Journal of Hydroelectric Engineering

水力发电学报

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2016 Vol. 35, No. 3 Published: 2016-03-25

	1	Computational method for post-construction settlement for high-fill embankments
		YAO Yangping, QI Shengjun, CHE Liwen
		DOI: 10.11660/slfdxb.20160301
		Owing to their great height and large volume, high-fill embankments are subject to differential settlement that often reduces their safety and stability, and therefore the post-construction settlement of such embankments should be examined carefully. This paper develops a practical creep calculation method based on the finite element method for calculation of post-construction settlement by a time-dependent UH model and the simplified one-dimensional creep deformation computation method that could be combined with the layer-wise summation method. Field observation data collected at the Chengde airport are used to verify this method. Comparison of the calculations and field data shows that new method is able to achieve reliable predictions of post-construction settlement and hence to provide useful guidance for the following construction of the airport.
		2016 Vol. 35 (3): 1-10 [Abstract] ( 638 ) PDF (1022 KB) ( 643 )

	11	Effects of bentonite-cement mix ratio on strength characteristics of plastic concrete
		JIAO Kai, DANG Faning, XIE Kaijun
		DOI: 10.11660/slfdxb.20160302
		Strength characteristics of plastic concrete have been investigated in this study using conventional triaxial compression tests under low confining pressure for different mix ratios of bentonite and cement. According to the Mohr-Coulomb strength theory, the peak strength of plastic concrete under low confining pressure were used to derive four typical intensity parameters of plastic concrete: uniaxial compressive strength, cohesion, internal friction angle, and tension-compression strength ratio. The results show that as bentonite-cement mix ratio increases, cohesion and uniaxial compressive strength decrease significantly and peak strain increases, while internal friction angle and tension-compression strength ratio change insignificantly. This indicates little effects of the mix ratio on the sensitivity of plastic concrete strength to hydrostatic stress or on tension-compression strength ratio.
		2016 Vol. 35 (3): 11-18 [Abstract] ( 309 ) PDF (645 KB) ( 389 )

	19	Causes for cracking of culverts through the embankment on soft soil foundation
		JIANG Yan, YANG Guanghua, HUANG Zhongming, HUANG Zhixing
		DOI: 10.11660/slfdxb.20160303
		In engineering practice, problems of cracking of the channel-buried culverts on a soft soil foundation often appear as a result of unevenness in settlement and stress. Using a case study of the culvert project in Guangdong, this paper provides an analysis on the mechanics and causes for the cracking, based on field investigation, in-situ tests, and finite element simulations. This study reveals that the loads on the culvert depend on the effects of foundation treatment. If the foundation is much more rigid after treatment, the differential settlement between the pile and foundation soil will be relatively large and as a result, culvert load will also be larger than the weight load of soil columns. Without a full consideration, such a large load in this situation would exceed the bearing capacity of culvert structure, hence causing cracking. The results also indicate that for the culverts buried on a rigid pile composite foundation, a cushion layer could coordinate the distribution of stress, which is a significant guidance to the design of culverts on soft soil foundation. And on this basis, precautions against culvert cracking are suggested for similar projects.
		2016 Vol. 35 (3): 19-27 [Abstract] ( 333 ) PDF (1220 KB) ( 518 )

	28	Analysis on envelopes for potential slip surfaces of slopes
		JIE Yuxin, BAI Yongliang, ZHANG Bin
		DOI: 10.11660/slfdxb.20160304
		Envelope of potential slip surfaces of a slope at certain safety factors can be obtained by drawing the contours of the factors. For a given point in the computational domain of a slope, limit equilibrium method can be used to calculate the minimum safety factor among the potential slip surfaces passing this point. Then, safety factor contours, which show the spatial patterns of safety factors, are easily achieved after the minimum safety factors of all the LEM nodes have been calculated. This approach can be extended to calculation of those envelopes of potential slip surfaces at certain acceleration and inertial force. This paper presents the contours of safety factors, accelerations, and inertial forces calculated for a simple slope and two-step slopes with different bench widths. The results reveal that for the two-step slopes, the contours of safety factors and accelerations are similar to those of simple slopes if bench width is small, while their critical slip surfaces at the minimum safety factor and maximum acceleration tend to go through the steps of the slope if bench width is large. In contrast, the contours of inertial forces are less affected by the bench width of slopes.
		2016 Vol. 35 (3): 28-35 [Abstract] ( 392 ) PDF (4127 KB) ( 632 )

	36	Study on water resources allocation in Shanxi in conditions of uncertainty
		LIU Zhonghua, YU Hua, YANG Fangting, SUI Jie, SHAO Lei
		DOI: 10.11660/slfdxb.20160305
		This paper presents a study on the water resources allocation in Shanxi province to achieve a balance between supply and demand of water resources. First, we formulate a three-level water allocation framework (3-WRAF) suitable for the water resources supply and demand system of this province, including its water divisions, administrative divisions, and water use industries. Then, based on 3-WRAF we develop a two-stage water scheduling model (T-WRAP) considering the given plan of initial allocation and the actual situations of water resources. There exist strong stochastic and fuzzy uncertainties in water supplies and demands, water economic benefits, etc. under different scenarios of precipitation, and therefore this T-WRAP model is converted into a two-stage stochastic fuzzy programming model for water resources allocation (TSF-WRAP). Finally, TSF-WRAP is solved by making compromises between the satisfaction degree of objective and the feasible degree of constraints. Results show that optimal water scheduling plans for Shanxi can be achieved for different scenarios of precipitation.
		2016 Vol. 35 (3): 36-46 [Abstract] ( 304 ) PDF (477 KB) ( 553 )

	47	Spatio-temporal variability of soil moisture in a vineyard in arid region
		REN Yanqiu, LI Tao, LENG Dong, HAO Xinmei
		DOI: 10.11660/slfdxb.20160306
		Soil moisture content as an important variable in the land surface system, has significant influences on other components of hydrological cycles, and it is a key parameter in many hydrological models. Previous studies have shown that soil moisture in field conditions is highly variable in time and space. Therefore, knowledge of the characteristics of its variability is essential for understanding water flow processes in the field and for more accurate simulation of water movement in the field, and thus helpful to develop precision irrigation management practices. In this study, soil moisture contents were measured in a 7.6 hm2 vineyard located in the arid region of Northwest China during early May to later September in three consecutive years (2012-2014) using time domain reflectometry (TDR). Measurements were taken 17, 16 and 19 times for these years, respectively. Soil moisture data were collected for three soil layers (0 ~ 20, 20 ~ 40 and 40 ~ 60 cm) on a regular grid of 25 m × 25 m with additional points arranged near some grid nodes. There were 135 points for 2012 and 147 points for the other two years. The spatial structure of soil moisture were described using a variogram model, and evolutions of the fitted model parameters including the range and degree of spatial dependence (ratio of nugget to partial sill) were analyzed within the same year and between the three different years. In addition, possible relationships of the model parameters versus mean soil moisture were investigated for the three years, and simple linear regressions were conducted between the range and degree of spatial dependence in terms of mean soil moisture. The main results were: (1) Soil moisture generally had a wide range, and the range tended to be wider for the surface soil than the deeper soil in a wet year while the trend was opposite for a relatively dry year; (2) Higher degrees of spatial dependence were found for surface soils of a dry year and deeper soils of a wet year, and the range and degree of spatial dependence were increasing with increasing soil moisture, indicating that higher overall soil moisture in soil profile generally lead to greater correlation length but also often intensify the random component of overall spatial variability. The results of this study would help better describe and simulate the spatial distributions of soil water content in field conditions, and thus help develop site-specific precision irrigation management practices.
		2016 Vol. 35 (3): 47-55 [Abstract] ( 250 ) PDF (747 KB) ( 371 )

	56	Impact of underlying surface changes on risk rate of reservoir flood control
		GUO Junfeng, FENG Ping
		DOI: 10.11660/slfdxb.20160307
		The underlying surface of the Hai River basin has changed significantly in recent years due to human activities. This has caused a change in infiltration, runoff and other hydrological characteristics, and thus a significant impact on the risk rate of reservoir flood control in this basin. To study such an impact in the case of the Wangkuai reservoir, we adopted a rainfall-runoff relationship method and peak-volume correlation method to modify the flood volume and flood peak series of the main flood period, and made frequency analysis of the flood series with and without the modification separately. Then the corresponding flood control risk rates were obtained for these two cases through flood regulating calculation under given different flood control levels. The results show that the underlying surface changes have caused a reduction of different degrees in various flood control risk rates of this reservoir. To ensure its flood control safety, an appropriate measure is to raise the flood control level up to 193 m for the main flood period.
		2016 Vol. 35 (3): 56-65 [Abstract] ( 285 ) PDF (1018 KB) ( 574 )

	66	Turbulent characteristics of plunging region of oblique submerged jet in plunge pool
		LI Naiwen, LIU Chao, LI Longguo
		DOI: 10.11660/slfdxb.20160308
		Particle image velocimetry (PIV) was used to characterize the fine structure of flows in a plunge pool with an oblique submerged jet, and jet velocity distributions and turbulent characteristics in the jet-plunging region have been studied systemically. The results showed self-similarity in cross-sectional profiles of velocity and turbulent intensity in this region. Peak velocity at the jet center decreased in inverse proportion to the length of jet path, while turbulent intensity and jet half-width increased linearly with the path length. Equations for jet velocity distribution and turbulent intensity distribution are given in this paper, along with empirical formulas for calculations of jet velocity, turbulent intensity, jet half-width at different lengths of jet path.
		2016 Vol. 35 (3): 66-72 [Abstract] ( 216 ) PDF (845 KB) ( 461 )

	73	Behavioral characteristics of fouling organisms limnoperna fortunei in hydraulic engineering in different environmental conditions
		WEI Xiaoxi, YANG Zhengjian, LIU Defu, MA Jun, TAN Qianru
		DOI: 10.11660/slfdxb.20160309
		In recent years, serious hazards of limnoperna fortunei occurred in hydraulic projects. These hazards may block the pipeline, lower the ability of water transportation, and foul the surfaces of hydraulic structures, etc., thus emerging as a new problem that affects the operation safety of hydraulic projects. This study has conducted experimental tests to explore the behaviors of limnoperna fortunei in different environmental conditions, such as light, temperature and pH, focusing on the variations of four behavior indicators, i.e. soft foot protruding rate, movement distance, adhesion rate, and mortality rate, to characterize the degree of the environmental factors on the behaviors. We draw the following conclusions from the experiment. Limnoperna fortunei has obvious negative phototaxis and prefers to attach to dark adhesion matrix. The appropriate temperature for its survival was varying from 16 ?C - 28 ?C, and its activity was obviously inhibited under extremely low temperature of 4 ?C while enhanced as the temperature rose within this range. However, it died quickly when the temperature reached up to 32 ?C. Limnoperna fortunei was also sensitive to the acid-base property. Neutral environment was the most suitable environment for its survival.
		2016 Vol. 35 (3): 73-80 [Abstract] ( 428 ) PDF (883 KB) ( 578 )

	81	Transients of the hydroelectric system with along diversion tunnel in water-turbine-electricity coupling conditions
		ZHOU Kunxiong, ZHANG Lixiang, ZENG Yun
		DOI: 10.11660/slfdxb.20160310
		This paper concerns analytical modeling of water-turbine-electricity (WTE) coupling in the hydroelectric system with a long diversion tunnel, surge tank and penstock at a hydroelectric station. The flow transients in the tunnel are described using the classical rigidity water hammer theory, and the fluid dynamics in the surge tank considered as a transient accumulator, is modeled with the surge equations and dynamically connected with the tunnel outlet and penstock inlet. We have applied the fluid-structure-interaction (FSI) theory to develop a four-equation model for simulation of the transient flows in the penstock, and adopted the FSI junction coupling mode for dynamic connection of the penstock with the turbine wicket gates. A first-order equation of electricity-generating units and a governor equation of their control system are used to fully couple the hydro turbine system. Hence, we have constructed a WTE coupling model that is solved by the inverse Laplace transform of its state equations, and formulated a holistic analysis method of the transients in WTE coupling system. The simulation results show that this approach makes it possible to model various types of transients in WTE coupling system and the modeling has good responses to power load rejection and predicts the system dynamical parameters satisfactorily and efficiently.
		2016 Vol. 35 (3): 81-90 [Abstract] ( 308 ) PDF (966 KB) ( 560 )

	91	Analysis of rotor-stator interaction and vibration in high-head Francis turbines
		LIU Pan, CHEN Xueli, WANG Quan, LI Dezhong
		DOI: 10.11660/slfdxb.20160311
		This paper describes a study on rotor-stator interaction (RSI) and frequencies of flow-induced vibrations in the spiral casing of a high-head Francis turbine unit #1 at the Xiaotiandu hydropower station, using prototype tests and numerical simulations. The tests were aimed at the amplitude and frequency of pressure fluctuations and vibrations, and whole passage simulations of unsteady turbulent flows were focused on an analysis of the RSI between the guide vanes and runner and a detailed examination on pressure fluctuations in the spiral casing and vaneless space. Both the tests and simulations verified that RSI had induced abnormal vibrations in this turbine unit. We analyzed the RSI effects produced by different combinations of runner blade number and guide vane number to solve the problem of vibrations observed during the field tests. Through an analysis on resonance conditions and by applying the principle of optimally matching these two cascade systems to the results obtained from the combinations, we developed an effective method for reducing pressure fluctuations in vaneless space. The results would provide a practically feasible scheme for vibration and noise reduction at hydropower stations.
		2016 Vol. 35 (3): 91-98 [Abstract] ( 480 ) PDF (1839 KB) ( 630 )

	99	Setting conditions of surge chambers at hydropower station in elastic model based on operation stability
		LIU Yanna, YANG Jiandong, ZENG Wei
		DOI: 10.11660/slfdxb.20160312
		The setting condition of surge chamber is a key criterion in primary designs of hydropower stations, and in the case of long conduits it depends on the elasticity of water significantly. This paper describes a simplified water hammer elastic model based on frequency domain characteristics and a mathematical model of operational stability using Laplace transform theory. We derive a surge chamber stability setting criterion by applying simplified elastic water hammer equations and Hurwitz criterion, and analyze the stability limits corresponding to different governor parameters and the dependence of divergent fluctuations on the elasticity of water. An analytical equation of speed fluctuations is derived by identifying the dominant poles of the equation system, and verified by comparison with numerical results, and then it is used in formulation of the setting conditions for different governing qualities. Application of the theoretical procedure to practical cases shows the maximum inertia time constant of water with compressibility in effect as well as the significance of compressibility by comparison with common setting criterions.
		2016 Vol. 35 (3): 99-104 [Abstract] ( 308 ) PDF (523 KB) ( 433 )

	105	Reconstruction of micromechanics hierarchical models of concrete based on CT images
		LEI Guangyu, HAN Jichang, ZHANG Yang, DANG Faning, LI Qian
		DOI: 10.11660/slfdxb.20160313
		This paper presents a random model for concrete materials from CT scanning of concrete sections and a reconstruction model using the information abstracted from CT images. According to the physical meaning of CT number, we have developed a computer code for the reconstruction by integrating the characteristics of existing models. This reconstruction model considers various types of information abstracted from the CT images, including the shapes and gradation of aggregates and the features of pores. Adhesion of mortar to aggregates is modeled using a new method of adding one layer of interface elements between aggregates and mortar, in replacement of the traditional method of adding contact elements. We conducted a detailed analysis on the mechanical behaviors of concrete under dynamic loads, compressive or tensile, and made a comparison with the CT test results. The analysis shows that the reconstruction model has good performances in numerical tests of concrete.
		2016 Vol. 35 (3): 105-112 [Abstract] ( 260 ) PDF (2186 KB) ( 507 )

	113	Comparison and modification of empirical formulas for calculation of water temperature in reservoirs in cold region
		SUN Wanguang, LIU Tianpeng, SU Jialin, LI Runwei, FAN Baoshan
		DOI: 10.11660/slfdxb.20160314
		Reservoir water temperature has been calculated using Zhu Bofang's method and statistical analysis method and compared with the measured temperature in the case studies of three typical reservoirs in cold region. The results show that for the water temperature in winter, the statistical analysis method is better while in summer, the results of both methods are close to the measurements. For the autumn and winter seasons, neither of these empirical formulas can take into account the mixing phenomenon driven by instable stratification. Overall, the statistical method, though better than Zhu Bofang's method, still needs further modification. We have examined the causes for its deviations in temperature calculation and developed a correction method and corresponding procedure for calculation of the effects of vertical mixing in large water bodies. The corrected results are in good agreement with the measured temperature. The statistical analysis method after correction shows a better accuracy in calculation of the water temperature in reservoirs in cold region. The results would help temperature control design and operation management of concrete dams.
		2016 Vol. 35 (3): 113-120 [Abstract] ( 251 ) PDF (930 KB) ( 441 )

	121	Study on influence of contact sliding along new-old concrete joint interfaces on gravity dam stability
		WANG Yujie, YANG Haitao, ZHOU Xingbo, WU Chao
		DOI: 10.11660/slfdxb.20160315
		In construction of concrete dams, raising the height of certain built dams appropriately is an important means of improving utilization efficiency and preventing disasters, but the joint interfaces of new-old concrete are prone to slide and become a weak plane that is sensitive to temperature. To solve this problem, we have developed a new contact sliding mode of multiple slices to analyze the slide stability of dam heightening. This paper uses a rigid limit equilibrium method to derive a calculation formula for three sliding interfaces, considering two calculation models of uplift water pressure. We applied this formula to the Danjiangkou dam heightening of the mid-route south-to-north water transfer project, and successfully rechecked the safety factors against sliding for the new-old concrete joints in the right dam blocks No. 1 and 7. For the recheck calculation, we also derived a corresponding formula for the case of N sliding interfaces. The results presented would help stability analysis for dam heightening in similar cases.
		2016 Vol. 35 (3): 121-128 [Abstract] ( 363 ) PDF (688 KB) ( 508 )