农业饱和土场地速度结构实测与反演研究

发布时间：2018-04-26 04:35

本文选题：农业饱和土 + 速度结构　；参考：《黑龙江八一农垦大学》2017年硕士论文

【摘要】：农业饱和土是土壤含水率超过85%的土,占农业用地面积的5.56%。农业饱和土场地速度结构反映土层厚度及剪切波速度的分布,直接影响场地环境振动特性,是设施农业结构、农田灌溉工程及大型农业设备振动设计、抗震设计的重要依据。Rayleigh波勘探是一种对场地无损伤的检测方法,已广泛应用于场地的岩土勘查、检测等领域。通过地表布设台阵观测地脉动信号,得到场地Rayleigh波频散曲线,以其为目标,应用遗传算法和最小二乘法得到场地剪切波速度结构。为了将Rayleigh波勘探方法应用于农业工程领域,寻求适合农业饱和土场地速度结构的反演方法。选择大庆市龙凤湿地为观测场地,利用地表台阵获取地脉动信号,进而利用频率-波数法提取观测场地Rayleigh波频散曲线。在验证两种正演方法的基础上,对模型参数进行敏感性分析。应用遗传算法和最小二乘法对观测场地剪切波速度结构进行反演,并对反演结果进行对比分析。主要开展了如下工作:(1)介绍观测仪器、观测台阵的布置及频率-波数法的基本原理,并利用频率-波数法提取观测场地Rayleigh波频散曲线,为反演实测场地剪切波速度提供依据。(2)为寻求准确计算Rayleigh波频散曲线的方法,利用Knopoff法和标量传递法分别计算3种典型地质模型的基阶和4个高阶Rayleigh波频散曲线,并进行比较,从而确保正演方法的正确性。剪切波速度、纵波速度、土层厚度、土层密度等参数的变化均会对频散曲线产生一定的影响,利用Knopoff法对上述四个参数进行敏感性分析,为后续反演提供理论基础。(3)以频率-波数法计算得到的频散曲线为目标,Knopoff法为正演程序,利用遗传算法反演场地剪切波速度结构。利用遗传算法对三种典型地质模型进行反演,验证遗传算法的正确性。并利用遗传算法对两种土层划分方法的实测场地进行反演,分别得到二十层土层的剪切波速度结构和四层土层的剪切波速度结构。(4)利用最小二乘法对三种典型地质模型进行反演,验证最小二乘法的正确性。利用最小二乘法对观测场地剪切波速度结构进行反演,得到观测场地为四层土层的剪切波速度结构。
[Abstract]:Agricultural saturated soil is more than 85% soil moisture content, accounting for 5.56% of the agricultural land area. The velocity structure of agricultural saturated soil site reflects the distribution of soil thickness and shear wave velocity, and directly affects the vibration characteristics of the site environment. It is the structure of facility agriculture, farmland irrigation project and vibration design of large agricultural equipment. Rayleigh wave exploration is a non-damage detection method for site, which has been widely used in geotechnical exploration, detection and other fields. The ground Rayleigh wave dispersion curve is obtained by using the ground array to observe the ground pulsation signal, and the velocity structure of the site shear wave is obtained by genetic algorithm and least square method. In order to apply the Rayleigh wave exploration method to the field of agricultural engineering, the inversion method suitable for the velocity structure of agricultural saturated soil site is sought. The Longfeng Wetland in Daqing City was selected as the observation site, and the ground pulsation signal was obtained by using the ground array, and then the frequency wave dispersion curve of the observation site was extracted by the frequency-wavenumber method. Based on the verification of the two forward modeling methods, the sensitivity analysis of the model parameters is carried out. Genetic algorithm and least square method are used to invert the shear wave velocity structure of the observation site, and the inversion results are compared and analyzed. The main work is as follows: (1) introduce the observation instrument, the arrangement of observation array and the basic principle of frequency-wavenumber method, and use frequency-wavenumber method to extract the dispersion curve of Rayleigh wave in observation site. In order to search for an accurate method to calculate the dispersion curve of Rayleigh wave, the basic order and four higher order Rayleigh wave dispersion curves of three typical geological models are calculated by Knopoff method and scalar transfer method respectively, and compared with each other. In order to ensure the correctness of the forward method. The variation of shear wave velocity, longitudinal wave velocity, soil layer thickness and soil density will have a certain effect on the dispersion curve. The sensitivity of the above four parameters is analyzed by Knopoff method. This paper provides a theoretical basis for subsequent inversion. (3) taking the dispersion curve calculated by frequency-wavenumber method as the object and using the Knopoff method as the forward program, genetic algorithm is used to inverse the shear wave velocity structure of the site. Genetic algorithm is used to inverse three typical geological models to verify the correctness of genetic algorithm. Genetic algorithm is used to invert the measured site of two soil layer partition methods. The shear wave velocity structure of 20-layer soil layer and the shear wave velocity structure of four-layer soil layer are obtained respectively. The least square method is used to inverse the three typical geological models to verify the correctness of the least square method. The shear wave velocity structure of the observation site is inversed by the least square method, and the shear wave velocity structure of the observation site is obtained.
【学位授予单位】：黑龙江八一农垦大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：S29

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