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Guo W.,Wuhan University | Guo W.,Purdue University | Yang J.,Wuhan University | Teng Y.,Wuhan University | Teng Y.,Chengdu Hydroelectric Investigation And Design Institute
Renewable Energy | Year: 2017

In order to reveal the surge wave characteristics and provide design guidances for the hydropower station with upstream series double surge tanks in load rejection transient, this paper studies the water level oscillations in the surge tanks. Firstly, the mathematical model that describes the unsteady flow for pipelines system is established. Then, for undamped upstream series double surge tanks system, the water level oscillations in two surge tanks are studied by deriving the analytical formulas with a novel method and analyzing the oscillation characteristics and superposition mechanism of water levels. The effects of damping on water level oscillations are analyzed. Finally, the application guidances of the results for the design of surge tanks and headrace tunnels are proposed. It is demonstrated that: Under the assumption of step discharge change in penstock, the proposed method for the derivation of analytical formulas for water level oscillations is effective, and the obtained analytical formulas are reasonable and have good accuracy. For the water level oscillations in two surge tanks, there are two kinds of frequency for the subwaves (i.e. subwave 1 and subwave 2). Subwave 1 and subwave 2 are the fundamental wave and the harmonic wave, respectively. The amplitude of subwave 1 determines the basic range of the water level oscillation. The damping mainly affects the attenuation of the water level oscillations. The analysis results for surge wave characteristics can be applied to the design of real projects. © 2017 Elsevier Ltd


Lin P.,Tsinghua University | Ma T.,Dalian University of Technology | Liang Z.,Dalian University of Technology | Tang C.A.,Dalian University of Technology | Wang R.,Chengdu Hydroelectric Investigation And Design Institute
Engineering Failure Analysis | Year: 2014

A code of practice for three dimensional cracking and a failure process analysis of high arch dams, based on the finite element method, dam failure process analysis (DFPA) has been developed. In this code, by changing mesh density, consideration of heterogeneity when calculating the elements is achieved. Random strength and elastic modulus are assigned to the elements in accordance with a Weibull distribution. A stress analysis is carried out based on consideration of the deformation of an elastic material containing an initial random distribution of microcracks, which simulates the progressive failure of solids. The dam cracking and failure process associated seismicity accumulation can be analyzed using acoustic emissions. The proposed method was applied in investigating the failure mechanism, and overall stability of the Xiluodu high arch dam. The numerical mesh model was fine, and the total number of hexahedral elements was 300. million. The DFPA analysis results, when compared with those derived by the Tfine code, and the 3D geomechanical model test show that the DFPA code is effective in fully simulating the failure processes of the dam and foundation. The analysis results were used to successfully guide the design of the Xiluodu high arch dam. The proposed DFPA method may also be of value to the reinforcement design and construction of high arch dams, associated with similar hydropower projects worldwide which are also located in complicated rock foundation areas. © 2014 Elsevier Ltd.


Lin P.,Tsinghua University | Liu X.,Tsinghua University | Zhou W.,Tsinghua University | Wang R.,Chengdu Hydroelectric Investigation And Design Institute | Wang S.,University of Newcastle
Arabian Journal of Geosciences | Year: 2015

The aim of this study is to examine cracking and instability of the high and steep left bank slope with weak rock mass structures, and effectiveness of the reinforcements designed for the slope at the Jinping hydroelectricity power station, southwestern China. A new geomechanical model testing method is first proposed for evaluating slope safety factors. In the proposed geomechanical model test, the slope is constructed on a flat testing bed, which can be rotated by hydraulic lifts. By increasing the rotation angle of the testing bed, the forces tending to induce the sliding of the slope are increased, which may cause crack initiation and propagation in the slope and result in rock mass slippage. Thus, through the proposed geomechanical model test, the slope failure mechanism, progressive failure process and final failure pattern can be studied. Moreover, the stability safety factors can be evaluated according to displacement data monitored by sensors installed in the geomechanical model. The geomechanical model test of the Jinping left-bank slope reveals that the bending and toppling cracks occur simultaneously in the unreinforced zone of the slope together with strong relaxation and tension cracks. It is found that the factor controlling the rock mass failure and instability is the structurally weak rock mass and the dominant failure mode is the integral catastrophic instability mode, in which the slope energy is totally dissipated and the slope destabilizes at a limit state. The reinforcement installed in the large area above the elevation of the dam-slope abutment and the unloading action due to the excavation of rocks lying above the dam platform have effectively improved the anti-slide safety factor of the slope, and thus increased its inherent safety factor. On the basis of the geomechanical model testing results and their comparisons with field monitoring results, it is concluded that the installed rock bolts and long anchor reinforcement measures are very effective in keeping the cracks closed in the rock mass and maintaining the slope stability. © 2014, Saudi Society for Geosciences.


Zhou D.,Hohai University | Mi Z.,Hohai University | Mao Y.,Chengdu Hydroelectric Investigation And Design Institute
Nongye Jixie Xuebao/Transactions of the Chinese Society for Agricultural Machinery | Year: 2013

Sediment deposition in the pumping station has a huge negative impact on unit operation. 3-D CFD method was used to simulate pumping station inlet structure flow based on Eulerian solid-liquid two-phase flow model. Numerical results of preliminary scheme show that sediment deposition occurs in the forebay of pumping station because of poor flow pattern therein. In order to improve hydraulic configuration in the forebay, one modified measure was reconstructing water diversion weir shape, and another measure was setting a water retaining sill in the approach channel. The simulation results of modified scheme prove that back flow in the forebay was eliminated and sediment deposition region was also reduced greatly.


Lin P.,Tsinghua University | Huang B.,Zhejiang University | Li Q.,Tsinghua University | Wang R.,Chengdu Hydroelectric Investigation And Design Institute
Engineering Geology | Year: 2015

The primary aim of this research is to analyze the hazards and seismic performance of reservoirs and typical large dams based on a field investigation following the Wenchuan 8.0 earthquake. The current seismic performance standards being achieved are discussed and further suggestions are given for super high dams. Based on field investigations, statistics are also given on damaged small reservoirs and damage severities, due to the many various types of earthquake threat. It is of interest to note that the major structures of the medium-sized hydropower stations on the Minjiang river did withstand the Wenchuan earthquake, despite earthquake intensity exceeding engineering design expectations. All the dams remained overall stable. The Shapai roller-compacted concrete (RCC) arch dam and the Zipingpu concrete-faced rockfill (CFR) dam suffered damage. The main earthquake-induced hazards to the dam structures and to both abutments are detailed. Case study analyses of the hazards and reinforcement provision revealed that: 1) The Wenchuan earthquake proved very dangerous for small reservoirs, with destroyed reservoirs widely distributed. The risk of failure of small dams can be classified into three levels based on field investigation. 2) The damage to and behavior of the large dams in the area affected by the earthquake prove that the Chinese codes relating to the seismic design of large dams are appropriate. 3) Appropriate reinforcement can increase the overall stiffness of abutments, riverbed foundation and the adjacent slopes, further improving the seismic performance of dams. 4) The design and management of emergency responses, to cope with extreme conditions, should be improved, and a unified response platform, covering all hydropower engineering projects in each valley should be established. The effects to be expected and the seismic design measures to be taken still pose great challenges for engineers in respect of large dams. © 2014 Elsevier B.V.


Song S.,Chengdu Hydroelectric Investigation And Design Institute | Xiang B.,Chengdu Hydroelectric Investigation And Design Institute | Xiang B.,University of Sichuan | Yang J.,Chengdu Hydroelectric Investigation And Design Institute | Feng X.,Chengdu Hydroelectric Investigation And Design Institute
Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and Engineering | Year: 2010

The arch dam in Jinping I hydropower station is the highest arch dam under construction in the world; the height of excavated slopes at abutments is over 500 m. The power station is located in high mountains and narrow canyons in Southwest China, where natural slopes are very high and steep with high geostress, intensive rock mass unloading, developed faults, interlayer compressive belts and deep unloading fissures. Based on detailed geological investigation, models of the slope structure and the corresponding failure mode are determined, such as tensile rip rock body at left bank above elevation 1 800 m; zoning and analysis of slope stability are also implemented. According to the characteristics of slope structure, the excavation and harnessing principles are determined as follows: little excavation, slight blasting and strong reinforcement, reinforcing each zone and layer respectively, holistic control and covering local weak points with global measures, local and global, implementing shallow and deep reinforcement controlling systems of slope with prestressed cables and shearing-resistance tunnels as main measures and bolts and concrete grids as complement. Time sequence of construction and blasting technique are precisely designed and firmly controlled to guarantee the quality of excavated rock mass; and dynamic design schemes and reasonable management rules are implemented to ensure the safety of construction. Monitoring data from July 2006 to September 2009 indicate that maximum displacement in surface part of the slope is 79.5 mm, in direction perpendicular to the river; and maximum deformation in deep unloading fissures is 60 mm with the maximum rate of 0.1 mm/d. The displacement tends to converge; and it meets the designed safety standards. The successful implementation of high slopes in Jinping I hydropower station provides new practical experience and reference for future construction of projects, and it indicates a new stage of the research and design of rock mechanics and engineering in China.


Song S.,Chengdu Hydroelectric Investigation And Design Institute | Feng X.,Chengdu Hydroelectric Investigation And Design Institute | Xiang B.,Chengdu Hydroelectric Investigation And Design Institute | Xing W.,Chengdu Hydroelectric Investigation And Design Institute | Zeng Y.,Chengdu Hydroelectric Investigation And Design Institute
Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and Engineering | Year: 2011

There is rich hydroelectric resource in Southwest China with high mountains and deep canyons, and many hydropower projects with high dams and large reservoirs are located in this area. Due to specific topographic and geological condition, stability of the complex high slopes in these projects has become one of the key technical problems which restrict the effective development of hydroelectric resource and project construction. Taking the hydropower project practice in Southwest China into consideration and combining the corresponding research achievements, main technical features and key problems of slope engineering have been summarized and analyzed, and research approaches and contents of rock engineering has been brought forward. On this basis, some new ideas and methods such as genesis of deep fissures in slope, slope structure, parameter values, safety criterion, reinforcement design method, feedback analysis, etc. have been put forward from several aspects including geological condition, slope engineering design theory, and construction process controlling, etc. These methods and theories have been successfully applied in the design and construction of slopes in hydropower projects. Particularly, the extremely high slopes in Jinping I project(530 m) and Dagangshan project(420 m) consisting of deep unloading and relaxation rock masses have been successfully constructed. These research achievements bear beneficial reference significance to the investigation and design of slope engineering and the development of rock mechanics.


Gao C.-Y.,University of Sichuan | Xu J.,University of Sichuan | Li Z.-H.,Chengdu Hydroelectric Investigation And Design Institute | Deng J.-H.,University of Sichuan
Yantu Lixue/Rock and Soil Mechanics | Year: 2011

The sandy slate samples are taken from the Xuefeng mountain tunnel rock. To study the effect of micro-bedding on strength properties and deformation characteristics of samples, a series of uniaxial and triaxial compressed tests are carried out with MTS815 Flex GT rock mechanics test system. The experiment results show that mechanical properties of the rock is obvious anisotropy. The stress-strain curves display unstable broken feature when the bedding parallels to axial stress (angle 0°) and failure faces development along the bedding. Softening rapidly happened after peak when the bedding is perpendicular to axial stress(angle 90°) and failure faces belongs to shear failure. The numerical results of uniaxial test show that compression strength, elastic modulus and deformation modulus of angle 0° is 20%, 50% and 80% higher separately than them of angle 90°. The results of triaxial test show the principal stress difference of them is close in the peak intensity; elastic modulus and deformation modulus of angle 0° is 6% and 20% higher than them of angle 90°. Confining pressure of triaxial tests has weakening effects on anisotropic features of the sandy slate. These conclusions reveal the sandy slate possesses anisotropic mechanical properties and offers important reference to solve practical engineering problems.


Su H.,Xihua University | Liu X.-B.,Xihua University | Ji L.,Xihua University | Mu J.-Y.,Chengdu Hydroelectric Investigation And Design Institute
Energy and Buildings | Year: 2012

An air-earth (rock)-tunnel system has often been used for building energy saving. A computing model of the air-earth (rock) heat exchanger is necessary to predict the thermal performance. A numerical simulating model has been developed for the deeply buried air-earth (rock)-tunnel system, in which a 1-D implicit transient convection-diffusion sub-model describes the air temperature and humidity, and a 1-D transient explicit heat conduction sub-model computes the rock temperature. Based on an appropriate discrete scheme, a sequential computing algorithm has been given for solving the air sub-model and the rock sub-model respectively. The accuracy of this numerical model has been verified by comparisons of temperatures of the air and rock and the relative humidity between numerical results and the test data. © 2011 Elsevier B.V. All rights reserved.


Qi Z.-F.,Wuhan University | Jiang Q.-H.,Wuhan University | Tang Z.-D.,Chengdu Hydroelectric Investigation And Design Institute | Zhou C.-B.,Wuhan University
Yantu Lixue/Rock and Soil Mechanics | Year: 2012

The geological conditions of the high and steep abutment slope at left bank of Jinping-I Hydropower Project are very complicated, mainly developed with the faults of f 5, f 8, f 42-9, the lamprophyre veins of X, the release fractures oriented parallel to slope surface and deep fractures. The combination of the fault of f 42-9, the lamprophyre veins of X and the deep fracture of SL 44-1 form a tensile dehiscent deformable body at the abutment slope of the left bank; the stability of the abutment slope is very bad during construction, especially when the slope is excavated to the elevation of 1 780 m, all rock masses that prevent the tensile dehiscent deformable body from sliding are excavated; the outcrop of the fault of f 42-9at the surface of the excavated slope makes the stability of the tensile dehiscent deformable body abruptly become worse. The strength reduction FEM considering excavation process is applied to calculate the stability safety factor of the abutment slope; and a new slope instability criterion is proposed as follows: in finding the mutant site on the relationship curves between Δδ/ΔF t of key points and the strength reduction factors, the critical state of instability of the slope could be determined; in this criteria, Δδ/ΔF t, which stands the change rate of horizontal displacement with the strength reduction factors, is the ratio of the horizontal displacement's increment and the strength reduction factor's increment. Comparing with other slope instability criteria, a new criterion is proved to be a reasonable and practical slope instability criterion; based on this criterion, the stability safety factors are calculated when the slope is excavated and reinforced to different elevations; the overall stability and security of the abutment slope at the left bank are reasonably evaluated during its construction.

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