Abstract:In this study, we comprehensively compared the rainfall, water level, flood discharge & storage and water project regulation of two flood events occurred in 2016 and 1991 for the Taihu Lake Basin with the method of mathematical statistic. Results show that: (a) Rainfalls leading to floods of these two events were similar in amount and occurring date, but different in temporal distribution, and rainfall in 2016 was severer to flood control than 1991; (b) Influenced by rainfalls, two obvious rising periods of the Taihu water level were observed in 1991, while a continuous rise was observed in 2016; (c) During the flood period of 2016, the water quantity into the Taihu Lake from the Huxi area and the Zhexi area, which are main sources of water into the Taihu Lake, significantly exceeded that of 1991. Besides, the rainfall over the lake area in 2016 also took over that in 1991, which could mostly account for the highest water level of Taihu Lake in 2016 exceeding that in 1991; (d) Fundamental changes have occurred in the drainage pattern of 2016 due to the construction of water projects in the Taihu Lake Basin and methods for regulation also became mature in 2016, resulting in much lower damage accounting for the proportion of GDP caused by floods than 1991.

Abstract:The current range of variability approach(RVA)usually ignores the low and moderate variation index, and is difficult to distinguish the relative importance between different indicators when evaluating the overall hydrological regime of a river. Therefore, according to the response analysis of indicators of hydrological variation(IHA)including 33 hydrological indexes from 5 sorts to ecological system, this study improved the RVA approach based on projection pursuit clustering model, which is called PP-RVA and can be used for the effective analysis of river hydrological variation degree. Then, on the basis of runoff data before and after the construction of the Liujiaping Hydropower Station in Hunan Province, the hydrological situation was evaluated by the proposed PP-RAV approach. From the comparison, the overall variability is 83. 21%, which belongs to a high variability. The average flow, high flow rate and 7-day minimum flow in May have the greatest influence on the hydrological regime. The evaluating results fit the overall information of river and distribution characteristics of change degree of index corresponded with the objective reality. Moreover, this study indicates that the current operation mode of Liujiaping Hydropower Station has influenced the ecological system of lower reaches. Therefore, it is urgent to carry out the ecological operation practice to realize the coordinated development of regional economy and ecological environment.

Abstract:This study derived an analytical solution of 1D convection-dispersion-linear dissipation equation with variable boundary using the Green’s function method, then compared the analytical solution with the numerical solution, and after that applied it to the heat conduction and solute transport experiments of a soil column. Results showed that the contributions of initial, upper and lower boundary conditions were independent. At the same time, analytical results matched the numerical simulation and the observed results of experiments well. As a conclusion, the analytical solution can represent the heat conduction and solute the transport processes well.

Abstract:In order to explore the effect of different sluice dispatching schemes on the improvement of water quality in Qinhuai River, water diversion tests were carried out during the flood season, the wet season, the dry season and the initial part of one rainfall event, respectively. The results show that reasonable controlling of gates and pumps can have a positive effect on the river’s water quality and this effect is definitely affected by the quality and scheduling time of upstream water.

Abstract:This study analyzes the causes and forming conditions of valley deformation based on the geological environment of Xiluodu hydropower station and the evolution of regional hydrogeological conditions induced by the impoundment. It reveals that the foundation and valley deformation are related to facts that the dam is located within the Yongsheng synclinal basin and the basalt layer consisting of the dam foundation situates above a thick confined aquifer consisting of Yangxin limestone. The patterns of valley and foundation deformation are closely related to the regional geological conditions, hydrogeological conditions and the reservoir impoundment process, etc. On such basis, internal and external factors of foundation and valley deformation are revealed. At the same time, it has been pointed out that the foundation and valley deformation belong to a special bank deformation. At last, definitions and classification of two deformation types are provided.

Abstract:The stress change of deck-U rib joint weld in the steel bridge was studied considering different structural parameters. Meanwhile, the stress mechanism was also analyzed to compare the stress distributions of two different U rib structures. The stress gradient of the deck weld was extracted to investigate the law of stress change. After that, the fatigue stress distribution of deck-U rib joint weld under different structural parameters was analyzed. The result shows that cut U rib and full U rib can both reflect the mechanical performance of deck-U rib joint weld faithfully. The greater the deck thickness and penetration rate are, the smaller the stress of deck-U rib joint weld is. Therefore, increasing the deck thickness can improve the mechanical performance. Besides, the U rib thickness and weld leg size exert little influence on the stress of deck-U rib joint weld.

Abstract:To investigate the temperature distribution of box girder, an experiment is conducted to reveal the temperature distribution of a section of Fenghe Bridge, which is a single box three-room concrete bridge located in the Xixian New District of Xi’an City. Experimental results show that the concrete temperature of outside surface was greatly affected by the ambient temperature that fluctuates rapidly every day, but the temperature of inside surface was relatively constant except the top plate. From the viewpoint of vertical temperature distribution, the one-dimensional heat transmission theory is suitable for the upper and bottom flange, but not for the web. Meanwhile, the temperature difference between outside and inside bottom flange is obvious. In addition, the maximum gradient of positive temperature mainly appeared in summer, while the maximum gradient of negative temperature mainly appeared in winter. According to the experimental data, the temperature distribution pattern and temperature base of box girder were discussed, and a new temperature gradient function has been proposed by combing with exponential and linear functions.

Abstract:Bio-clogging is a novel technology in soil seepage prevention and consolidation, and this technology was applied in 3 bank sections of Dawa Reservoir in Chuzhou, Anhui Province. Bacillus pasteurii was chosen as the agent to generate carbonate ions, which could precipitate with calcium/magnesium ions to clog pores and fractures inside the earth bank. In these applications, inside water heads were monitored using installed piezometers and the flow rate of leakage was also measured. Results showed that the reduction rate of the bank soil conductivity can reach 99% in a short time. The whole process of in-situ test can be divided into three main stages: 0-80 h is the development period of bio-clogging; 80-120 h is the peak period and then followed by the tailing period. The soil conductivities were around 10^-5-10^-6 cm/s after bio-clogging treatment, meanwhile the soil strength increased by 13% according to UU tests. Samples inside of the pores were detected using electronic microscope and EDS detector, and main composition was proved to be calcium carbonate.

Abstract:In order to describe the strain softening behavior and time-dependent characteristics of rock, an elasto- viscoplastic constitutive model is proposed considering the influence of time-dependent strain softening behavior. The new model was based on the sub-loading surface theory of over-consolidated soil and adopted the Hashiguchi' s sub-loading yield surface as a referenced yield surface. Besides, a relative overstress relation is used to obtain the dynamic loading surface at any strain rate based on the referenced yield surface. Two material parameters, c0 and m', which are related to the rate sensitivity, were added into the new model, and they can be determined by triaxial compression tests with different strain rates. The expansion index κand compression index λin the original model were replaced by elastic modulus E0 and deformation modulus Ed respectively, combining the characteristics of rock. A dynamic equilibrium condition, using the current stress, viscoplastic strain and viscoplastic strain rate as state variables, was adopted as a convergence criterion. After that, this model has been implemented into ABAQUS with the Newton-Raphson iteration. Simulations on the rate sensitivity triaxial tests of rock were conducted to verify the proposed model. The results show that the predicted results of model are in good agreement with experimental data. Meanwhile, material parameters are easy to understand and measure with clear physical meaning. Therefore, the proposed model can be used in the finite element calculation of complex boundary value problems.

Abstract:For the alternatively soft and hard interbedded rock mass of JinPing HydroJunction project, three failure modes of rock samples under uniaxial compression stress are analyzed based on laboratory experiments, and the influence of dip angle, quantity, distribution and volume ratio of weak intercalations on the deformation property, strength characteristics and failure mechanism of rock mass are discussed by the numerical simulation. The results show that the failure of soft and hard interbedded rock mass of JinPing follows the multicrack splitting mode of uniaxial compression failure. For the case of gentle dip angle, the failure of layered rock mass is controlled by the property of rock mass itself, while for the case of large dip angle, the influence of weak intercalations is the dominant factor. Besides, the number of weak intercalations has no significant effect on the "U" type strength characteristics of layered rock mass, but with the increase of weak intercalations, minimum value of failure load tends to move forward. With the increase of the volume ratio of the weak intercalation, the failure loading totally shows a downward trend, and when the volume ratio of weak intercalation is close in rock samples, the effect of increasing weak intercalation on the decrease of failure load is positively related to the dip angle of weak intercalations. At last, it can also be found that the increase of weak intercalations has no effect on the strength if the rock layer is horizontal.

Abstract:The breakwater with multi-compartment single-bucket structure is a new type of structure applied in soft foundations. To explore the stress characteristics of multi-compartment single-bucket structure breakwater under horizontal loading is of great importance in its stability analysis. In this study, quasi-static force is adopted to analyze the motion mode and the earth pressure development acting on the structure as horizontal load increases. The results show that the structure rotates around a point below its foundation base under the acting of horizontal force. The rotation center moves to the axis position of the structure when reaching limit state. Meanwhile, earth pressures on the foundation bucket can be divided into active pressure, passive pressure and static pressure. On the basis of above conclusions, the limit equilibrium method is derived to analyze its stability. In addition, comparison of the anti-overturning safety factor between critical equilibrium method and finite element calculation shows that the difference between two data sets is about 20%~25%, because of their different assumptions. Theoretical results are larger and the parametric changing tendency in limit equilibrium method agrees well with that of numerical simulation, which provides some reference data for theoretical design system of breakwater with multi-compartment single-bucket structure.

Abstract:The Variational Mode Decomposition(VMD)method is introduced into the GPR signal processing. According to the non-stationary characteristic of GPR signal, the method of signal de-noising based on VMD principle has been established. The VMD is used to decompose the radar wave signal into the intrinsic mode function(IMF), and then the entropy of sample is used to determine whether the higher-order IMF is reserved to remove the noise. The accuracy and validity of the method are verified by GPR with Ricker wavelet and forward model test of de-noising, and the proposed method is compared with the traditional wavelet transform and the EEMD(ensemble empirical mode decomposition)method. After that, this method is used to analyze the GPR signal of a practical engineering. The results show that the method can effectively remove the noise in the GPR data and can obtain above 20 dB signal-to-noise ratio(SNR)even under strong background.

Abstract:In order to investigate the effect of rotational speed on the hydraulic performance of inlet and outlet conduits for S-shaped shaft extension tubular pumping system, three dimensional and steady turbulent flow in the pumping system was simulated by the computational fluid dynamics technology. Then, the CFD results are compared with the experiment results to validate the application of numerical analysis. The hydraulic performance parameters of inlet and outlet conduits were quantitatively analyzed considering the hydraulic interaction of conduits and impeller. Results indicated that the change trend of relationship curves between hydraulic loss ratio and flow rate coefficient is same in different rotational speed. With the increase of flow rate coefficient, the hydraulic loss ratio gradually increases, the hydraulic efficiency increases firstly then decreases gradually, and the average velocity circulation of outlet section firstly increases then decreases gradually under the same rotational speed. Meanwhile, with the increase of rotational speed, the average velocity circulation gradually increases under the same flow rate coefficient. In addition, the relative swirl angle decreases firstly, then increases with the increase of flow rate coefficient under different rotational speed. It could also be concluded that with the increase of rotational speed, the static pressure ratio of outlet conduit increases gradually and the distribution of drift angle in inlet section of outlet conduit is same. There is no linear functional relationship between square of hydraulic loss and flow rate for outlet conduit.

Abstract:In order to rationally design the water seal of ship lift gate in the Three Gorges Project and reduce the cost of sealing experiment, the computer simulation design of air-pressure telescopic water seal for the ship lift gate of the Three Gorges Project was presented based on the basic principle of solid mechanics and nonlinear calculating theory. In the design, the tightness of cavity behind the air-pressure telescopic water seal and the expansive probability of seal head were also verified in the simulation. We obtained the required back pressures of sealing water under different initial clearance between seal head and sealing panel, as well as different working pressure of reservoir, providing data for the manufacturing and operation of seal device. The key technology during the design was the water-tightness simulating method of air-pressure telescopic water seal, and can effectively replace the traditional tightness experiment to greatly reduce the cost of design.