基于非匀速修正圆锥指数的土层厚度测量方法

Soil Thickness Measuring Method Based on Non-uniform Speed Modified Cone Index

为快速获取土层厚度信息,提出利用土壤机械阻力判别土壤层次结构,设计了一种能够自动记录土壤机械阻力、测量深度、加速度等参数的便携式圆锥仪,在加速度补偿修正非匀速误差的基础上,利用圆锥指数,基于包络检波和Hilbert瞬时振幅特征值聚类算法实现土层结构及土层厚度信息的精细获取。仿真试验和实地测量对比分析结果表明,对于土层物理特性差异明显的土体结构,该方法能有效获取土层厚度信息,相对误差不超过10%,本研究可为耕层厚度的测量提供有效的方法。

Soil thickness is an important parameter affecting soil quality. Rapid acquisition of accurate soil thickness information is an important data basis for the analysis and evaluation of the quality of cultivated land resources and its changing trend. Current mainstream measurement methods are inefficient or inaccurate,such as radar detection method and borehole sampling method. The rapid measurement of soil thickness was realized based on soil mechanical resistance with optimized cone meter. Data were acquired by a cone soil thickness measuring instrument which was an optimized hand-held cone meter attached with acceleration sensor, position sensor and other sensors. Acceleration compensation technology was adopted to reduce the measurement error of soil mechanical resistance caused by nonuniform speed penetration of cone meter. Envelope detection and Hilbert instantaneous amplitude eigenvalue clustering algorithm were introduced to identify soil structure and calculate the thickness of soil layer. The simulation results based on Ayers semi-empirical model showed that the conical soil thickness measuring instrument based on Hilbert transform algorithm can effectively acquire the information of soil thickness with relative error no higher than 7. 50%. The measuring results for outdoor measured data showed that the absolute error of soil thickness measured by Hilbert instantaneous amplitude spectrum based on lower envelope was not more than 1 cm,and the relative error was not more than 10%. This method can meet the needs of actual measurement for plough layer soil depth and provide a reference for future soil layer measuring application.