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提出了一种提高单孔法剪切波速测量精度的新方法——能量变化率的自回归曲线法。首先把剪切波的时程曲线变换为能量变化率时程曲线;然后对能量变化率时程曲线进行长短平均处理,拾取各测点P波和S波的大致初至;最后提出采用一种二次方自回归模型对初至附近的能量变化率曲线进行二次方自回归处理,精确拾取出各测点P波和S波的精确到时。采用此方法、互相关函数法和人工拾取法对某场地的剪切波速进行了对比分析。分析结果表明:此方法相比互相关函数法,具有更好的噪声抑制能力,不仅能精确地自动拾取出各测点的S波的到时差,也能更准确地自动拾取出各测点的P波的到时差。以人工拾取结果为参考,此方法在实际测试中具有很高的准确率和稳定性。此方法丰富了场地剪切波速分析方法。基于此方法、互相关函数法和人工拾取法,设计了一套剪切波波速的测试系统,此系统能自动分析出各测点的剪切波速和形成完整的报告。
A new method to improve the measurement accuracy of single-hole shear wave velocity is proposed, which is the autoregressive curve method of energy rate of change. Firstly, the time history curve of the shear wave is transformed into the time history curve of the energy rate of change. Then, the time history curve of the energy rate of change is averagely processed to obtain the first arrival of the P wave and the S wave of each measuring point. Finally, The quadratic autoregressive model performs quadratic autoregression on the energy rate-of-change curve near the first arrival to accurately pick out the exact arrival time of P and S waves at each measurement point. Using this method, the cross-correlation function method and the manual pick-up method were used to analyze the shear wave velocity of a field. The analysis results show that this method has better noise suppression ability than the cross-correlation function method. It not only can automatically pick out the S-wave arrival time of each measuring point accurately, but also can pick up the measuring points automatically P wave to the time difference. Taking the result of manual picking as a reference, this method has high accuracy and stability in practical testing. This method enriches the field shear wave velocity analysis method. Based on this method, a cross-correlation function method and a manual pick-up method, a test system of shear wave velocity is designed. The system can automatically analyze the shear wave velocity of each measuring point and form a complete report.