深海钴结壳超声传播机理及测厚方法研究

In deep sea cobalt crust mining, the mixing of bedrock will seriously affect the mining efficiency of cobalt crust. Measuring the thickness of cobalt crust is the basis of establishing accurate mining system. So the method of measuring the thickness of cobalt crust by ultrasonic echo is proposed and the micro-topography and thickness of cobalt crust of intelligent ultrasonic detection system in deep sea environment is established. The main research contents are as follow: acoustic propagation characteristics of the cobalt crust and bedrock are studied. The acoustic attenuation model of the cobalt crust and the acoustic energy distribution model of the interface between the cobalt crust and the bedrock are established. These are used to determine the ultrasonic frequency and waveform et al. The relationship between sound velocity, elastic modulus, Poisson's ratio, density and other physical and mechanical property parameters of cobalt crust was studied to determine the sound velocity calculation method for different types of cobalt crusts. The sound velocity measurement experiment was performed using cobalt crust simulation materials and the sound velocity calculation method was modified.The method of reflection echo detection is studied. Based on the theory of pattern recognition and the feature extraction , the reflection echoes of the interface between cobalt crust and bedrock are identified, and the method of accurately calculating the echo arrival time is studied. Combined with the velocity of wave in the crust, an acoustic thickness measurement model for cobalt crust is established. A cobalt-crust micro-topography and thickness intelligent ultrasonic detection system was built to solve the basic theory and key technical problems of thickness measurement of deep-sea cobalt crust through theoretical, simulation and experimental research.

深海钴结壳开采时，基岩的混入将严重影响钴结壳的采集效率，对钴结壳厚度进行测量是提高采集效率的基础。本项目提出利用超声回波法测量钴结壳厚度，并搭建深海环境下微地形与厚度智能超声探测系统。研究钴结壳内部及钴结壳—基岩分界面的声学传播特性，建立钴结壳声衰减模型及分界面声波能量分配模型，以此确定超声探测频率、波形等参数；研究钴结壳声速与弹性模量、泊松比、密度等物理力学参数的关系，确定不同类型钴结壳的声速计算方法；利用钴结壳模拟料进行声速测量实验，修正声速计算方法；研究反射回波检测方法，基于特征提取与模式识别理论对钴结壳-基岩界面回波进行识别，并研究精确计算回波到达时间的方法，结合钴结壳中的波速，建立钴结壳声学测厚模型。搭建钴结壳微地形与厚度智能超声探测系统，通过理论、仿真、实验研究，解决深海钴结壳测厚基础理论及关键技术问题。

为实现钴结壳精确采集，钴结壳三维重构是前提保障。针对钴结壳采矿混响环境声衰减严重问题，探究超声在钴结壳测厚环境中声传播特性，提出降低混响测厚环境声衰减方法，实现钴结壳厚度测量。首先，研究了影响钴结壳声传播特性的因素，制作了钴结壳声学方面的模拟料，解决了天然钴结壳难以制作成标准样品的难题，为后续钴结壳声学研究提供了样本支撑；其次，研究了钴结壳声传播特性，建立了钴结壳声速与声衰减预测模型，为精确测量钴结壳厚度提供理论基础；然后，研究了模拟采矿钴结壳测厚环境声衰减特性，建立了测厚环境声衰减模型，发现降低发射频率可以有效降低测厚环境的声衰减，搭建了钴结壳测厚系统，实现了钴结壳厚度精确测量，为水下孔隙介质测厚系统提供了设计方案；最后，建立了钴结壳的三维矿体重构模型，形成了钴结壳三维重构测量技术，为钴结壳精确采集提供数据与理论支持，同时，该方法还可用于其他水下资源测量与预估。

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