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Stability analysis of bank slope under conditions of reservoir impounding and rapid drawdown

Journal of Rock Mechanics and Geotechnical engineering 2011年第S1期3卷 429-437页

作者： Xiaoping Chen Jingwu Huang College of Science and Engineering Jinan UniversityGuangzhou510632China Key Laboratory of Disaster Forecast and Control in Engineering Jinan UniversityGuangzhou510632China Guangdong Hydropower Planning and Design Institute Guangzhou510170China

Stability of an ancient landslide in a reservoir area is analyzed by using centrifugal model tests, soil laboratory tests and numerical analysis. Special attention is paid to variation in water level, simulation of large-scale heterogeneous prototype slope, and strength reduction of sliding zone soils after slope sliding. The results of centrifugal model test show that reservoir impounding can reduce sliding resistance at the slope toe, followed by toe collapsing and front cracking of slope. Rapid drawdown can produce hydrodynamic pressure towards reservoir at the front of slope. Deformation is observed in the middle and upper slope, which reduces the slope stability further and forms the pull-typed landslide trend. Reinforcement of slope toe is effective for preventing the progressive failure. The results of laboratory test show that slope toe sliding will lead to the redistribution of soil density and moisture content, which will reduce the shear strength of soil in sliding zone, and the cohesion of immersed soil is reduced gradually and finally vanishes with time. The numerical results show that the strength reduction method used in finite element method (FEM) is very effective in capturing the progressive failure induced by reservoir water level fluctuations, and the evolution of failure surface derived from numerical simulation is very similar to that observed in centrifugal model test.

关键词： slope stability reservoir impounding centrifugal model test strength reduction progressive failure

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Calculation of Normal Rock Breaking Force by Disc Cutter Based on Dimensional Analysis

Calculation of Normal Rock Breaking Force by Disc Cutter Bas...

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第四届国际机械工程与力学会议

作者： Qixing WU Xiangshang QI Hongwei MA Department of Mechanics and Civil Engineering Jinan University The Key Laboratory of Disaster Forecast and Control in Engineering Ministry of Education of ChinaJinan University College of Science & Engineering Jinan University

Based on the analysis of parameters used in the existing main calculation formulas of rock breaking force by disc cutter, by using dimensional analysis theory, a function has been developed among the normal rock breaking force by disc cutter and the parameters of Young's modulus of rock, uniaxial compressive strength of rock, cutter spacing and penetration of cutter. In combination with the measured data tested by linear cutting machine (LCM), by the method of multiple linear regression, the empirical regression formula of calculating normal rock breaking force by disc cutter is determined.

关键词： Dimensional Analysis, Disc Cutter, Normal Rock Breaking Force, Shield Machine

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GREEN QUASIFUNCTION METHOD FOR FREE VIBRATION OF SIMPLY-SUPPORTED TRAPEZOIDAL SHALLOW SPHERICAL SHELL ON WINKLER FOUNDATION

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Acta Mechanica Solida Sinica 2010年第4期23卷 370-376页

作者： Shanqing Li Hong Yuan (moe key laboratory of disaster forecast and control in engineering, Institute of Applied Mechanics, Jinan University, Guangzhou 510632, China) [a] MOE Key Laboratory of Disaster Forecast Control in Engineering Institute of Applied Mechanics Jinan University Guangzhou 510632 China

The idea of Green quasifunction method is clarified in detail by considering a free vibration problem of simply-supported trapezoidal shallow spherical shell on Winkler foundation.A Green quasifunction is established by using the fundamental solution and boundary equation of the *** function satisfies the homogeneous boundary condition of the *** mode shape differential equation of the free vibration problem of simply-supported trapezoidal shallow spherical shell on Winkler foundation is reduced to two simultaneous Fredholm integral equations of the second kind by Green *** are multiple choices for the normalized boundary *** on a chosen normalized boundary equation, the irregularity of the kernel of integral equations is ***, natural frequency is obtained by the condition that there exists a nontrivial solution in the numerically discrete algebraic equations derived from the integral *** results show high accuracy of the Green quasifunction method.

关键词： Green function integral equation shallow spherical shell free vibration Winkler foundation

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Peeling behavior and spalling resistance of CFRP sheets bonded to bent concrete surfaces

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Acta Mechanica Sinica 2010年第2期26卷 257-264页

作者： Hong Yuan Faping Li MOE Key Lab of Disaster Forecast and Control in Engineering Institute of Applied Mechanics Jinan University 510632 Guangzhou China

In this paper, the peeling behavior and the spalling resistance effect of carbon fiber reinforced polymer （CFRP） sheets externally bonded to bent concrete surfaces are firstly investigated experimentally. Twenty one curved specimens and seven plane specimens are studied in the paper, in which curved specimens with bonded CFRP sheets can simulate the concrete spalling in tunnel, culvert, arch bridge etc., whereas plane specimens with bonded CFRP sheets can simulate the concrete spalling in beam bridge, slab bridge and pedestrian bridge. Three kinds of curved specimens with different radii of curvature are chosen by referring to practical tunnel structures, and plane specimens are used for comparison with curved ones. A peeling load is applied on the FRP sheet by loading a circular steel tube placed into the central notch of beam to debond CFRP sheets from the bent concrete surface, meanwhile full-range load-deflection curves are recorded by a MTS 831.10 Elastomer Test System. Based on the experimental results, a theoretical analysis is also conducted for the specimens. Both theoretical and experimental results show that only two material parameters, the interfacial fracture energy of CFRP-concrete interface and the tensile stiffness of CFRP sheets, are needed for describing the interfacial spalling behavior. It is found that the radius of curvature has remarkable influence on peeling load-deflection curves. The test methods and test results given in the paper are helpful and available for reference to the designer of tunnel strengthening.

关键词： FRP sheet · Interfacial fracture energy ·Debonding · Spalling resistance · Bent concrete surface

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Quasi-Green’s function method for free vibration of simply-supported trapezoidal shallow spherical shell

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Applied Mathematics and Mechanics(English Edition) 2010年第5期31卷 635-642页

作者：李善倾袁鸿 Key Laboratory of Disaster Forecast and Control in Engineering Ministry of Education of China Institute of Applied Mechanics Jinan University

The idea of quasi-Green＇s function method is clarified by considering a free vibration problem of the simply-supported trapezoidal shallow spherical shell. A quasi- Green＇s function is established by using the fundamental solution and boundary equation of the problem. This function satisfies the homogeneous boundary condition of the prob- lem. The mode shape differential equations of the free vibration problem of a simply- supported trapezoidal shallow spherical shell are reduced to two simultaneous Fredholm integral equations of the second kind by the Green formula. There are multiple choices for the normalized boundary equation. Based on a chosen normalized boundary equa- tion, a new normalized boundary equation can be established such that the irregularity of the kernel of integral equations is overcome. Finally, natural frequency is obtained by the condition that there exists a nontrivial solution to the numerically discrete algebraic equations derived from the integral equations. Numerical results show high accuracy of the quasi-Green＇s function method.

关键词： Green function integral equation shallow spherical shell free vibration

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Analysis of transient temperature field in coke drums

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Applied Mathematics and Mechanics(English Edition) 2010年第3期31卷 291-304页

作者：宁志华刘人怀 Key Laboratory of Disaster Forecast and Control in Engineering Ministry of Education of ChinaJinan University Institute of Applied Mechanics and Department of Mechanics and Civil Engineering Jinan University

One of the primary reasons leading to bulging and cracking in a coke drum is the severe temperature gradient due to cyclic temperature variation. Based on the twodimensional heat conduction theory, an analytical solution of the transient temperature field in the coke drum is obtained, which is different from the known FEM results. The length of the coke drum is considered finite. The dynamic boundary conditions caused by fluid uninterrupted rising in oiling and watering stages are simulated with the iteration method. Numerical results show that the present theoretical model can accurately describe basic features of the transient temperature field in the coke drum. Effects of the geometry of the coke drum and the rising velocity of quench water on the axial temperature gradient are also discussed.

关键词： coke drum cylindrical shell transient temperature field temperature gradient

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Study of dynamic longitudinal impedance of tapered pile considering lateral inertial effect

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Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and engineering 2011年第SUPPL. 2期30卷 3618-3625页

作者： Wu, Wenbing Wang, Kuihua Wu, Denghui Ma, Boning MOE Key Laboratory of Soft Soils and Geoenvironmental Engineering Zhejiang University Hangzhou Zhejiang 310058 China Key Creative Team of Disaster Control Engineering Zhejiang Province Hangzhou Zhejiang 310058 China

Based on Rayleigh-Love rode model, the longitudinal vibration of tapered pile embedded in layered soil is theoretically investigated by considering lateral inertial effect of tapered pile. At first, considering stratification of the surrounding soil and variable cross-section of the tapered pile, the pile-soil system is discretized into finite segments. Then, by virtue of Laplace technique and impedance function transfer method, the analytical solution of complex impedance of tapered pile under longitudinal exciting force is derived. Finally, by means of parametric study method, the influence of the design parameters of tapered pile on complex impedance at the pile head is investigated within the low frequency range, and the complex impedance of tapered pile is compared with that of uniform cross-section pile with same volume. The results show that: (1) When other design parameters of tapered pile remain unchanged, dynamic damping increases as the cone-angle increases, dynamic stiffness also increases as the cone-angle increases, but the increase magnitude decreases gradually as the frequency increases;(2) When other design parameters of tapered pile remain unchanged, dynamic stiffness decreases as the cone-angle increases, and dynamic damping increases as the cone-angle increases;(3) When the volume and length of tapered pile are the same as that of uniform cross-section pile, dynamic stiffness decreases as the cone-angle increases, and dynamic damping increases as the cone-angle increases. When the volume and radius at the pile tip of tapered pile are the same as that of uniform cross-section pile, dynamic stiffness increases as the cone-angle of tapered pile increases, and dynamic damping increases as the cone-angle increases within a small range of cone-angle.

关键词： Piles

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Experimental studies on crack parameters identification in the pipe based on L(0, 2) ultrasonic guided wave

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Beijing Ligong Daxue Xuebao/Transaction of Beijing Institute of Technology 2011年第SUPPL.1期31卷 8-11页

作者： Zhang, Wei-Wei Zhao, Jun Nie, Zhen-Hua Sun, Jin-Lan Ma, Hong-Wei Mechanics Department Taiyuan University of Science and Technology Taiyuan Shanxi 030024 China The Key Laboratory of Disaster Forecast and Control in Engineering Jinan University Ministry of Education of China Guangzhou Guangdong 510632 China

PZT5-sensors were used to excite and receive the guided wave signal for crack detection. A piezoelectric ring was an excited sensor and 16 piezoelectric patches distributing the circle pipe wall were received sensors. At first, the disperse curve of both the group velocity and the attenuation for L(0, 2) guided wave were plotted. Next, crack detection was performed by the guided wave inspection. For reducing the noise from the guided wave signal, eight points FFT smoothing technology is used to denoise the guided wave signal. Based on the denoised signal, the crack location can be detected successfully. To evaluate the size of the crack, the reflection coefficient, a ratio of the peak of the echo from the crack to the peak of the incident wave, is defined. When the modify factor is 0.8, it could be found that the crack size identification is in good agreement with the theoretical prediction.

关键词： Damage detection

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Visualization of damage detection for circular arch based on stochastic subspace identification

Visualization of damage detection for circular arch based on...

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International Conference on Artificial Intelligence and Computational Intelligence (AICI)

作者： Nie, Zhenhua Zhao, Jun Ma, Hongwei Cheng, Liangyan Key Laboratory of Disaster Forecast and Control in Engineering Jinan University Ministry of Education of China Guangdong Guangzhou China School of Civil Engineering Henan Polytechnic University Jiaozuo China

ISBN: (纸本)9780769542256

When performing vibration tests on civil engineering structures, it is often unpractical and expensive to use artificial excitation (shakers, drop weights). Ambient excitation on the contrary is freely available (traffic, wind), but it causes other challenges. The ambient input remains unknown and the system identification algorithms have to deal with output-only measurements. The empirical mode decomposition (EMD) based stochastic subspace identification procedure utilizing operational vibration measurements is presented in this paper. The SSI method is then applied to the decomposed signals to yield the modal parameters of the hinged circular arch which is divided into sixteen elements, and then the strain mode shapes are obtained. In order to let the non-specialist to understand the message of the damages, the strain modes of the arch are presented with visual images. Visualization of damage detection has great potential for development of On-line structure health monitoring. © 2010 IEEE.

关键词： Damage detection

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Redevelopment of liftoff rates of saltating sand grains based on a simple optimization model

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Science China Earth Sciences 2010年第4期53卷 568-574页

作者： CHENG Hong & ZOU XueYong State key laboratory of Earth Surface Processes and Resource Ecology,Beijing Normal University,Beijing 100875,China moe engineering Center of Desertification and Blown-sand control,Beijing Normal University,Beijing 100875,China key laboratory of Environmental Change and Natural disaster of the Ministry of Education of China,Beijing Normal University,Beijing 100875,China 1. State Key Laboratory of Earth Surface Processes and Resource Ecology Beijing Normal University Beijing 100875 China2. MOE Engineering Center of Desertification and Blown-sand Control Beijing Normal University Beijing 100875 China3. Key Laboratory of Environmental Change and Natural Disaster of the Ministry of Education of China Beijing Normal University Beijing 100875 China

This paper is a redevelopment result of liftoff rates of saltating sand grains based on our previous *** sand flow is a complex multi-phase flow because of a special two-phase gas-solid flow near ground *** extensive research on the movement of blowing sand,no model fully characterizes aeolian sand flow,and large differences often exist between simulations of aeolian sand movement and field *** key problem is a few of sufficient research on liftoff rates of saltating sand grains(also called the number of liftoff sand grains per unit time and per unit bed area).It is necessary to re-search in advance liftoff rates of saltating sand *** redeveloped liftoff rates of saltating sand grains by establishing an optimization model based on the flux of aeolian sand flow at different heights of the sampler in wind tunnel and the simulated capture of saltating sand grains by different heights of the sampler that are from different liftoff position(distance from the sampler) in order to revise previous inversion condition of liftoff rates of saltating sand *** rates increased rapidly with increasing wind *** frictional wind velocities of u=0.67,0.77,0.82,0.83,and 0.87 m s-1,liftoff rates were 3840,954502,5235114,5499407,and 7696291 sand grain s-1 m-2,*** rates could be expressed as the square of the instantaneous frictional wind velocity and a constant(0.663) that differs from the critical(threshold) frictional wind velocity at which saltation *** our results require additional experimental validation and the simple optimization model must be improved,they nonetheless provide a strong basis for future research.

关键词： liftoff rates of saltating sand grains optimization model wind tunnel two-phase gas-solid flow

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