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Discrete element simulation of crushable rockfill materials

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Water Science and Engineering 2013年第2期6卷 215-229页

作者： Lei SHAO Shi-chun CHI Liang-jing ZHOU Yu-zan WANG Faculty of Infrastructure Engineering Dalian University of Technology Hydrochina Chengdu Engineering Corporation changjiang institute of survey Planning Design and Research Changjiang Water Resources Commission

A discrete element method was used to study the evolution of particle crushing in a rockfill sample subjected to triaxial shear. A simple procedure was developed to generate clusters with arbitrary shapes, which resembled real rockfill particles. A theoretical method was developed to define the failure criterion for an individual particle subjected to an arbitrary set of contact forces. Then, a series of numerical tests of large-scale drained triaxial tests were conducted to simulate the behaviors of the rockfill sample. Finally, we examined the development of micro-characteristics such as particle crushing, contact characteristics, porosity, deformation, movement, and energy dissipation. The simulation results were partially compared with the laboratory experiments, and good agreement was achieved, demonstrating that the particle crushing model proposed can be used to simulate the drained triaxial test ofrockfill materials. Based on a comparison of macro behaviors of the roekfill sample and micro structures of the particles, the microscopic mechanism of the rockfill materials subjected to triaxial shear was determined qualitatively. It is shown that the crushing rate, rather than the number of crushed particles, can be used to reflect the relationship between macro- and micro-mechanical characteristics of rockfill materials. These research results further develop our understanding of the deformation mechanism of rockfill materials.

关键词： discrete element simulation triaxial shear test," roclcfill material geometric construction of particles particle flow code microscopic mechanism

Parameters inversion of high central core rockfill dams based on a novel genetic algorithm

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Science China(Technological Sciences) 2016年第5期59卷 783-794页

作者： ZHOU Wei LI Shao Lin MA Gang CHANG Xiao Lin MA Xing ZHANG Chao State Key Laboratory of Water Resources and Hydropower Engineering Science Wuhan University changjiang institute of survey Planning Design and Research

Parameters identification of rockfill materials is a crucial issue for high rockfill dams. Because of the scale effect, random sampling and sample disturbance, it is difficult to obtain the actual mechanical properties of rockfill from laboratory tests. Parameters inversion based on in situ monitoring data has been proven to be an efficient method for identifying the exact parameters of the rockfill. In this paper, we propose a modified genetic algorithm to solve the high-dimension multimodal and nonlinear optimal parameters inversion problem. A novel crossover operator based on the sum of differences in gene fragments(So DX) is proposed, inspired by the cloning of superior genes in genetic engineering. The crossover points are selected according to the difference in the gene fragments, defining the adaptive length. The crossover operator increases the speed and accuracy of algorithm convergence by reducing the inbreeding and enhancing the global search capability of the genetic algorithm. This algorithm is compared with two existing crossover operators. The modified genetic algorithm is then used in combination with radial basis function neural networks(RBFNN) to perform the parameters back analysis of a high central earth core rockfill dam. The settlements simulated using the identified parameters show good agreement with the monitoring data, illustrating that the back analysis is reasonable and accurate. The proposed genetic algorithm has considerable superiority for nonlinear multimodal parameter identification problems.

关键词： rockfill dam parameters back analysis genetic algorithm crossover operator sum of differences in gene fragments

Control performance comparison between tuned liquid damper and tuned liquid column damper using real-time hybrid simulation

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Earthquake Engineering and Engineering Vibration 2019年第3期18卷 695-701页

作者： Zhu Fei Wang Jinting Jin Feng Lu Liqiao State Key Laboratory of Hydroscience and Engineering Tsinghua University Beijing 100084 China changjiang institute of survey Planning Design and Research Wuhan 430010 China

Tuned liquid damper (TLD) and tuned liquid column damper (TLCD) are two types of passive control devices that are widely used in structural control. In this study, a real-time hybrid simulation (RTHS) technique is employed to investigate the diff erence in control performance between TLD and TLCD. A series of RTHSs is presented with the premise of the same liquid length, mass ratio, and structural parameters. Herein, TLD and TLCD are physically experimented, and controlled structures are numerically simulated. Then, parametric studies are performed to further evaluate the diff erent performance between TLD and TLCD. Experimental results demonstrate that TLD is more eff ective than TLCD under diff erent amplitude excitations.

关键词： tuned liquid damper tuned liquid column damper real-time hybrid simulation control effi ciency structural control parametric study

Efficiency analysis of numerical integrations for finite element substructure in real-time hybrid simulation

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Earthquake Engineering and Engineering Vibration 2018年第1期17卷 73-86页

作者： Wang Jinting Lu Liqiao Zhu Fei State Key Laboratory of Hydroscience and Engineering Tsinghua University Beijing 100084 China changjiang institute of survey Planning Design and Research Wuhan 430010 China

Finite element（FE） is a powerful tool and has been applied by investigators to real-time hybrid simulations（RTHSs）. This study focuses on the computational efficiency, including the computational time and accuracy, of numerical integrations in solving FE numerical substructure in RTHSs. First, sparse matrix storage schemes are adopted to decrease the computational time of FE numerical substructure. In this way, the task execution time（TET） decreases such that the scale of the numerical substructure model increases. Subsequently, several commonly used explicit numerical integration algorithms, including the central difference method（CDM）, the Newmark explicit method, the Chang method and the Gui-λ method, are comprehensively compared to evaluate their computational time in solving FE numerical substructure. CDM is better than the other explicit integration algorithms when the damping matrix is diagonal, while the Gui-λ（λ = 4） method is advantageous when the damping matrix is non-diagonal. Finally, the effect of time delay on the computational accuracy of RTHSs is investigated by simulating structure-foundation systems. Simulation results show that the influences of time delay on the displacement response become obvious with the mass ratio increasing, and delay compensation methods may reduce the relative error of the displacement peak value to less than 5% even under the large time-step and large time delay.

关键词： real-time hybrid simulation computational efficiency numerical integration storage optimization time delay

Calibration and performance of two different constitutive models for rockfill materials

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Water Science and Engineering 2016年第3期9卷 227-239页

作者： Lin-ke Li Zhan-jun Wang Si-hong Liu Erich Bauer institute of Applied Mechanics Graz University of Technology changjiang institute of survey PlanningDesign and Research College of Water Conservancy and Hydropower Engineering Hohai University

In this paper, two different concepts for the constitutive modeling of the mechanical behavior of creep-sensitive rockfill materials are presented. Specifically, the performance of an extended generalized plasticity model proposed by Wang is compared with a simplified version of the hypoplastic constitutive model for weathered rockfill materials proposed by Bauer. Both models can reflect the influence of the mean stress on the incremental stiffness, the peak friction angle, and the dilatancy angle. The so-called solid hardness defined for a continuum description and originally introduced by Bauer is embedded in both models. Hydrochemical, thermal, and mechanical weathering are usually caused by environmental changes and are taken into account in a phenomenological description with an irreversible and time-dependent degradation of the solid hardness. A degradation of the solid hardness is usually accompanied by creep deformation of the stressed rockfill material. It is shown that appropriate modeling of creep deformation requires at least a unified description of the interaction between the time-dependent process of degradation of the solid hardness and the stress state. In this context, the solid hardness can be understood as a key parameter for describing the evolution of the state of weathering of the rockfill material. Particular attention is also paid to the necessary procedure for determining the constitutive constants of the two different constitutive models. Finally, the performance of the two different constitutive models is demonstrated by comparing the results obtained from numerical simulations with experimental data from the creep-sensitive rockfill material.

关键词： Rockfill material Creep Generalized plasticity Hypoplasticity Constitutive model

Analysis and Modeling of Slope Stability in the Three-Gorges Dam Reservoir (China)——The Case of Huangtupo Landslide

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Journal of Mountain Science 2011年第2期8卷 166-175页

作者： R.COJEAN Y.J.CA Centre de Géosciences Mines-ParisTech Paris France changjiang institute of survey Planning Design & Research CWRC Wuhan China

The water level in the Three Gorges Dam reservoir is expected to change between the elevations of 145 m and 175 m, as a function of the flood control implementation and the intensity of the annual flood. As a matter of fact, the hydraulical and mechanical loadings, related to the water level modifications, will result in alterations in the slope stability conditions. The town of Badong (Hubei), of 20 000 inhabitants, is one of the towns which was submerged by the impoundment of the reservoir. As a consequence, the new town of Badong was constructed on a nearby site which appeared to be partly an unstable site. A part of this site corresponds to an old landslide, the Huangtupo landslide, the base of which had to be submerged by the water of the reservoir. The analysis of the Huangtupo landslide, taking into account various events scenarios, drainage and reinforcement measures and monitoring devices, allows to illustrate the general process implemented all along the reservoir in order to mitigate the landslide hazard.

关键词： Three Gorges Dam Landslide Modelling

EXPERIMENTAL FEEDBACK ON THE INVESTIGATION OF HYDRAULIC CHARACTERISTICS FOR THE SHIP-LOCK FILLING AND EMPTYING SYSTEM OF TGP

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Journal of Hydrodynamics 2005年第6期17卷 770-775页

作者： NIU Xin-qiang JIANG Xiao-min School of Hydropower and information Engineering Huazhong University of Science and TechnologyWuhan 430074 China changjiang institute of survey Planning Design and Research CWRC Wuhan 430010 China

Where hydraulic characteristics of ship lock filling and emptying system are concerned, there are much bigger differences between prototype and model experiments. Based on the results of the prototype experiments fur the Three Gorges Project （TGP）, experiments on the feedback model were conducted of the ship-lock filling and emptying system, by means of technologies of drag reduction, under similar conditions as the operation of the prototype project. The experimental results show that the difference of drag co efficient reached-44% hetween the prototype and the model for the filling and emptying system of the ship-lock No. 3 for TGP and the difference of discharge coefficient was ahout 33% between them. The technologies of drag reduction are more efficient in the simulation of a ship lock filling and emptying system in order to he consistent for discharge, water level, time average pressure and pulsating pressure between prototypes and models.

关键词： hydraulic characteristics filling and emptying system ship-lock feedback experiment

Anti-Crack Performance of Low-Heat Portland Cement Concrete

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Journal of Wuhan University of Technology(Materials Science) 2007年第3期22卷 555-559页

作者：杨华全 changjiang River Scientific Research institute

The properties of low-heat Portland cement concrete（LHC） were studied in detail. The experimental results show that the LHC concrete has characteristics of a higher physical mechanical behavior, deformation and durability. Compared with moderate-heat Portland cement（MHC）, the average hydration heat of LHC concrete is reduced by about 17.5%. Under same mixing proportion, the adiabatic temperature rise of LHC concrete was reduced by 2 ℃-3 ℃,and the limits tension of LHC concrete was increased by 10× 10^-6-15×10^-6 than that of MHC. Moreover, it is indicated that LHC concrete has a better anti-crack behavior than MHC concrete.

关键词： low-heat portland cement mass concrete high crack resistance moderate-heat portland cement

Sensitive Evaluation on Early Cracking Tendency of Concrete with Inclusion of Light-burnt MgO

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Journal of Wuhan University of Technology(Materials Science) 2011年第5期26卷 1018-1022页

作者：陈霞 changjiang River Scientific Research institute

The advanced temperature and stress test machine was introduced to determine the early cracking tendency of concrete with inclusion of light-burnt MgO under full restraint by tracking the development of thermal,physical and deformation *** showed that light-burnt MgO being incorporated ranging between 4 wt% and 6 wt% of cementitious materials was beneficial to increase the maximum compressive stress and cracking stress of concrete by 0.37 MPa and 0.2 MPa on average *** second zero stress temperature was reduced by 11.4 ℃ and the maximum temperature was slightly reduced while cracking thermal impact was significantly enhanced from 59.8 ℃ to 66.2 ℃.Sensitive anti-cracking coefficient F was forwarded to assess the early cracking tendency of concrete and the inclusion of 4 wt% light-burnt MgO with activity of 109 s ranked the best in crack resistance.

关键词： crack resistance cracking stress light-burnt MgO concrete sensitive evaluation