Cen W.-J.,Hohai University |
Wang J.,Hohai University |
Wang S.,Guangdong Hydropower Planning and Design Institute |
Xiong K.,Chang Jiang Survey Planning Design and Research LLC
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2013
Rapid drawdown of reservoir has a great influence on the seepage, deformation and stability of an earth-rock dam. Under earthquakes, it may pose a new threat to the dam safety. Combined with a 300 m-super high core wall earth-rock dam to be constructed, the unsteady and saturated-unsaturated seepage analysis of the dam under the rapid drawdown of reservoir is carried out and the pore water pressure is acquired. Based on the seepage and static stress field, the seismic response of the dam is analyzed to get the basic dynamic response. Meanwhile, the evaluation of seismic stability and permanent deformation of dam slope are also conducted to evaluate its seismic safety. The results show that rapid drawdown of reservoir mainly affects the distribution of pore water pressure of the core and upstream dam body, causes the large change of static average effective stress field of the upstream region of the dam for the high core wall rockfill dams with good barrier performance core and upstream filter protection. The occasional earthquake will significantly affect the dynamic response and the seismic performance of upstream dam slope, and more attention should be paid to it. The change of water level does not affect the distribution of seepage field of the downstream dam body obviously. Therefore, the rapid drawdown of reservoir has little influence on the seismic safety of downstream dam body.
Zhang M.-Y.,Wuhan University of Technology |
Song H.-Z.,Wuhan University of Technology |
Li B.,Changjiang Survey Planning Design and Research Co. |
Li Y.,Hubei Engineering University
Yantu Lixue/Rock and Soil Mechanics | Year: 2012
A predictive model of ultimate bearing capacity for large-diameter and super-long steel pipe piles is established based on Support Vector Machine(SVM) and Independent Component Analysis(ICA). Firstly the FastICA algorithm of independent component analysis is imported to abstract the independent components, which can better express the essence in sample data and keep statistics independent without correlation as well as obey the Gaussian distribution, from large-diameter and super-long steel pipe pile data measured in an actual engineering. Secondly, by determining the support vector machine as classifier, whose input are the previously extracted components and whose output is the predicted bearing capacity, ICASVM_Q model is established to predict bearing capacity of large-diameter and super-long steel pipe piles. By data testing of a bridge engineering, it is shown that the predicted results of ICASVM_Q are better than SVM_Q which uses original engineering data as input of SVM model. Studies indicated that the modeling method by combining SVM and ICA used to predict ultimate bearing capacity of large-diameter and super-long steel pipe piles is feasible and the predicting bearing capacity of the ICASVM_Q model can be referred by designers in engineering. This method can also serve as a reference of intelligent forecast in other areas.
Sun W.,Wuhan University |
He Y.,Wuhan University |
Xiong K.,Changjiang Survey Planning Design and Research LLC |
Miao J.,Wuhan University
Sichuan Daxue Xuebao (Gongcheng Kexue Ban)/Journal of Sichuan University (Engineering Science Edition) | Year: 2014
In order to carry out the simulation of dam structure joints mechanical behavior more reasonably, a thin-layer joints element, of which the normal and tangential constitutive models both adopt hyperbolic models, was used. Firstly, a numerical example verified that the thin-layer joints element can reflect well on the alternating tension and compression phenomenon of contact surface under cyclic loading. And the sensitivity analyses of contact surface stiffness coefficient, friction coefficient and element thickness and other factors were done. Then the methods to simulate transverse joints, induced joints using the thin-layer joints element were introduced in detail. Finally, the thin-layer joints element was used to simulate a real RCC arch dam engineering joints. The results showed that setting the transverse and induced joints can release tensile stress evidently on the areas besides them and the thin-layer joints element can also provide a reference for the simulation of other similar structure joints.
Liu X.,Wuhan University |
Zhang C.,Wuhan University |
Zhang C.,Changjiang Survey Planning Design and Research Co. |
Chang X.,Wuhan University |
And 3 more authors.
Applied Thermal Engineering | Year: 2015
Thermal analysis is one of the main components in the design and construction of mass concrete structures. A procedure for a heat-fluid coupling model (HFCM) is presented to simulate the thermal field of mass concrete with a pipe cooling system, which can accurately reflect the temperature gradient near the pipe and the temperature rise along the pipe. Additionally, to make it suitable for the simulation of forced-convection during pipe cooling, a modified particle swarm optimization (MPSO) method, based on particle migration is adopted for parameter identification of the Dittus-Boelter equation used by the heat-fluid coupling model, according to field tests. To verify the accuracy and computation efficiency of the method, a simplified 3D model is simulated and compared to other numerical models. Subsequently, the model is applied to the analysis of a monolith of the Dagangshan high arch concrete dam in the construction period. The actual climatic conditions, cooling pipe system, cooling schedule and thermal properties of the materials are considered in the analysis. The simulation results indicate that the proposed method can effectively simulate the cooling pipe state, water temperature rise along the flow, and directional changes of the flow in the thermal field of mass concrete. Moreover, the temperatures determined by the numerical simulation are in good agreement with the monitoring values. Findings in this research show that the proposed HFCM is feasible and has attractive advantages in the simulation of the thermal field in practical complex mass concrete engineering projects with cooling pipe systems. © 2014 Elsevier Ltd.
Sun W.,Wuhan University |
He Y.-L.,Wuhan University |
Yuan S.,Wuhuan Engineering Corporation |
Xiong K.,Chang Jiang Survey Planning Design and Research LLC
Shuili Xuebao/Journal of Hydraulic Engineering | Year: 2014
Based on the collection, sortation, statistics and analysis of Hardfill material mechanics performance indexes, Monte-Carlo stochastic finite element method is adopted to study the static working behavior of Hardfill dam with considering the heterogeneity of material mechanical properties influence and the random field of the modulus of elasticity has been built. The results show that the displacement response is small and the amplitude of changes is not more than 13.7%, while the stress response is relatively greater and the amplitude of changes is not less than 18.8% and maximum reaches 110.5%. The mean responses of stress and deformation of dam are consistent with the homogeneous model. The variability of stress and deformation of the upstream and downstream, the top, the heel, and the toe of the dam is strong and the maximum variation coefficient reaches 0.21, while the internal part of the dam is not very prominent and the coefficient of variation is not more than 0.08. After the superposition with three times standard deviation, the rate of the displacement of the extreme points is not more than 5%, while the rate of the stress of the extreme points is not less than 18.4% and maximum reaches 375%.
Feng K.,Southwest Jiaotong University |
He C.,Southwest Jiaotong University |
Zou Y.-L.,Changjiang Survey Planning Design and Research Ltd Co.
Gongcheng Lixue/Engineering Mechanics | Year: 2012
The effect of assembling method on the inner force of segmental lining for cross-river shield tunnel with large cross-section has been concerned for a long time. Different assembling plan yields different distribution characteristics of inner force. In this paper, theoretical analysis is carried out to discuss the mechanism of assembling effect of circular shield tunnel, especially the effect of longitudinal interaction on circumferential inner force. Then based on Nanjing Yangtze River Shield Tunnel project, a prototype test is conducted to study the mechanical distribution characteristic of circumferential inner force in different assembling plan and the mechanical distribution characteristic of inner force of target segment (B5) along the circumference and width direction. The results show that, the effect of the interaction intensifies bending moment in local area when using staggered assembling, and the growth of bending moment and decline of axial force become larger near the longitudinal bolts. And along the width direction, the positive bending moment distributes as a concave type, the negative bending moment and axial force distribute as a convex type. The result can provide valuable references to design and construction of large-profile underwater shield tunnels; meanwhile it can also provide important reference to the correlative studies.
Wang H.,Wuhan University |
Wang H.,Changjiang Survey Planning Design and Research Ltd CO. |
Yang J.,Wuhan University
Shuili Fadian Xuebao/Journal of Hydroelectric Engineering | Year: 2015
By theoretical analysis, numerical calculation and engineering example, it is proved that stage-discharge relation of downriver decrease surge-chamber ground swell, and makes little difference to other guaranteed regulations because of buffer action of surge-chamber. Boundary condition of constant water level is safe because stage-discharge relation reduces stable sectional area of tailrace surge tank, and improves governing quality. But which is unsafe in power station without tail surge tank because fluctuation of tail water directly influence pressure in the draft tube and make it worse. ©, 2014, 10031243 Tsinghua University Press. All right reserved.
Yuting Z.,Yangtze River Scientific Research Institute |
Xiuli D.,Yangtze River Scientific Research Institute |
Qitao P.,Yangtze River Scientific Research Institute |
Zhiguo Z.,Changjiang Survey Planning Design and Research Co.
Open Civil Engineering Journal | Year: 2015
The mechanical response of geological fault structure and its interaction with surrounding rock are crucial for the stability of caverns in hard rocks. Geological fault structure exhibits unique mechanical response subjected to rock excavation. Potential failure patterns and their corresponding criterions of geological faults, including open failure, slip failure and block instability, are summarized. Corresponding numerical models and proper supporting measures are recommended for open and slip failures, respectively. Rock damage model is adopted to better illustrate the interaction of rockmass and geological faults. Safety factor for anti-sliding is introduced to quantify the safety extent of caverns subjected to open and slip failures caused by geological faults. Case study shows that the presented methods are effective to describe the mechanical response of geological faults and also to provide quantitative references for reinforcement design of rock caverns. © Yuting et al.
Zhou W.,Hubei Engineering University |
Feng C.,Hubei Engineering University |
Liu X.,Hubei Engineering University |
Liu S.,Hubei Engineering University |
And 2 more authors.
Materials | Year: 2016
This work is a contrastive investigation of numerical simulations to improve the comprehension of thermo-structural coupled phenomena of mass concrete structures during construction. The finite element (FE) analysis of thermo-structural behaviors is used to investigate the applicability of supersulfated cement (SSC) in mass concrete structures. A multi-scale framework based on a homogenization scheme is adopted in the parameter studies to describe the nonlinear concrete behaviors. Based on the experimental data of hydration heat evolution rate and quantity of SSC and fly ash Portland cement, the hydration properties of various cements are studied. Simulations are run on a concrete dam section with a conventional method and a chemo-thermo-mechanical coupled method. The results show that SSC is more suitable for mass concrete structures from the standpoint of temperature control and crack prevention. © 2016 by the authors.
Zhang C.,Hubei Engineering University |
Zhang C.,Changjiang Survey Planning Design and Research Company Ltd |
Zhou W.,Hubei Engineering University |
Ma G.,Hubei Engineering University |
And 2 more authors.
Computers and Concrete | Year: 2015
Cooling by the flow of water through an embedded cooling pipe has become a common and effective artificial thermal control measure for massive concrete structures. However, an extreme thermal gradient induces significant thermal stress, resulting in thermal cracking. Using a mesoscopic finite-element (FE) mesh, three-phase composites of concrete namely aggregate, mortar matrix and interfacial transition zone (ITZ) are modeled. An equivalent probabilistic model is presented for failure study of concrete by assuming that the material properties conform to the Weibull distribution law. Meanwhile, the correlation coefficient introduced by the statistical method is incorporated into the Weibull distribution formula. Subsequently, a series of numerical analyses are used for investigating the influence of the correlation coefficient on tensile strength and the failure process of concrete based on the equivalent probabilistic model. Finally, as an engineering application, damage and failure behavior of concrete cracks induced by a water-cooling pipe are analyzed in-depth by the presented model. Results show that the random distribution of concrete mechanical parameters and the temperature gradient near water-cooling pipe have a significant influence on the pattern and failure progress of temperature-induced micro-cracking in concrete. Copyright © 2015 Techno-Press, Ltd.