大坝水平位移监测数据的小波变换去噪处理

将实际观测到的一组大坝水平位移监测数据作为通常意义下的时序信号，并对其进行小波变换分析。根据噪声和有用信号的小波变换系数模极大值在不同分解尺度上的传播特点，提出了根据模极大值的传播规律来区别噪声和有用信号的方法，并给出了具体的算法和计算程序。对模拟数据和实测数据的处理结果表明，基于小波分解模极大值的去噪方法能够有效剔除土木工程变形监测数据中的噪声，识别被噪声湮没的有用信号。     

SIMILARITY LAW OF FLUCTUATING PRESSURE WITHIN HYDRAULIC JUMP AREA

Through a series of model tests of five scales for 2-D free hydraulic jump, the da-ta of fluctuating pressure acting on the floor level within the hydraulic jump were obtained. Dur-ing the experiments, Froude number varied from 2.94 to 8.61, and Reynolds number rangedfrom 2×10~4 to 6×10~5. Experiment results indicate that the amplitude scale of fluctuating pres-sure is the length scale of model, i. e. P'=L, which agrees with gravity similarity law: Thefrequency scale of the fluctuating pressure is a unity i. e., f=1, which does not satisfy thegravity similarity law.     

泄漏检测信号滤波技术比较

通过泄漏检测模型试验分析测量信号中的噪声来源,在对比研究传统小波去噪、改进神经网络去噪、最小二乘拟合去噪等方法在实测数据中去噪效果的基础上,借鉴神经网络反向传播学习算法的思路,提出了信号预滤波结合阈值自学习小波去噪的综合滤波方法。该方法通过对恒定状态下带噪压力信号阈值自学习使得重构信号与期望输出均方误差最小来获得单一工况下的最佳去噪阈值,再将此阈值用于同一工况下整个时间段的去噪,这样根据不同工况下得到的最佳阈值可以获得最优输出。数值计算结果比较表明该方法对噪声的抑制作用明显,比传统小波去噪、改进神经网络去噪等方法效果更好。     

A FIELD TEST DATA RESEARCH BASED ON A NEW HYDRAULIC PARAMETERS QUICK TEST TECHNOLOGY

The hydraulic parameter quick test system in accordance with the oscillation principle can overcome the shortcomings of traditional methods in determining hydraulic parameters which, besides having complex hydrogeological restrictions and needing complex equipment in the field, are often both time and energy consuming, and high cost. Based on the hydrogeological conditions in the north anchorage of Taizhou Yangtze River Highway Bridge, a quick hierarchical test is carried out for different depths of single-hole drilling to verify the function of the system in this case. Meanwhile, with a purification of the raw data gathered in the test by wavelet denoising, the hydraulic parameters are worked out by adopting the Kipp model. A comparison between the Kipp model results and stratigraphic data as well as pumping test results justifies the reliability and accuracy of the new method. The study finds other advantages of the method like high efficiency in operation, flexibility in stratified test, as well as environmental-friendliness. Therefore, the technology is of significant practical value and application prospect.     

锚杆静压混凝土桩在小型水利工程中的应用

简要介绍了锚杆静压桩法的基本原理,通过实践证明,该法在小型水利工程中的应用效果良好,值得推广.     

NUMERICAL SIMULATION AND ANALYSIS OF PRESSURE PULSATION IN FRANCIS HYDRAULIC TURBINE WITH AIR ADMISSION

In this article, the three-dimensional unsteady multiphase flow is simulated in the whole passage of Francis hydraulic turbine. The pressure pulsation is predicted and compared with experimental data at positions in the draft tube, in front of runner, guide vanes and at the inlet of the spiral case. The relationship between pressure pulsation in the whole passage and air admission is analyzed. The computational results show: air admission from spindle hole decreases the pressure difference in the horizontal section of draft tube, which in turn decreases the amplitude of low-frequency pressure pulsation in the draft tube; the rotor-stator interaction between the air inlet and the runner increases the blade-frequency pressure pulsation in front of the runner.     

NUMERICAL SIMULATION STUDY ON SURFACTANT FLOODING FOR LOW PERMEABILITY OILFIELD IN THE CONDITION OF THRESHOLD PRESSURE

Based on the non-Darcy flow characteristics of surfactant flooding in the low permeability oilfield, considering the changes of threshold pressure and influence of surfactant on convection, diffusion, adsorption and retention, a mathematical model is established for a three-dimensional, two-phase, three-component surfactant flooding. A new treatment for the changes of threshold pressure and a novel correction method for the relative permeability curve in the process of surfactant flooding are derived, which enhances the matching degree between the mathematical model and field practice. The mathematical model was used to perform the numerical simulation study for a pilot test of surfactant flooding in Chao 45 Block of Daqing Oilfield, a proper injection plan was optimized. After the optimized plan was carried out in oilfield, the desirable effects, like pressure-reducing, injection rate increase, and the increase of oil recovery, were achieved. The average oil increase for single well reaches 37%, the ratio of cost to revenue is above 1：4, so the economic effect of scale is promising.     

WELL TESTING ANALYSIS FOR HORIZONTAL WELL WITH CONSIDERATION OF THRESHOLD PRESSURE GRADIENT IN TIGHT GAS RESERVOIRS

A fundamental solution for homogeneous reservoir in infinite space is derived by using the point source function with the consideration of the threshold pressure gradient. The fundamental solution of the continuous point source function is then derived based on the Green function. Various boundary conditions of the reservoirs are considered for this case and the corresponding solutions are obtained through the mirror image reflection and the principle of superimposition. The line source solution is obtained by integration. Subsequently, the horizontal-well bottom hole pressure response function for a non-linear gas flow in the homogeneous gas reservoir is obtained, and the response curve of the dimensionless bottom hole pressure and the derivative for a horizontal well in the homogeneous gas reservoir are obtained. In the end, the sensitivities of the relevant parameters are analyzed. The well test model presented in this paper can be used as the basis of the horizontal well test analysis for tight gas reservoirs.     

基于小波分析以及ε-SVR的隧道围岩位移时序预测

根据龙滩地下洞室围岩现场长期的观测数据,利用小波变换阈值去噪法对数据信号的高频系数进行量化处理,恢复原有的监测信号。实例结果表明,小波变换阈值去噪法能够有效地去除噪声的影响,获得围岩变形的真实信号。同时将去噪后的数据用于支持向量机(ε-SVR)建立时序分析模型中,并与GA-BP模型进行对比,结果表明ε-SVR模型的误差更小,预测效果更佳。更多还原     

基于改进EMD-LSTM的混凝土坝变形预测模型

针对混凝土坝变形监测数据的非线性和复杂性等特征,为提高混凝土坝变形预测的精度,提出了一种基于改进经验模态分解(EMD)法和长短期记忆(LSTM)神经网络的混凝土坝变形预测模型。该模型采用小波阈值方法对EMD法分解的高频分量进行优化处理,在去除数据噪声的同时,尽可能保留原始数据的特征信息,并运用LSTM神经网络对处理后的数据进行时序预测。实例验证结果表明,该模型能够准确模拟坝体变形过程,具有较高的预测精度。