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Showing 6 results for Yang

Q. Q. Zhang, Sh. C. Li, F. Y. Liang, M. Yang, Q. Zhang,
Volume 12, Issue 2 (Transaction B: Geotechnical Engineering April 2014)

A simplified approach for nonlinear analysis of the load-displacement response of a single pile and a pile group is presented using the load-transfer approach. A hyperbolic model is used to capture the relationship between unit skin friction and pile-soil relative displacement developed at the pile-soil interface and the load-displacement relationship developed at the pile end. As to the nonlinear analysis of the single pile response, a highly effective iterative computer program is developed using the proposed hyperbolic model. Furthermore, determinations of the parameters related to the hyperbolic model of an individual pile in a pile group are obtained considering interactions between piles. Based on the determinations of the parameters presented in the hyperbolic model of an individual pile in a pile group and the proposed iterative computer program developed for the analysis of the single pile response, the conventional load-transfer approach can then be extended to the analysis of the load-settlement response of an arbitrary pile in a pile group. Comparisons of the load-settlement response demonstrate that the proposed method is generally in good agreement with the field-observed behavior and the calculated results derived from other approaches.
Mr. L. Yanlong, Mr. L. Shouyi, Mr. Y. Yang, Miss T. Xing,
Volume 13, Issue 4 (Transaction A: Civil Engineering December 2015)

This study simulates the temperature field and temperature stress of concrete face slabs, considering the cold waves that occur during construction as well as the contact friction between the face slabs and the cushion layer. The results show that when a cold wave occurs during construction, the surface and center temperature of the face slabs continually drop with the outside air temperature, with the surface temperature drop being the largest. In addition, the surface and center of face slabs are subjected to tensile stress, with the maximum principal stress on the surface being greater than that on the center. The maximum principal stress of the surface and center occurs at approximately half of the dam height. This study also examines the surface insulation of concrete face slabs. Surface insulation can significantly improve the temperature drop range and the maximum principal stress amplitude caused by the cold wave. A stronger heat preservation results in smaller tensile stress and an increase in the amplitude of face slabs.

Jungang Luo, Xue Yang, Jiancang Xie,
Volume 14, Issue 1 (Transaction A: Civil Engineering 2016)

Due to the nonlinear relationship between storage and discharge existing in the nonlinear forms of the Muskingum model, the model parameters and outflow cannot be directly determined. The traditional routing procedure has been widely applied to model calibration and flood routing. However, most studies have focused only on the accuracy of parameter estimation methods which adopt the traditional routing procedure, ignored the correctness and effectiveness of routing procedure itself. In this study, three routing schemes of traditional routing procedure are evaluated by simulation experiment and the results demonstrate that the routing scheme 1 is the best, and scheme 3 is followed, the worst one is scheme 2. But the scheme 1 and 3 yield parameters estimates and corresponding outflow hydrographs lead to violation of the routing equations in terms of residuals. The scheme 2 is legitimate, however, the accuracy is not high enough. As an alternative, a new routing procedure based on iterative method is proposed for parameter estimation and flood routing of the nonlinear Muskingum models. The proposed routing procedure is applied to model calibration and flood routing for three examples involving single-peak, multi-peak, and non-smooth hydrographs. The results show that the proposed routing procedure is not only satisfying the routing equations for all time stages in the routing process, but also superior to the routing scheme 2. Therefore, it can confidently be applied to parameter estimation and flood routing for the nonlinear Muskingum models.

Jiuping Xu, Qiurui Liu, Zhonghua Yang,
Volume 15, Issue 1 (Transaction A: Civil Engineering 2017)

To fully explain hydropower unit operational problems, an optimal multi-objective dynamic scheduling model is presented which seeks to improve the efficiency of reservation regulation management. To reflect the actual hydropower engineering project environment, fuzzy random uncertainty and an integrated consideration of the natural resource constraints, such as load balance, system power balance, generation limits, turbine capacity, water head, discharge capacities, reservoir storage volumes, and water spillages, were included in the model. The aim of this research was to concurrently minimize discharges and maximize economic benefit. Subsequently, a new hybrid dynamic-programming based multi-start multi-objective simulated annealing algorithm was developed to solve the hydro unit operational problem. The proposed model and intelligent algorithm were then applied to the Xiaolongmen Hydraulic and Hydropower Station in China. The computational unit commitment schedule results demonstrated the practicality and efficiency of this optimization method.

Yang Wang, Kai Su, Hegao Wu, Zhongdong Qian,
Volume 15, Issue 4 (Transaction A: Civil Engineering 2017)

The reinforced concrete bifurcation in hydropower station is consistently under high internal water pressure, and its diameter is usually larger than common duct junctions. In order to diminish or to decrease the heavy plastic zone and stress concentration, structure rounding is commonly used on bifurcation. This will bring some changes to the flow characteristic of bifurcation, and it is an interesting attempt to figure out the influence of structure rounding optimization. The Realizable k-ε model was employed in Computational Fluid Dynamics numerical simulation. The water pressure distribution was compared quantitatively at several certain sections. Furthermore, uneven pressure is analyzed by relative standard deviation. Hydraulic characteristics are discussed as well, including flow pattern, excavation volume and head loss in different working conditions. The results indicate that the pressure of pipe wall is uneven, and the maximum and minimum pressure value has a differential of 0.3% - 1.2% compared to relative static water pressure. The pressure unevenness will increase after structure rounding, and it has a positive correlation with structure rounding radius. At the same time, it is more reasonable for structure rounding in obtuse angle region than that in acute angle region, on account of well-distributed flow conditions and better economic benefit.

Junxin Liu, Chunhe Yang, Jianjun Gan, Yutian Liu, Wei Liu, Qiang Xie,
Volume 15, Issue 6 (Transaction B: Geotechnical Engineering 2017)

Abstract: Rainfall is an important triggering factor influencing the stability of soil slope. Study on some influences of the rainfall on the instability characteristics of unsaturated soil embankment slope has been conducted in this paper. Firstly, based on the effective stress theory of unsaturated soil for single variable, fluid-solid coupling constitutive equations were established. Then, a segment of red clay embankment slope, along a railway from Dazhou to Chengdu, damaged by rainfall, was theoretical and numerical-simulating researched by considering both the runoff-underground seepage and the fluid-solid coupling. The failure characteristics of the embankment slope and the numerical simulation results were in excellent agreement. In the end, a sensitivity analysis of the key factors influencing the slope stability subjected to rainfall was performed with emphasis on damage depth as well as infiltration rainfall depth. From the analysis in this paper, it was concluded that the intensity of rainfall, rainfall duration and long-term strength of soil have most effect on slope stability when subjected to rainfall. These results suggest that the numerical simulation can be used for practical applications.

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