forward, and existing problems of current works was studied as well.

Abstract: Anti-sliding stability in deep foundation of Shatuo gravity dam is studied in this paper. Combined with the static and dynamic analysis of anti-sliding stability in deep foundation of gravity, strength reduction finite element method is used to do static calculation of anti-sliding stability firstly. The horizontal seismic strength can be gotten in order to be applied to the baseplane based on response spectrum method, thus dynamic calculation of anti-sliding stability can be carried out. The calculation result shows that static and dynamic anti-sliding stabilities in deep foundation of gravity meet the requirements.

Abstract: Controlling crack of hyperbolic arch dam with a height of 305 m in Jinping hydropower station is an important problem. To improve the anti-cracking ability and reduce cracking risk of hydraulic concrete, polyvinyl alcohol (PVA) fiber and polypropylene thick fiber were used in hydraulic concrete using four gradations of aggregates. Indoor and productive tests were carried through to comparatively analyze workability, physical and mechanical properties and anti-cracking ability. Workability of fiber reinforced concrete was improved to be in favor of construction. When two kinds of fiber were used in concrete, the anti-cracking ability was greatly enhanced with lower elastic modulus-to-strength ratio and lager ultimate tensile strain. Concrete using PVA fiber had better anti-cracking ability than that of concrete using polypropylene thick fiber. PVA fiber reinforced concrete was applied in Jinping hydropower station. It is proved that PVA fiber reinforced concrete has good properties reaching design requirements of workability, compressive strength, ultimate tensile strain, frost resistance, permeability resistance.

Abstract: A numerical calculation method and a new type element of EFM for the simulation of the RCC dams is presented. It takes into account the more relevant features of RCC, such as the transversely isotropic, the layered character, the strength unequal to tension and compress and the discontinuities. A 3D model of RCC Dam, built in South-West of China, is used to perform the corresponding analyses. The result shows the location of third height to dam heel in upstream dam will be crack between layers. So it is very dangerous for arch dam. In the the locations of third height to dam toe and dam crest of the downstream of the dam will occur the stresses concentration, so some of engineer measures must be adopted to avoid the damage.

Abstract: When pseudostatic method is employed to analyze slope seismic stability of high earth- rock dams, earthquake load is computed according to dynamic seismic coefficient figure in the present Specifications for Seismic Design of Hydraulic Structures (DL5073-1997). The figure is only suitable for earth-rock dams lower than 150m. While at the present time, many earth-rock dams to be constructed are higher than 150m. Compared with low dams, high order self-vibrating period of high dams is easy to coincide with seismic predominant period, and high order vibrations are constantly to be activated and amplified, which result in seismic acceleration distribution is different from low dams. With analytical and finite element method respectively, seismic acceleration distribution of high earth-rock dams is analyzed. Suggested dynamic seismic coefficient figure of earth-rock dams 300m-level in height is put forward, which offer a supplement for the present Code for Seismic Design of Hydraulic Structure.

Abstract: Considering the uncertainty and the time variation of frequency contents of real seismic excitation, a new versatile stochastic strong ground motion model named general stochastic seismic ground motion (GSSGM) model is presented in this paper. Some essential assumptions for the earthquake process used in this paper are first given. The intensity and energy of the target seismic ground motion are used to determine the model parameters. The frequency contents are demanded to be agreed with the main characteristics of the target ground motions. The GSSGM model is appropriate to simulate the stationary, intensity non-stationary and fully non-stationary stochastic processes. Additionally, a simple non-stationary stochastic seismic response analysis procedure based on the GSSGM model and the pseudo excitation theory is put forward. The presented non-stationary stochastic seismic response analysis procedure is later applied in the seismic response analysis of a real homogeneous earth dam. The non-stationary analysis results display the effects of non-stationarity on the seismic response of the dam and reflect the main phenomena of dynamic embankment-foundation interaction. The results indicate that the GSSGM model and the presented analysis procedure are effective.

Abstract: The uniaxial compression test was performed on artificial freshwater ice with a precise control-temperature unit compression tester of ice under -5, -10, -15, -20 and-30°C temperatures and strain rates ranging from 10^-8 to 10-2 s^-1. The loading direction was parallel to ice surface. The results showed that the compressive strength was very sensitive to the strain-rate. The uniaxial compressive strengths reached the maximum value at the ductile-brittle transition region, and the region was gradually close to the lower strain-rate with the decreasing temperature of test. Both the strain-rate and uniaxial compressive strength dependences could be expressed in terms of power function in the relevant ductile range of strain-rate. The tests also revealed that failure stress of ice increases with decreasing of temperature at the same strain rate.