Advanced Materials Research Vols. 255-260

Abstract: At present the flat plunge pool and inverted-arch plunge pool are usual plunge pool shape styles in high dam construction. we improve the plunge pool shape according to the study of special flow pattern in the plunge pool and the plunge pool scour mechanism, the high-speed submerged jet diffusion rule in plunge pool, impingement pressure variation rules with the jet flow route changment and some other hydraulic factors, combining with a series of scour experimental results. We analyze the specific situations in the transverse profile and longitudinal profile of the plunge pool respectively and then make corresponding changes. The creative longitudinal profile curve of the inverted-arch plunge pool make a double inverted-arch plunge pool, which makes the hydrodynamic elements and the structure of the plunge pool are in a harmonious state ensuring the safe operation of the plunge pool.

Abstract: There are many factors, such as climate, flood, material, geology, structure, management, to influence dam safety. So dam safety evaluation, involving many fields, is very complicated, and very difficult to establish mathematic model for assessment. Artificial Neural Network (ANN) has many obvious advantages to deal with these problems influenced by multi-factor, consequently is widely used in engineering fields. This paper considered water level, temperature, main factors influencing dam deformation, as random variables, employed ANN and statistical model to establish performance function of dam hidden trouble deformation and abnormal deformation. Then reliability theory was used to analyze dam safety reliability and sensitivity. The results show that temperature has great effect on probability of dam hidden trouble deformation and abnormal deformation than reservoir water level, due to great variability of temperature. Change of Reliability index of dam is contrary to reservoir water level. Temperature, especially average temperature in 10 days and 5 days, has great effect on sensitivity of reliability index than water level.

Abstract: Dam deformation is characterized with periodicity, tendency, randomicity. So dam deformation can be regarded as sum of periodic deformation, tendency deformation, and random deformation, of which periodic and tendency deformation, gained by deterministic method, are researched sufficiently, but study on random deformation is inadequacy. Because dam random deformation at time t is mainly influenced by dam state at time t-1, little influenced at time t-2 or earlier, dam random deformation can be idealized as stochastic process described by Markov chain. In this paper, a new dam safety monitoring model is established using Markov chain, based on statistic model. First, regression analysis was applied to establish dam deformation statistic model, by which dam deterministic deformation can be obtained. Then dam random deformation component can be gained by subtracting deterministic deformation from total dam deformation. Consequently, by analysis of time series of random deformation, transition probability matrix of random deformation can be obtained and used to analyze dam deformation. Case study showed that this new model is superior to traditional statistic model, and can be applied to establish dam safety monitoring model.

Abstract: The ensemble Kalman filter (EnKF) is employed to simulate of streamflow of a slope sub-catchment during the rainfall infiltration process. With this method the whole process is treated as a dynamic stochastic system, and its streamflow is taken as the variable to describe the state of system. Furthermore, it is coupled with a hydrology model to cope with system uncertainty. Thus, the dynamical estimation of hydrological parameters is performed; the model variables and their uncertainty are obtained simultaneously. Numerical examples show that this strategy can effectively deal with observation noises and can provide the inversion results and the posteriori distribution of the priori information together. Compared with the conventional optimization algorithm, the new strategy combined with EnKF shows better character of real time response and model reliability.

Abstract: The initial soaking of coarse-grained soil will trigger significant slaking deformation of this material. In order to study the slaking deformation of a certain dam during impounding process and its impacts on the dam body, we have adopted the slaking constitutive model by singe-line method and relevant test parameters from Changjiang River Scientific Research Institute, and conducted numerical simulation on the whole process from rock filling to impounding and slaking process of high earth core rockfill dam. The result has shown that, after considering slaking deformation of upstream shell materials, the upstream settlement is generally larger than downstream settlement on the same horizontal line, and the settlement of downstream shell materials generally stays unchanged after considering slaking deformation; at the early impounding period, the settlement of dam body is increasing, and the horizontal displacement of upstream side shell materials is pointing towards upstream. These findings can adequately explain the slaking deformation of the dam caused by impoundment, testify the new slaking constitutive model by single-line method and relevant test parameters, and provide reasonable basis for engineering design.

Abstract: Earthquake occurred on May 12, 2008 in Wenchuan, Sichuan Province, China, with magnitude of 8.0 and epicenter intensity of VI. Chencun hydropower station in southern Anhui Province has been shocked strongly during Wenchuan Earthquake, which stations 1,500 km away from Wenchuan. Tectonic stress caused by strong earthquakes inevitably led to the changes of stress state, groundwater level and pore pressure in the dam foundation. Seepage water level observation of the dam foundation had been encrypted immediately. According to the experimental data, it was conformed that significant effects were displayed on the dam foundation seepage because of Wenchuan earthquake, shunhe fault near dam sites was the main effect zone of earthquake tectonic stress, the downrange of groundwater depth was self-evident. As the existence of acrylamide curtain, swelling-shrinkage property of the acrylamide gel restricted the change of groundwater level and rock stress state in the dam foundation caused by seismic tectonic stress; the groundwater level behind the acrylamide curtain had a small decline, and recovering quickly.

Abstract: In the paper, scour mechanism and factors influencing the scour width of roadbed along river are analyzed. Through the method of theoretical analysis and experiment study, the formula of the maximum width depth of prevention wall in concave bank of G315 is put forward. The formulation of the maximum width depth is theoretics and technic bases of protecting water scour.

Abstract: The gully shapes of Debris flow are generally classified into formation area, circulation area and accumulation area, these three sections . That wide formation region, narrow circulation area and wide, slow deposition area is the typical geomorphology of fluctuant type gully erosion and deposition Debris flow.The key area of the debris flow’s movement and development is the circulation area. Based on analysis the turbulent debris flow’s moving characteristic in circulation area with the solid-liquid two-phase flow’s standpoint, energy equation and the formulation of impact force for the block structure of turbulent debris flow in circulation area are deduced. It affords important idea for the further investigation about the debris flow’s protection engineering, but some parameter in the formulation need fit from the model examination.

Abstract: Drainage segment lining is a new structure type formed by setting up drainage holes on the conventional segment lining. Based on continuum fluid-solid coupling analysis model of fractured rock mass, the distribution patterns of water pressure behind the lining walls and in surrounding rock are studied under three kinds of water pressure, while the segment lining with double drainage holes at each side of one ring has been applied. The results show that the water pressure behind segment lining wall could be effectively reduced by setting up drainage holes, and the pressure distribution patterns are in horseshoe shape approximately. The reduction effect of water pressure is more and more obvious from the tunnel crown to the elevation where the drainage holes are provided. But the drainage hole leads to uneven distribution of water pressure, causing the increase of local moment. So, more attention should be paid to the drainage segment lining during design.

Abstract: The somatotype of flaring gate pier (FGP) is a main parameter in project design. Based on Suofengying project, in which X-shape FGP was used at first time, the hydrodynamic characteristics of two FGP types, including flows pattern and pressure distribution, were compared by using the RNG k-ε turbulent model in this paper. The figures of the water wings and free jets with multiple hydropneumatic interfaces were obtained by numerical simulation successfully. The calculated results were in good agreement with the experimental data. It indicates that the X-shape FGP is better than the Y-shape, especially when it is connected with the stepped spillway. Being an applied and trial study, the results obtained are of theoretical and practical significance.