石振明,沈健,刘鎏,等. 2021. 桩底溶洞探测中瞬时相位差强度计算方法的优化及应用[J]. 工程地质学报,29(5):1545-1554. doi: 10.13544/j.cnki.jeg.2021-0510.
    引用本文: 石振明,沈健,刘鎏,等. 2021. 桩底溶洞探测中瞬时相位差强度计算方法的优化及应用[J]. 工程地质学报,29(5):1545-1554. doi: 10.13544/j.cnki.jeg.2021-0510.
    Shi Zhenming, Shen Jian, Liu Liu, et al. 2021. Optimization and application of instantaneous phase difference intensity calculation method to cavity detection beneath cast-in-place pile [J]. Journal of Engineering Geology, 29(5): 1545-1554. doi: 10.13544/j.cnki.jeg.2021-0510.
    Citation: Shi Zhenming, Shen Jian, Liu Liu, et al. 2021. Optimization and application of instantaneous phase difference intensity calculation method to cavity detection beneath cast-in-place pile [J]. Journal of Engineering Geology, 29(5): 1545-1554. doi: 10.13544/j.cnki.jeg.2021-0510.

    桩底溶洞探测中瞬时相位差强度计算方法的优化及应用

    OPTIMIZATION AND APPLICATION OF INSTANTANEOUS PHASE DIFFERENCE INTENSITY CALCULATION METHOD TO CAVITY DETECTION BENEATH CAST-IN-PLACE PILE

    • 摘要: 双通道桩底溶洞声呐探测方法是岩溶地区钻孔灌注桩特殊泥浆施工环境下一种有效的溶洞探测方法,其中所运用的瞬时相位差强度(IPDI)分析方法可以用于提取溶洞顶底板的微弱反射信号并揭示溶洞位置。但该溶洞探测方法中一些关键参数的取值对溶洞探测效果的影响规律不明确,可能导致计算所得溶洞顶底板位置及溶洞大小的精度发生损失。本文旨在得到IPDI计算中关键影响因素及其影响规律从而达到优化效果,并将其运用于模拟工况以及实测信号的IPDI分析验证其有效性。首先,采用二维黏弹性波方程和交叉网格时域有限差分建立了溶洞探测仿真数值模型。接着将其用于探索IPDI计算过程中采样率、总体平均经验模态分解(EEMD)中总体平均次数、标准差等关键参数的影响规律并进行优化,尝试运用灰色预测模型抑制探测结果的端点效应。最后,将优化方法运用于工程实测信号IPDI分析过程。结果表明,当采用0.5~1MHz的采样率,并在EEMD过程中选取0.1作为标准差以及300~600作为总体平均次数能够使溶洞顶底板位置和溶洞大小的探测精度得到提升。当采用灰色预测模型抑制IPDI图像端点效应时,能够有效减缓其两端的异常“飞逸”现象。在进行实测信号优化分析时,发现针对实测信号的零漂现象采用将重构信号减去EEMD过程所得到的趋势项的优化方法,能够得到原先被掩盖的溶洞底板反射信号并计算出溶洞底板位置,并且经与钻孔柱状图对比,其计算结果准确可靠。相较任意选取参数时的探测结果,本文提出的优化方法的确能够帮助提升双通道溶洞声呐探测方法的精确度。

       

      Abstract: The two-receiver sonar method for cavity detection beneath piles is an effective detection method in the special environment of mud during the construction of bored holes. The Instantaneous Phase Difference Intensity(IPDI)can be applied to extract weak reflection signal from the top and bottom of a cavity,hence discovering the location of the cavity. However,during the process,how the specific valuing method of some critical parameters influence the detecting results remains unknown. The uncertainty may lead to loss in accuracy. The purposes of this paper are to find out(1)how these critical parameters,such as sampling rate,the number of ensemble members and standard deviation,can influence the results of cavity detecting and (2)the suitable way to value these parameters. First of all,we establish a numerical mode for simulating cavity detection. Secondly,we explore the optimization of valuing the critical parameters through lots of tests of simulated numerical signals. At last,we apply the optimization results to the IPDI analysis of a real-field signal to verify its effectiveness. The gray prediction model is applied to deal with the end effect appearing in the IPDI image. The result shows that a sampling rate of 0.5~1MHz,accepting 0.1 as standard deviation and 300~600 as the number of ensemble members can improve the accuracy of cavity's location and size's detecting results. In addition,grey prediction model can help release the end effect of IPDI image. A solution to address signal's zero drift phenomenon is promoted. By subtracting the trend item from the reconstructed signal,the hidden reflection signal from the bottom of the cavity is discovered. The calculated depth of the cavity's bottom is identical to what it demonstrates in borehole logs. Compared with the original detection results,the optimization method is proved effective in elevating the accuracy of two-receiver sonar method for cavity detection.

       

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