Application of wavelet to strength log from scratch test
Application of wavelet to strength log from scratch test
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DOI：
10.1016/j.jrmge.2022.09.002
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发表时间：
2022-09
影响因子：
7.3
通讯作者：
He Zhang;J. Le;E. Detournay
中科院分区：
文献类型：
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作者：
He Zhang;J. Le;E. Detournay
本文提出了一种方法来构建日志的岩石强度从切削力信号记录在划痕试验中进行的韧性制度。该方法，这是基于离散小波变换的应用程序，认识到存在两个长度尺度的dlc和dlr。强度长度标度c表示测量强度有意义的长度，而可重复性长度标度r与必须观察到的力信号对刀具运动触发的随机微故障事件不敏感的分辨率有关。据推测，原始的切削力信号，假设在一个足够高的频率采样，可以分解成一个确定性的信号固有的岩石和随机的离散岩石破坏事件。采用基于最大重叠离散小波变换的多分辨率分析技术对原始切削力信号进行低通滤波，滤除与随机岩石破坏事件相关的高频成分。根据滤波后信号间的相关系数，讨论了确定低通滤波器最佳截止频率和相应重复性长度尺度的准则。结果表明，在最佳截止频率下获得的低通滤波信号具有两个显著特征：（i）在同一样品上以相同切割深度进行的不同测试的重复性，以及（ii）沿着切割距离的可变性。良好的重复性表明，确定性的背景趋势的原始力信号是相关的岩石强度属性，和背景趋势的变化捕捉岩石强度的空间变化。
This paper proposes a methodology to construct logs of rock strength from the cutting force signal recorded in scratch tests conducted in the ductile regime. The approach, which is based on the application of discrete wavelet transforms, recognizes the existence of two length scales ℓ c and ℓ r. The strength length scale ℓ c represents the length over which it is meaningful to measure strength, while the repeatability length scale ℓ r is related to the resolution at which the force signal must be observed to become insensitive to the stochastic micro-failure events triggered by the motion of the cutter. It is postulated that the original cutting force signal, assumed to be sampled at a high enough frequency, can be decomposed into a deterministic signal intrinsic to the rock and a stochastic one resulting from discrete rock failure events. The technique of multiresolution analysis based on the maximal overlap discrete wavelet transform is applied as a low-pass filter to the original cutting force signals so as to wipe out the high-frequency components associated with the stochastic rock failure events. A criterion to determine the optimum cutoff frequency of the low-pass filter and the corresponding repeatability length scale is discussed in terms of the correlation coefficients between different filtered signals. It is shown that the low-pass filtered signals obtained at the optimum cutoff frequency have two salient features:(i) repeatability over different tests conducted at the same depth of cut on the same sample, and (ii) variability along the cutting distance. The excellent repeatability reveals that the deterministic background trend of the original force signals is relevant to the rock strength property, and the variability of the background trend captures the spatial variation of the rock strength.