Study on water hysteresis in aerated soil

WANG Jin-sheng1,YANG Zhi-feng1,CHEN Jia-jun
WANG  Jin-sheng¹,YANG Zhi-feng¹,CHEN Jia-jun¹,WANG Zhi-ming²
(1.Beijing Normal University,Beijing 100875;2.China Institute for Radiation Protection)

Abstract£ºWater hysteresis in aerated zone of soil is significant to the development and utlization of water resources as well as the protection of water environment.Based on the empirical Van equation,the imbibition and drainage curves are estabilished.An algorithm to acquire 4 unknown parameters is developed by means of coupling the least square method and nonlinear simplex method,and the application of the hysteresis curve to numerical simulation is discussed.Furthermore,the method to calculate the water characteristic curves in aerated zone are verified by in-situ data,and the modeling for imbibition and drainage test in 4 kinds of soil with different characteristics is performed.The results show that the algorithm to acquire the water characteristic curves adopted in this paper is convenient to use and possesses good fitting effect to test data.
Key words:aerated zone;imbibition curve;drainage curve;hysteresis;unsaturated hydraulic conductivity

Transfer function approach of solute transport in unsaturated
homogeneous soil under unsteady flow condition

REN Li¹,LIU Zhao-guang¹,LI Bao-guo¹
(1.China Agricultural University)

Abstract£ºBased on the theory of transfer function model,the transport of surface-applied and indigenous nitrate and chloride in unsaturated homogeneous soil under unsteady condition is investigated experimentally.The mean and variance of log-normal distribution probability density function(pdf) of the travel time are evalutated by the maximum likelihood method,and then the quantity of leached nitrate-nitrogen is determined accordingly.The process of nitrogen leaching is predicted using the transport of the indigenous chloride in soil.The median travel time and mean travel time as well as the transport volume are also estimated.
Key words£ºsolute transport;transfer function model;stochastic modeling;unsteady flow; unsaturated soil

Vortex flow and cavitation inception in a slot

NI Hangen¹,CHEN Xia²
(1.Dalian University of Technology)
(2.China Institute of Water Resources and Hydropower research)

Abstract£ºIn this paper,the mechanism of the vortex flow in a slot is described and the approximate equations for total vorticity and energy ofthe vortex are established.The expression of cavitation inception index of the slot is deduced.The calculated results are in accordance with the experimental data.
Key words£ºslot;vortex;incipient cavitation

Dynamic response of earthquake and liquefaction
analysis of the Heihe Earth Dam

Abstract£ºBased on the dynamic consolidation model of the saturated soil,the Duncan-Chang Model and the Hardin model are used for the purpose of the dynamic response ana lysis of the Heihe Earth Dam under the seismic load.The development of the gener ation,dispersion and dissipation of the pore water pressure in the dam is studied and the identification of the liquefaction of the dam is conducted.The analysis results show that no liquefaction will happen to the dam during earthquake.
Key words£ºearth dam;seismic response;liquefaction analysis

The hydraulic and aeration characteristics of low Froude
number flow over a step aerator

YANG Yongsen¹,YANG Yongquan²,Shuai Qinghong²
(1.Tsinghua University 2.Sichun University)

Abstract£ºThe effect of water contained in cavity to hydraulic and aeration characteristics of step aerator in low Froude number flow(Fr<7) is investigated experimentally and theoretically. The mathematical model for predicting the hydraulic and aeration characteristics of aerator is established and the correction for the emergence angle of the jet is deduced. The expressions for calculating the volume of the water contained in cavity, length of cavity, pressure incavity and the air entrained are proposed. It is concluded that the water contained in cavity may significantly affect the characteristics of flow and aeration¡£
Key words£ºstep aerator; Froude number; hydraulic and aeration characteristics

Abstract£ºIn this paper, the study on construction of hydraulic fillash dam in plain is presented. The feasibility of using slurry pump to transport fly ash for dam construction is demonstrated. The technological process for dam construction is investigated and the result is proved to be effective, safe and feasible.
Key words£ºfly ash; hydraulic fill dam, plain, construction technology

Experimental study on liquefaction characteristics of saturated sandy gravel

WANG Kunyao, CHANG Yaping, CHEN Ning
(China Institute of Water Resources and Hydropower research£©

Abstract£ºLarge scale cyclic triaxial tests on saturated sandy gravel with specimen size ¦¼30¡Á75 cm were performed to investigate the effect of different gravel content and drainage condition on the liquefaction behavior of sandy gravel. Test results show that, with initial liquefaction as failure criterion,gravel contents have little influence on liquefaction resistance strength of sandy gravel under undrained condition, but under drained condition the liquefaction resistance of sandy gravel increases significantly with increase of gravel content. It is found that drainage conditions exert a significant effect on liquefaction characteristics of sandy gravel. Cyclic strength of drained sandy gravel specimen is much higher than that of undrained sandy gravel specimens, and the deformation is much smaller.
Key words£ºsaturated sandy gravel; liquefaction;gravel content;drainage condition

Probability analysis of linear cracking trajectories of arch dam

CHEN Zuping
(SHougang University)

Abstract£ºThe 3 D stochastic finite element method for solid mechanics is applied to analyze the arch dam. The different strength criterions are used to establish the performance function. The reliability index field of arch damis solved by first order second moment method. The point with minimum reliability index is identified as the emergence of cracking. Note down this failure probability and modify the stiffness of this cracked point and the whole dam accordingly. The cracking trajectory can be traced in accordance with the progression of cracking point by repeat this procedure. The conditional probability vector of cracking trajectory is in terms of the progression of conditional probability.
Key words£ºcracking trajectory; arch dam; stochastic finite element method;probability  vecto

A bivariate method of rainstorm and flood for design flood and its application

FENG Ping, CUI Guangtao, HU Minggang
(Tianjin University)

Abstract£ºThe calculation method for flood design is investigated on the basis of risk analysis. In this method, the possibility of the occurrence of rainstorm and flood with different frequency of occurrence, which is always occurred to hydrologic phenomenon, is considered.
Key words£ºrainstorm; flood;flood risk; design flood

Research on reliability of pumping unit operation

ZHANG Zixian, LIU Jiachun
(Hebei Engineering and Technical College)

Abstract£ºIn this paper, the formula for evaluating the reliability of pumping unit operation
during coordinated operation of pump and motive power machine. The probability theory and statistical method are applied to establish the calculation model. The reliabilities of 30 types of centrifugal and axial flow pumps with various spare coefficients are calculated. Some valuable conclusions have been drawn.
Key words£ºpumping unit; reliability; spare coefficient, random factor, probability distribution, characteristics curve

LI Ran, ZHAO Wenqian, LI Jia, LI Kefeng
(The State Key Hydraulics Lab.of High Speed Flows,Sichuan University)

Abstract£ºBased on turbulent diffusion theory and the mechanism of liquid-gas interfacial mass transfer,a conceptual model of turbulent re-aeration process is proposed.The oxygen fluxes caused by molecular diffusion and turbulent diffusion are studied separately.According to the experimental data and theoretical analyses,the interfacial mass transfer coefficients of quiescent water and turbulent water with different turbulence are obtained.The relationship between interfacial mass transfer coefficient and interfacial ki-netic energy is established.
Key words£ºre-aeration; turbulence; interfacial masstransfer coefficient

HU Baoqing
(Wuhan University of hydraulic and Electric Engineering)

Abstract£ºThe concept of matter-element matrix with the same characteristics is introduced and the con-cept of level variable characteristic value of extension assessment method is suggested.The method for determination of extension weights by using simple dependent function is proposed.On these bases,the extension assessment method is firstly applied to stability classification of surrounding rocks.
Key words£ºstability of surrounding rocks; matter-element; extension method; assessment

LU Tinghao¹,BAO Fubo²
(1.Geotechnicla Engineering research Institute 2.Fujian Building Research Institute)

Abstract£ºSimple shear test shows that there is a shear zone in soil nearby the contact surface, in which the shear dilation/compression effect exists during shearing. In order to simulate the stress-strain relation of this shear zone and to simulate the interaction between soil and structure, a coupled constituive model is proposed and the thickness is discussed.
Key words£ºsimple shear test, interface, thin-layer element; coupled constitutive model

CHEN Gaixin, HUANG Guoxing, JI Guojin
(China Institute of Water Resources & Hydropower Research)

Abstract£ºThis study is conducted specially in connection with Shapai RCC arch dam, the highest one under construction in the world at present. Based on the latest experiences summarized by the authors, a scheme of the general layout of the grouting pipeline system and the details of the rubber sleeve valve, which served as the outlet of grouting, are proposed. The properties of different ultra-fine cements with various additives for grouting are studied. The experiment results show that the rubber sleeve valve can be opened at a pressure of 0.06¡«0.16MPa and re-grouted 2¡«3 times in a month. The grouting material based on ultra-fine cement can be injected into the cracks about 0.2¡«0.3mm in width.
Key words£ºroller compacted concrete; arch dam; joint; repeated grouting; grouting material; ultra-fine cement